Student’s Book 3
2.5 Healthy plants
Plants need healthy roots, leaves and stems to grow well. Plants grow best with plenty of water and soil that is rich in minerals.
Modern farming and technology can help plants to grow well and be healthy. Fertiliser can be added to soil to increase the amount of minerals in it and improve the soil quality.
1 What do you think would happen if a plant had unhealthy leaves or roots? Explain your answers.
2 Look at the photographs. Why is there a difference between the plants grown with fertiliser and the plants grown without fertiliser?
3 Do all soils need fertiliser? Explain your answer. ell. Key words
4.2 Materials from Earth
All the materials we use – solids, liquids and gases – come from Earth, the planet we live on. Some useful materials from Earth which we use are oil (liquid), natural gas (gas) and metals (solid). Oil comes from organic material which was quickly buried in mud at the bottom of ancient oceans and lakes. Over time, with pressure and heat, it changed into oil. Examples of these oils are crude oil and petroleum.
Natural gas is an invisible, odourless in deep underground rock formations or in coal beds. The gas is found in layers of rock with tiny holes – the rock holds the gas like a sponge.
Natural gas is formed when layers of decomposing plants and animals are put under pressure and heat over millions of years. The decomposing material turns into coal, petroleum and natural gas. An example of natural gas is the gas used for cooking.
6.7 Shadows
Look at picture A.
Can you see the dark area in front of Joshua?
Joshua’s body is blocking the path of light from the Sun. When the path of light is blocked, a dark area, called a shadow, forms in front of the object blocking the light.
1 What do you notice about the shape of Joshua’s shadow?
Look at Joshua’s shadow in picture B.
2 What has happened to his shadow?
3 Why has the shape of the shadow changed in this picture?
7.2 The moving Earth and Moon
The Earth spins around once every 24 hours. The Moon moves around the Earth in an orbit which is almost circular. The Moon travels once around the Earth roughly every 29 days. This means that the Moon goes all the way around the Earth in the same amount of time as it takes the Earth to spin around just once. Because of this, we only ever see one side of the Moon.
1 Why are there clear nights when you cannot see the Moon from Earth?
You already know that the Moon rises and sets as the Earth spins. The rotation of the Earth is what gives us day and night. The Earth moves in an anticlockwise direction, which is why the Sun and the Moon rise in the east and set in the west.
2 In what direction does the Moon orbit the Earth?
