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Glossary

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).

Above the cellular level

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

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.

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


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.

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.

Collecting and processing information

Processing could involve: listing, sorting, collating, highlighting, reformatting, summarising, etc.

For example:
In biology, it may involve calculations such as averaging, and/or graphing, to establish a relevant pattern or trend.

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.

Compare and contrast

To discuss similiarities and differences.

An example of this type of question is “compare and contrast complete and incomplete combustion”.

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.


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 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.


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.

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.

Demonstrate understanding

This involves defining, using annotated diagrams, and giving characteristics of, or an account of science ideas.

 

Demonstrate in-depth understanding

This involves explaining and relating science ideas.

 

Demonstrate comprehensive understanding

This involves linking science ideas and may involve explaining, elaborating, applying, justifying, relating, evaluating, comparing and contrasting, or analysing.

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.

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.

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.

Elaborate

To give further detail and explanation to a scientific idea.

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).

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).

Explain

This instruction requires you to provide a reason 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)'

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.

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 expression

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

Gene pool

The total number of alleles a population.

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)

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.


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 on the website What is a Scientific 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.

Interpolate

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

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 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).

  

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 reactions. 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).

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.

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.

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

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 investigation

A science investigation is an activity covering the complete process from planning to reporting and involves collecting primary data. You will have opportunity to make changes to your initial method as you work through the investigation. An investigation at NCEA level two will be based on situations arising from the content of your curriculum. Your teacher will guide you.

An investigation may involve a fair test, correlation, or other comparison.

For example: In biology, the nature of the investigation could be the manipulation of variables (fair test) or the investigation of a pattern or relationship.

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 or information

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

Processing data or information may involve calculations (for example, average a set of numbers and/or graphing the data). Your aim is to try to find a meaningful pattern or trend.

Properties

In chemistry the word property refers to a basic attribute or characteristic shared by all members of a substance. Properties of substances can be divided into physical properties and chemical properties.

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.

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.

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 have got 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.

Relate

To explain how two or more aspects of a topic are connected.

An example of this type of question is “ relate the properties of alkanes to their use as fuels”.

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.

Report on

Involves refining questions or purposes, describing biological ideas, collecting and processing data from a range of sources, taking a position on the issue and presenting findings.

Report in depth on

Involves refining questions or purposes, explaining biological ideas, collecting and processing data from a range of sources, giving evidence for at least two different points of view, taking a justified  position on the issue and presenting findings.

Report comprehensively on

Involves refining questions or purposes, linking biological ideas, collecting and processing data from a range of sources, evaluating sources, taking a position on the issue with recommendations for action and presenting findings.

Research

In research, the student collects 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 students will carry out their own research rather than the research being teacher-directed.

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.

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. 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 (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:
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.

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.

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.

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 a method 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

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.

Anticodon

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

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.

Variables

While you carry out a practical investigation, things will change. These are called variables. In an investigation you will measure one variable and record its change and all other variables must be controlled each time you repeat the experiment.

Example: You are investigating the reaction of an acid on a metal. Some of the variables may be:

  • type of acid
  • concentration of the acid
  • volume of the acid
  • type of metal
  • surface area of the metal
  • mass of metal
  • temperature at which the reaction takes place
  • time it takes for the reaction to be complete.

In your investigation you may choose the time it takes for a particular metal to react completely with a particular acid. This means the variable you measure will be time. All other variables will have to be the same for each repeat of the experiment.

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 supervision

This means that your teacher will give you guidelines for the investigation, such as the context for the investigation and equipment available (including chemicals to use, if applicable). You will then work individually to design or develop, carry out, and report on the investigation. You may be required to:

  • prepare your own planning sheet and trialing the plan before writing a detailed, step-by-step method
  • discuss with your teacher or other students to clarify your ideas.


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 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.


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-.

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