Skip to content | Accessibility - list of access keys used on this site | Sitemap
Find what you need to know

Absolute uncertainty

Also known as absolute error.

The uncertainty in a measured quantity is due to inherent variations in the measurement process itself. The uncertainty in a result is due to the combined and accumulated effects of these measurement uncertainties that were used in the calculation of that result. When these uncertainties are expressed in the same units as the measured value itself they are called absolute uncertainties. Uncertainty values are usually expressed:

(measured value) ± (absolute uncertainty in that quantity).

Adequate report

Your report will include evidence that you have:

  • followed a design in which you have:
    • an aim/testable question
    • a method
    • identified variables – independent variable, dependent variable, and some fixed variables
  • collected information
  • recorded information
  • processed information
  • interpreted information or made a conclusion on information from the investigation.

Allotrope

Allotropes are elements that can exist in different forms of the same state (gas, liquid, or solid). The allotropes of the element will have different physical properties.

Examples of allotropes:

  • carbon (solid) – diamond, graphite
  • oxygen (gas) – oxygen O2, ozone O3
  • sulphur (S8 crystalline solid) – rhombic and monoclinic sulphur. These different forms of sulphur are determined by the way the S atoms are packed together and influence their different solubilities and melting points.
  • tin (solid) – white tin, grey tin
  • phosphorus (solid) – black, red and white forms of phosphorus.

Analytical chemistry

Analytical chemistry is the science whose aim is to provide information about the chemical composition of a substance. The field of analytical chemistry can be divided into two broad categories:


Analyse

You are required to apply understanding to some information that you are given.

Example of an analyse question:
The lens is focused on an object only 0.45 m away. You will notice that the lens is now further away from the camera body (and the film). Discuss, with the help of ray diagram(s) drawn in the boxes below, why the lens must be further way to form an image on the film when the object is this close to the camera.

Anticodon

An anticodon is a sequence of three bases on tRNA that bonds to the codon of mRNA during protein synthesis.

Appropriate format

The format of the processed data is presented so that it accurately represents the field data, is suitable for the type of data, and clearly shows the relationship or pattern. Suitable formats could be kite diagrams, bar graphs, pie charts, profile diagrams, or tables.

Appropriate processing

This means that you have used a processing method that is suitable for the type of field data, to ensure that any relationship or pattern in the field data will be meaningful and accurate. You could show the relationship or pattern as a kite diagram, a bar graph, a pie chart, a profile diagram, or a table. Note that only one format is required to show an interrelationship or pattern.

Appropriate recording

This involves including the field data itself with all the information that will allow the field data to be used, or that will allow the investigation to be repeated by another person. The information with the field data could include:

  • the location of sample sites in a stream transect
  • areas where samples are taken in a distribution study
  • where measurements of size are taken in an age structure, or
  • quadrat size in a density study.

Apply

This instruction requires to you consider the information supplied with the question (it may be in the form of words, a chart, a drawing, or a graph) and use it to answer the question.

Example: 'Examine the periodic table. Apply your knowledge and describe two trends between the properties of metals and non-metals.'

Apply understanding

This means you are required to solve problems by applying acquired knowledge, facts, techniques, and rules in a different way. The question will involve some information, for example as words, a chart, a drawing, or a graph, that you will have to consider. Use the information to answer the question.

Example: 'Examine the periodic table. Apply your knowledge and describe two trends between the properties of metals and properties of non-metals.'

Example: 'Use the information in the diagram to discuss how diorite can be distinguished from basalt.'

Bias

Bias refers to a factor of sampling of the variables of an investigation when the conclusions obtained from the investigation do not accurately describe the characteristics of the whole population. That is, the differences between the sample and the whole population are not just from random chance.

For example, bias may be caused by faulty measuring devices such as a tape measure that has been stretched, so that all measurements are too small.

Binary compounds

Binary compounds are compounds composed of two elements. These compounds are made up of a positive half (always written first) and a negative half (written second).

Examples:

  • H2O
  • NaCl
  • H2O2
  • CaCl2

Bipedalism

A description of an animal having the ability to move by two legs, for example primates, humans, kangaroos.

Biological concept

This can be called a biological idea or theory.

For example, during osmosis water moves from an area of high water concentration to an area of low water concentration.

Biological process

A biological process outlines how or why something, for instance osmosis, happens.

Bottleneck effect

A severe reduction in population size can reduce the diversity of a population. This genetic change can be caused by an intense natural selection or a disaster, and is called the bottleneck effect. The survivors have very little genetic variability and little chance to adapt if the environment changes.

Example: The population of northern elephant seals was severely reduced to only 20 individuals by hunters by the 1890s. Although the population has increased since then to 30 000, there is no genetic variation in the 24 alleles sampled. In contrast, the southern elephant seal which has never reduced by such intense hunting, has wide genetic variation.

If the bottleneck effect exists, inbreeding can cause serious problems for many endangered species, and make them vulnerable to disease and to any changes in their environment. This phenomenon has been observed in the cheetah.

Catalyst

A substance that increases the rate of a chemical reaction, but is not itself changed during the reaction. Enzymes are catalysts for many biochemical reactions.

Chemical properties

In chemistry, chemical properties of an element or compound can be observed in chemical reactions. For example, the fact that sodium reacts with water is a chemical property.

Chemical equilibrium

A state of a chemical reaction when the concentrations of all reactants and all products remain constant with time, that is, there appears to be no change in the concentrations of reactants and products of the reaction. The forward and reverse reactions are occurring simultaneously at the same rate. This state will stay the same provided there is no change in the concentrations of the reactants and products or temperature or pressure of the system or the addition of a catalyst to the system.

Classify and describe

This means you are required to demonstrate understanding of facts and ideas by organising, comparing, translating, interpreting, giving descriptions, and stating main ideas.

Example: 'Classify the igneous rocks and complete the key to allow for easy identification of the rocks described.'

Codon

A codon is a sequence of three bases on mRNA that codes for an amino acid.

Colorimetric analysis

Colorimetric analysis is a quantitative analysis of solutions by estimating the colour produced by the reaction of the sample under analysis with a reagent and comparing it with the colours produced by known standard solutions or by using a colorimeter.

Complete and balanced research report (science level 3)

Your research report must show evidence of the following:

  • a clear account of why the topic is scientific, and is a controversy, with reference to key points
  • scientific information collected from a wide range of sources on more than one side of the controversy
  • information processed to describe key aspects of the controversy
  • a complete and balanced conclusion including:
    • comment on bias and validity of the information researched
    • interpretation and detailed, balanced discussion on information related to the controversy
    • discussion of the candidate's point of view
    • evaluation of the findings
  • a detailed reference list using a recognised reference system
  • acknowledgement of sources used within the report.

