This unit deals with the concept of temperature and heat transfer. As an object is gaining or losing heat, its temperature varies with time. By monitoring the temperature change, students are able to build assumptions regarding how and where heat transfers. Students come to understand the concept of temperature through touching and using a thermometer. They discover that heat is traveling from a higher-temperature object to a lower-temperature object, and that the temperatures of the two objects will eventually equalize.

The grade 5 English science unit, Heat and Temperature, meets the academic content standards set in the Korean curriculum, which state students should:

a) Perceive the difference between cold and warm objects and measure their temperature using a thermometer.

b) Understand that the temperature of an object or environment can change over time.

c) Understands that heat transfers from a higher-temperature object to a lower-temperature object when the two are brought in contact, as well as the temperatures of the two objects will equalize as time passes.

d) Find appropriate examples of heat transfer by observing objects in students’ environments whose temperature change.

What do I need to do? You will need a glass jar, a stopper with a hole, a straw, red food coloring, clay, warm water, colored markers, card, scissors and ice-cold water or a fridge.

Some useful information

1. Add 3 drops of red food coloring to a glass jar and fill it to the very top with warm water. Put in a stopper that has a straw through it and make it airtight with clay.

2. Cut out a small piece of card and slide it onto the straw. Mark the height of the red liquid up the straw with a black marker.

3. Put your glass jar in a fridge or ice-cold water. Use a blue marker to mark the new height of the red liquid. Try putting the jar in a hot bath to see what happens.

What happened? Draw a picture of your thermometer before and after you put it in the water.

What did I learn?

1. Why does the red liquid go down when the thermometer touches something cold?

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2. Draw the particles of the water in the pictures you drew above to show how the speed and distance between them change when they are cold and hot.

A thermometer measures how hot or cold something is. If the thermometer touches something hot, the red liquid goes up the tube. The is because the particles, the things that make up the red liquid, also get hotter and start to move faster and farther apart. If the thermometer touches something cold, the red liquid goes down the tube. This is because the particles that make up the red liquid start to move slower and get closer together.

Water particle Slow moving Fast moving

Cold

Hot

These days, the red liquid in a thermometer is alcohol. In earlier days, a silver liquid called mercury was used. However, mercury is toxic, so it is not used so often now.

Before (warm)

After (cold)

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What do I need to do? You will need 3 cups, hot water, cold water, ice, and a thermometer.

Some useful information

1. Fill up one cup with hot water, one with tap water and another with tap water and ice.

2. Use a thermometer to measure the temperatures of the different water.

3. Put your fingers on one hand in the cold water and the other fingers in the hot water. Notice how the water feels.

What happened?

What did I learn?

1. When does your body feel hot?

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2. In which direction does heat move?

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3. Draw arrows in your hand pictures above to show the transfer of heat.

Water Temperature

Cold

Room

Hot

Draw a picture of your fingers in the cold water and in the hot water.

Heat is a form of energy. It always moves from hot objects to colder objects. For example, the water in the glass to the right is warmer than the ice. The heat energy from the water moves to the ice. In science, we say that the heat energy from the water is transferred to the ice. This causes the particles, the things that make up the ice, to start moving faster and they get hotter. As the particles in the ice move faster and farther apart, it starts to melt.

Your body temperature is about 36.5 degrees Celsius if you are healthy. If you touch cold water, your fingers feel cold because your body heat is being transferred to the cold water. If you put your fingers in hot water, you feel hot, because the heat energy from the water is being transferred to your body.

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What do I need to do? You will need a piece of Dars milk chocolate, a piece of Dars dark chocolate, a stopwatch, green tea teabag, hot water, and a cup.

Some useful information

1. Put a piece of Dars dark chocolate in your mouth. Don’t chew or suck it. Time how long it takes to melt.

2. Put a piece of Dars milk chocolate in your mouth. Don’t chew or suck it. Time how long it takes to melt.

3. BONUS: Put a green tea teabag in some warm water. Hold the outside of the cup with both hands and notice the feeling. What happened?

What did I learn?

1. Why does chocolate melt in your mouth?

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2. Which chocolate melted faster? Why?

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Chocolate Type Time it took to melt

Milk

Dark

When you put chocolate in your mouth, your body begins to transfer heat to the chocolate. This causes the chocolate to melt, which is a good thing, because you can only taste the chocolate once it starts melting.

