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    This module and collection are included inLens: Siyavula: Natural Sciences (Gr. 4-6)
    By: Siyavula

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Energy as a source of heat

Module by: Siyavula Uploaders. E-mail the author

NATURAL SCIENCES

Grade 5

ENERGY AND CHANGE

Module 35

THE USE OF ENERGY BY HUMANS

ACTIVITY 1:

To discuss energy as a source of heat

[LO 1.3.1; LO 2.1]

Let us take a look at how we can make use of direct sunlight.

  • Do this exercise first to determine the POWER of the light of the sun. (POWER has to do with how much energy it has)

Use a magnifying glass to burn your name onto a sheet of paper.

Figure 1
Figure 1 (graphics1.png)

Describe what happened (use the words solar energy, concentrate, heat, burn):

Why should empty glass bottles not be left lying around in the veld?

Activity 2:

To use solar energy to heat water by means of solar panels

[LO 3.1.1]

Figure 2
Figure 2 (graphics2.png)

These solar panels collect the thermal energy of the sun. This simple method can supply a house with warm water without the use of electricity. The panels consist of long pipes that lie folded against each other to increase the surface that gets radiated as much as possible. The pipes are linked to the water system in the house.

Unfortunately the sun does not shine all day and the heat that is radiated in some seasons, e.g. during winter, is not adequate. We therefore have to make plans to also make use of other sources.

Activity 3:

To use stored energy for heating

[LO 3.1.1]

In the past the most common way of obtaining warmth was to burn some substance to release the stored energy as warmth or heat.

Wood is still used for this, particularly in rural areas. Open fires and fires in fireplaces or drums supply many people with heat in winter. South Africans are also known for their love of braaiing.

Unfortunately people often use valuable wood that is collected from the veld. This wood should be left to decay so that the valuable substances in it can return to the soil from which the tree obtained it. If the wood is collected and burned, the soil is impoverished and plants will eventually not be able to grow in it. This results in disturbance of the natural balance and causes deviations like the warming of the earth.

Fortunately people also often use wood from trees that are planted in plantations.

Figure 3
Figure 3 (graphics3.png)

Coal is burnt in some old-fashioned stoves and fireplaces to generate heat to cook food or to release warmth. It is interesting to realise that this actually means that we release solar energy that was stored millions of years ago!

Paraffin is still widely used by people in remote areas. These areas often do not have electricity yet and the people make use of Primus stoves. Paraffin is burnt in the unit to release energy that cooks the food.

Figure 4
Figure 4 (graphics4.png)

Describe in five sentences how the people’s methods to release stored energy by combustion, has improved over course of time.

Activity 4:

To use friction to supply energy

[LO 1.1.1; LO 3.1.1]

  • Friction can also be used to release stored energy in the form of heat.

Rub your hands together hard and fast. What do you feel?

Place a piece of sandpaper against a piece of wood and rub it hard and fast against the wood for ± 20 seconds. Can you feel that your fingers feel heat?

Now list some more examples where heat is released through friction:

How did cave dwellers start a fire by means of friction?

Figure 5
Figure 5 (graphics5.png)

Activity 5:

To use energy for mechanical purposes

[LO 2.1]

  • Mechanical systems such as engines cannot function without energy. In the past a lot of the energy was obtained directly from nature.

Wind mills work, for example, with wind.

Figure 6
Figure 6 (graphics6.png)

Steam trains were used (from 1712 until the 1900s) to transport people and goods. Coal was burnt to heat water that released steam. The steam was used to drive the engine that turned the wheels. You can visit the museum in George where old steam locomotives are exhibited.

Figure 7
Figure 7 (graphics7.png)

Think of three more examples where energy is applied for mechanical purposes and describe each one briefly.

Assessment

LEARNING OUTCOME 1: SCIENTIFIC INVESTIGATIONSThe learner will be able to act confidently on curiosity about natural phenomena and to investigate relationships and solve problems in scientific, technological and environmental contexts.

ASSESSMENT STANDARDS

We know this when the learner:

1.2.1 follows instructions for setting up apparatus and executing observations;

1.2.2 collects data from observation by means of sketches and labels;

1.2.3 perseveres until a result is obtained or continues to observe over an extended period of time;

1.3 evaluates data and communicates findings: provides feedback on progress in group context, as well as the eventual result:

1.3.1 presents data obtained from observation that are relevant to the target question.

LEARNING OUTCOME 2: CONSTRUCTING SCIENCE KNOWLEDGEThe learners will know and be able to interpret and apply scientific, technological and environmental knowledge.

ASSESSMENT STANDARDS

We know this when the learner:

2.1 recalls meaningful information: the minimum requirement is the ability to describe the features and characteristics of objects, materials and organisms in simple terms.

2.1.3 say whether energy can be converted from one form to another.

LEARNING OUTCOME 3: SCIENCE, SOCIETY AND THE ENVIRONMENTLearners are able to show understanding of the underlying connections of technology, the community and the environment.

ASSESSMENT STANDARDS

We know this when the learner:

3.1 understands science and technology in the context of history and indigenous knowledge:

3.1.1 describes traditional shelters and connects some features of such shelters with modern dwellings.

Memorandum

Activity 1

The magnifying glass concentrates the sunlight energy onto one point; thus the heat is concentrated and the paper is ignited.

Parts of the bottle, especially the bottom, function as a magnifying glass and can start a fire.

Activity 3

Initially only wood was used. A lot of wood is necessary because wood does not burn for long. Open fires were used and a lot of heat was lost. Later the fires were made in containers. The coal was used. Coal burns longer than wood. Paraffin is needed in even smaller quantities. Learners can expand on this topic and mention things that have not been referred to in previous paragraphs.

Activity 4

The hands become warm.

Any examples: tyres on tar, spacecraft entering earth’s atmosphere; engine that is running without oil; fishing line that runs swiftly over one’s finger; drilling into wood or iron: smoke forms as a result of the heat; a match drawn against the side of the box (in earlier times against the sole of a shoe); cigarette lighter.

A thin stick was twirled between the palms while its point rested in a hole or hollow in a larger piece of wood. The hole caused the friction area to be greater. The thinner wood eventually ignited.

Activity 5

Petrol/diesel engines: the energy in the fuel explodes and sets energy free; this creates pressure that makes the piston move and the engine turn.

Electrical equipment, for example a doorbell. The current creates forces that make the little hammer vibrate.

Water that makes a water-wheel turn, which then activates a mill.

A cyclist that transfers energy by pedalling which makes the wheels turn.

A person who turns a hand grinder, for example to mince meat.

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A lens is a custom view of the content in the repository. You can think of it as a fancy kind of list that will let you see content through the eyes of organizations and people you trust.

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