Conservation of Energy - Science Lesson for Grade 7 Students

Understanding conservation of energy is a crucial concept for grade 7 students in science as it teaches the significance of sustainable energy consumption. By learning about the conservation of energy, students grasp the idea that energy cannot be created or destroyed but only transformed from one form to another. This knowledge empowers them to make informed choices about using energy efficiently in their daily lives, ultimately contributing to a more sustainable future. So, let's explore together how we can conserve energy and make a positive impact on the environment!

Conservation of Energy

What can neither be created nor be destroyed, but can change from one form to another? The answer is energy. Let us examine the conservation of energy that occurs in the diagram below.

Light energy from the Sun is taken in by plants and is converted into chemical potential energy. Animals depend on plants and meat from other animals for this energy. Animals and plants, when dead, decompose. The chemical potential energy from dead plants and animals is stored as fossil fuels such as crude oil and coal. This process happens over millions of years. The fossil fuels are then processed into other usable forms where the chemical potential energy is converted into kinetic, electrical, heat, light and sound energy.

Alternative sources of energy

Do you think coal, natural gas and crude oil will be available forever? Of course not. They are non-renewable sources of energy. They will be used up one day. And then what do we do for our energy needs?

Enter renewable sources of energy. They can be used repeatedly and will not be used up.

Forms of alternative sources of energy

For the coming generations, some non-renewable sources of energy may not be available. Thus, the need to find alternative means of generating energy is urgent. The chart below summarizes alternative forms of energy.

Hydroelectrical power station

A wall is built across a river which causes the water to rise behind it, thus forming a large reservoir. This wall is called a dam.

The diagram below shows how a hydroelectrical power station generates electricity. Water is stored behind the dam. The water level is higher than the position of the turbines. Water flowing in from the reservoir turns the turbines.

Geothermal energy

The Earth’s core is the source of geothermal energy. In some places, very hot rocks found deep underground heat up the underground water, turning it into steam. The jet stream that results is channelled to a turbine that can be used to generate electricity.

Fuel cells

A fuel cell converts chemical energy in fuel into electricity. A hydrogen fuel cell is an example of a fuel cell. To produce electricity, it makes use of hydrogen and oxygen. In space, hydrogen fuel cells are used in space vehicles. Some cars also use hydrogen cells.

Biomass

Heat and electricity can be generated from organic matter. Such organic matter is called biomass. It can be obtained from plant and animal waste. Biomass resources can be restocked through cultivation of crops such as fast growing trees and grass.

Solar energy

The Sun is the source of solar energy. Have you seen solar water heaters installed on the roofs of houses? They can trap the Sun’s heat to produce hot water for household use. It may also be converted into electrical energy, which can be used for household appliances. Solar cells that are placed on a roof absorb sunlight during the day and convert it into electricity. It can generate enough energy to power a whole house.

Wind energy

To generate electrical energy, wind turbines use kinetic energy of wind. Wind turbines are set up in a large open area of land or sea called a wind farm. The disadvantage of a wind turbine is that it can only function in the present of strong winds. Furthermore, it needs open, windy areas to operate.

Nuclear energy

In nuclear power plants, radioactive metals such as Uranium and Plutonium break down into lighter atoms, releasing large amounts of heat energy. This energy source is called nuclear energy. The heat boils water to generate steam which turns the turbines in the nuclear plant and produces electrical energy.

Tidal energy

Tidal power stations convert potential energy of the tide to electrical energy. The following summarizes how tidal energy is obtained.

Across the mouth of the bay, a long wall is built. The sea water flows through the wall at high tide, to get into the bay. Through the turbines along the wall, sea water flows, causing the generators to turn and produce electricity.

The water in the bay flows out to sea at low tide through the same turbines and again, they will turn the generators and produce electricity. The generation of electricity is allowed by this continuous movement of the tides as the turbines are driven by the power of the sea in both directions.