GoalDo a simple test to find out how a bigger push squashes a sponge more, and record the results in a table.
New words
measure · to find out how long, tall or heavy something isheight · how tall something isresult · what you find out in a testfair test · a test where you change one thing and keep everything else the same
Explanation
Leo wants to find out what happens to a sponge when he pushes down on it harder. He predicts that the bigger the push, the flatter the sponge will get. He puts a kitchen sponge on a table and measures its height with a ruler. It is 6 cm tall. Then he puts one book on top and measures again. He adds a second book, then a third. More books push down with a bigger force. Leo changes only the number of books. He keeps the same sponge and the same kind of book, so it is a fair test.
Books on top
Height of the sponge
0
6 cm
1
5 cm
2
4 cm
3
3 cm
Worked examples
Leo’s results can be drawn as a bar chart. The bars get shorter as he adds more books. The bigger the push, the flatter the sponge.
When Leo lifts the books off, the sponge springs back to 6 cm. A sponge stays squashed only while the force pushes on it.
Leo measures the same way every time: the ruler stands straight up on the table, next to the sponge. Then his results are fair.
Class activity
Squash test (with an adult): put a kitchen sponge on a table and measure its height with a ruler. Predict what will happen. Put one book on it and measure again. Add a second and then a third book, measuring each time. Write the heights in a table. Take the books off: what happens to the sponge?
Practice
1
Look at Leo’s table. How tall was the sponge with 2 books on top?
Books on top
Height of the sponge
0
6 cm
1
5 cm
2
4 cm
3
3 cm
4 cm.
2
How much flatter was the sponge with 3 books on top than with no books?
3 cm flatter (6 − 3 = 3).
3
This arrow shows a big push down on a sponge. Finish the sentence: the bigger the push, the …
flatter the sponge gets.
4
Name one thing Leo must keep the same to make it a fair test.
For example: the same sponge, the same kind of book, or the same way of measuring.
