Energy

Natural sciences

Grade 9

Energy, forces and machines

Module 18

Energy

Activity:

Naming, discussing and identifying energy sources and different forms of energy

[lo 2.2; lo 2.3; lo 2.4]

What is energy?

• Energy is the ability to do work: to make things happen and to bring about change.

Forms of energy:

• Energy occurs in different forms, e.g. as sound, warmth, light, chemical compounds and electricity.
• Some objects have energy because they have motion, or simply because of their position. This has to do with kinetic energy (motion) or potential energy (position).
• Energy cannot be seen or felt through touch, but is present everywhere: in the surrounding air, in each piece of matter, in each of the cells that make up our bodies. Energy is the only thing that existed before the big bang that marked the origin of the universe!

Sources of energy

• Energy in ELECTROMAGNETIC form plays an important role in technological innovations like radio transmission towers, microwave ovens and X-ray machines.Scanners are machines that reveal images of things that are normally invisible, e.g. the internal organs of the body. The scanner sends sound waves into the body. When the patterns formed by the waves change, it shows an image that is of value in helping medical practitioners to make a diagnosis. The image that is produced is known as an MRI or Magnetic Resonance Image. This process is invaluable in the field of medicine.
• We can distinguish three important sources of energy, namely:

• the sun
• atomic nuclei
• the movement of the earth and its gravity, and the effect that other planets have on the earth.

• Solar energy originates from the collision and fusion of atoms (nuclear fusion). This energy reaches us in the form of light and warmth. Heat energy causes atmospheric currents that result in wind, another important potential source of energy. Heat energy also results in evaporation of water, which leads to the formation of clouds which bring rain. When rain falls in high-lying areas, rivers are formed, yet another important source of energy.Solar energy is also captured in foodstuffs when photosynthesis occurs in plants. The food we eat and the fuel we use (e.g. petroleum) are derived from this process.
• Nuclear energy is obtained when people use advanced technology to split atoms. Nuclear power stations convert nuclear energy into electrical energy.
• The movement of the earth and its gravity, together with the influence that other planets exert on the earth , work together to create ocean currents and to cause the downward flow of rivers. Such energy can be utilised in different ways, e.g. for transportation or for driving machines, like turbines.

Try to identify the form of energy illustrated by each of the following examples and explain the sources of such energy.

[LO 2.2; LO 2.3; LO 2.4]

Activity

Illustrating the law of energy conservation by means of different examples of energy conversion

[lo 2.4]

Conservation of energy

• Herman Helmholtz (1821 – 1894) developed the law of ENERGY CONSERVATION.
• This law states that ENERGY CANNOT BE CREATED OR DESTROYED . It can only be converted from one form to another.

Indicate the form of conversion that is relevant in each of the following instances:

• A ball rolling from the top of a hill

• A piece of wood burning

• The ESKOM power stations

• Pumping up your bicycle wheel

• Sun panels attached to a satellite

• A boy eating an ice-cream

• A torch shining

• A modern submarine travelling along the coastline

• A person skating on ice

• A water wheel

• A pistol shot

• A glowing electric light bulb

Write critical comments on the following statement: A steam train runs on solar energy .

Assessment of insight into the conservation of energy

Could you provide examples of the law of energy conservation?

[LO 2.4]

Assessment

LO 2: Constructing Science Knowledge:

The learner will know and be able to interpret and apply scientific, technological and environmental knowledge.

This is evident when the learner:

• categorises information;
• interprets information;

2.4 applies knowledge.

Memorandum

Energy

Activity

Forms of energy illustrated:

• Mill: Kinetic
• Atomic bomb: Nuclear/atomic
• Radio tower: Radiation
• Heater: Radiation
• Battery: Chemical
• Light bulb: Radiation
• Food: Chemical

Table:

Activity

• Ball: potential to kinetic and sound
• Wood: chemical / potential to sound, light, heat
• Eskom: chemical / potential to electrical
• Bicycle wheel: chemical / potential to kinetic/mechanical
• Satellite: radiation to electrical
• Ice-cream: chemical / potential to chemical / potential (stored in the body) to kinetic
• Torch: chemical / potential to light and heat
• Submarine: atomic / nuclear / chemical to electrical to kinetic
• Skating: chemical / potential to kinetic
• Water wheel: kinetic to electrical
• Pistol: chemical / potential to kinetic, heat and sound
• Light bulb: electrical to light and heat
• Yes: Steam is derived from coal, which is dead plant material formed means of photosynthesis, with the help of sunlight (radiation by energy).