Year 7 Science · Unit 4 · Lesson 5
Master Worksheet
Learning Goals
Find the error: Zara’s field notes
Zara’s notebook, headed “Observations at the wetland”
(1) The pond water is cloudy and green. (2) The pond is full of algae. (3) The air thermometer reads 14 °C. (4) The frogs are hiding because it is too cold. (5) A heron is standing still in the shallow water. (6) The heron is waiting to catch a fish.
1. Three of Zara’s six notes are not observations. Give the number of each one and explain why it is an inference.
Fix the prediction
Explain why each prediction cannot be tested. Then rewrite it as an “If … then …” prediction that names something you could measure.
| Prediction | Why it cannot be tested | Testable version |
|---|---|---|
| 1. Our class goldfish enjoys music. | ||
| 2. Our dog is smarter than the neighbour’s dog. |
Read the data: guess the temperature
Scenario
A classmate claims: “I can judge the temperature of water by hand just as well as a thermometer can.” Five cups of water were set out. Before each cup, the classmate held their hand in room-temperature water for one minute. They then guessed each cup’s temperature by touch, and a thermometer gave the reading.
| Cup | Guess by hand (°C) | Thermometer (°C) | How far off (°C) |
|---|---|---|---|
| 1 | 20 | 18 | 2 |
| 2 | 35 | 42 | 7 |
| 3 | 28 | 25 | |
| 4 | 10 | 4 | |
| 5 | 40 | 48 | 8 |
Source: sample class results.
2. Fill in the two empty cells. Then calculate the average of the “How far off” column. Show your working.
Average °C
3. Describe the pattern: for which cups was the hand closest to the thermometer, and for which was it furthest off? Do the data support the classmate’s claim? Use numbers.
4. Another student says the test was unfair, because the classmate could see steam rising from cup 5 before touching it. Explain how seeing the steam could change the guess, and suggest one way to improve the test.
5. Evaluate this claim: “Because instruments are so accurate, scientists never need to use their senses at all.” Support your judgement with evidence from Table 1 and from Zara’s notes.
Find the error: Zara’s field notes
1. (2) She cannot see algae; she worked it out from the cloudy green water (1). (4) She did not see why the frogs hide; “too cold” is worked out from the 14 °C reading (1). (6) She cannot see what the heron is thinking; she used what she knows about herons (1). Notes 1, 3 and 5 are observations. [3 marks]
Fix the prediction
Per row: 1 why (“enjoys” and “smarter” cannot be measured) and 1 a testable “If … then …” version with a measurement. E.g. 1: if music plays beside the tank, then the goldfish will swim more laps per minute than with no music. 2: if both dogs watch a treat being hidden, then our dog will find it in less time, measured with a stopwatch. [4 marks]
Read the data: guess the temperature
2. Cup 3: 3; cup 4: 6 (1). (2 + 7 + 3 + 6 + 8) ÷ 5 = 26 ÷ 5 = 5.2 °C (1). [2 marks]
3. Closest for cups 1 and 3 (2 and 3 °C off), near room temperature (1). Furthest for the hot and cold cups 2, 4 and 5 (6 to 8 °C off) (1). Not supported: on average the hand was 5.2 °C off, while the thermometer gives an exact number (1). [3 marks]
4. Steam tells the classmate the water is hot, so the guess becomes an inference from sight, not a judgement by touch (1). Improve: blindfold the guesser or hide the cups (1). [2 marks]
Question 5
Marking guide: 1 position (disagree); 1 the senses start every observation and are used to read instruments; 1 the senses can be fooled and give no exact number; 1 evidence from Table 1 (up to 8 °C off, 5.2 °C on average); 1 instruments extend the senses and give numbers others can check; 1 inferences (e.g. Zara’s notes 2, 4, 6) are worked out from observations (notes 1, 3, 5) and can be wrong, and testable predictions are checked with new observations. [6 marks]
Model answer: I disagree. Scientists use their senses to notice things and to read their instruments. But the senses can be fooled: in Table 1 a hand was up to 8 °C off. Instruments extend the senses and give exact numbers that others can check. Zara saw cloudy green water (note 1) but only inferred algae (note 2), and an inference like that can be wrong. Testable predictions are checked with new observations, so science needs both senses and instruments.
Common error: labelling any statement that sounds sensible as an observation. If it was worked out, not seen or measured, it is an inference.