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.