Year 3 Science: Differences, similarities and evidence
Part of the Year 3 Science working scientifically chapter. Chapter overview · whole chapter on one page
Differences, similarities and evidence
To compare two things, look for differences (what is not the same) and similarities (what is the same). A change is something that becomes different over time, or after a test.
Evidence is information that helps us answer a question or support an idea. Measurements from our own test are evidence. So are facts from a reliable source, checked with a grown-up.
| Feature | Rubber ball | Sponge ball |
|---|---|---|
| Shape | round | round |
| Material | rubber | sponge |
| Bounce from 50 cm | 38 cm | 9 cm |
Evidence supports a finding when it points to the same answer. One test with one of each ball is some evidence, but it is not enough to be sure about all balls.
Practice only: pattern seeking means looking across your results for things that go together, such as taller stacks having more books. Secondary sources means finding facts in a book or a reliable website, checked with a grown-up. These are practice only, and they are not separate statements.
Key ideas
- A difference is something that is not the same.
- A similarity is something that is the same.
- Evidence is measured, or reliable, information that helps to answer a question.
- One test is not always enough to prove something for all cases.
Method. Decide which statement describes something that is not the same.
- Read A. Both balls are round, so this is a similarity.A: same
- Read B. The rubber ball bounced to 38 cm and the sponge ball to 9 cm, so the heights are different.B: different
- Write the answer. B
Check. The bounce heights are different. ✓
Method. Find a feature that is the same in both columns.
- Look at the shape. The table says round for both balls.round: rubber, round: sponge
- Find the same thing. The same word in both columns is a similarity.round = round
- Write the answer. both are round
Check. The shape is the same for both balls. ✓
Method. Read the evidence, and check whether it supports the idea.
- Read the evidence. The rubber ball bounced to 38 cm.38 cm
- Compare it with the other ball. The sponge ball bounced to only 9 cm, so the rubber ball bounced higher in this test.38 is more than 9
- Write the answer. yes
Check. The measurements point to the same answer. ✓
Watch out
Watch out: “I think” is not evidence. A measurement is evidence, because someone else can measure it again and check it.
Try it at home or school (with a grown-up). Drop two different balls from the same height, with a grown-up. Measure how high each one bounces, using a ruler. Write one difference and one similarity from your results. Then decide whether one test is enough to say what happens for all balls.
Exam tip
Grown-up tip. Ask: “Is that a measurement or a guess? How could someone else check it?”
Exercise 1F Differences, similarities and evidence
Method. A difference is a feature that is not the same in both columns.
- Look at the material. Rubber and sponge are different materials.rubber and sponge
- Look at the bounce height. The bounce heights are 38 cm and 9 cm.38 and 9
- Write the answer. Accept any difference in the table, such as the material or the bounce height.
Check. The two balls differ in material and in bounce height. ✓
Method. Compare the two bounce heights.
- Read the heights. Rubber ball 38 cm, sponge ball 9 cm.38 and 9
- Find the lower one. 9 cm is less than 38 cm.sponge ball
- Write the answer. sponge ball
Check. 9 cm is the smaller bounce. ✓
Method. Find the two bounce heights, then take the smaller one away from the bigger one.
- Read the rubber ball bounce. It bounced to this height.rubber ball: 38 cm
- Read the sponge ball bounce. It bounced to this height.sponge ball: 9 cm
- Take the smaller height away from the bigger one. The difference is how much higher.38 − 9 = 29
- Write the answer. 29 cm
Check. 9 + 29 = 38, so the sums match. ✓
Watch out. Subtract the smaller number from the bigger number.
Method. Evidence is a measurement or reliable information, not a personal view.
- Read A. This is a personal view, so it is not evidence.opinion
- Read B. This is a measurement, so it is evidence.measurement
- Write the answer. B
Check. A measurement can be checked by someone else. ✓
Method. Look for a number with a unit.
- Look for a number. The sentence gives 38 cm.38 cm
- Decide. A number with a unit is a measurement.measurement
- Write the answer. measurement
Check. The number and unit come from a measurement. ✓
Method. Look across the three results for a pattern.
- Read the heights. The heights are 3 cm, 6 cm and 9 cm.3, 6, 9
- Compare them. Each extra book makes the stack taller, so the height goes up.goes up
- Write the answer. yes
Check. The heights get bigger each time. ✓
Method. A reliable source is one that is checked, not a guess.
- Read A. A checked book or website gives facts that someone recorded.A: checked
- Read B. A guess is not a reliable source.B: a guess
- Write the answer. A
Check. A reliable source gives checked facts. ✓
Method. Compare the two bounce heights.
- Read the heights. Rubber ball 38 cm, sponge ball 9 cm.38 and 9
- Find the higher one. 38 cm is more than 9 cm.rubber ball
- Write the answer. rubber ball
Check. The rubber ball bounced higher. ✓
Method. Think about what is being measured.
- Think about the measure. A bounce height is a length.length
- Choose the unit. Lengths are measured in centimetres, cm.cm
- Write the answer. cm
Check. Millilitres measure volume, not height. ✓
Method. Think about how much evidence one test gives.
- Count the balls tested. Only one rubber ball and one sponge ball were tested.one of each
- Decide. One test with one ball of each kind is not enough to prove what happens for all balls.not enough
- Write the answer. no
Check. More tests would be needed to be sure. ✓
Method. Take the smaller amount away from the bigger amount.
- Read the two amounts. Towel A soaked up 70 ml. Towel C soaked up 55 ml.70 and 55
- Take the smaller away from the bigger. The difference is how many ml more.70 − 55 = 15
- Write the answer. 15 ml
Check. 55 + 15 = 70, so the answer is right. ✓
Method. Think about how many balls were tested.
- Think about the test. We tested one rubber ball and one sponge ball.one of each
- Decide. The word always needs evidence from many balls, so more tests would be needed.more tests
- Write the answer. Accept any answer that says one test with one ball of each kind is not enough evidence to say always, and more tests would be needed.
Check. Evidence from a few balls cannot prove a rule for all balls. ✓
Method. A pattern question asks what goes together in the results.
- Choose a pattern. Taller stacks may go with more books.taller and more
- Say what kind of question it is. Looking for patterns is practice only in this chapter.practice only
- Write the answer. Accept any pattern question about our results, such as “Do taller stacks have more books?”, and the words practice only.
Check. A question that looks across results is pattern seeking. ✓