The milk chocolate should melt faster than the dark chocolate in your mouth. This is because milk chocolate has more fat in it. Dark chocolate has more cocoa in it, which makes it melt slower.

Draw a picture of your hands holding the green tea cup and draw arrows to show the direction heat is moving.

Would a flashlight melt the chocolate faster than your mouth? Try it.

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What do I need to do? You will need 2 identical small glass jars, aluminum foil, a corkboard, a large glass jar, small Styrofoam balls, warm water, and a thermometer.

Some useful information

1. Pour warm water into two identical small glass jars. One of the glass jars should be covered with aluminum foil and placed in a bigger jar that has corkboard in it. Measure the starting temperature of both small jars.

2. Put the lid on the small jar that is in the big jar. Pour Styrofoam balls into the bigger jar. Then, put on the bigger jar’s lid.

3. After 10 minutes, use a thermometer to measure the temperature of the water in both glass jars. Take note of any differences.

What happened?

What did I learn?

1. Why was the thermos good at slowing down heat transfer?

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2. If you wait long enough, what will happen to the temperature in both the glass jars?

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Water Start Temp. Final Temp.

In glass jar

In thermos

Draw a cross-section of your “thermos.”

You may use a thermos to keep your cold drinks colder for a longer time, or to keep your drinks or soups hotter for a longer time. It does a better job than just leaving your drinks in a normal glass, but eventually even the drink inside the thermos will lose or gain heat to the things, such as air, around it. If you leave it long enough, the temperature of the liquid in the thermos will be the same as the liquid in the normal glass. In other words, they will both reach the temperature of the room.

Your thermos is good at slowing down heat transfer because it is made up of two glass containers, one inside the other. The shiny surface of the inner jar and the empty space between the jars helps to stop heat moving.

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What do I need to do? You will need two identical glass bottles, blue food coloring, yellow food coloring, a playing card, warm tap water, cold tap water, and a thermometer.

Some useful information

1. Add some blue food coloring to the first bottle and fill it close to the top with warm water. Measure the temperature.

2. Add some yellow food coloring to the second bottle and fill it close to the top with cold water. Measure the temperature.

3. Top up each bottle with water. Put a playing card on top the yellow water. Turn it upside down and place it on top of the blue water. Pull out the playing card. Measure the temperatures in both bottles at the end.

What happened?

What did I learn?

1. Why did the warm water go up and the cool water go down?

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2. What happened to the temperature of the water in both bottles at the end?

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When particles in liquids become warm, they move apart and become lighter. In science, we say they become less dense. Then, as the liquids become cooler, the particles get closer together and become heavier. In science, we say they become denser.

Warm liquids go up because they are less dense and cool liquids go down because they are denser. These movements in liquids are called convection currents.

If you take away the heat source, the liquids will eventually all become the same temperature. This happens because the hotter liquid has transferred its heat to the other liquid and to other things, such as the air around it.

Draw or describe what you saw.

Heat Source

Heated liquid particles move apart, get lighter, and go up.

Cooled liquid particles move together, get heavier, and go down.

Bottle Temperature Hot water Cold water

Mixed water

CONVECTION

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What do I need to do? You will need a paper plate, thread, scissors, a marker, and a heat source.

Some useful information

1. Draw a spiral that starts from the middle of the plate. Keep the width of the spiral about the same all the way through.

2. Cut out the spiral. Draw pictures of gliders at different points of the spiral.

3. Tie a thread around the top of the spiral. Hold it above a heat source. WARNING: Keep the paper plate away from the heat source or it might catch on fire. What happened?

What did I learn?

1. How do gliders go up in the sky without a motor?

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2. Why does warm air go up and cool air go down?

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When gases in the air get hotter, they start to go up. The particles in warmer air move farther apart and become lighter. This is why warmer air rises in the sky. This warm, rising air is also what lets gliders go up even though they don’t have a motor. These gliders move in a spiral path upwards.

As warm air rises, cooler air goes down. This is because the particles in cooler air get closer together and become heavier. When this cool air sinks, it begins to heat up again when it is near the ground. The particles in the air begin to move apart again and start to go up again. The movement of warmer air going up and cooler air going down is known as convection currents.

Draw or describe what you saw.

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What do I need to do? You will need spoons and dishes that are wooden, plastic and metal, beads, toothpicks, butter, hot water, a beaker, a stopwatch, and a bowl.

