Day: January 21, 2010

Energy makes change possible. We use it to do things for us. It moves cars along the road and boats over the water. It bakes a cake in the oven and keeps ice frozen in the freezer. It plays our favorite songs on the radio and lights our homes. Energy is needed for our bodies to grow and it allows our minds to think.

Scientists define energy as the ability to do work. Modern civilization is possible because we have learned how to change energy from one form to another and use it to do work for us and to live more comfortably.

Energy is found in different forms including light, heat, chemical, and motion.

Can you identify which energy type(s) is found from these appliances?

Solar cells can be used to convert light energy into electrical energy, but they are expensive. Solar panels are a much cheaper way of using energy from the Sun. Solar panels will absorb heat energy from the Sun to heat water.

Some houses have solar panels, which help to heat water that is used for washing and for heating. Even on cloudy day, the water in the panels will absorb some heat. The water may not quite get hot enough to heat the house, but less fuel will be needed to bring it up to the right temperature.

1. Loft insulation 2. Super efficient LED lights 3. Micro CHP system 4. Household waste collected to feed CHP system

5. Ground source heat pump 6. Cut bills by about £425 a year 7. Double glazing and shutters 8. Solar thermal panels to provide hot water

reference: http://news.bbc.co.uk/2/hi/7113165.stm

If lots of different things are jumbled up together, we have a mixture.

Continue reading “Dissolving”

Solids, liquids and gases are the three states of matter. We can tell solids, liquids and gases apart by looking at how each material behaves. The materials have different properties.

Materials come in 3 forms, solid, liquid and gas.

1. Solids

• Do not flow and keep their own shape.
• Cannot be squashed.
• Solids are more dense than liquids or gases.
• (Examples) Solids include, wood, iron, bricks.

1. Liquids

• Flow easily and take on the shape of the container holding them.
• If we want to carry a liquid, we need a sealed container.
• Cannot easily be squashed into a smaller volume.
• Less dense than solids
• Examples: Liquids include, water, orange juice, tomato ketchup.

1. Gas

• Gases flow easily and do not have a shape.
• Can easily be squashed into a much smaller volume.
• Examples:  Gasses include, air, oxygen, carbon dioxide, nitrogen.

Diver carries all the air that she will need to breathe during her dive. The small cylinder her back contains enough air to let her stay under the water for about an hour.

In one day, a person normally breathes the volume of air contained in a small room. We can only get all this air in to a small cylinder if we squash it.

When we squash a gas, we make its volume smaller. Gases do not have a fixed volume – this fill the whole of the space they are in. When we put the gas into the cylinder, we change its shape and its volume.

Substances can change state when energy is added to or taken away from them. Phase describes a physical state of matter. The key word to notice is physical. Things only move from one phase to another by physical means. If energy is added (like increasing the temperature or increasing pressure) or if energy is taken away (like freezing something or decreasing pressure) you have created a physical change.

One compound or element can move from phase to phase, but still be the same substance. You can see water vapor over a boiling pot of water. That vapor (or gas) can condense and become a drop of water. If you put that drop in the freezer, it would become a solid. No matter what phase it was in, it was always water. It always had the same chemical properties. On the other hand, a chemical change would change the way the water acted, eventually making it not water, but something completely new.

Play game and learn about states of matter