Think about how Andy should carry out his investigation. First he sets out to determine how much water each brand of nappy can absorb. Remember that a scientist changes only one variable at a time.
6 Describe, using a diagram and a set of instructions, how Andy could find out which nappy is the most absorbent.
7 How would Andy make sure that this is a fair test?
From his investigations, Andy found that brand X absorbed 250 cm3 of water, brand Y absorbed 150 cm3 of water and brand Z absorbed 145 cm3 of water.
8 Draw a results table that could be used to record the results of this investigation.
9 What additional tests (other than testing which nappy is the most absorbent) could Andy carry out to find differences between each of the brands?
Step 4: Observations in the real world Andy realises that urine is not just water. It is a solution of urea, salt and water.
10 Predict how a salt solution will affect the results that Andy obtained in his original investigation.
11 How will Andy need to adjust his investigation to take this into account?
12 How can Andy investigate how to make a salt solution with a concentration that imitates the effect of urine on the nappy’s absorbency?
Step 5: Presenting and interpreting data
Once Andy has gathered all of his results, he will need to present them in a way that will explain his findings to his mother.
13 Would a table of results alone demonstrate Andy’s findings clearly? 14 Draw a graph that Andy might use to represent the data he collected.
Think about…
If you were the materials scientist in a nappy manufacturing company, what key questions would you ask before deciding which material to use in the manufacturing of nappies?
