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Inside Collection (Course): Natural Sciences Grade 5
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All matter around us consists of very small particles (atoms) that constantly move back and forth and collide with each other. These particles and their movements are so minute that we are unable to observe it. To our eyes, a piece of iron looks like a hard, solid piece of metal, but even the hardest metal consists of moving particles (atoms).
Matter expands because the particles (atoms) of which objects consist absorb energy when they are heated and therefore move around more. When the movement increases, more space is needed. Expansion therefore forces particles to move further away from one another.
When the temperature decreases (the matter loses heat), the particles have less energy and move at a slower pace. Because the movements are smaller, less space is needed and contraction occurs.
Expansion
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Contraction
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Let us have a look at how energy affects solid substances, liquids and gases.
Refresh your memory. Complete the following sentence by writing solid substances or liquids or gases in the spaces:
Under normal conditions (room temperature, normal air pressure)
has the same form as the container in which it is
kept, but the form of does not
change and most spread out in all directions and
fill the available space.
Your educator will do a demonstration. Carefully observe what happens and answer the questions that follow.
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Why is this?
Does it open more easily?
Explain:
Let us take a look at examples from everyday life:
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When railway girders are laid, spaces must be allowed at the joins because the metal will expand when it becomes warm (with rising temperatures) and the railway line would bend.
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Windowpanes are cut smaller than their frames because both will expand on warm days and contract on cold days.
What would happen if the pane fitted the frame exactly?
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Do you notice how these pictures differ?
Explain the difference to a partner. Make your own deduction and write your response in the following space.
See if you can find the following in the science laboratory:
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A copper ball-and-ring
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A composite bar
Can you explain why it is like this?
Complete:
All solid substances do not expand equally when they are
and they do not contract equally when they are .
More interesting facts:
Gaps are necessary when concrete slabs are laid for pavements. Why?
A dentist cannot simply use any material as a filling for a cavity.
Explain the reason for this:
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.
Activity 1
Refresh your memory: liquids, solids and gases (in this order).
Activity 2
Difficult to unscrew: When the food was preserved, it was hot. The lid was screwed on tightly. Because it is made of metal, it shrank when it cooled down. The food also shrank. This means the lid became smaller and was sucked down tightly by the shrinking food.
Hot water makes it easy to open: solids do not expand to the same extent. The lid is made of metal and expands more than the glass. When the hot water flowed over the jar, the lid expanded more than the glass and it could be unscrewed without much effort.
A tight-fitting pane: the pane can crack because it expands when it becomes hot and is constricted by the frame.
Telephone wires: the wires become longer when it is hot. They may have been put up on a cold day, and when it becomes hot, they hang loose.
Composite rod:
1. The rod bends.
2. Copper expands more rapidly than iron. Therefore it becomes longer than the iron and the curve is towards the iron side.
3. The ball does not go through, because it has expanded through heating.
4. The ball has cooled down and shrunk.
Fill in:
Heated, cooled.
Something interesting:
Concrete expands when it becomes hot. Therefore it will crack in order to move out of position if it has no space in which to move. It must be a material that reacts to heat in the same way that teeth do, otherwise it would expand or shrink more rapidly. It would cause it to become loose, or the tooth could crack.
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Last edited by Siyavula Uploaders on Mar 14, 2009 8:31 am -0500.