Energy - ESO 2 Science - Science Helpdesk

What to Learn?

In this section: - Summary of contents covered by this page.

Concepts of work and energy.
Types of material systems with regards to the exchanges of energy and matter.
Forms of energy: kinetic, gravitational potential, elastic potential, chemical, electric, nuclear, heat, light.
Transfers and transformations of energy.
Changes caused by transfers of energy; reversible and irreversible changes.
Energy in human societies: foods, fossil fuels, nuclear, biomass, aeolic, hydraulic, solar.
Types of power plants.

Basic Information

Types of Material Systems with regards to the Exchanges of Energy and Matter

The physical bodies (a living being, the Sun, the atmospheric air...) can be classified according to whether the body can exchange matter and/or energy or not:

	Exchange E	Exchange M	Examples
Open systems	Yes	Yes	Any living being: a plant, for example, takes in solar energy, takes in matter (nutrients from the soil and the air), releases energy (heat) and releases matter (O₂, seeds, leaves, etc.).
Closed systems	Yes	No	The Earth is said to be very much like a closed system, as it exchanges energy (receiving solar radiation and giving off heat) but almost no matter; but think for example of a meteoroid falling down to the Earh or an astronaut losing a screwdriver in outer space... these are exchanges of matter.
Isolated systems	No	No	They just don't exist in Nature: it is difficult to think of any object that never receives any kind of radiation from any star some light years away.

Forms of Energy

Kinetic	It is the kind of energy that results from the movement of a body. The greater the speed and the mass of a body, the more the kinetic energy it has. It is a type of mechanical energy.
Gravitational potential	It is the kind of energy that results from the position of a body with regards to the centre of gravity of the planet (or other type of celestial body) it is in. The greater the altitude, the mass of the body and the mass of the planet, the more the gravitational potential energy it has. It is a type of mechanical energy.
Elastic potential	It is the kind of energy that results from the deformation of an elastic body. The greater the deformation, the more the tendency of the object to get back to its original shape, and so, the more the elastic potential energy it has. It is a type of mechanical energy.
Chemical	It is the kind of energy that makes up the chemical bonds in the molecules, this is, the kind of energy that keeps the atoms together in a molecule.
Electric	It is the kind of energy that shows up when the electrons of a group of atoms move in an specific direction, as in an electric current: the electrons of the copper threads move continuously from one end to the other.
Nuclear	Different to electrons, which are fairly easy to detach from their atoms, the protons and the neutrons of the nucleus of an atom are very difficult to separate. The nuclear energy is the kind of energy stored in those very powerful forces that keep together the particles of an atom's nucleus.
Light	Light, and the other types of electromagnetic radiations (infrared, ultraviolet, etc.), is a type of energy transmitted by waves.
Thermal	Or heat. It is a form of energy associated with the motion of atoms or molecules in a body: the quicker they move, the greater the amount of heat that that body contains. Heat shows up as a measurable property of the bodies: the temperature.

Sources of Energy

Foods	It is the kind of energy source that heterotroph living beings (or consumers) use. We use the chemical energy contained in the food molecules (the nutrients), and although all the nutrients have chemical energy (because they are molecules and have chemical bonds), the living beings get most of the energy they need from just carbohydrates and lipids, so you are more likely to obtain energy from pasta (rich in carbohydrates) than from chicken meat (rich in proteins).
Fossil fuels	Coal, oil (or petroleum) and natural gas. They are called fossil fuels because they come from the buried and highly transformed remains of organisms that lived in the past (plankton for natural gas and oil, woody ferns for coal). They are mixtures of molecules called hydrocarbons (such as the octane of the petrol or gasoline), and they are widely used as fuels because the chemical energy of the hydrocarbons is transformed into large amounts of heat when the hydrocarbons are ignited.
Nuclear	It takes advantage of the large amounts of heat released when the nucleus of an atom is broken. This is achieved by making lonely neutrons strike the nuclei of atoms of uranium or plutonium, thus making two or three neutrons beeing expelled away from bombarded nuclei, along with a lot of heat, that can later be used in a nuclear power plant to produce electricity.
Biomass	Burning certain structures of living beings that are rich in chemical energy (such as the wood or the peat) also releases great amounts of heat that can be harnessed by humans with several purposes, that range from heating a house to producing electricity in a biomass power plant.
Aeolic	The kinetic energy of the moving air can be used by humans: in a windmill to grind flour, in an aerogenerator to produce electricity, etc...
Hydraulic	The kinetic energy of a water current (such as a river) can also be used for similar purposes, for instance in a watermill or in a hydroelectric power station.
Solar	The energy contained in the light radiations can be used, for instance, to heat water for domestic supply, or to produce electricity in a solar field.

Power Plants

The goal of power plants is to produce electricity that is later dumped into the general supply network. That electricity is produced by an electrical generator driven by a turbine, in all cases. The differences between the several types of power plants come with the way in which that turbine is moved:

· In the hydroelectric power stations, it is the water flow of a river what moves the turbine.
· In an aerogenerator it is the wind what moves the turbine (which consists of a set of three big blades).
· In the rest of the cases it is water vapour at a very high pressure what moves the turbine. That water vapour is produced by heating water, and the heat can come from...

· igniting coal or other fossil fuels or biomass (in thermal power plants);
· breaking nuclei of uranium or plutonium (in nuclear power plants).

This way, the production of heat in a power plant goes through a series of stages in which a transfer and a transformation of energy take place. The following diagram summarizes what happens in a coal-fueled thermal power plant:

Chemical energy in the coal -> Thermal energy in the water vapour -> Kinetic energy in the turbine -> Electric energy in the generator and to the supply network wires

External Links

Sources of Energy

KEWL - Energy.A basic introduction to the main renewable and non-renewable sources of energy.

Special report: energy and fuels.New Scientist extensive collection of resources to take you through a deep insight on energy and fuels.

Are biofuels bad?A scientific study says that biofuels are even worse than the gasoline for the current climatic change. Learn why.

The big thirst.Article in The New York Times pondering the worrying future of our most wanted fuel: oil.

Movies, Animations and Audios

In this section: - Series of movies and animations related to this page's topic.

DownloadPreviousNextClose

Please, Get the Flash Player to open this file.

Work

Eureka! - Work.Energy is the ability to do work, so it' time to learn what work is and how it relates to force.

Forms of Energy

Eureka! - Kinetic energy.Kinetic energy explained through billiard balls.

Eureka! - Potential energy.Let David and Goliath explain to you what potential energy is and how can it be transformed into kinetic energy.

Links List

Contact the webmaster

The following form is provided for you to help on the development of this website by sending interesting links, ideas or telling about incidental problems when browsing the site. The message will be sent to the webmaster's mailbox who, eventually, will give you a reply. All fields are mandatory.