Science at key stage 3    (Year 8)

• distinguish between elements and compounds
• relate formulae to the numbers and types of atom in a compound

• describe differences between compounds and the elements from which they are made
• interpret formulae for compounds in terms of the relative numbers of atoms of different elements

• identify appropriate indications of chemical reactions
• state that chemical reactions took place between the compounds
• summarise what they observed and explain what this showed

• link ideas in an appropriate way
• recognise additional links when these are pointed out

• name some everyday mixtures, eg air, seawater, mineral water
• identify that mixtures can vary in composition

• name the main gases present in air and give approximate proportions of these
• explain clearly how air can be separated into its components
• describe clearly some uses of the components of air
• sequence and organise ideas into coherent, continuous text

• identify the melting and boiling points of a range of elements and compounds
• explain that these are characteristic of the element or compound
• describe how the melting point or boiling point of a mixture varies with composition

• identify differences between the graphs and explain that these show one is a pure liquid and the other is not
• suggest additional tests, eg evaporating both liquids, finding the boiling point of both liquids, explaining what these might show

• identify characteristics of elements, compounds and mixtures, explaining the basis for their decisions