Year 3 Science: Water through soils: a fair test
Part of the Year 3 Science rocks, fossils and soils chapter. Chapter overview · whole chapter on one page
Water through soils: a fair test
The children put the same amount of each soil in a funnel. They pour 100 ml of water into each funnel. After 1 minute, they measure how much water has come through into the cup. They do three trials for each soil, and find the mean (the average) of the three trials.
The one thing they changed was the type of soil. The thing they measured was the water collected. Everything else was kept the same, so the test is fair.
Sandy soil has big pieces, with big gaps between them, so water runs through quickly. Clay soil has tiny pieces that fit closely, so the gaps are small and the water moves slowly. Garden soil is a mixture, so it lets water through at a speed in between.
| Soil | Trial 1 (ml) | Trial 2 (ml) | Trial 3 (ml) | Mean (ml) |
|---|---|---|---|---|
| sandy soil | 88 | 92 | 90 | 90 |
| garden soil | 42 | 38 | 40 | 40 |
| clay soil | 12 | 8 | 10 | 10 |
Key ideas
- A fair test changes only one thing. Here the thing changed is the type of soil.
- The thing that is measured is the water collected in the cup after 1 minute.
- Do three trials and find the mean, so that one odd result does not mislead you.
- Sandy soil let the most water through. Clay soil let the least.
Method. Find the highest mean in the Mean (ml) column.
- Read the means. The means are 90 ml for sandy soil, 40 ml for garden soil and 10 ml for clay soil.90 ml
- Choose the highest. The highest mean is 90 ml, for sandy soil.sandy soil
- Write the answer. sandy soil
Check. Sandy soil lets water through fastest. ✓
Method. Add the three trials for garden soil, then divide by 3.
- Add the trials. The trials are 42 ml, 38 ml and 40 ml. 42 + 38 + 40 = 120.120
- Divide by 3. The mean is 120 divided by 3, which is 40.40
- Write the answer. 40
Check. The mean is 40 ml, which matches the table. ✓
Method. Subtract the mean for clay soil from the mean for sandy soil.
- Read the means. The mean for sandy soil is 90 ml. The mean for clay soil is 10 ml.90 and 10
- Subtract. The difference is 90 minus 10, which is 80.80
- Write the answer. 80
Check. Check: 10 + 80 = 90. ✓
Watch out. Use the means, not the single trials, so the answer is fair.
Watch out
Watch out: the water left in the soil was not measured. Only the water that came through into the cup counts.
Try it at home or school (with a grown-up). With a grown-up, cut the top off a clean plastic bottle to make a funnel. Put a little cotton wool in the neck. Put the same amount of sand in one funnel and the same amount of garden soil in another. Pour the same amount of water into each, and count for one minute. Which soil lets the water through fastest? Wash your hands afterwards.
Exam tip
Grown-up tip. Ask: “What did you change? What did you keep the same? Which funnel was fastest?” Let your child use the words fair test and mean.
Exercise 7D Water through soils: a fair test
Method. Look at the cup with the most water in it.
- Read the cups. The sandy soil cup has the most water in it.most water
- Name the soil. So sandy soil let the most water through.sandy soil
- Write the answer. sandy soil
Check. The clay soil cup has the least water. ✓
Method. Look at the cup with the least water in it.
- Read the cups. The clay soil cup has the least water in it.least water
- Name the soil. So clay soil let the least water through.clay soil
- Write the answer. clay soil
Check. Clay soil has tiny pieces and small gaps. ✓
Method. Read the Mean (ml) column for clay soil.
- Read the table. The mean for clay soil is 10 ml.10
- Write the answer. 10
Check. The three trials were 12, 8 and 10 ml. ✓
Method. Read the text about the test.
- Read the text. The children poured 100 ml of water into each funnel.100 ml
- Write the answer. 100
Check. The same amount was used for each soil, so the test is fair. ✓
Method. Think about what was different in each funnel.
- Read the text. The one thing changed was the type of soil.type of soil
- Write the answer. the type of soil
Check. Everything else was kept the same. ✓
Method. Think about what the children counted in the cup.
- Read the text. The children measured the water collected in the cup after 1 minute.water collected
- Write the answer. water collected
Check. The water collected is the measurement. ✓
Method. Find the shortest bar.
- Look at the bars. The bar for clay soil is the shortest.shortest
- Read the label. The bar for clay soil shows 10 ml.10 ml
- Write the answer. clay soil
Check. The tallest bar is for sandy soil, at 90 ml. ✓
Method. Subtract the mean for clay soil from the mean for garden soil.
- Read the means. The mean for garden soil is 40 ml. The mean for clay soil is 10 ml.40 and 10
- Subtract. The difference is 40 minus 10, which is 30.30
- Write the answer. 30
Check. Check: 10 + 30 = 40. ✓
Method. Use the means: the bigger the mean, the more water came through.
- Read the means. Sandy soil is 90 ml, garden soil is 40 ml and clay soil is 10 ml.90, 40, 10
- Put them in order. From the biggest mean to the smallest, the order is sandy, garden, clay.sandy, garden, clay
- Write the answer. sandy soil, garden soil, clay soil
Check. The order follows the means. ✓
Method. Think about why one result might not be enough.
- Think about one trial. One trial could be affected by a mistake or by chance.one trial
- Give the reason. Three trials show whether the result is the same each time, and the mean is fairer.three trials
- Write the answer. Accept any reason that says three trials show whether the result is reliable, and the mean is a fairer answer.
Check. Repeating a test makes the result more reliable. ✓
Method. Think about what the test measured.
- Think about the test. The test only measured the water collected in the cup.water collected
- Decide. Nutrients were not measured, so the test cannot show that sandy soil has more of them.no
- Write the answer. No. Accept any reason that says the test only measured how much water came through.
Check. A test can only answer the question it measured. ✓
Method. Think about the size of the pieces and the gaps.
- Think about clay. Clay has tiny pieces that fit closely together.tiny pieces
- Give the reason. So there are only small gaps, and water moves slowly through them.small gaps
- Write the answer. Accept any sentence that says clay has tiny pieces that fit closely, so there are only small gaps for water.
Check. Sandy soil has bigger gaps, so water runs through it quickly. ✓
Method. Think about what could be different between the funnels.
- Think about the funnels. If the soil is packed differently, the test is not fair.packed differently
- Describe the change. Pack the same amount of soil in the same way for each funnel.same packing
- Write the answer. Accept any sensible change, such as: pack the same amount of soil in the same way for each funnel.
Check. Keep everything the same except the type of soil. ✓