Complete report

Your report will include evidence that you have:

  • designed a plan for your practical investigation
  • trialled and modified, if required, the plan
  • followed a feasible design which has:
    • an aim/testable question
    • a method
    • independent variables with ranges
    • dependent variables
    • some fixed variables with values
  • collected sufficient information with full range for independent variable, recording repeats
  • recorded information systematically
  • processed information using averages and/or graphs
  • interpreted information from the investigation
  • a conclusion relating to aim/testable question
  • discussion relating to the science ideas OR evaluation of the investigation.

Complete report (science level 3)

This means that your report will include:

  • processed information using statistical techniques where appropriate, and graphs where relevant
  • interpretation of information from the investigation including some identification of trends, relationships and patterns in recorded information, where appropriate
  • valid conclusion(s)
  • a discussion of an evaluation of the investigation.

Complete research report (science level 3)

Your research report must show evidence of the following:

  • an account of why the topic is scientific, and is a controversy
  • scientific information collected from a range of sources on more than one side of the controversy
  • information processed to identify key aspects of the controversy
  • a complete conclusion including:
    • comment on bias or validity of the information researched
    • interpretation and balanced discussion on information related to the controversy
    • the candidate's point of view
    • some evaluation of the findings
  • A reference list using a recognised reference system.
  • Some acknowledgement of sources used within the research report.

Complete valid report (science level 3)

This means that your report will include:

  • processed information using statistical techniques where appropriate, and graphs where relevant
  • interpretation of information from the investigation including identification of trends, relationships and patterns in recorded information, where appropriate
  • justified conclusion(s) relating to the aim/testable question
  • discussion relating to science ideas AND evaluation of the investigation.

Complex problem (in physics)

A complex problem will involve more than one process. The recognition of at least two different concepts must be involved.

Comprehensive discussion (of a practical biological investigation)

A comprehensive discussion will include a discussion of the validity of an investigation and will link to statistical procedures that you use. Statistics can also establish the reliability of the conclusions you make from the data. A comprehensive discussion will consider:

  • the investigation as a whole
  • the significance of the results in relation to the ecological niche of the organism and relevant scientific information
  • the validity of the investigation in terms of either
    • the validity of the conclusion by using statistical methods such as mean and standard deviation, confidence intervals, standard error, or other appropriate test; or
    • the reliability of the data by consideration of factors such as how sources of error were eliminated, how limitations were overcome, or how the effects of bias were reduced.

Comprehensive plan (chemistry level 3)

A comprehensive plan means that you have met the requirements for achievement with merit and also have included:

  • modifications where necessary
  • a description of the method that shows clear understanding of the overall analytical technique (which would allow a peer to duplicate the investigation).

And in carrying out the plan you would have:

  • collected and recorded data in a way that allows independent checks on all calculations
  • sufficient duplication of experiments to allow checks on reliability and validity
  • collected data within the typical uncertainty levels inherent in the method and appropriate for the equipment used.

Comprehensive report

Your report will include evidence that you have:

  • designed a plan for your practical investigation
  • trialled and modified, if required
  • followed a justified design, with repeats, which has:
    • an aim/testable question
    • a method
    • independent variables with ranges
    • dependent variables
    • most fixed variables with values
  • collected sufficient and reliable information, ignoring extremes, recording repeats to confirm the accuracy of the information
  • recorded information systematically
  • processed information using averages and/or graphs
  • interpreted information from the investigation
  • a conclusion relating to aim/testable question
  • discussion relating to the science ideas AND evaluation of the investigation.

Comprehensive research report (science level 3)

Your research report must show evidence of the following:

  • a detailed account of why the topic is scientific, and is a controversy with a discussion of key points
  • detailed scientific information collected from a comprehensive range of sources on more than one side of the controversy
  • information processed to explain the key aspects of the controversy and the implications of these
  • a comprehensive and balanced conclusion including:
    • discussion on bias and validity of the information researched
    • interpretation and comprehensive, balanced discussion on information related to the controversy
    • discussion of the candidate's point of view, with supporting evidence
    • critical evaluation of the findings
  • a detailed reference list using a recognised reference system
  • acknowledgement of sources used within the report
  • acknowledgement of ideas not generated by the candidate.

Comprehensive valid report (science level 3)

This means that your report will include:

  • interpretation of information from the investigation including full identification of trends, relationships and patterns in recorded information, where appropriate
  • justified and suitably qualified conclusion(s) relating to the aim/testable question
  • a well-reasoned discussion relating to science ideas AND evaluation of the investigation AND possible future investigations.

Computational error

An error that relates to a mathematical calculation

Examples:

An error created when cancelling incorrectly.

An error when entering the numbers into a calculator.

Concentration

The concentration of a solution is the 'strength' of a solution. It is typically given in molarity.

Conclusion

A conclusion links to the aim of the experiment and is drawn from information calculated from the linear graph.

Constitutional isomers

Constitutional isomers are those that have the same molecular formula but a different structural formula.

Correlation

A correlation involves:

  • how data for the two variables will be collected and processed
  • an indication of the proposed range of the variables
  • mention of some other variables or factors that could influence the investigation.

Critical evaluation

The method you have used should provide you with valid and reliable data, and a critical evaluation will discuss the key features of your method and why these the results gained will be valid and reliable.

Current scientific controversy

Current scientific controversy refers to a controversy currently in the scientific literature, and where more than one scientific point of view exists supported by evidence derived using scientific methodology.

Describe

This means you are required to recognise, list, name, draw, define or give characteristics of or an account of.

Examples:
'List two other environmental factors that fungi need so that they grow well.'
'Name three properties that could be used to group the minerals.'
'What distance had Jim travelled at six seconds?' (from reading a graph)

Design a practical investigation

At NCEA level one, you were directed to plan a practical investigation with direction. At NCEA level two, you are required, with supervision, to design a practical investigation. This means that you will individually be able to prepare a plan of a practical investigation and show to your teacher the steps you will take to carry out the investigation. This means that you will:

  • state the purpose of your investigation
  • make a hypothesis
  • decide on an experimental procedure that will test the hypothesis
  • Identify the key factors that will be studied
  • identify the equipment and materials you will need decide how you will use them.

Detailed method

A detailed method is achieved if your method includes sufficient detail and clarity of instruction for others to carry out the experiment and achieve consistent outcomes.

Detailed, workable investigation (science level 3)

This means that your investigation is workable and that you have designed a plan with detail to include:

  • evidence that you have trialled, modified if required, and justified the investigation
  • an aim/testable question
  • a method
  • independent variable with a range, dependent variable, most fixed variables with values
  • repeats.

Develop the investigation

This means you must demonstrate in your investigation some form of trialing or checking before developing your initial plan into a method.

Difference between data and information

Data is factual information, especially information that is used for analysis or reasoning. Data on its own has no meaning, but becomes information when it is interpreted and placed in a context. Information is a collection of facts or data. However, often the terms data and information are used interchangeably as synonyms.

