Heat, light and electricty.

1.What is heat?

Heat is a means of tranferring energy between two bodies that are at different temperatures.

When a hot body and a cold body are in contact, there is a tranfer of energy from the hot body to the cold body. For example; when we put an hot egg that it,s 80C inside the water that it,s 15 C, and pass a determinated time, the water became mild.

The effects of heat on matter: bodies which receive heat, can change in size, as well as state.

Changes in size:

Expansion: occurs when body size increases when it is heated.

Contraction: occurs when a body cools down.

Changes in state:

Matter is found in one of these three states:solid,liquid or gas. When it is heated,it can change state.

2.Light.

What is light? Light is a form of energy.

Characteristics of light: - -Light travels in straight line. -It travels in all directions at great speed: 300,000 kilometers per second.

Light sources:: light can be natural or artificial. Natural light: the sun. Artificial light.: the light bulb.

Materials and light::

Types of materials:

Trasparent materials.: these materials allow light to pass through them without dispersing the light.

Transluscent materials: these materials allow light to pass through them but disperses the light.

Opaque materials:these materials do not allow light to pass throught them.

Reflection and mirrors: the reflection is when light hits an object it changes direction. it is a property of light that allows us to see. -Flat mirrors; produce images indentical to the actual image. - Curved mirrors: produce images different to the actual image.

Refraction and lenses: refraction is when light changes direction.- Convering lens: they make the light rays meet at a point .- Diverging lens: they make the light rays move apart.

3.Electricity.

Static electricity: Matter has a fundamental property called electrical charge.There are two different types of electrical charge, positive and negative.

Neutral bodies:are the bodies that have the same number of positive and neative charges.

Electrically charged bodies: are the bodies that get the energy when they are rubbed together.

How materials react to static energy: if two bodies come together, they will behave differently depending on the type of charge each one has:

Same type of charge: materials with the same type of electrical charge repel each other.

Different type of charge: materials with a different type of electrical charge attract each other.