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Science 1.5 Demonstrate understanding of aspects of acids and bases

Achievement criteria

This achievement standard involves demonstrating understanding of atomic structure, particle theory and rates of reaction relating to acid and base properties, uses and reactions.

On this page: Achievement | Achievement with Merit | Achievement with Excellence

Achievement

This achievement standard involves demonstrating understanding of aspects of acids and bases. This involves describing, identifying, naming, drawing and giving an account of aspects of acids and bases. The correct use of chemical vocabulary, names, symbols and formulae is required. Completion of word equations to represent the reactions is also required. 

Make sure you can:

• Work out the numbers of protons, electrons and neutrons in atoms and monatomic ions of elements 1 – 20. 
• Write electron arrangements for the atoms and monatomic (single atom) ions of elements 1 – 20 (a periodic table will be provided)
• Understand that protons and neutrons contribute to the mass of an atom
• Understand what is meant by the term “isotope” and compare different isotopes of the same element for protons, electron, neutron numbers, masses and chemical reactivity
• State what an ions is and know that atoms form ions by gaining/losing valence/outermost electrons
• Describe how positive and negative ions combine to form neutral ionic solids
• Write names and formulae for ionic compounds from an ion chart (provided). This includes the use of polyatomic ions such as CO₃^2- as shown on the chart and the correct use of brackets where necessary.
• Give the names and formulae for hydrochloric, sulfuric and nitric acids.  Other acids may be included in examination questions but their names and formulae would be supplied in the question.
• Recognise  that the oxide, hydroxide, carbonate and hydrogen carbonate compounds of metals are bases
• Recognise acidic solutions as ones containing  hydrogen ions (H⁺) and basic/alkaline solutions as ones containing hydroxide ions (OH^-).
• Link pH numbers from 1 to 14 to acidic, neutral and basic solutions
• State the acidic, neutral and basic colours for litmus and universal indicators
• Recognise that some uses of acids and bases are: neutralisation, carbon dioxide formation and salt formation.
• State how limewater can be used to identify carbon dioxide
• Give names and associated observations for the reactions of the required acids and bases.  Reactions of acids with bases to form salts are required.
• Recognise that particles must collide with sufficient energy for a reaction to occur and that an increase in effective/successful collisions per second leads to an increase in the rate of reaction
• State how changes in surface area of a solid, concentration of a solution or temperature can alter the rate of reaction
• Describe how the rate of a reaction changes as time progresses
• Use correct Chemistry words, symbols and formulae
• Complete word equations for any reactions involved

Achievement with merit

This achievement standard involves demonstrating in depth understanding of aspects of acids and bases.

Make sure you can:

• Meet the requirements for Achievement.
• Explain that atoms form ions by gaining/losing valence/outermost electrons until the outermost energy level is full.  Words, electron arrangements and diagrams are some ways of doing this.
• Compare and contrast different isotopes of the same element
• Explain that hydrogen ions and hydroxide ions react together to form water molecules which are neutral.
• Explain, using particle/collision theory, how changes in surface area of a solid, concentration of a solution or temperature can alter the rate of reaction
• Explain, using particle/collision theory, why the rate of a reaction changes as time progresses
• Write word equations and complete symbol equation for any reactions involved (these may not have to be balanced for merit but all formulae must be correct)

Achievement with excellence

This achievement standard involves demonstrating comprehensive understanding of aspects of acids and bases. This may involve linking aspects of chemical reactions when explaining, elaborating, justifying, relating, evaluating, comparing and contrasting or analysing the classification of reactions.

Make sure you can:

• Meet the requirements for Merit.
• Link the charges formed on ions to the position of the element on the periodic table
• Explain why the ratios of positive and negative ions are not always the same  in different ionic compounds
• Link the pH of a solution (and/or indicator colour) to the proportion and type of ions present in the solution
• Explain why the type of reaction occurring is a neutralisation reaction
• Make links between observations of reaction speeds and the relative abundance/availability of the particles involved
• Discuss in detail the effect of changing temperature, surface area, and concentration on reaction rate, using collision theory.
• Write balanced symbol equations for reactions.

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