Difference between rocks and minerals

Minerals occur in nature. Minerals can be pure substances (elements) or combination of substances (compound). Minerals are the raw materials of rocks. Rock types are characterised by the types of minerals present in their relative proportions, and the processes by which the rocks were formed. Of these processes, heat, pressure, and time are the most important.

Minerals have definite chemical and physical properties. Some common minerals are feldspar, quartz, calcite, mica, and hornblend. Some minerals are valuable enough to be mined. Some of these are the metal ores from which we obtain iron, lead, copper, aluminum, zinc, gold, and silver.

Minerals make different rocks look different. For example, the minerals of a granite rock are different from the minerals in and a basalt rock. However, even rocks with the same minerals may look different due to variations in the relative amounts of minerals and the processes by which they are formed.

Check out the Rock Cycle at SciLinks The Rock cycle.

Directed use of graphs and diagrams

This means that you will be required to read information directly from graphs and diagrams (including interpolate and extrapolate values) or draw graphs or diagrams from given information.

Discuss

This instruction requires you to show understanding by linking scientific ideas. It may involve you to elaborate, apply, justify, relate, evaluate, compare and contrast, analyse.

Examples:
'Discuss the biological reasons for the different storage conditions needed before and after the yeast has been opened.'
'Discuss how marble is formed from limestone and why we can now find marble on the surface of the earth.'
'Compare the amount of work done by the engine of the bus to the gravitational potential energy gained by the bus. Discuss any differences.'

Discussion (about a conclusion to an experiment)

A discussion may include limitations of the experiment, other variables that had not been foreseen, difficulties in measuring, difficulties in the use of equipment, limitations of the findings and impact on the outcome.

Discussion (of a practical biological investigation)

A discussion considers the significance of the results of the investigation in relation to the ecological niche of the organism.

Diversity in animals and plants

Diversity relates to different adaptations and ways to carry out life processes.

Electronegativity

The power of an atom in a molecule to attract electrons to itself.

For example, in the ionic compound hydrogen chloride (or hydrochloric acid) – HCl, the chlorine atom is more electronegative than the hydrogen. This means that the pair of electrons in the H-Cl bond are pulled a little more towards the Cl atom giving it a partial negative (-) charge. The hydrogen atom has less electron density and has a partial positive (+) charge. The partial charge is shown by the symbol delta ( d ).

  d + d
  H ------ Cl

Endemic

Endemic means any plant or animal native to, and restricted to, a particular geographical region, for example, the takahe, weta, and pingao are endemic to New Zealand.

Endocranial

Refers to the interior of the braincase.

Environmental issue

For the environmental issue, information should:

  • identify and give background on the issue
  • give different views on the issue
  • identify supporting evidence including relevant data/scientific information.

Epistasis

A general term for any interaction between genes at different loci, includes collaborative genes, complementary genes, and supplementary genes (these may all be referred to as epistasis).

Error (in an investigation)

Sources of error can come from human error while carrying out each measurement (for example parallax error) and from the equipment you use. You can minimise error by carrying out several measurements and using the average of your measurements as your data. However, if the differences between repeat trials are too large, then you may need to look at improving or modifying your investigation.

Evaluate

To evaluate something means you need to show understanding by considering, discussing, analysing, judging, or assessing the importance of a scientific idea. You will be able to base this on a sound knowledge of facts (from your reading or from a data collection).

Evaluate (researched information)

Evaluate requires you to:

  • comment on sources and information, considering ideas such as validity (date, peer reviewed, scientific acceptance), bias (attitudes, values, beliefs), weighing up how science ideas are used by different groups, own opinions, attitudes and beliefs
  • provide a justified position that supports or opposes aspects of the issue or an implication of the issue. Justified means to demonstrate, with supporting evidence, why the position has been chosen.

Explain

This instruction involves describing as well as giving reasons as to how or why something occurs.

Examples:

'Explain what the results of this investigation show.'
'Calculate Jim's average speed over the whole 11 second journey. (m s-1)'
'Explain the observation you have just made, in terms of the calculations involved in this oxidation-reduction process.'

Extended practical chemistry investigation

This will involve:

  • developing and carrying out a procedure to collect data about a possible trend in the amount of a substance
  • collecting and recording a sufficient quantity of data to enable a conclusion to be reached
  • processing of the data to reach a conclusion
  • presenting a report that contains:
    • a statement of the purpose of the investigation
    • a description of the procedure that includes preparation of samples and solutions used, control of significant variables, and the analytical technique used
    • summary of the collected and processed data
    • a conclusion based on the processed data.

Extended practical investigation

An extended practical investigation refers to a significant investigation that includes one extended process or several smaller related processes. The entire investigation may take about 6-8 week's work.

Extrapolate

This means to extend a range of values for a graph or curve based on trends of existing values.

Fair test

A fair test involves:

  • identification of the dependent and independent variables
  • the range of the independent variables
  • some other variables to be fixed or controlled
  • how the dependent variable will be measured and the data processed.

Feasible investigation

A feasible investigation means that you have designed a plan that:

  • states a purpose, which might be an aim, testable question, prediction or hypothesis, linked to a scientific concept or idea
  • has a scientific method to collect relevant data so that a report can be written. The method identifies:
    • the key variables or data to be measured or collected. Key variables will be the dependent and independent variables for a fair test or data/samples to be collected when investigating a pattern or relationship, for example, for biology – zonation. Other variables that need to be controlled or other factors that could influence the investigation will also be identified.

However, the method lacks some detail and cannot be independently followed without further clarification.

Feasible method

A feasible method is achieved if you have provided a means for changing the independent variable and for measuring the dependent variable, and you have shown awareness that there may be other variables that could affect the results.

Feasible plan

A feasible plan is a plan that looks like it will work but does not have a lot of detail. Compare to a workable plan.

Feasible plan (chemistry level 3)

A feasible plan is one that can be followed and includes:

  • the purpose of the investigation
  • a description of a standard analytical method (which may include a list of the required chemicals and equipment)
  • a limited range for which the independent variable is to be investigated
  • some background research may be included.

And in carrying out the plan you would have collected and recorded some data.

Feasible plan (science level 3)

A feasible plan will include:

  • an aim/testable question
  • method
  • identification of independent variable, dependent variable, and some fixed variables.

Fully process data

Fully process data involves transforming sufficient raw data/results to produce a linear graph that shows correctly labelled (including unit) axes and an error line.

Gene pool

The total number of alleles a population.

Genetic expression

Conversion of the information encoded in a gene first into messenger RNA and then to a protein.

Genetic processes

Genetic processes refer to genetic expression and applications of gene technology.

Gravimetric analysis

A type of quantitative analysis that allows you to calculate the exact percentage composition of a particular substance within a mixture of substances. This method involves determining the exact mass of both the mixture and the particular substance of interest within the mixture.

