Energy

 What is energy?

Energy makes things move or change. For example, it makes machines work and living organisms grow.

Wind moves the boat. 

Fuel makes the car move. 

People get energy from food.

What are the forms of energy?

Light energy. The Sun is a natural source. Candles and lightbulbs are man-made sources of light energy.

Thermal energy. A hot oven, a fire and the Sun are all sources of thermal energy.

Mechanical energy is anything that moves. Examples are kicking a ball, the wind moving a tree and a car moving.

Electrical energy. Lighting is a natural source. Energy from power stations and batteries are man-made sources.

Sound energy. This is produced by vibrations we hear. Examples are musical instruments and a phone ringing.

Chemical energy. It comes from burning fuel, such as wood, coal, natural gas or petrol.

Energy is constantly transformed from one form to another. When you switch on a light, you are transforming electrical energy into light energy. 

Mixtures and their components

 What are mixtures?

Mixtures contain two or more substances or components. Mixtures have specific properties that are different from their individual components.

Filtration is used to separate small, solid particles that are suspended in water or air. 

Evaporation separates mixtures of solid and liquid solutions by boiling them until the liquid evaporates. 

Distillation separates mixtures of pure substances by boiling. The evaporated substance is collected and cooled back into a liquid.  

Magnetic separation is used for separating mixtures with solid components, where one of the components is magnetic.

What are heterogeneous mixtures and homogeneous mixtures?

Heterogeneous mixtures have visible components. We can see the components with the naked eye or under a microscope. Rocks with different minerals are heterogeneous mixtures. Homogeneous mixtures, or solutions, don’t have visible components.

 • Water solutions are mainly water, but contain other components. An example is salt water. 

• Gas mixtures, are made up of different gases. The air we breathe contains nitrogen, oxygen, argon, carbon dioxide and water vapour. 

• Alloys are mixtures of two or more metals that are melted and mixed together. An example is bronze, which is an alloy of copper and tin.

Materials

Materials are made of matter and have a physical shape. We classify materials into two main groups: man-made and natural.

What are man-made materials?

We use natural materials to make man-made materials. Paper is made from wood and resin. Man-made metals are made by combining natural metals. Glass is made by melting sand and mixing it with minerals. Petroleum is used to make many different materials. 

• Plastic is a waterproof material and can be moulded .

 • Nylon and polyester fibres are made from petroleum. 

 • Petrol for cars is also made from petroleum.

VERBOS TERMINADOS EN -GER, -GIR Y VERBOS TERMINADOS EN ABA

 

States of matter

 How do we classify matter?

Matter is found as a solid, liquid or gas.

Solids have a fixed shape, mass and volume. We can change the properties of the object by using force or heat. 

 Liquids don’t have a fixed shape. They take the shape of the container. They keep the same mass and volume unless we heat them. 

Gases have a fixed mass, but they don’t have a fixed shape or volume. Gases expand to fill the space around them.

El estado plasma

How can matter change?

We can change the shape of matter by applying a force. If we squeeze a plastic bottle, we change its shape. We can change the state of matter by heating or cooling it. When we burn a candle, the wax melts and becomes a liquid. When it cools down, it becomes a solid again.

What are the three states of water?

Liquid water freezes at 0 degrees celsius (0oC) and becomes solid water. Ice is solid water. When we heat ice, it melts and becomes liquid water. Liquid water becomes a gas when we heat it. Water boils and the gas, called water vapour, evaporates into the air. When water vapour cools down, it condenses and becomes liquid water again.

What is combustion?

Matter changes when we burn it. When something burns there is a chemical reaction called combustion that produces light and heat. Three elements are involved in combustion. 

 • The material that burns is the fuel. We often use wood or coal. 

 • A spark or small flame starts the process. 

 • Oxygen combines with the fuel and this produces a change.

 For example, burning wood becomes ash . Smoke is released into the air. Smoke is made up of different gases.