UNIT 8. ENERGY,HEAT, SOUND and LIGHT

UNIT 8. ENERGY, HEAT, SOUND and LIGHTWHAT IS ENERGY? 

Energy is everything that can produce a change in matter. 

CHARACTERISTICS OF ENERGY: 

• Energy has not got mass or volume.
• You cannot see energy, but we can measure energy.
• Energy can be contained with matter.
• Energy cannot be destroyed.
• Energy can be perceived in various ways.

 TYPES OF ENERGY 

• KINETIC ENERGY: energy that produces movement. Such as: wind, water…
• CHEMICAL ENERGY: energy of chemical substances.
• THERMAL ENERGY: energy that produces heat.
• LUMINIUS ENERGY: energy that produces light.
• ELECTRICAL ENERGY: energy that produces electrical currents through the movement of electrons.
• MAGNETIC ENERGY: energy that attracts metals.

 ENERGY SOURCES 

Energy sources are certain materials or natural events which emit energy that we can use. They can be: 

• Renewable energy: cannot run out because there is a lot or it can be replaced as we use it.

Examples: sun, water, wind, biomass…

• Non renewable: can run out because it cannot be replaced as we use it.

Examples: pretoleum, natural gas, coal…

 HEAT 

Temperature is the amount of thermal energy that we can measure. Heat is the transfer of thermal energy from one type of matter to another type of matter with lower temperature. This transfer can be: 

• By contact: when the two types of matter are in contact.
• At a distance: for example when we receive the heat from the Sun.

 The effects can be: 

• Variations of temperature: when heat is transferred to an object, the temperature decreases.
• Physical changes: matter can change in state. For example from solid, to liquid.

 SOUND 

Sound is the transfer of movement. Sound has got kinetic energy, the vibration is transferred to whatever is around the object (air, water, another object…) 

The effects can be: change shape, vibrate or break.

 LIGHT There are natural sources of light (Sun, stars…) and artificial ones (bulbs). Characteristics of lights: 

• It travels in a straight line.
• It travels in all directions.
• It travels faster than any other type of energy.

 Matter and light: there are different types of materials: 

• Transparent materials: allow light to travel through them.
• Examples: air, water, glass.
• Translucent materials: allow some light to pass through them.
• Examples: plastic
• Opaque materials: don’t allow light to travel through them.
• Examples: wood, iron, mirror…

Some materials react to light and produce a light phenomenon. There are three types: 

• Dispersion: when the white light separates into different colours when it passes through a substance. An example is the rainbow.
• Reflection: occurs when a light ray bounces off a surface and changes direction. An example is a mirror.
• Refraction: is the bending of light as it passes from one transparent substance into another. There are two types of lenses:

              A convex lens curves outwards

               A concave lens curves inwards.