The final stage of the gravimetric analysis will always involve weighing (hence the name gravimetric or ‘of gravity measure’).

For example: The amount of silver in a solution of silver salts could be measured by adding excess hydrochloric acid to precipitate silver chloride, filtering the precipitate, washing, drying, and weighing.

Heterogeneous system

A system where all components of a reaction (reactants and products) are not in the same physical state. An example of chemical equilibrium where at least one component is a different physical state from the other components in the system, is:

CaCO3(s) = CaO(s) + CO2(g)

High quality extended practical chemistry investigation

This will involve:

  • checks to determine the reliability of the procedure
  • accurate processing of data using appropriate significant figures
  • in the report:
    • a description of the final procedure that shows an understanding of the technique used, and reasons for any modifications to the procedure
    • a comprehensive evaluation of the whole investigation that considers:

Historical development of a scientific idea

For the historical development of a scientific idea, information should:

  • give details of the model(s) or view(s) at given times
  • state new observations or experimental evidence that refined previous model(s) or view(s)
  • show how accepted model(s) or view(s) were changed to accommodate the new evidence.

Hominins

The term hominins refers to living and fossil species belonging to the human lineage. This is a subgroup of hominids which includes both humans and the great apes.

Homogeneous system

A system where all components of a reaction (reactants and products) are in the same physical state. An example of chemical equilibrium for an homogeneous system where all components are in the gaseous state is:

N2O4(g) = 2 NO2(g)

Compare an heterogeneous system.

Hypothesis

A statement that you will test to prove or disprove in a practical investigation. Check out more information with examples on this website under the heading Hypothesis and Problem statement and hypothesis.

Identify

Be able to select correctly or match to some description or part of a diagram, from information given to you.

Example of an identify question:

Draw the flat mirror so that it will reflect the light ray into the pentaprism along the path shown in the diagram.

Integrate (researched information)

Integrate means that you bring together and organise relevant information and opinions from a range of sources.

Interaction between humans and an aspect of biology

Selection of your research could focus on:

  • the impact of a human activity on an ecosystem. The impact of human activities needs to be considered in relation to the biology of the ecosystem and/or the organisms; or
  • the use of an applied biology technique. The use of an applied biology technique needs to be considered in relation to the human need or demand and the biological concepts and processes used in the technique.

Interpolate

In mathematics this means to estimate a value by calculating it from surrounding values.

Interpret

This instruction requires you to provide reasons for how and why, or to explain with reason.

Interpreting and reporting information

  • Appropriate formats could include: booklets, brochures, posters, flow charts or annotated timelines with supporting notes or visual and/or oral reports.
  • In your report, you will be expected to interpret the processed information in your own words and comment on your findings.

Interpretation

An interpretation is made as a result of thinking about some information such as a graph and expressing your ideas in some way.

Example: 'Make an interpretation of the time graph.'

Interpretation and reporting the findings (of a practical investigation)

This means you have reported the findings and processed the data appropiately. Intepretation of the data must relate to the purpose of your investigation.

The report follows the format clearly specified in written guidelines by your teacher and would usually include the following sections:

  • plan, including the purpose of the investigation and final method used
  • recorded data
  • processed data, showing links to the recorded data
  • interpretations and a conclusion, including a generalised statement linking the findings of the investigation with the purpose of the investigation
  • evaluation or discussion, which may include limitations of the investigation, other variables that had not been foreseen, difficulties in measuring, difficulties in the use of equipment, limitations of the findings, and impact on the outcome, and, where relevant, suggested solutions or pathways for further investigation and links to science concepts or ideas.

Justified

Explained with reason(s).

Justified conclusion

A conclusion is justified if it is relevant to the aim of the experiment, it is based on the data, and the calculated information from which it is drawn has a processed uncertainty that includes an uncertainty in the graph.

Knowledge-based questions

These questions rely on your ability to recall information.

Example of a knowledge-based question:

Draw the formula of propane.

Link

This requires you to show a relationship between two things or situations, especially where one thing affects another.

Example of a link question:

Explain why grapes are crushed, de-stemmed, and pressed.

Monatomic

In chemistry, this means consisting of a single atom or element.

Example: A monatomic ion is an ion made of one atom, for example calcium ion (Ca+2), chlorine (Cl-1).

Molarity

Defined as the number of moles of a solute (that is, what is actually dissolved in the solution) divided by the litres of solution (that is, the total volume of what is dissolved plus what it has been dissolved in).

  

Multi-cellular

This involves aspects of structure of groups of cells that perform a similar function, such as tissues, organs, and organ systems.

Nucleotide

The building block of DNA and RNA comprising a base, a sugar, and a phosphate. Thousands of nucleotides are linked to form a DNA or RNA.

Observation

An observation is made by using your senses, for example by looking at, hearing, thinking about, touching, or smelling something.

Example: 'Give an observation that Jill would make if she added red litmus to potassium hydroxide.' Your answer may simply state that 'Jill will observe a colour change of the litmus paper from red to blue/purple.'

Oxidant

A molecule or atom that accepts electrons in an oxidation–reduction reaction and is reduced. Oxygen is an oxidant, but not the only one. Despite the name, an oxidant does not necessarily need to involve oxygen. Also referred to as an oxidising agent.

Common oxidants are:

  • oxygen, O2
  • iodine, I2
  • chlorine, Cl2
  • iron(III) ion, Fe3+
  • hydrogen peroxide, H2O2
  • permanganate ion, MnO4-(aq)/H+
  • dichromate ion Cr2O72-(aq)/H+

Oxidation–reduction reactions

Many reactions in chemistry involve the gain and loss of electrons. These are called oxidation–reduction reactions. Electrons are transferred from a donor or reducing agent (the reductant) to an acceptor molecule or oxidising agent (that is, the oxidant). Also known as REDOX reactions (from the words REDuction and OXidation).

Pathogen

A pathogen is a disease-causing agent. Examples of pathogens include micro-organisms (such as bacteria or protozoa), viruses, and toxins.

Particles

In chemistry, particles are atoms, ions, and molecules.

Pattern seeking

Pattern seeking involves:

  • the factors that will be studied
  • the proposed range of these factors
  • how the data will be processed
  • trialling to establish the above three items.

Parallax error

A parallax error can be introduced when you carry out a measurement if you do not read the instrument directly from its front. This is because the indicator may be separated from the scale.

Percentage uncertainty

Also known as relative uncertainty.

The uncertainty of a measurement is compared to the measured value itself, usually expressed as a percentage ratio of the absolute uncertainty to the size of the quantity. For example:

Physics formula

Physical properties

In chemistry physical properties of an element or compound can be observed without a chemical reaction of the substance. Examples of physical properties could include the state of a substance (Is it gas, liquid, or solid?), colour, density, and the solubility in water of a substance.

Example: 'A study of the physical properties of calcium...'

