Q9. The table below gives information about the planets of the Solar System. They are listed in alphabetical order.

planet name	average distance from the Sun /million km	diameter /km	time for one orbit round the Sun	time for one rotation on its axis /hours	temperature on surface of planet /°C
Earth	150	13 000	365 days	24	+22
Jupiter	780	140 000	12 years	9.8	–150
Mars	230	6800	687 days	25	–23
Mercury	58	4900	88 days	1400	+350
Neptune	4500	51 000	165 years	16	–220
Pluto	5900	2300	248 years	150	–220
Saturn	1400	120 000	29 years	10.2	–180
Uranus	2900	51 000	84 years	17	–210
Venus	110	12 000	225 days	5800	+480
(Data obtained from The Guinness Book of Astronomy, Patrick Moore; published by Guinness 1992)

(a) Explain why Neptune and Pluto are the coldest planets.

They are furthest from the Sun. (They therefore receive the Sun's energy at a lower intensity - the energy is more spread out over the planet surface).

Do not accept 'They are far from the Sun'

All of the planets are far away from the Sun - the examiner wants you to compare the planet distances they are the cosldest because they are further away - furthest...

1 mark

(b) Explain why there could be no liquid water on the surface of:

(i) Mars

On Mars the surface temperature is -23°C. The melting point of water is 0°C - so water would be solid - ice.

(ii) Venus

On venus the surface temperature is +480°C. The boiling point of water is 100°C - so water would be gas - steam.

2 marks

(c) On which planet would the time between sunrise and sunset be shortest?

Sunrise and sunset relate to the time taken for the planet to spin on its own axis - the day length.

Jupiter

1 mark

(d) Which planet has the shortest year?

A planet's year relates to the orbital period.

Mercury

1 mark

(e) Give the name of the force which keeps the planets in their orbits.

Gravity

do not accept ‘weight’

1 mark

Maximum 6 marks