Earth & the Solar System: IGCSE Physics questions with answers
Free Earth & the Solar System questions for IGCSE Physics (0625), part of Space physics. Each question has the answer and the marking points an examiner would look for.
The Solar System contains planets, minor planets and comets.
(a)
Describe how the orbital speed of a comet changes as it approaches the Sun.
[2]
(b)
Explain why the inner planets are rocky and the outer planets are gaseous.
[2]
Show answers and mark scheme
Part
Answer and marking points
Marks
(a)
increases
speed increases as it gets closer to the Sun B1 because gravitational potential energy is converted to kinetic energy B1
2
(b)
temperature during formation
Any 2 of: near the Sun it was too hot for gases to condense; only rocky materials remained; further away gases could condense B2
2
Question 2Structured · 3 marksA* challenge
Light from the Sun takes about 500 s to reach the Earth. The speed of light is 3.0 × 10⁸ m/s.
(a)
Calculate the distance from the Sun to the Earth.
[2]
(b)
State what force keeps the planets in orbit around the Sun.
[1]
Show answers and mark scheme
Part
Answer and marking points
Marks
(a)
1.5 × 10¹¹ m
d = vt = 3.0 × 10⁸ × 500 C1 1.5 × 10¹¹ m A1
2
(b)
gravity
the gravitational attraction of the Sun B1
1
Question 3Structured · 4 marks
The Earth orbits the Sun and the Moon orbits the Earth.
(a)
State the approximate time for the Moon to orbit the Earth.
[1]
(b)
Explain why we have day and night.
[1]
(c)
Explain why we have seasons.
[2]
Show answers and mark scheme
Part
Answer and marking points
Marks
(a)
about one month
about 27–28 days (one month) B1
1
(b)
Earth rotates on its axis
the Earth rotates on its axis once every 24 hours B1
1
(c)
tilted axis
the Earth’s axis is tilted B1 so different hemispheres face the Sun more directly at different times of the year B1
2
Question 4Structured · 10 marks
This question is about the Solar System.
(a)
Explain why the Sun appears to rise in the east and set in the west, and why we have seasons.
[3]
(b)
Name the force that keeps planets in orbit around the Sun, and state how its size depends on distance.
[2]
(c)
Jupiter orbits the Sun at an average distance of 7.78 × 1011 m and takes 4330 days for one orbit. Calculate its average orbital speed.
[3]
(d)
Describe the difference between the inner and outer planets.
[2]
Show answers and mark scheme
Part
Answer and marking points
Marks
(a)
Earth spins on its axis once a day; seasons because axis is tilted as Earth orbits Sun
the Earth rotates on its axis (once in 24 h) B1 the axis is tilted B1 so as the Earth orbits the Sun each hemisphere gets more direct sunlight for part of the year B1
3
(b)
gravity; decreases with distance
gravitational force (attraction of the Sun) B1 decreases as the distance from the Sun increases B1
2
(c)
13100 m/s
v = 2πr/T C1 T = 4330 × 24 × 3600 s C1 13100 m/s A1
3
(d)
inner: small, rocky; outer: large, gaseous
inner planets are small and rocky B1 outer planets are large and made mainly of gases B1
2
Question 5Structured · 3 marks
The Moon shows phases.
(a)
Explain why we see phases of the Moon.
[2]
(b)
State the time for the Earth to orbit the Sun.
[1]
Show answers and mark scheme
Part
Answer and marking points
Marks
(a)
see different amounts of the sunlit half
the Moon reflects sunlight B1 as it orbits the Earth we see different amounts of its lit half B1
2
(b)
365 days
about 365 days (one year) B1
1
Question 6Structured · 10 marks
This question is about the Earth and the Moon.
(a)
State the approximate time taken for the Earth to orbit the Sun and for the Moon to orbit the Earth.
[2]
(b)
Explain why the Moon shows phases.
[3]
(c)
Light from the Moon takes about 1.3 s to reach the Earth. Calculate the distance to the Moon from this time.
[2]
(d)
The gravitational field strength on the Moon is 1.6 N/kg. Calculate the weight on the Moon of an astronaut of mass 80 kg, and explain why it is less than on Earth.
[3]
Show answers and mark scheme
Part
Answer and marking points
Marks
(a)
365 days (one year); about one month (27–29 days)
about 365 days B1 about one month / 27–29 days B1
2
(b)
Moon reflects sunlight; half always lit; we see different amounts of the lit half as it orbits
the Moon does not emit light, it reflects sunlight B1 half of the Moon is always lit by the Sun B1 as it orbits the Earth we see different proportions of the lit half B1
3
(c)
3.9 × 10⁸ m
d = 3.0 × 10⁸ × 1.3 C1 3.9 × 10⁸ m A1
2
(d)
128 N; Moon has smaller mass, weaker field
W = 80 × 1.6 C1 128 N A1 the Moon has a much smaller mass so its gravitational field is weaker B1
Riyaz Shaikh has mentored IGCSE, IB and A Level students for 15+ years, one-on-one, online and in Mumbai. The hardest questions on this site are the ones he uses to find a student's weak points.
Original Cambridge-style practice questions written for mentorriyaz.in. These are not Cambridge past paper questions, and this site is not affiliated with or endorsed by Cambridge University Press & Assessment. Updated 2026-11-04. Paper generator · mentorriyaz.in