Acids occur in many foods, drinks and even within our stomachs
Students learn to:
- define acids as proton donors and describe the ionisation of acids in water
- identify acids including acetic (ethanoic), citric (2-hydroxypropane-1,2,3-tricarboxylic), hydrochloric and sulfuric acid
- describe the use of the pH scale in comparing acids and bases
- describe acids and their solutions with the appropriate use of the terms strong, weak, concentrated and dilute
- identify pH as -log10 [H+] and explain that a change in pH of 1 means a ten-fold change in [H+]
- compare the relative strengths of equal concentrations of citric, acetic and hydrochloric acids and explain in terms of the degree of ionisation of their molecules
- describe the difference between a strong and a weak acid in terms of an equilibrium between the intact molecule and its ions
Students:
- solve problems and perform a first-hand investigation to use pH meters/probes and indicators to distinguish between acidic, basic and neutral chemicals
- plan and perform a first-hand investigation to measure the pH of identical concentrations of strong and weak acids
- gather and process information from secondary sources to write ionic equations to represent the ionisation of acids
- use available evidence to model the molecular nature of acids and simulate the ionisation of strong and weak acids
- gather and process information from secondary sources to explain the use of acids as food additives
- identify data, gather and process information from secondary sources to identify examples of naturally occurring acids and bases and their chemical composition
- process information from secondary sources to calculate pH of strong acids given appropriate hydrogen ion concentrations