"Thermal Expansion and Cold Contraction" Cold and Heat PPT Courseware 3

Description

"Thermal Expansion and Cold Contraction" Cold and Heat PPT Courseware 3

Think about it:

How to make a flat table tennis ball inflate?

abnormal expansion of water

Water above 4 ℃ has the same properties of thermal expansion and contraction as other objects, but in the range of 0 ℃ to 4 ℃, it does shrink with heat and expand with cold.

Activity 1: What methods can you use to verify whether metal expands with heat and contracts with cold?

Experimental materials: metal balls, metal rings, alcohol lamps, matches, cold water

Do solids expand with heat and shrink with cold?

1. Heating a metal ball, the metal ball _____(can/can't) pass through the metal ring. Explain that the volume of metal at temperature _____ is _____.

2. After immersing the metal ball in the cold water in the beaker, the metal ball _____ (can/cannot) pass through the metal ring. Explain that the volume of metal at temperature _____ is _____.

Summary: Solids also expand with heat and shrink with cold.

The purpose and structure of alcohol lamp

Purpose: The heating temperature of the alcohol lamp is between 400-500, which is suitable for operations where the temperature does not need to be too high.

Structure: The alcohol lamp is composed of a lamp pot, a lamp cap and a wick tube.

One use

1. Use a match to light the alcohol lamp.

2. When heating, use external flame heating.

3. When extinguishing the alcohol lamp, cover it with the lamp cap.

Second check

1. Check whether the wick is intact.

If the top of the wick is uneven or burnt, cut off a little.

2. Check whether there is an appropriate amount of alcohol in the lamp.

Generally, it should not be less than 1/4 of the volume of the lamp kettle, nor should it exceed 2/3 of its volume.

Three strictly prohibited

1. It is strictly forbidden to use a burning alcohol lamp to light another alcohol lamp, or to light a fire on a burning alcohol lamp.

2. It is strictly prohibited to add alcohol to the burning alcohol lamp.

3. Do not use your mouth to blow out the alcohol lamp.

practise

1 When pouring cement on the road surface, use thin wooden boards to divide it into small pieces for the purpose of ( )

AConvenient construction

B Prevent water from seeping down

C Prevent pavement damage due to thermal expansion and contraction

2 Xiao Ming put the empty bottle with the rubber stopper in the refrigerator and took it out after 15 minutes. The stopper could not be removed. The main reason was ( )

The air in bottle A leaked out

B bottle mouth shrinks when exposed to cold

The gas in bottle C shrinks when it gets cold

When the water boils, the aluminum kettle whistles, revealing the truth.

After the water is boiled, the water vapor in the aluminum kettle expands due to heat, and a large amount of gas escapes out of the kettle, which blows the whistle on the lid of the kettle and makes a whistle.

knowledge application

1. When the can cannot be opened, how can you open the lid of the can?

2. Why are the wires between two telephone poles tight in winter and loose in summer?

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For more information about the PPT courseware "Cold and Heat Thermal Expansion and Cold Contraction", please click the Cold and Heat ppt Thermal Expansion and Cold Contract ppt tag.

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Update Time: 2024-10-05

This template belongs to science courseware Hunan Education Edition Third Grade Science Volume 2 industry PPT template

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