Year 7 Science · Unit 4 · Lesson 14
Master Worksheet
Learning Goals
1. State the purpose of science. Then give two things that must be true of a scientific idea.
Find the error
Priya wrote this summary of the unit
(1) Day and night happen because the Earth orbits the Sun once every day. (2) In a fair test, you change only one variable at a time. (3) Our model of the Solar System has always been Sun-centred. (4) Measuring something with a ruler is an example of making an inference.
2. Three of Priya’s sentences contain an error. For each one, give the sentence number and the correct science.
3. The Parkes radio telescope (Murriyang) and space telescopes detect things our eyes never could. Use one of them to show why more sensitive, accurate observation leads to better understanding of space.
Read the data: Leo’s crater test
Scenario
Leo wanted to know if letting a ball fall from higher up makes bigger dents in flour. He let a ball fall once from each height, grabbing whichever ball was closest. He concluded: “The dents get wider and then narrower, so height makes no clear difference.”
| Height of fall (cm) | Ball | Width of dent (mm) |
|---|---|---|
| 20 | golf ball | 28 |
| 40 | golf ball | 34 |
| 60 | tennis ball | 52 |
| 80 | tennis ball | 58 |
| 100 | marble | 26 |
Source: made-up results for this worksheet.
4. Identify two problems with the way Leo ran his test: one that makes it unfair, and one that makes it less reliable.
5. Use only the rows of Table 1 that can be fairly compared to judge Leo’s conclusion. Explain the drop at 100 cm.
Plan a short investigation
Question to test: “Does the type of powder in the tray (flour, fine sand or cocoa powder) affect the crater diameter?”
Hypothesis
Variables
Method (3 steps)
Results table: write the column headings, with units, and the name of each powder
Graph: which kind would you draw, and why?
6. Evaluate this claim: “A model made in a classroom cannot give real evidence about impacts on other worlds.”
Question 1
To build knowledge of the world through observation, experimentation and analysis (1). Two of: evidence-based; testable; open to change (1). [2 marks]
Find the error: Question 2
(1) Earth spins on its axis (1). (3) It changed from Earth-centred to Sun-centred with new evidence (1). (4) A measurement is an observation (1). Sentence 2 is correct. [3 marks]
Question 3
They detect what eyes cannot: Parkes picks up radio waves; space telescopes capture faint light from distant galaxies (1). More sensitive, accurate observations (1) give new evidence that improves knowledge (1). [3 marks]
Read the data: Question 4
Unfair: he changed the ball as well as the height, so two variables changed (1). Less reliable: one drop per height, no repeats (1). [2 marks]
Question 5
Golf ball 28 → 34 mm (20 to 40 cm); tennis ball 52 → 58 mm (60 to 80 cm) (1). In both fair pairs, the same ball dropped from higher made a wider dent, so Leo’s “no clear difference” conclusion is not supported (1). At 100 cm a marble, a smaller ball, was used (1). [3 marks]
Plan a short investigation
Hypothesis: a testable prediction naming a powder (1). Change: powder type; measure: crater diameter (mm) (1). Three of: ball, drop height, powder depth, tray (1). Method: smooth flat, drop from the set height (1); measure with a ruler, repeat three times and average (1). Table: Powder | Trial 1 | Trial 2 | Trial 3 | Mean diameter (mm); rows flour, fine sand, cocoa (1). Graph: column graph, as powders are categories (1). [7 marks]
Question 6
Marking guide: 1 judgement (disagree); 1 we cannot watch a real crater form, so a model tests ideas; 1 what it shows well (round craters, bigger impacts make wider craters); 1 a difference (real rocks bigger and faster; rock and dust, not flour); 1 one variable changed, others controlled; 1 repeats and averages give reliable evidence. [6 marks]
Model answer: I disagree. We cannot watch a real crater form, so a model tests ideas. It shows impacts make round craters, and bigger impacts wider ones. Real rocks are far bigger and faster. Changing one variable and repeating drops makes it reliable evidence.
Common error: thinking a model must match reality exactly.