Lesson 1 What varies?
The terms ‘variable’ and ‘value’ (as it applies to variables) and ‘relationship’ are introduced, together with recognising the possible relationships between two variables. These are described in terms such as: ‘when one goes up, the other goes up’; ‘when one goes up, the other goes down’; ‘they are not related’. Pupils work through a set of illustrated examples to get used to using the words and concepts of ‘variables’, ‘value’ and ‘relationship’. This activity is almost all concrete preparation, although the weight and size of beakers causes some cognitive conflict.
New key words: variables, values, relationships
For the introduction and demonstration
- Workcards – 1 for each group
- Notesheets for each group
- Collection of about 15 books, varying in colour, size, fiction/non-fiction, exercise/text, etc.
For activity 1: coloured shapes
Two sets of coloured squares and triangles, large enough to be seen by whole class. Shapes can be made from coloured card and laminated or from coloured acetate so that they can be used on the overhead projector. (A template for the shapes can be found on the CD-ROM).
It is a good idea to mark each shape in each set with the number 1 or 2 so that they do not get muddled together. Small, large and medium sizes must be the same dimensions in each set.
Set 1, six shapes as follows
|small blue medium blue
medium red large red
Set 2, four shapes as follows
|medium red large blue||medium red large blue|
Set 1 has
|colour shape size||red, blue
small, medium, large
Colour is related to shape (the relationship between variables).
Set 2 has
The same three variables but one of the values for size missing (small). Here the relationship has changed, the variable colour is related to the variable size.
For activity 2: coloured containers
Four coloured containers A, B, C and D. Two containers are red and the same large size; two containers are blue and the same small size. They are weighted with sand or lead shot as follows:
- Small blue container A is weighted to have same mass as empty large red container C.
- Small blue container B is weighted to have same mass as large red container D, which contains a 100 g mass.
Use coffee jars or plastic containers. The containers can be painted inside or have coloured paper wrapped inside. Lids should be sealed on with strong glue once the containers are correctly weighted. You may make up different loadings, as long as one large and one small container match to make one pair and the other large and small container match with a different mass as a second pair.
The contents of the containers should not be visible to pupils.
A top pan balance (ideally weighing to nearest gram or even 5 g) is also required or an old pair of kitchen scales. It is best to use an analogue reading, rather than digital to give pupils some indication of quantity.
For activity 3: pictures of relationships
Workcard 1 One set of cards between two pupils is adequate
unless you want them to be used for homework.