seegongsik
Grade 5 (age 10-11)

grade 5 Temperature and Heat

Temperature is a number for how hot or cold something is, and we measure it with a thermometer. The tiny particles that make up an object never stop moving, and the higher the temperature, the faster they move. When two objects at different temperatures touch, heat passes from the hotter one to the colder one, and once their temperatures are equal the flow of heat stops. This is called thermal equilibrium. In the first picture, change the temperature and watch the particles; in the second, change the two water temperatures and see which way heat flows and what temperature they end up at.

Temperature and moving particles

36 °C
🌡 What does temperature tell us?
①Temperature is a number for how hot or cold something is. We use the unit °C (degrees Celsius).
②The tiny particles that make up an object are always moving, and the higher the temperature, the faster they move.
③How hot something feels to the touch can differ from person to person, so we use a thermometer for an exact reading.
④In an alcohol thermometer, the red liquid expands and rises when the temperature goes up.

Which way does heat move?

80 °C
20 °C
🔥 Which way heat moves
①Heat always moves from a hotter place to a colder place.
②When hot water and cold water touch, the hot water cools and the cold water warms up.
③After a while, once both waters reach the same temperature, the heat stops moving. This is thermal equilibrium.
④With equal amounts of water, the final temperature is about halfway between the two.

How are temperature and heat different?

Temperature and heat
Temperature: how hot or cold / Heat: energy that moves because of a temperature difference
Temperature describes the state an object is in; heat is the energy that moves.
💡 Temperature and heat are easy to mix up
①Temperature tells how hot something is, in °C.
②Heat is the energy that moves between two objects at different temperatures.
③Warming a cup of water and a full bathtub both to 40 °C takes far more heat for the bathtub.
④So even at the same temperature, different amounts of water need different amounts of heat to warm or cool.

Summary

How heat moves
Heat: hot side → cold side (until the temperatures are equal)
Once two objects are at the same temperature, heat stops moving.
🎯 Key points
①Temperature is a number for how hot or cold something is.
②The higher the temperature, the faster the particles in an object move.
③Heat moves from a higher temperature to a lower one.
④When two objects reach the same temperature, heat stops moving (thermal equilibrium).
⑤Temperature and heat are different ideas.

Examples and Unit Test

Example 1
If you put a cold spoon into hot water, which way does the heat move?
1
Heat always moves from the hotter object to the colder one.
2
So heat moves from the hot water into the cold spoon, and the spoon gradually gets hot.
▸ Hot water → cold spoon
Once the spoon and the water are at the same temperature, the heat stops moving.
Example 2
Equal amounts of water at 80 °C and 20 °C are put in contact. What happens after a while, and what is that state called?
1
Heat moves from the 80 °C water to the 20 °C water, so the hot water cools and the cold water warms.
2
Because the amounts are equal, they meet at about 50 °C, halfway between, and then the heat stops moving.
▸ Both waters reach about 50 °C. This state is called thermal equilibrium.
The second picture starts at exactly 80 °C and 20 °C, so it shows about 50 °C underneath.
Unit-test style
Which statement about temperature and heat is correct?
①Heat moves from a cold place to a hot place.
②The higher the temperature, the faster the particles in an object move.
③Temperature and heat mean exactly the same thing.
④Even when two objects reach the same temperature, heat keeps flowing one way.
⑤Heat is energy that only cold objects have.
▸ ② The higher the temperature, the faster the particles in an object move.
1
The higher the temperature, the faster the particles in an object move.
2
Heat moves from hot to cold (①), temperature is how hot something is while heat is energy that moves (③), heat stops moving at equal temperatures (④), and heat is energy that moves because of a temperature difference (⑤).
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