Planning a practical investigation

In science, the plan of an investigation will contain the purpose of the investigation. This may include an aim, testable question, prediction, or hypothesis based on a scientific idea. A plan will involve some form of trialling or checking of the plan so it can be adapted if required.

Polyatomic ion

In chemistry, this means an ion consisting of more than one atom.

For example, sulphate ion SO4-2 or hydroxide ion OH-1. The compound Ca(NO3)2 is made up of the polyatomic ion, nitrate.

Practical biological investigation

A practical biological investigation will involve:

  • a statement of the purpose – this may be an aim, testable question, prediction, or hypothesis related to the ecological niche of an organism
  • a method that describes:
    • for a fair test: the independent variable and its range, the measurement of the dependent variable and the control of some other key variables
    • or pattern seeking: the data that will be collected, range of data/samples, and consideration of some other key factors
  • collecting, recording, and processing data (quantitative or qualitative) relevant to the purpose (processing data would usually involve calculations or graphing)
  • interpreting and reporting on the findings with a conclusion reached based on the processed data in relation to the purpose of the investigation.

Practical investigation

An investigation is an activity covering the complete process: planning, collecting and processing data, interpreting, and reporting on the investigation. It will involve the student in the collection of primary data.

A practical investigation will involve:

  • a statement of the purpose – this may be an aim, prediction, or hypothesis based on a scientific idea
  • identification of a range for the independent variable or sample
  • measurement of the dependent variable or the collection of data
  • collecting, recording and processing data relevant to the purpose
  • a conclusion based on interpretation of the processed data.

Precision

When you repeat a measurement in one practical investigation on the same parameter, you may find that readings will be different from each other. The cause may be:

  • a small difference in the way you use the instrument each time, or
  • random changes in the instrument, due to small changes in the parameter you are measuring.

You are advised to use or quote the average of the readings as the best value. However, it is also a good idea to fins the variability of your readings. You can do this by:

  • finding the range of values you have measured, i.e. the difference between the largest and smallest reading, or better still by
  • calculating the variance of the readings. The bigger the variance the less precise is the reading, and the smaller the variance the more precise is the reading.

Prediction

In a scientific investigation you need to say what you think will happen in your experiment using your scientific knowledge. This is called a prediction. For example: if you are going to measure lots of temperatures, explain why you are going to do this and what you expect to observe about the temperature.

Present a report (chemistry level 3)

A report of the investigation will include:

  • a purpose
  • background information may be presented
  • a method
  • results
  • a conclusion that links experimental data to the purpose.

For Achievement with Merit, you will have presented a concise and well-organised report that has also included:

  • relevant background information where appropriate
  • the analytical method used
  • an outline or specific example of the mathematical steps used to process the data
  • summary of collected data used for processing
  • a clear summary of the overall findings, with conclusions matching the processed data and the purpose of the investigation
  • the use of concise, well-organised language, in your own words
  • a bibliography or acknowledgement of sources.

To have presented a comprehensive report (to gain Achievement with Excellence), you will have done the above, and also included:

  • the relationship between the background research and the outcomes of the investigation where appropriate
  • justification of any modifications made to the method
  • statements on the validity of the results
  • an evaluation of the investigation that could include suggestions for possible improvements or future extensions, and a statement on the significance of the conclusion.

Primary data

The first data that is collected in an investigation. For example, in a practical investigation on changes in heat of an object, the primary data that is collected will be temperature and time.

Primary growth in plants

Primary growth in flowering plants is responsible for growth in height. It involves the making of new tissue and is achieved by multiplication and elongation of cells in special regions of the plant roots and stems called apical (or tip) meristems. These cells differentiate and specialise in order to carry out the function of the tissue.

Problem (in physics)

A problem in physics involves process(es) to find a physical quantity.

  • the relevant concept or principle is not immediately obvious
  • the method involves the use of a complex formula or rearrangement, or
  • the information is not directly usable or immediately obvious.

Process (in physics)

A process in physics involves:

  • recognising the relevant concept or principle
  • selecting the method (for example, formula, graph, diagram, logical deduction)
  • selecting the relevant information.

Process data (chemistry level 3)

Processing data for Achievement includes:

  • using appropriate methods
  • processing in a way that enables a conclusion to be drawn (limited calculation error is permitted).

To process data correctly (to gain Achievement with Merit), means you also have included calculations, graphs and/or tables that enable a valid conclusion to be drawn.

To process data accurately (to gain Achievement with Excellence), means that you have done all the above plus:

  • used appropriate units
  • provided a discussion of sources of error or reliability of data
  • used appropriate numbers of significant figures.

Process data or information

To process data or information is about organising the data that you collect to make some sense. It may involve listing, sorting, collating, highlighting, reformatting, summarising, graphing, calculating etc.

Processing data or information may involve calculations, for example, average a set of numbers or graph the data, to try to find a meaningful pattern or trend.

Note that for the purpose of your school work, the words data and information mean the same. However, you might like to check out difference between data and information.

Qualitative analysis

An analysis that determines what is in a sample, without regard to the quantity of each ingredient.

For example: To identify unknown ions in a solution, a chemist may observe reactions involving the formation or decomposition of complex ions and precipitation reactions.

Compare quantitative analysis.

Qualitative data

Data that is collected, recorded and processed in an investigation may be qualitative or quantitative. Qualitative data provide labels, or names, for categories of like items, i.e. a set of observations where any single observation is a word or code that represents a class or category. Some examples of qualitative data would be: gender, colour, hot/cold, yes/no.

Quality extended practical chemistry investigation

  • Developing and carrying out a procedure to collect quality data about a possible trend in the amount of a substance.
  • Collecting and recording a sufficient quantity of data to enable a valid conclusion to be reached.
  • Accurate processing of the data as appropriate to the procedure used, to reach a valid conclusion.
  • Presenting a report that contains:
    • a statement of the purpose of the investigation and relevant background information
    • a description of the final procedure in sufficient detail for the investigation to be duplicated
    • an example, using experimental data obtained, of the mathematical steps used to process the data
    • a summary of the collected and processed data
    • a valid conclusion based on the processed data relevant to the purpose of the investigation
    • a discussion that evaluates the procedure used or the reliability of the data.

Quality practical biological investigation

A quality practical biological investigation enables a valid conclusion to be reached. A valid conclusion is relevant to the aim and justified by correctly processed data. The characteristics of a quality investigation would normally involve:

  • a statement of the purpose – this may be an aim, testable question, prediction, or hypothesis related to the ecological niche of the organism
  • a method that describes:
    • for a fair test: a valid range for the independent variable, the valid measurement of the dependent variable
    • for pattern seeking: a valid collection of data
    • how other variables will be controlled and/or how other factors that might influence the investigation will be taken into account
  • collecting, recording, and processing data (quantitative or qualitative) to enable a trend or pattern (or absence), relevant to purpose of the investigation, to be determined
  • interpreting and reporting on the findings with a valid conclusion reached based on the processed data in relation to the purpose of the investigation.

