Primary General Studies | Earth, Moon and Sun teaching guide | Rotation, seasons, lunar phases and four common errors

2026-11-13

Tutor lesson-prep guides · Primary General Studies

The usual answer for lunar phases is that the Earth casts a shadow on the Moon. Stop there. Phases come from the changing angle at which we see the sunlit half of the Moon; the Earth shadow falling on the Moon is an eclipse, which happens only at full moon. The other stubborn error is that summer happens because Earth is closer to the Sun, when in July Earth is in fact farthest away. This lesson separates the three bodies with three periods: 24 hours, 29.5 days and 365 days, each fixed with one division worked out on the board.

Objectives — Students can (1) explain day and night with one rotation of 24 hours and calculate 15 degrees per hour; (2) explain the seasons with the 23.5-degree axial tilt and day length rather than distance from the Sun; (3) order the four phases, calculate about 7.4 days between them, and state that phases show an angle while an eclipse shows whose shadow falls where.

01 Prerequisites (3-minute check)

If any of these fails, fix it before the lesson starts.

Skill	Quick check	Pass mark
A day is 24 hours and a year is 365 days	How many months are there in a year?	Twelve, of 30 or 31 days
A full circle is 360 degrees	360 degrees shared into 24 parts: how many each?	15 degrees
Light travels in straight lines and opaque objects cast shadows	Why is half of the Moon always dark?	The sunlit half faces the Sun; the other half is night

02 Lesson flow (60 minutes)

Time	Stage	Tutor does	Student does
0-6 min	Opening judgement	Ask why we have day and night; write answers on the left of the board	Most will say Earth goes around the Sun; do not correct yet
6-18 min	Rotation	Globe and torch demonstration, then work out 360 divided by 24	Turn the globe a full circle so one point moves from light into dark
18-30 min	Revolution and seasons	Draw two positions with the 23.5-degree tilt and compare day length	Distance is not the cause; July is near aphelion
30-42 min	Four phases	Order new moon, first quarter, full moon, last quarter; work out 29.5 divided by 4	Match to lunar calendar dates about day 7 and day 22
42-54 min	Phases versus eclipse	One line separates them: whose shadow	A student who says Earth lies between Sun and Moon has it
54-60 min	Exit check	Three oral questions and one written item	See the exit section

03 Teaching script (read it out)

Scene 1: Day and night come from one motion: rotation

Earth spins on its axis once every 24 hours, so the side facing the Sun has day and the other side has night. Do not introduce revolution first: if both motions arrive together, students swap one day with one year and every later answer on phases and seasons goes wrong. Use a globe and a torch with the torch still and turn the globe slowly while students watch a marked point move from light into dark. Then write 360 divided by 24 equals 15 degrees per hour. Hong Kong and London differ by 8 hours, which is 120 degrees. Once students compute that themselves, time zones stop being memorised facts.

Close by asking which city would stay in daylight forever if Earth stopped turning.

Scene 2: Seasons come from a 23.5-degree tilt, not distance

The second act must confront the most stubborn intuition directly: summer is not caused by Earth being closer to the Sun. The orbit is close to circular, and in July, northern summer, Earth is actually farthest from the Sun. The real cause is the 23.5-degree tilt, which makes sunlight strike the northern hemisphere more directly and lengthens the day. Draw two positions: one with the northern hemisphere leaning towards the Sun and long days, one leaning away with short days, and ask students to count what fraction of a marked latitude line is lit. Each season lasts about 365 divided by 4, that is 91.25 days; write that number down, because most students assume the seasons are equal in length.

Close with two dates on the board, July aphelion and January perihelion, and let students state the contradiction.

Scene 3: Phases: four positions in a 29.5-day orbit

Only now bring in the Moon. The Moon does not emit light; we see the half that the Sun lights. The Moon orbits Earth in about 29.5 days, and during that time we see that lit half from different angles, which produces the phases. Draw them around a circle: new moon, with the Moon between Sun and Earth and the lit side away from us; first quarter, right half lit; full moon, with Earth between Sun and Moon and the whole lit side facing us; last quarter, left half lit. Divide 29.5 by 4 to get 7.4 days between phases, and match that to lunar calendar dates around day 7 and day 22. Close with the line students must be able to repeat: a phase is the angle at which we see the lit side; an eclipse is Earth shadow falling on the Moon, which happens only at full moon and not every month.

