Year 8 Science · Unit 1 · Lesson 16
Challenge Worksheet
Learning Goals
Find the errors
Noah’s investigation report
Question: Does the length of time I spend skipping affect my breathing rate?
Prediction: Breathing will change.
Method: I counted my breaths for one minute at rest. Then I skipped for 30 seconds, then 60 seconds, then 90 seconds, one straight after the other with no rest. After each one I counted my breaths for one minute. I repeated the whole thing three times.
Pattern: The averages were 15, 23, 26 and 35.
Conclusion: Skipping for longer makes breathing go up, so my prediction was proved right. This shows that skipping makes everyone fitter.
1. Noah’s prediction is weak. State the two things a useful prediction should include, and rewrite his prediction.
| Skipping time (s) | Trial 1 | Trial 2 | Trial 3 | Average |
|---|---|---|---|---|
| 0 (resting) | 15 | 16 | 14 | 15 |
| 30 | 22 | 24 | 23 | 23 |
| 60 | 29 | 19 | 30 | |
| 90 | 34 | 36 | 35 | 35 |
Source: sample class results.
2. One result for 60 s does not fit the others. Identify it. Calculate the 60 s average with this result (as Noah did) and without it. Write the better value in the table.
Answer breaths per minute (with; without)
3. Find one weakness in each of Noah’s Method, Pattern and Conclusion sections. For each, say why it is a problem.
4. Rewrite Noah’s Pattern and Conclusion so that they use numbers from Table 1 and do not go beyond the evidence.
Plan an investigation
Question to test: Does moving air (from a desk fan) affect how much water a leafy shoot takes up in one hour? Each shoot stands in a measuring cylinder of water with a thin layer of oil on top, so water cannot evaporate from the surface.
Prediction
If ... then ... because ...
Variables
Method
Making the results trustworthy
Give two things you would do, and say how each one helps.
5. Evaluate this statement: “A good investigation is a laboratory experiment whose results prove the prediction right.” Use Noah’s report and at least one other kind of investigation as evidence, and finish with a clear judgement.
Find the errors
1. What will happen (direction of change) and a reason linked to the living system. Model: “The longer I skip, the higher my breathing rate will be, because my muscles will need more oxygen.” [2 marks: 1 both features, 1 rewrite]
Your Turn
2. Trial 2 (19) does not fit. With it: (29 + 19 + 30) ÷ 3 = 26. Without it: (29 + 30) ÷ 2 = 29.5 (write about 30 in the table). [3 marks: 1 identify, 1 each average]
3. Method: no rest between skips, so each result includes the earlier exercise (or: skipping speed not controlled). Pattern: lists numbers (one skewed by the odd result) with no trend. Conclusion: “proved” is too strong, his prediction never said “up”, and “fitter” and “everyone” were not measured. [3 marks: 1 per section]
4. Model pattern: “The longer I skipped, the higher my average breathing rate: 15 at rest, 23 after 30 s, about 30 after 60 s and 35 after 90 s.” Model conclusion: “For me, skipping for longer increased my breathing rate. More people would need testing before saying this about others.” [3 marks: 1 trend with numbers, 1 conclusion answers the question, 1 stays within the data]
Plan an investigation
Prediction: with the fan on, the shoot takes up more water, because water evaporates from the leaves faster in moving air. Independent: fan on or off. Dependent: water taken up in one hour (mL). Controlled (any two): kind and size of shoot, number of leaves, light, temperature, time. Method: set up cylinders with similar shoots and oil; record starting volumes; place some in front of the fan, some away; read volumes after one hour and subtract. Trustworthy: three or more shoots per condition, averaged; change only the fan; read the scale at eye level.
Show What You Know
5. Marking guide (points expected): 1 investigations need not be in a lab (field work or secondary data count, e.g. frog-call records); 1 data support an idea rather than “prove” it; 1 a result that disagrees with the prediction is still useful evidence; 1 Noah’s conclusion was weak because it went beyond his data, not because of where he worked; 2 judgement: wrong; a good investigation has a testable question, reasoned prediction, safe fair method, repeated data and an evidence-based conclusion (1 if no reasons). [6 marks]
Common error to watch for: keeping the odd result in the average “because it is real data”, or deleting it without saying so. Students should point it out and explain what they did with it.