ENERGY by pablo gomez

SCIENCE 6.

C.E.I.P. SANTA ANA (Madridejos)

UNIT 6. ENERGY.

CONTENTS: 1.– Energy. 2.– Forms of energy & transformation: 2.1.– Mechanical: kinetic / potential 2.2.– Chemical 2.3.– Thermal 2.4.– Nuclear 2.5.– Electrical 2.6.– Light 2.7.- Sound 3.– Renewable / Non-renewable energies 4.– Light: 4.1.– Propagation of light 4.2.– Types of bodies 4.3.– Reflexion / refraction 5.– Sound: Characteristics

ENERGY is the ability to do a work. .- There are different types of energy. .– It can be stored. .– It can be transformed. 1

1.– ENERGY: Energy is the property of objects to produce different changes in themselves or other objects like performing a mechanical work, emitting light, heating a material... Energy is the ability to do a work. Energy can be used when it is needed, but it can be stored: .- Plants store sunlight energy, and many years later it is transformed into petrol, gas, coal… that we use when we want to get heat or when we use a car or a motorbike. .- Animals store energy (fats, carbohidrates…) that they use to grow, to run, to live… They are natural ways to store energy. .- Energy can be stored in artificial ways too (when we use a battery…) There are different types of energy, and energy can be transformed from one kind to another. For example, plants have energy (chemical energy), and when we burn a piece of wood we get heat, so we are transforming chemical into thermal energy.

2.– FORMS OF ENERGY: There are several forms of energy, and they can be transformed into other ones. 4

USEFUL WORDS: .– energy .- to store .– thermal .– electrical

.– mechanical energy .– magnetic

.– kinetic energy .– chemical

.– potential energy .– nuclear

2 C.E.I.P. SANTA ANA (Madridejos)

2.– FORMS OF ENERGY: There are several forms of energy, and they can be transformed into other ones. 1

MECHANICAL ENERGY is the energy associated with the motion and position of an object. Mechanical energy is the sum of potential energy and kinetic energy. 2.1.– MECHANICAL ENERGY: Mechanical energy is the energy associated with the motion and position of an object. It is the sum of potential energy and kinetic energy.

A roller coaster train on the top has got a great potential energy.

A.– Potential energy: Potential energy is the stored energy depending of the position of an object. A bike on the top of a hill has a potential energy because it can go down without any effort, only by the force of gravity. B.– Kinetic energy: Kinetic energy is the energy of an object depending of its movement. For example, the wind is air in movement, and it has a kinetic energy that can move mills or wind turbines. A wind turbine is a device that converts kinetic energy from the wind into electrical power.

2.2.– CHEMICAL ENERGY: Chemical energy is stored in food, fuel, wood, coal, batteries... and it is related with a chemical transformation of some substances into other ones releasing heat, light, movement... Wood is transformed into smoke and ash, and releases thermal energy and light.

2.3.– THERMAL ENERGY: Thermal energy is also called heat. It is a kind of internal energy in substances that produces an increase of temperature. The vibration of atoms or molecules in substances produces heat. The Sun provides heat to us. We also use thermal energy stored in fossil fuels to warm our houses, cook our food or obtain electrical energy. The thermal energy from the Sun is transformed into chemical energy by plants. Plants provide us wood, and it can be transformed into coal, petroleum or gas that we can burn to get heat. 4

2.4.– NUCLEAR ENERGY: Nuclear energy is created by reactions inside the atoms of some substances like uranium or plutonium. These kind of reactions are also produced inside the sun and release a great amount of light and heat. We use nuclear energy in nuclear power plants to obtain electricity.

FORMS OF ENERGY: 1.– Mecanichal energy: potential + kinetic. 2.– Chemical. 5.– Electrical. 3.– Thermal. 6.– Light. 4.– Nuclear. 7.– Sound

USEFUL WORDS: .– mechanical energy .– kinetic energy .– thermal energy .– to release

.– potential energy .– gravity .– wind turbine .– increase of temperature

3 C.E.I.P. SANTA ANA (Madridejos)

1 2.5– ELECTRICAL ENERGY: We can see this type of energy in lightnings in storms. Electrical energy is the flow of electrons through a conductor substance. Electricity give us light, movement, heat… It also makes machines to work, like computers, microwaves ovens, TVs… We obtain electricity from the wind, rivers, the Sun, thermal power plants, nuclear plants… It is the type of energy that we use the most, because it is very easy to transform in other types of energy (light, heat, sound, kinetic, heat…)

High: Potential energy

A hydropower plant transforms kinetic energy from water into electric energy.

