"Thermal Expansion and Cold Contraction" Cold and Heat PPT Courseware 2

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"Thermal Expansion and Cold Contraction" Cold and Heat PPT Courseware 2

What should you pay attention to when using an alcohol lamp?

① Strike a match and approach the wick from the side to light the alcohol lamp.

②The outer flame has the highest temperature, so use the outer flame when heating.

③ Never use one alcohol lamp to light another alcohol lamp.

④When extinguishing the alcohol lamp, hold the lamp body with your left hand, take the lamp cap with your right hand and cover it quickly and lightly. After the flame goes out, lift the lamp cap and cover it again. Do not blow out the alcohol lamp with your mouth, otherwise it will easily catch fire.

Why did the rail break into several sections?

For every 1°C change in temperature, a 1-meter-long rail expands and contracts approximately 0.000018 meters. If the temperature changes by 60°C in a year, a 1,000-kilometer-long railway will expand and contract 708 meters. If there is no gap left, it will shrink due to cold in winter. The rails are frozen and cracked into several sections. In the summer, the rails are heated and expand, and they become twisted and some are arched upward. Because of thermal expansion and contraction, there must be gaps between the rails.

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 shrinks with heat and expands with cold.

There are many phenomena of thermal expansion and contraction in life.

Telescopic bridge;

When erecting high-voltage lines, keep the wires drooping to a certain extent;

Peel the eggs (soak the boiled eggs in cold water. Since the eggshells and egg whites shrink to different degrees, they can be separated, making it easy to peel);

If the bottle cap cannot be unscrewed, you can unscrew it by scalding the bottle cap with hot water;

Removable wheels on trains, cement slab pavement, etc.

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.

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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: 2024-11-12

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

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