Student’s Book 4
Bones in museums and the bones of dead animals in the environment are dry and they crumble easily. Living bones are not dry and are very strong.
I have I learned
Activities
1
2
Describe some differences between the bones that make up the human skeleton.
3
Find out what happens when you break (fracture) a bone. What is the difference between a complete fracture, a greenstick fracture and an open fracture?
When you break a bone you may have to wear a splint or a cast. Make a poster to teach young children what they can expect if they have to wear a splint or a cast.
● Humans have bony skeletons inside their bodies.
● Skeletons are made of different kinds of bones connected to each other at joints.
3.5 Freezing and melting
When you add heat to solids, such as ice or butter, they get soft and turn to liquid. This process is called melting. Some solids need more heat than others to make them melt. For example, if you melt butter in a metal pan, the butter will melt but the metal pan will not melt.
1 Do you think all ice melts at the same rate?
2 If you heated ice, butter and candle wax in three identical pans, over the same amount of heat, which one do you think would melt first? Why?
heat
melting
freezing
solidify
cooling
When liquid is cooled enough, it turns to a solid. It solidifies or freezes. To solidify or to freeze a liquid is the reverse of melting it. In science, freezing means the same as to solidify, so freezing is not just a term used for water turning to ice.
3 Do you think all liquids solidify at the same temperature? Solidifying (or freezing) and melting are the reverse changes to the states of liquid and solid matter. This means that if you melt a solid by heating it, you can reverse the change of state by cooling the liquid and causing it to solidify or freeze.
4.3 Energy and movement
Energy allows objects to do work. In scientific language, work means more than just physical labour – it includes things such as breathing, moving, cooking food and objects falling to the ground as a result of gravity.
Look at these pictures. They all show energy making things work.
6.2 Volcanoes
There are more than 1500 active volcanoes on the Earth. Some of these volcanoes are in the oceans. The largest active volcano is in Hawaii. A volcano is a mountain that opens downwards to a pool of molten rock below the Earth’s crust. When the pressure builds up under the surface of the Earth, the mountain will erupt. Gas and rock shoot up out of an opening at the top of the mountain and lava flows down the slopes of the mountain.
1 Use the diagram of a volcanic eruption to explain what happens when the lava pours out. The Earth’s crust is like a jigsaw puzzle, with the huge slabs of crust fitting together. These huge slabs are known as tectonic plates. The plates are all moving very, very slowly across the surface of the Earth.
Earth’s crust
A cross-section through a volcano magma chamber