Warm feet

This task is about creating a fair test.

Question 1Change answer

Sarai had cold feet.
Her grandmother said, "Put on 2 pairs of socks and your feet will stay warm". 
Sarai wanted to carry out an investigation to test her grandmother's advice. She decided to use plastic containers of hot water for 'feet'.
She put a container inside 1 sock and the other inside 2 socks which provided double thickness. She measured the temperature of the water every 2 minutes.
List four things that Sarai must do for her test to be 'fair'.
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