Close with one line: a phase is an angle, an eclipse is a shadow.

04 Question types and worked steps

Type	Example	Steps	Answer
Explanation	Explain why Earth has day and night	Name rotation, name the sunlit and dark sides, add one rotation in 24 hours	Only saying Earth spins, with no lit and dark sides, earns nothing
Calculation	How many degrees per hour if 360 degrees take 24 hours? Hong Kong and London differ by 8 hours: how many degrees?	Divide 360 by 24, then multiply 15 by 8	Units required; a bare 15 is not enough
Ordering	Put new moon, first quarter, full moon and last quarter in order	Start at new moon, go round the circle, label days between phases	Full order needed; wrong day counts get an oral correction
Comparison	How does a phase differ from an eclipse?	Say whose shadow, say how often, say a phase is an angle	The answer must contain Earth shadow and full moon only

Sanity check (teach this): Sanity check: the chapter rests on three periods only, 24 hours, 29.5 days and 365 days, each paired with one division worked on the board (360/24 = 15, 29.5/4 = 7.4, 365/4 = 91.25), so no decimals have to be memorised. The seasons act deliberately avoids distance from the Sun, because the closer-in-summer intuition is the hardest to remove and needs the July aphelion fact. Phases and eclipses are split by one line about whose shadow falls. The demonstration needs only a globe and a torch, so it works indoors on a rainy day. P6 needs only four phases and the eclipse distinction, not tidal locking or leap-month rules.

05 Independent practice (3 questions)

Question	Answer	What to watch
Ordering	Order four phase pictures and write the lunar calendar date for each	Check order and dates agree
Calculation	How many degrees per hour? If one lunar orbit is 29.5 days, how many days between phases?	15 degrees and 7.4 days, both with units
Explanation	A classmate says summer happens because Earth is closer to the Sun. Correct this in two sentences	The tilt or the July aphelion should appear

06 Common mistakes and what to say

Mistake	Student writes	Say this
Thinking day and night come from revolution	Earth goes round the Sun once a day	Going round the Sun once is a year, not a day. That is revolution. One day is Earth turning once on its axis.
Thinking seasons come from distance	Summer is hot because we are closer to the Sun	In July we are farthest from the Sun, yet July is our hottest month. So the cause is not distance; it is the tilt, which changes the angle of sunlight and the length of the day.
Thinking phases are Earth shadow	Earth blocks the Moon, so we see phases	Earth blocking the Moon is an eclipse, which happens a few times a year and only at full moon. Phases come from the angle at which we see the lit side, and they repeat every month.
Thinking the Moon makes its own light	The Moon glows at night	The Moon reflects sunlight. On a new moon night the Moon is still up there, but its lit side faces away from us, so we cannot see it.

07 Homework (paper, section and question numbers)

Independent practice in this chapter, with answers — Use practice items 1 to 3, plus two written items: a time zone calculation and the phase versus eclipse distinction
P6 General Studies paper for mixed practice — For revision week mixed practice; this paper has no Earth and space items, so treat it as question-reading training

08 Exit check (last 5 minutes)

Question	Answer	Decision
Why do we have day and night	Earth rotates; the sunlit side has day and the other side has night, once every 24 hours	Rotation plus lit and dark sides both needed
What causes the seasons	The 23.5-degree tilt changes the angle of sunlight and day length	Correct on the spot if the answer is distance
Phase versus eclipse	A phase is the angle we see; an eclipse is Earth shadow on the Moon at full moon	Both points needed to pass

09 Tutor FAQ

Why not teach revolution before rotation?

Teaching both motions together makes students swap one year with one day, and every later answer on phases and seasons breaks. Fix 24 hours with the torch demonstration first, then introduce 365 days.

What if students refuse to believe July is farthest from the Sun?

Do not appeal to authority. Draw an ellipse with July and January marked, then ask whether the southern hemisphere should have winter or summer in July if distance controlled temperature. The contradiction does the work.

Should eclipse types be taught?

Not at P6. Saying that Earth shadow falls on the Moon and that this happens only at full moon is enough; total and partial eclipses belong to secondary school.

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A TutorZone lesson-prep guide. Written by the TutorZone team; questions and lesson flow are original and are not taken from any school or publisher material.