Quantitative analysis

An analysis that involves the separation of a compound substance, by a chemical process, into its constituents, to find out how much of a given component is present in a sample.

Examples:

  • A chemist will use a quantitative analysis to find out that a sample of ore has 42.88% silver by mass.
  • A chemist uses volumetric analysis, involving titration to determine the concentration of an acid.

There are many techniques available to separate, detect, and measure chemical compounds. The oldest methods required painstaking separation of substances in order to measure the weight or volume of a final product. Many modern, sensitive, and accurate devices rely on the principles of spectroscopy. By measuring the absorption of light by a solution or gas, we can calculate the amounts of several species, often without separation.

Compare qualitative analysis.

Quantitative data

Data that is collected, recorded and processed in an investigation may be qualitative or quantitative. Quantitative data measures either how much or how many of something, i.e. a set of observations where any single observation is a number that represents an amount or a count. Some examples of quantitative data would be: weight, count, area, age.

Reactivity of metals

Some metals are more reactive than others. This is because very reactive metals lose electrons easily. Metals such as sodium are very reactive and are explosive in air. Metals such as copper are not as reactive and therefore do not corrode or tarnish in air. Some metals may even be non-reactive.

Metals can be put in an order based on how reactive they are, compared to others:

Sodium – Na Most reactive
Calcium – Ca arrow up
Magnesium – Mg
Aluminium – Al
Zinc – Zn
Iron – Fe
Lead – Pb
Copper – Cu
Gold – Au Least reactive

Reductant

A reductant is a molecule or atom that loses electrons in an oxidation–reduction reaction and is oxidised. Often known as a reducing agent.

Common reductants:

  • metals
  • carbon, C
  • carbon monoxide, CO
  • hydrogen, H2
  • iron(II) ion, Fe2+
  • bromide ion, Br-
  • iodide ion, I-
  • sulphur dioxide, SO2
  • bisulphate ion, (HSO3-).

Referenced sources

In carrying out your research you will get information from a number of different sources, such as articles, books, or websites. In your report you are required to provide a reference list which is made up of these sources. Each reference must be described in such a way that another person can locate, read and use each of the sources for information too.

A reference can be used to:

  • validate any information that you write in your report
  • show to the assessor the amount of reading you have done about your research.

Reliability

You want to be sure that if someone else carried out your investigation they would get the same results and come to the same conclusions. Unreliable conclusions are worthless, other than telling you that your investigation should be modified and improved.

Report (for practical biological investigation)

The report will include:

  • an introduction that summarises the ecological niche of the organism and links this to the purpose of the investigation
  • the purpose of the investigation
  • the final method used
  • recorded observations, measurements, and data
  • processed data showing a trend or pattern
  • a conclusion based on processed data relevant to the purpose of the investigation
  • a reference list.

Report findings for biology level 2

Your report may be a written document, seminar, poster, web page or multi-media presentation, and should include:

  • the purpose and final method used
  • recorded and processed data
  • a conclusion analysing processed data in terms of the purpose of the investigation
  • a discussion of the biological concepts or processes involved in the investigation
  • an evaluation considering the validity of the investigation, for example:
    • reliability of the data
    • sources of error
    • the limitations of the investigation
    • bias.

Research

In research, you will select data from sources where the data have been initially produced or collected by another person. This is secondary data. Examples of sources of secondary data may come from books, encyclopaedia, magazines, newspapers, other research articles/papers, or Internet addresses (URLs). The research process involves planning, collecting or gathering data/information, processing, interpreting, and presenting a report.

Some use of primary sources, for example, through interviews, is acceptable.

At NCEA level two, it is expected that you will carry out your own research and reference their material.

At NCEA level three, it is expected that you will drive the research.

Resource-based questions

You will be given information about something or situation and will be required to answer questions relating to the thing or situation.

Example of a resource-based question:

Beer has certain flavours. Explain how the alcohol in beer improves the flavour of the beer that is produced.

Results of the research

Present the results of the research as a written report, newspaper article, seminar, video, web page, or power point presentation.

Salts

These are chemical compounds formed as a result of a neutralisation reaction between acids and a neutraliser, like a metal.

The most common salt is sodium chloride or NaCl or as we know it 'table salt'. This has been made from the sodium (Na) metal and the acid, hydrochloric acid.
sodium + hydrochloric acid arrow right sodium chloride + water

Examples of salts:
Type of salts

  • AB where valency of the ions of the acid and neutraliser are the same:
    • NaCl – sodium chloride
    • KCl – potassium chloride
    • NaHCO3 – sodium bicarbonate (or baking soda)
    • CaCO3 – calcium carbonate
    • KNO3 – potassium nitrate
  • A2B where only one atom of the acid is needed to balance the valency of the other ion:
    • K2SO4 – potassium sulphate
    • Li2SO4 – lithium sulphate
  • AB2 where two atoms of the acid ion are needed to balance the valency of the other ion:
    • CaCl2 – calcium chloride
    • MgCl2 – magnesium chloride
    • Cu(NO3)2 – copper nitrate

Sampling

In most investigations you can not measure all data of the entire situation or population, so you measure just some data (called a sample). The process of measuring just some data is called sampling. Sampling is important because you want the results from the sampling process to reflect the trends and patterns of the whole situation or population.

Scientific notation

Also known as Standard form or Standard index notation.

Scientific notation is a concise way of recording very large or very small numbers by integer powers of ten. Such notation is used to record physical quantities without including trailing, or leading, zeros:

  • 101 = 10
  • 102 = 100
  • 103 = 1000
  • 106 = 1,000,000
  • 109 = 1,000,000,000
  • 1020 = 100,000,000,000,000,000,000

Additionally, 10 raised to a negative integer power -n is equal to 1/10n or, equivalently 0. (n-1 zeros)1:

  • 10-1 = 1/10 = 0.1
  • 10-3 = 1/1000 = 0.1
  • 10-9 = 1/1,000,000,000 = 0.000000001

Thus:
A large number such as 156,234,000,000,000,000,000,000,000,000 can be concisely recorded as 1.56234 × 1029, and a small number such as 0.0000000000234 can be written as 2.34 x 10-11.

For example:
The distance to the edge of the observable universe is ~4.6 x 1026 metres. The mass of a proton is ~1.67 x 10-27kg.

Most calculators and many computer programs present very large and very small results in scientific notation; the 10 is usually omitted and the letter E for exponent is used; for example: 1.56234 E29. Note that this is not related to the base of the natural logarithm that is also commonly denoted by e.

Scientific notation is highly useful for quoting physical quantities, as they can only be measured to within certain error limits and so quoting just the digits that are certain (the 'significant digits') gives all the information required without wasting space.

