2. Group work to investigate solids
In Section 1 we considered properties of matter when we compared the compressibility of solids, liquids and gases. Now we consider a few more properties in relation to solids.
Here is one to think about. Why is it that some solid objects feel cold to the touch and others don’t? Think of a wooden spoon and a metal spoon. When we first pick them up off the table, they must be at the same room temperature – yet the metal spoon feels colder.
Some materials carry, or conduct, heat better than others. Metals have the property of being good thermal conductors. The metal spoon conducts heat away from our hand and hence feels colder. The wooden spoon is a poor thermal conductor – it is a good thermal insulator.
In Activity 2 you investigate the property of solubility with your pupils. What other properties could you investigate? Electrical conductivity? Density?
Case Study 2 shows how a teacher with a large class supported groups of pupils to investigate one particular group of materials. (See Key Resource: Working with large classes. )
Case Study 2: Properties of metals
On a Monday, Mrs Efua Mandela brings from home a range of different metal items and displays them on her table at the front of the class. They include a gold ring, old silver and copper coins, iron, steel and brass nails and screws, and wires of different sorts.
While the rest of the class is busy with other work, she gathers the group that will inquire into and investigate the properties of metals around her. They handle and discuss what is displayed. They argue about whether metals bounce. They start to raise questions: Are all metals shiny? Which is the hardest/strongest metal? Is tarnishing and rusting a property?
Efua also suggests some questions: Do all metals conduct electricity? What about magnetism? What are alloys? They realise that there are many properties to be investigated, but some at a later stage. (See Resource 2: Looking at properties of solids for more ideas about how to organise a lesson on solids.)
She supports them for the week as they prepare to present the results of their inquiry. Next week, another group will be supported when they do their work on a different set of substances such as plastics or wood.
Activity 2: Disappearing acts – the property of solubility
This builds on the work you may have done with pupils in the Key Activity of Section 1, where pupils investigated unknown white powdery substances.
- Start by discussing what happens when you add something soluble like sugar to your tea. How can you tell something has dissolved? Perhaps with older pupils you will use this as a chance to introduce terms like solvent (the hot liquid tea), solute (the sugar) and solution (the resulting sweet liquid).
- Give groups five different named substances and containers of water. Which of these substances are soluble in water? Ask them to make predictions and to record the results of their investigation in the form of a table using words like ‘slightly soluble’ and ‘readily soluble’. (See Key Resource: Using investigations in the classroom.)
- Finally, ask each group to plan their own investigation of a different variable (something that can change) that might affect solubility of sugar in water. Think of things like temperature of liquid (solvent); granular size of sugar (solute), stirring or shaking the container. You might want to suggest pupils think how to present their results as a graph. (See Resource 3: Lesson plan on solubility for more detailed advice.)