2.6.– LIGHT: Some objects emit a form of energy called light. These objects are called light sources. The Sun, the flame of a candle, or a light bulb are examples of light sources. Most of light on the Earth comes from the Sun, but at night we use light bulbs (electrical energy), or candles (chemical energy), or a torch with batteries (chemical energy).

The Sun or a light bulb are light sources.

2.7.– SOUND: Sound is an energy made of vibrations. Vibrations spread from a sound source, and they travel through the air, liquids or solids, except in vacuum. We can hear sounds with our ears. 3.– RENEWABLE / NON-RENEWABLE ENERGIES: An energy source is everything which can be used to produce energy for light, heat, machines... There are two groups of energy sources: Renewable and non-renewable. 3 3.1.– NON-RENEWABLE SOURCES OF ENERGY: A non-renewable resource is a finite resource. They run out as we consume them. Most of them are fossil fuels (coal, petroleum, natural gas, uranium…). They are very polluting for the environment, but nowadays most of energy consumed by human is from fossil fuels. A.– Coal: was formed by decomposition of great dense forests. They were buried under the soil, and temperature and pressure change them into coal. We use coal to produce electricity in thermal power stations. B.– Petroleum: was formed millions of years ago, when large quantities of dead organisms (zooplankton, algae…) were buried under intense heat and pressure. We get butane gas, petrol, diesel fuel… that we use mainly for transportation, producing plastics… They are obtained in refineries. C.– Natural gas: is formed by methane and other gases, and it is found in the extraction of petroleum or coal. It is used for heating, cooking in houses, and electricity generation. D.– Nuclear power: is the use of nuclear processes to generate useful heat and electricity. Nuclear fission of some radioactive elements (uranium…) produces a lot of energy in nuclear power stations. USEFUL WORDS: .– lightning .– hydropower plant .– vacuum .– to run out

.– flow of electrons .– light source .– renewable .– fossil fuel

.– microwave oven .– light bulb .– non-renewable .– to pollute

Extraction of coal in a mine.

Production of fuel in a refinery.

.– coal .– to bury .– refinery Structure of a nuclear power

C.E.I.P. SANTA ANA (Madridejos)

Solar panels.

3.1.– RENEWABLE SOURCES OF ENERGY:

There are never ending energy resources that do not pollute environment. The most common ones come from the Sun, the wind and the water. a.- Solar energy: Solar panels get energy from the Sun to produce electricity and thermal energy to heat water. b.– Wind energy: win turbines produce electrical energy from the wind. c.– Hydropower energy: stored water in reservoirs contains a large amount of energy. This water moves electric turbines to produce elecHydropower energy. tricity. d.– There are other renewable resources of energy like: .– Biomass: obtaining energy from organic matter to produce biofuel. .– Geothermal: is a type of energy generated and stored in the Earth’s crust, used for heating and electricity. 4

Light is a kind of energy that makes plants grow and it can be converted into electricity.

4.– LIGHT: Light is a kind of radiation (energy) from light sources that permits us to see objects and distinguish shape, size and colours. There are two types of light sources: .– Natural sources: like stars or the Sun. They produce their energy 5 from nuclear explosions on the Surface .– Artificial sources: like light bulbs, fluorescent tubes, candles… The rest of objects reflect light. In a dark room we can’t see anything because objects don’t reflect light, but we can see them when they reflect any kind of light. This is the reason because we see the Moon. The Moon reflects light from the Sun. When light meets an opaque object, this object blocks the light and forms a shadow on the opposite side of the object.

Sunlight is produced by nuclear explosions.

4.1.- PROPAGATION OF LIGHT. Light travels from one place to another, this movement is called propagation. Light moves in this way: a .– Light travels straight: we can see straight rays of light in a foggy day, or from the headlights of a car. b.– Light moves in all directions: the light from a candle in a dark room moves in all directions to everywhere. c.- Light travels very fast ( 300.000 km per second, through vacuum). Light can move through air, water, glass...

shadow The Moon reflects sunlight.

Light travels straight in all directions and very fast (300,000 km/s). USEFUL WORDS: .– solar energy .– wind energy .– biomass .– geothermal .– natural /artificial sources

.– hydropower energy .– light source .– shadow

Rays of light travel straight in all directions.

