SCIENCE FORM 2

MERCURY

• The closest planet to the sun.
• The smallest planet in solar system.
• Surface similar to surface of moon.
• The sky appear dark.

VENUS

 The second planet from sun.
 ‘Greenhouse’ planet because high

content of carbon dioxide.
 Rotate from east to west.

EARTH

 The third planet from sun.
 Only planet in solar system known to

sustain life.
 Has layer of air known atmosphere.
 Surface - 71% water and 29% land

MARS

 The fourth planet from sun.
 ‘Red planet’.
 Has 2 moons.
 Divided into 2 different areas.
Brighter area-dust and reddish sand.
Poles – frozen water and carbon dioxide.

JUPITER

 The fifth planet from the sun.
 Largest planet in solar system.
 Mass 320 times than earth.
 Has 67 moons.
 ‘Giant gas’ planet.

SATURN

 The sixth planet from sun.
 ‘Giant gas’ planet.
 Has ring (ice, rocky material and dust)
 Has 62 moons.

URANUS

• The seventh planet from sun.
• Has ring similar to saturn but darker and

thinner.
• Has 27 moons.
• Axis of rotation is tilted, almost parallel to

its orbit.
• ‘Ice planet’ @ ‘Giant gas’ planet

NEPTUNE

 The eight planet from sun.

‘Ice planet’ @ ‘Giant gas’ planet

Relationships between characteristics of
planet.

1. Temperature and distance.
❑ Planets that closer to sun, have high temperature.
❑ Planets that further from sun, have lower

temperature.

2. Density and gravitational force.
❑ Planets that are denser, have stronger gravitational force.
❑ Planets that are less dense, have weaker gravitational force.

3. Distance, time and speed.
❑ Planets that are far away from sun have larger orbits.
❑ They move slowly and take longer time to make a complete

revolution.

4. Direction of movement.
❑ Direction of rotation causes the Sun to rise in different directions.
❑ Planet rotates from west to east – Sun rise in the east
❑ Planet rotates from east to west (Venus) – Sun rise in the west

Astronomical unit (AU)

• Unit of measurement of distance
• One astronomical unit is average distance from

the centre of Earth to the centre of the Sun

1 AU = 1.5 x 10 ⁸ km

1.5 x 10 ⁸ km

Light year (ly)

• Is the distance travelled by light through
vacuum in one year.

• Light travels at speed of 300 000 km per
second.

• In one year, light can travel 9.5 x 10 12 km.

1 ly = 9.5 x 10 12 km

multiply 9.5 x 10 12
multiply 6.3 x 10 4 multiply 1.5 x 10 ⁸

ly AU km

divide 6.3 x 10 4 divide 1.5 x 10 ⁸

divide 9.5 x 10 12

Hypothetical situation related to the
solar system.

1. What happens if the rotation of the Earth slows down or stops
completely?

2. What are natural satellites?

3. How would the condition and appearance of the Earth be from the
Moon?