Effects of heat My Pals are Here! Science © 2008 Marshall Cavendish (Singapore) Private Limited

Questions to think about… What are some effects of heat in our everyday life? What are good and poor conductors of heat? How does heat affect solids, liquids and gases? My Pals are Here! Science © 2008 Marshall Cavendish (Singapore) Private Limited

Expansion and contraction What will happen when solids gain or lose heat? Look at the ball in the diagram below. Before heating, the ball can pass through the ring. My Pals are Here! Science © 2008 Marshall Cavendish (Singapore) Private Limited

Expansion and contraction What will happen when solids gain or lose heat? After the ball gains heat, it became bigger and cannot pass through the ring. The increase in size is because of heat gain and is called expansion. My Pals are Here! Science © 2008 Marshall Cavendish (Singapore) Private Limited

Expansion and contraction What will happen when solids gain or lose heat? After the ball has cooled down and lost heat, it becomes smaller. It can now pass through the ring. The decrease in size is because of heat loss and is called contraction. My Pals are Here! Science © 2008 Marshall Cavendish (Singapore) Private Limited

Expansion and contraction What will happen when liquids gain or lose heat? The conical flask on the right is fully filled with coloured water. glass tube original water level stopper My Pals are Here! Science © 2008 Marshall Cavendish (Singapore) Private Limited

Expansion and contraction What will happen when liquids gain or lose heat? When the flask is placed in a basin of hot water, the water level will rise up the glass tube. This shows that the water in the flask has gained heat and expanded. water level after expansion original water level My Pals are Here! Science © 2008 Marshall Cavendish (Singapore) Private Limited

Expansion and contraction What will happen when liquids gain or lose heat? When the flask is placed in a basin of ice water, the water level in the glass tube will fall. This shows that the water in the flask has lost heat and contracted. original water level water level after contraction My Pals are Here! Science © 2008 Marshall Cavendish (Singapore) Private Limited

Expansion and contraction What will happen when gases gain or lose heat? This boiling tube has air and a glass tube that contains a drop of red ink. glass tube original red ink level rubber bung boiling tube My Pals are Here! Science © 2008 Marshall Cavendish (Singapore) Private Limited

Expansion and contraction What will happen when gases gain or lose heat? When the boiling tube is placed in a basin of hot water, the air in the boiling tube gains heat. The air expands and pushes against the red ink. The red ink level moves up the glass tube. red ink level after expansion of air original red ink level My Pals are Here! Science © 2008 Marshall Cavendish (Singapore) Private Limited

Expansion and contraction What will happen when gases gain or lose heat? When the boiling tube is placed in a basin of ice water, the air in the boiling tube loses heat. The air contracts. As a result, the red ink level moves down the glass tube. original red ink level red ink level after contraction of air My Pals are Here! Science © 2008 Marshall Cavendish (Singapore) Private Limited

Expansion and contraction Gases, liquids and solids expand when they are heated and contract when they are cooled. What have you learnt from the experiments? My Pals are Here! Science © 2008 Marshall Cavendish (Singapore) Private Limited

Expansion and contraction in our daily lives We have to make sure that these processes can take place safely and not cause harm to us. The things around us expand and contract when the temperature changes. Let us take a look at a few examples of expansion and contraction in our daily lives. My Pals are Here! Science © 2008 Marshall Cavendish (Singapore) Private Limited

Expansion and contraction in our daily lives When it gets hot, concrete slabs on the pavement expand. The gaps in-between the concrete slabs allow space for expansion. My Pals are Here! Science © 2008 Marshall Cavendish (Singapore) Private Limited

Expansion and contraction in our daily lives The gaps in-between the bridge allow space for expansion. My Pals are Here! Science © 2008 Marshall Cavendish (Singapore) Private Limited My Pals are Here! Science © 2008 Marshall Cavendish (Singapore) Private Limited

Changes in state of matter What happens when matter gains or loses heat? When water is heated, it gains heat and changes from a liquid to a gas. My Pals are Here! Science © 2008 Marshall Cavendish (Singapore) Private Limited

Changes in state of matter A candle is made of wax. When wax is heated, it changes from a solid to a liquid. My Pals are Here! Science © 2008 Marshall Cavendish (Singapore) Private Limited My Pals are Here! Science © 2008 Marshall Cavendish (Singapore) Private Limited

Changes in state of matter How does heat affect matter? When matter gains or loses heat, it can change in state. heat gain heat gain Solid Liquid Liquid Gas heat loss heat loss My Pals are Here! Science © 2008 Marshall Cavendish (Singapore) Private Limited

Good and poor conductors of heat Materials that allow heat to flow through them easily are called good conductors of heat. Metals are examples of good conductors of heat. Good conductors of heat are best in making pots and pans as heat can flow through them easily to cook food. My Pals are Here! Science © 2008 Marshall Cavendish (Singapore) Private Limited

Good and poor conductors of heat Materials that do not allow heat to flow through them easily are called poor conductors of heat. Wood, plastics, rubber and air are examples of poor conductors of heat. Poor conductors of heat can be used to make the handles of cooking utensils to protect our hand from the heat during cooking. My Pals are Here! Science © 2008 Marshall Cavendish (Singapore) Private Limited

My Pals are Here! Science © 2008 Marshall Cavendish (Singapore) Private Limited

The end My Pals are Here! Science © 2008 Marshall Cavendish (Singapore) Private Limited