Year 7 Science · Unit 4 · Lesson 10
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Learning Goals
Match each term to its meaning
Write the letter of the correct meaning next to each term. Each letter is used once.
| Term | Letter | Meaning |
|---|---|---|
| Waxing | A. The lit part we see is shrinking towards new moon. | |
| Waning | B. Earth’s shadow falls on the Moon; only at full moon. | |
| First quarter | C. The Moon’s shadow falls on part of Earth; only at new moon. | |
| Full moon | D. The lit part we see is growing towards full moon. | |
| Solar eclipse | E. We see exactly half of the lit side, and it is still growing. | |
| Lunar eclipse | F. The whole lit half faces us; the Moon is on the far side of Earth. |
1. Why is there not an eclipse every month? Complete the chain by writing the two missing links. Each box is caused by the one before it.
Where is the Moon?
For each position, name the phase. Then say whether an eclipse could happen there, and if so which kind.
| Where the Moon is | Phase | Eclipse possible? Which kind? |
|---|---|---|
| On the far side of Earth from the Sun | ||
| We see exactly half of the lit side, and it is shrinking | ||
| Between the Sun and Earth |
Plot the data: how much of the Moon is lit?
Scenario
Priya used a sky app to record how much of the Moon’s face was lit on eight days of one cycle. Day 0 was a new moon.
| Day | 0 | 4 | 7 | 11 | 15 | 18 | 22 | 26 |
|---|---|---|---|---|---|---|---|---|
| Lit (%) | 0 | 17 | 46 | 85 | 100 | 89 | 51 | 13 |
Source: made-up sample values for one 29.5-day cycle, rounded.
2. Plot the data from Table 1 on the grid. Choose a scale for each axis, plot the eight points and join them with a smooth curve.
3. (a) On which day in Table 1 was the Moon full? Was it waxing or waning on day 22? (b) Use your graph to find the day when the Moon was half lit and growing, and name that phase. (c) Predict the percentage lit on day 29, and name that phase.
4. Explain why a lunar eclipse can never happen when the Moon is at first quarter.
5. Extended response. A news story says: “An eclipse will happen on the night of this month’s full moon. It is safe to watch with the naked eye.” Name the kind of eclipse, explain how it happens and why it can only happen at full moon, say why it is safe to watch, and explain why we do not see one at every full moon.
Match each term to its meaning
Waxing → D; Waning → A; First quarter → E; Full moon → F; Solar eclipse → C; Lunar eclipse → B. 1 mark for every two correct. [3 marks]
Question 1
Box 1: so at most new and full moons the Moon passes a little above or below the line joining the Sun and Earth (1). Box 2: the Sun, Earth and Moon do not line up exactly, so no shadow falls where we are (1). [2 marks]
Where is the Moon?
1 mark per row, both cells correct. Far side: full moon; yes, a lunar eclipse (only if the three line up exactly). Half lit and shrinking: last quarter; no, the three are not in a line. Between the Sun and Earth: new moon; yes, a solar eclipse (only if lined up exactly). [3 marks]
Plot the data: how much of the Moon is lit?
2. Even scales, day 0–30 and 0–100% (1); eight points plotted correctly (1); smooth hill-shaped curve, not dot-to-dot straight lines (1). [3 marks]
3. (a) Day 15 (1); waning (1). (b) About day 7 to 8 (accept 7–8); first quarter (1). (c) About 0% (accept 0–5%); new moon, as a cycle takes about 29.5 days (1). [4 marks]
Question 4
A lunar eclipse needs Earth between the Sun and the Moon, so Earth’s shadow falls on the Moon (1). At first quarter the Moon is only a quarter of the way round its orbit, not on the far side of Earth, so it is not in Earth’s shadow; that position is full moon (1). [2 marks]
Question 5
Marking guide: 1 lunar eclipse; 1 Earth is between the Sun and the Moon; 1 Earth’s shadow falls on the Moon, which may look dim red; 1 only at full moon, the only time the Moon is on the far side of Earth from the Sun; 1 safe because you look at the dim Moon, not the Sun; 1 the Moon’s orbit is tilted about 5°, so at most full moons it passes above or below Earth’s shadow. [6 marks]
Model answer: It is a lunar eclipse. Earth passes between the Sun and the Moon, and Earth’s shadow falls on the Moon, which often turns dim red. This can only happen at full moon, when the Moon is on the far side of Earth from the Sun. It is safe because we look at the dim Moon, not the Sun. Most full moons have no eclipse because the Moon’s orbit is tilted about 5°, so it usually passes just above or below Earth’s shadow.
Common error: swapping the two eclipses, e.g. putting the Moon between the Sun and Earth for a lunar eclipse.