Unit 6 Energy
Energy and its properties
Everything around us is constantly changing: living things grow, clouds move, rivers flow, volcanoes erupt ... Energy is the cause of all these changes.
Forms of energy
Energy can manifest itself in very different ways and in each case receives a different name.
Light. It is the one with the light. It is the energy that plants use to carry out photosynthesis and that makes vision possible, for example.
Thermal energy. All bodies have energy within them. The greater the thermal energy of a body, the higher its temperature.
Electric energy. It is the one that gives rise to lightning or the one that circulates through cables and operates many machines and household appliances.
Chemical energy. It is stored in some substances, such as food, fuels, and explosives. Also in objects such as batteries and batteries. We use the chemical energy of food.
Kinetic energy. It is the one with moving bodies, like a car or the wind. They also have bodies that are elevated, because they can begin to move.
Nuclear energy. It is the one with some substances, such as uranium or plutonium. A small amount of these substances contains a lot of energy.
Energy properties
Energy is transformed. One form of energy can be converted into another. In fans and dryers, electrical energy is transformed into mechanical and thermal energy.
Energy is stored. For example, cells or batteries store chemical energy and provide it in the form of electrical energy when needed.
When we hold a swing we are storing mechanical energy. When released, this energy gives rise to the movement of the swing.
Energy is transferred. The same form of energy can pass from one body to another. For example, the player's mechanical energy is transferred to the bat and then to the ball.
Thermal energy transfer is another example. It occurs between bodies that are at different temperatures.
Energy is transported. Energy sources, such as wood, coal or gas, are transported so that energy can be obtained from them far from where they are produced.
Energy sources
Energy sources are the natural resources from which we obtain the energy we use.
There are two types of energy sources: renewable and non-renewable.
Renewable energy sources
Renewable energy sources are those that are not spent even when used.
The most important renewable sources are:
• The Sun. The Sun emits energy in the form of light and heat.
The light is captured by photovoltaic plates and is transformed into electrical energy.
The heat is captured with solar collectors. It is used to provide heating or hot water in homes and can be transformed into electrical energy.
• Wind. The wind has mechanical energy, which is capable of moving objects such as the blades of mills or sailing ships. It is about wind energy.
Wind turbines are large mills that produce electrical energy when turned by the wind.
• Water. Water, when in motion, has mechanical energy. To take advantage of it, dams are built in rivers that create waterfalls. Its energy is transformed into electricity in hydroelectric plants. Electricity can also be produced from the mechanical energy of waves and tides.
• The internal heat of the Earth. The Earth has thermal energy inside, called geothermal energy. This type of energy can be used directly to heat water or for heating, or it can be transformed into electrical energy.
• The biomass. They are all the remains of living things, such as wood, straw or cattle feces. This biomass has chemical energy. From biomass, electrical energy or thermal energy can be obtained, and it can even be transformed into fuel for automobiles.
Non-renewable energy sources
Non-renewable energy sources are limited natural resources, so they can be depleted. There are two types:
• Fossil fuels. They are coal, natural gas, and oil. Coal and natural gas are used in thermal power plants to produce electricity or are used for heating homes.
From petroleum, gasoline and diesel are obtained, which are used in transportation, for heating and also in thermal power plants to obtain electrical energy.
• Uranium and plutonium. They are substances of mineral origin. They are used in nuclear power plants, where their nuclear energy is transformed into electrical energy.
Problems of energy use
Thanks to the use of energy, we have many comforts. For example, we can effortlessly travel long distances or use our appliances. But the use of energy also has negative consequences.
Depletion of resources
Fossil fuels and nuclear fuels are limited natural resources and therefore are non-renewable energy sources; therefore, if we continue to use them, there will come a time when they will run out.
Radioactive waste
Nuclear power plants do not emit carbon dioxide into the atmosphere, but produce waste by generating energy. These wastes are radioactive, that is, they emit radiation that can cause serious illness to living beings. Furthermore, radioactivity can last thousands of years on some of this waste.
Acid rain
When fossil fuels are burned, substances are released into the atmosphere that bind to rainwater and form acid rain. This rain is very damaging to plants. In addition, acid rain can affect areas far from where the pollution is emitted.
Greenhouse effect and global warming
The Sun's energy reaches Earth. The planet's surface absorbs a part of this energy.
Most of the energy received by Earth is emitted back into space.
Carbon dioxide from the atmosphere retains that energy and returns it to the Earth's surface, causing the planet's temperature to rise.
This is the greenhouse effect, and it allows the Earth's temperature to be adequate for life.
Large amounts of fossil fuels have long been used, the use of which causes an increase in the amount of carbon dioxide in the atmosphere. This causes the greenhouse effect to increase and, therefore, the planet's temperature to rise. This phenomenon is known as global warming.
Global warming is altering the planet's climate. This can have all kinds of consequences, such as rising sea levels, which would affect coastal areas.