Scientific report

A scientific report involves:

  • presenting scientific interpretations of information appropriate to the topic
  • presenting material in a reporting format suitable for scientific information
  • acknowledging sources of information in a traceable reference system.

Secondary growth in plants

Secondary growth in flowering plants is responsible for growth in girth or increase in diameter. This is achieved by special lateral meristems called the vascular cambium. The cambium makes large cells early in the year, and smaller ones later in the summer, and this cycling of large and small cells is responsible for the appearance of growth rings in wood, usually one ring per year.

Secondary information

Information that has been previously collected and processed by another person.

Significance of an idea or application

This requires a description of the importance or impact the idea or application has on our understanding of physics and relates to the usefulness and effect of the idea or application on humans.

Example:

The significance of nuclear power to generate electricity is huge. While the use of nuclear power may solve our electricity shortage in New Zealand and it may reduce global warming, the management and storage of the radioactive by-products will have to be considered.

Spectrophotometer

A spectrophotometer is an instrument used to measure the amount of light passing through (or not passing through) a sample held in a test tube. It is very commonly used in chemistry, biology, environmental science, etc to determine the concentration of chemical components (atoms, ions, or molecules) in solution.

Stoichiometry

Stoichiometry is the accounting, or mathematics, behind chemistry. Given enough information, you can use stoichiometry to calculate masses, moles, concentrations, and percents within a chemical equation.

Stop codon

A stop codon is a sequence of three bases on mRNA that signals the end of protein synthesis, but which does not code for any amino acid.

Straightforward problem (in physics)

A straightforward problem involves a single process, where:

  • the relevant concept or principle will be transparent
  • the method will be straightforward (a formula will need no more than a simple rearrangement), and
  • the information will be directly usable.

Sufficient data

Your collection of data involves repeats, trials, or an appropriate sample size and gives confidence to the conclusion of an experiment or investigation.

For example, if a physics investigation concludes with the identification of a relationship between variables, the assessor wants to be confident that if another investigation was carried out with the same method, that the data collected will result in the same conclusion.

Sufficient detailed information

Collection of sufficient detailed information means that you have:

  • enough data to draw valid conclusion(s), with a full range for the independent variable
  • recorded information systematically in a valid scientific format
  • recorded repeats.

Sufficient information (science level 3)

Collection of sufficient information means that you have:

  • enough data to draw valid conclusion(s), with a range for the independent variable
  • recorded information in a valid scientific format.

Sufficient and reliable information (science level 3)

Collection of sufficient and reliable information means that you have:

  • identified extremes and dealt with them appropriately
  • recorded sufficient repeats to confirm the accuracy of the information
  • recorded information systematically, with appropriate precision.

Systematically record

This means you have recorded the data in such a way (for example, table, tally chart) that allows it to be interpreted without reference to the collection method.

Thermochemical

This refers to the branch of chemistry concerned with the investigation of energy and heat in chemical reactions.

Tissue culture

A method of cloning plants where a small piece of plant tissue is grown in a gel growth medium containing nutrients and hormones so that shoots and roots develop. The technique allows rapid reproduction of genetically identical plants from a small original sample.

Titration

Titration is an analytical technique that is used to find the concentration of an acid or an alkali (or base). Typically a burette is filled with an acid of unknown concentration. The acid is very slowly (drop by drop) added to a known volume of an alkali of a known concentration, mixed with an indicator (such as phenolphthalein). The volume of acid need to neutralise the alkali in the flask can be used to calculate the concentration of the acid.

chemistry diagram

Titre

The concentration of a solution as determined by titration. In a volumetric analysis experiment, the burette reading of the amount required for a titration is called the titre and will be measured in mL.

This is simply:   final reading – initial reading

Toxin

A toxin is a poisonous substance, usually a protein that is produced by living cells or organisms and is capable of causing disease when introduced into the body tissues. It is also often capable of inducing neutralizing antibodies or antitoxins.

Transgenesis

Integration into a living organism of a foreign gene that confers upon the organism a new property that it will transmit to its descendents.

Transcription error

An error created when writing.

Triplet

A triplet is a sequence of three bases on DNA that codes for an amino acid.

Use of scientific knowledge

A use of scientific knowledge should be based on situations in keeping with content of your curriculum. Possible contexts are given in the curriculum documents and could be based on a technological application or a management practice, resolving an issue, or the development of a theory or model.

Valid and reliable data

Poor data collection will never give you good results.

To ensure 'good results' you need to understand the difference between:

  • Valid data where you must ask yourself: Am I collecting the right data to test the hypothesis? Is the measuring device giving me the 'right' data'? Valid data is the measure of what is meant to be measured, that is, it relates to the aim.
  • Reliable data where you must ask yourself: Have I tested the hypothesis enough to come to the same conclusion? Reliable data is where the same or similar data is gained and the same conclusion can be made if the investigation procedure was repeated by someone else.

Valid conclusion

A conclusion is valid if it is justified and the calculated information from which it is drawn has been correctly processed.

Validity (of method)

The validity of an experiment or practical investigation relates to your ability to choose a method that will test the hypothesis that you have made. Validity can also refer to you making a CORRECT decision based on your results. For instance, you conclude that the hypothesis is true when it IS true, or conclude a hypothesis is false when it IS false.

Variables

Variables are factors in an investigation that may affect your results.

  • The independent variable is one factor that you change and record its change when carrying out the investigation.
  • The dependent variable is the factor that you measure as it changes in response to changing the independent variable.
  • The controlled variables are all other factors that are kept constant each time you repeat the investigation.

Examples of variables in practical investigations:

  1. You are investigating the reaction of an acid on a metal. Some of the variables may include:
    • type of acid
    • concentration of the acid
    • volume of the acid
    • type of metal
    • mass of metal
    • temperature at which the reaction takes place
    • time it takes for the reaction to complete.

In your investigation you may measure the time it takes for a particular metal to react completely with a particular acid. This means that:

  • the type of metal could be the independent variable, and you will test a number of different metals of the same mass
  • time will be the dependent variable and you will measure the time it takes for the reaction of the metal with the acid to complete
  • you will keep the type and concentration of the acid constant during each different metal.

  1. You may want to carry out an investigation that tests the hypothesis that the colour red causes an increase in plant growth of a specific plant.
    A prediction might be that plants that receive a red light will have a more rapid growth rate than those plants that do not have red light.
    To test the prediction, the experimental group of plants will be grown in identical containers and exposed to only red light. For comparison, a control group of plants will be in identical containers and allowed to grow in normal light.
    • The presence or absence of red light is the independent variable.
    • The rate of growth is the dependent variable.

The variables such as type of soil, temperature and water will be held constant.

Variance

Variance, var, is a statistical measure obtained by calculating:

  • the difference of each reading, q, from the mean,
  • squaring these differences
  • adding the squares, and
  • taking the mean of all these squares.