C.E.I.P. SANTA ANA (Madridejos)

4.2.– LIGHT AND MATTER: When light gets to an object, light can pass through it or can’t do it depending on the material of the object. Materials can be classified in three groups: A.- Transparent materials: they allow light to pass through the material, and we can see clear images behind them (water, glass windows…). B.- Translucent materials: they allow light to pass through the material, but you can’t see clear behind them, you only can see blurred objects (some kinds of plastic or glass). C.- Opaque materials: they do not let any light to pass through the material, and you can’t see anything behind them. They produce a shadow (a dark space behind an opaque object with light in front of it (wood, metals…) Types of materials: .– Transparent. .– Translucent. .– Opaque. Properties of light: .– Reflection. 1 .– Refraction. .– Colour. Transparent

Translucent

Opaque

4.3.- PROPERTIES OF LIGHT. Light has two main properties: reflection and refraction. A.- Reflection: is the change in direction of light when it collides with a body, and light returns (is reflected) and then we can see this body. Reflection permits us to see objects. A mirror is an opaque body with a polished surface that reflects light and images. There are some types of mirrors: A.1.- Plane mirror: which has a flat surface, and doesn’t change shape and size from objects. A.2.- Curved mirrors: change shape and size from objects.

A curved mirror changes shape and size.

B) Refraction is the change of direction of light when it changes from one transmission medium to another (from air to water…).If we put a pencil into a glass of water, it looks like it is bent. This is because light speed in air is different than light speed in water. Refraction is used to make lens. A lens is a transparent piece of glass or plastic with one or two curved sides. Light is refracted inside, and changes its direction, and images are modified (We can see them bigger and more clear). Refraction in a glass of water.

C.- Colour. White light from the Sun is formed by seven colours from the rainbow: red, orange, yellow, green, blue, indigo and violet. Dispersion of light is the separation of white light into the seven colours. When it rains, and sunrays go through drops of water, white light disperses and forms the rainbow in the sky. When objects receive white light, they absorb different colours and reflect the rest of them. If we see an object in red, is because the object absorbs all colours and it reflects the red one. Snow reflects all colours, so we can see it in white. On the contrary, coal absorbs all colours and does not reflects any of 7 them, so we see coal in black.

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Dispersion of light in seven colours.

.– transparent .– reflection .- plane mirror .– dispersion of light

.– translucent .– refraction .– curved mirror

.– opaque .– lens .– sunrays

Reflection of white light in different objects.

C.E.I.P. SANTA ANA (Madridejos)

SOUND is a form of energy produced when objects vibrate, and transmit waves to the air or another material. 5.- THE SOUND. Sound travels in waves, and travels in all directions from the source of vibrations. Sound can travel very fast but not as fast as light (340 m/s). Sound waves can travel through gases, liquids and solids, but never through the vacuum because there are no particles to vibrate.

Vibrations can produce some changes in objects: the sound waves from an explosion can break window glasses. The sound can be produced in many ways: from a hit, a scratch, a blow… These actions make objects vibrate, so they produce different sounds. Waves travel through the air and come to our ears, make vibrations on our eardrum, ossicles… and finally our brain listens the sound.

Vibrations from guitar strigs produce sounds that travel to the ear.

When sound waves reach an obstacle, they can be reflected. If the obstacle is at a long distance (more than 17 metres), we can hear this reflected sound when it returns back. This phenomenon is called echo. So we hear two sounds: first the original sound and then the reflected sound, which is the echo. Echo is the reflexion of sound waves. You hear two sounds: the original and the reflected one.

Sound waves from an explosion break windows.

5.1.–CHARACTERISTICS OF SOUND. When an object vibrates, produces a special sound. This sound is transmitted by waves. These waves have a frequency. Human ear can identify different sounds because of their characteristics. 1.-Intensity (volume): is how much energy a sound can transfer. There are: .– Loud sounds (very intense: a scream). .– Quiet sounds (less intense: a whisper). 2.-Pitch: is the number of vibrations per second of the sound. There are: .– High pitched sounds (high frequency: lots of vibrations per second). .– Low pitched sounds (low frequency: few vibrations per second). Children have high voices and men have low voices. 3.- Quality or timbre: is the difference in the quality of sound. This is the reason because we can distinguish one source of sound from another one. We can identify one person from another one, or an instrument from another one. 4.– Duration: is the length of the sound from the moment that it starts, till the moment it finishes. There are short and long sounds.

Loud sound (high volume)

Quiet sound (low volume)

High pitched (a whistle)

Low pitched (a bass guitar)

Characteristics of sound: .– Intensity: loud / quiet. .– Pitch: high / low. .– Quality or timbre. .– Duration: short / long

USEFUL WORDS: .– sound wave .– vibration .– echo .– intensity/volume .– quite .– pitch .– low .– quality/timbre

.– vacuum .– loud .– high .– duration