Being cautious, statisticians calculate the mean by dividing the sum of the squares by the total number of readings, less one, i.e. n-1.

A measurement is said to be more precise, the smaller the variance, or vice versa, the bigger the variance, the less precise is the measurement.

Volumetric analysis

A chemical quantitative analysis involved in determining the concentration of a solution. A known volume of a solution of unknown concentration is reacted with a known volume of a solution of known concentration (standard). The standard solution is delivered from a burette so the volume added is known. This technique is known as titration.

Usually an indicator is used to show when the correct proportions have reacted. This is called the end-point. This procedure is used for acid–base, and some other reactions involving solutions.

With direction (in carrying out a practical investigation)

This means that your teacher will specify or guide you in choosing an investigation to carry out and will give you general instructions in writing about the investigation. You will choose from a range of equipment and/or chemicals that your teacher will provide for you. Your teacher will also give you a template or suitable format for planning the investigation.

With direction (in processing information to describe a use of scientific knowledge)

This means that your teacher will provide the context for the study and will give you general instructions in writing for processing.

With guidance

With guidance means that your teacher will support you throughout the investigation but the whole process must be driven by you. The sort of information that you can expect from your teacher will be general, for example, in the form of suggested topics, resource suggestions, appropriate timing, ethical considerations, or possible new directions. You will choose the context and purpose, experimental conditions, and will select and manipulate the variables to collect primary data.

With supervision (in carrying out a practical investigation)

This means that your teacher will give you guidelines for the investigation. These will include:

  • the context and question for the investigation
  • general experimental conditions such as the availability of equipment or chemicals and time
  • for level 1, instructions giving the requirements for a quality investigation
  • for level 2, you will select and manipulate the variables to collect the primary data.

You may also be required to discuss with you teacher to clarify your ideas. You will then develop and complete the investigation from the initial guidelines given by the teacher.

Workable investigation

A workable investigation means that in addition to the requirements for achievement with merit, your design is justified and you have produced a plan that:

  • describes a valid range for the independent variable or range of samples to be collected and a valid method for measuring the dependent variable or for collecting data
  • describes how other variables will be controlled and/or how other factors that might influence the investigation will be taken into account
  • recognises the need for sufficient data, for example, repeated measurements, large sample size.

The method of your plan can be independently followed (without further clarification) to obtain reliable data.

Workable investigation (science level 3)

This means that your investigation is workable and you have designed a plan that has been trialled and modified if required, and includes:

  • an aim/testable question
  • method
  • independent variable with a range, dependent variable, and some fixed variables with values.

Workable method

A workable method is achieved if your method includes a reasonable range and number for the values of the independent variable, describes the control of other variable(s) that could affect the results, and recognises the need to use techniques to improve the accuracy of measurements.

Workable plan

A workable plan will include the following:

  • a valid range for key variables and details of how they will be measured
  • evidence that the influences of other variables have been taken into account and, if necessary, methods for their control are stated
  • a scientific method to collect data is described
  • discussion of factors about how you collected the data to ensure that the investigation is robust (if you repeat the investigation, you will get the same results) and valid (that the calculations, trends and patterns from the investigation are true). You might consider such factors as sampling, bias, sources of error and sufficiency of data
  • evidence that you have made checks to ensure that the plan will work.

Workable plan (chemistry level 3)

A workable plan means that your plan has met the requirements for achievement and also includes:

  • a description of the method in sufficient detail for the assessor to duplicate the results
  • an appropriate range for the independent variable
  • required controls on significant variables
  • relevant background research may be included.

And in carrying out the plan you would have:

  • collected and recorded sufficient quality and quantity of data to enable a valid conclusion to be drawn
  • repeated individual measurements as a check for reliability
  • collected and recorded data in ways that allow independent checks to be made.

Writing formulae

A core skill for chemistry students is to know how to write formulae correctly. Key points are:

  • Know your symbols of elements, for example Cu, Zn, S.
  • An element always starts with a capital letter.
  • Brackets are used in formula of a polyatomic ion like NO3, where you want to show the ion with its charge or valency, for example (NO3)-2.
  • The number of atoms in a compound or polyatomic ion is written as a subscript (below the character, as in Cl2).
  • In a formula, the charge or valency of the ion is generally written as a superscript (above the line, as in Cu+2).
  • Some elements can make ions of more than one type of charge or valency, for example Cu, Fe, and are written as the element with the charge as a roman number inside brackets, for example Cu(II), Fe(II), Fe(III), iron(II)sulphate.
  • When balancing equations, the number of elements or compounds in the equation is written as a whole number preceding the formula.
  • While individual ions carry a charge, for example Cu+2 or Cu+2, when you write the formula of an ionic compound, do not include the charge. For example you write CuO not Cu2+O2-.

Back to top

0

People logged in

311

People surfing this site

Most recent posts

English Level 1
speech

Posted by: AtnEnoufr

11:36am 04.07.2019

English Level 2
91099 [2.2] Level 2 VISUAL text post all your Qs here

Posted by: rl16432

7:34am 20.11.2018

English Level 3 & Scholarship
Scholarship English

Posted by: macbookpro

4:26pm 13.11.2018

Mathematics Level 1
Geometric reasoning external (91031)

Posted by: mathsteacher

4:18pm 19.11.2018

Mathematics Level 2
2018 LEVEL 2 MATHEMATICS EXAMINATION COMMENTS

Posted by: 2019year13

4:41pm 16.11.2018

Mathematics Level 3 Calculus & Calculus Scholarship
2018 CALCULUS & SCHOLARSHIP EXAMINATIONS - How did they

Posted by: fafnir

6:44pm 14.11.2018

Mathematics Level 3 Statistics & Statistics Scholarship
3.14 (AS91586) Probability distributions

Posted by: mathsteacher15

7:58am 10.11.2018

Sciences Level 1
SCIENCE 1.7 ASTRONOMY QUESTIONS

Posted by: Sally176

9:13am 02.08.2018

Physics Level 2
how did everyone find the level2 physics exam?

Posted by: yummychocolate12

6:46pm 25.11.2017

Physics Level 3 & Scholarship
PHYSICS 3.3 WAVES

Posted by: scienceteacher3

9:42pm 19.11.2018

Biology Level 2, 3 & Scholarship
Bio 2.7 Gene expression AS 91159 External

Posted by: scienceteacher5

1:26pm 15.08.2018

Chemistry Level 2, 3 & Scholarship
Chem 3.7 Aqueous equilibria - all questions here

Posted by: bokchoyisyum

4:58pm 07.07.2019

Earth & Space Science
Resources other than the ESS Level 2 Workbook for learning

Posted by: mathsteacher

5:53pm 28.11.2017

Other
What's The Structure Of Writing "The Method"?

Posted by: scienceteacher3

8:17am 17.06.2019