Some useful information

1. Put 3 small pieces of butter at the top of 3 different spoons. Add a bead to the butter. Put the spoons in hot water and see which bead falls first.

2. Your teacher will demonstrate the same concept by making ships. Time how long it takes for the toothpick masts to fall down.

3. BONUS: Put down a piece of aluminum foil and a piece of carpet on a hard floor. Step on both with your bare feet and notice the feeling.

What happened?

What did I learn?

1. Which material was the best conductor in this experiment?

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2. Explain why pots and pans are usually made of metal but have plastic handles.

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Material Which bead fell first? Time for toothpick to fall

Wood

Metal

Plastic

Some materials get hot very quickly. These materials are called conductors. Metals are very good at conducting heat. When a fire or another hot object touches the metal, the particles closest to the heat start to move faster (vibrate). These fast moving particles bump into the particles next to them, making these particles vibrate faster. These fast moving particles are transferring their heat energy which is why the metal gets hotter. The same process will also happen with plastics and wood, but it takes longer for these particles to start vibrating, so they will get hot slowly. This makes plastic and wood good insulators and they are often used as handles for pots and pans.

You should find that the aluminum foil will feel colder to touch than the carpet. This is because the metal can spread the heat very quickly from your foot.

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What do I need to do? You will need bread, cheese slices, butter, ketchup, a knife, a plate, and an oven.

Some useful information

1. Spread some butter and ketchup onto a piece of bread. Add some cheese on top of the bread.

2. Put the bread into the oven and watch as the cheese melts. The teacher will take it out when it’s ready to eat.

3. Place a thermometer in an envelope made from black paper and another in aluminum foil. Place them under direct light and observe.

What happened?

What did I learn?

1. What form of heat transfer was used to make your cheese toasty?

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2. How is radiation different to convection and conduction?

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Draw or describe what you saw.

Convection is the movement of heat in gases and liquids. Conduction is the movement of heat in solids. Both convection and conduction transfer heat by particles moving around. However, heat can also be transferred by something called radiation.

Radiation does not need particles to move heat. It sends out energy that moves in electromagnetic waves. The sun is the best example of this. The waves from the sun heat up the Earth. Fires and light bulbs also transfer energy by radiation.

Dark colored objects absorb the radiation, which makes them get hotter Light colored objects reflect radiation, keeping things cooler.

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What do I need to do? You will need corn kernels, a popcorn machine, and a plate.

Some useful information

1. Look at the size and shape of the corn kernels.

2. Put the corn kernels in the popcorn maker.

3. Look at the size and shape of the corn kernels as they are heated.

What happened?

What did I learn?

1. What made the corn kernel go pop?

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2. How was the heat from the popcorn machine transferred to the corn kernel?

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Draw or describe what you saw.

The outside of a corn kernel is called the pericarp, which helps to keep a small amount of water inside the kernel. As the water is heated, it begins to change into a gas. The gas starts to expand and the pressure inside the kernel created by the evaporating water causes the pericarp to explode open and turns the kernel inside out. The sound that you hear is a “pop,” which is the gas escaping as the pericarp breaks. This is how popcorn got its name.

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What do I need to do? You will need milk, sugar, a teaspoon, a ½ teaspoon, vanilla extract or chocolate syrup, a small Ziploc bag, a large Ziploc bag, ice, salt, 1 cup, and a bin or newspaper.

Some useful information

1. Add 1 tsp. of sugar, 60mL of milk and a dash of vanilla extract or ½ tsp. of chocolate syrup into a small Ziploc bag. Seal the bag and mix it well.

2. Fill the larger Ziploc bag about half full of ice. Add 1 cup of salt. Put the small bag in the large bag and close everything.

3. Put the bags in a bin small bin or wrap in newspaper and shake for 10 minutes. It should be ready to eat.

What happened?

What did I learn?

1. How could you make ice cream without using a freezer?

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2. How is salt useful in places that get a lot of snow?

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Draw or describe what you saw.

Water usually freezes at 0 degrees Celsius as the particles lose a lot of energy. Water changes from a liquid to a solid. However, if salt is in the water, the temperature at which it freezes gets lower.

In winter, roads can become very dangerous when snow begins to melt and forms ice. It makes it slippery to walk on and also difficult for cars to drive on. This is why road workers put salt on the roads. Doing this makes the temperature needed for the ice to form to be much lower.

When the salt was added to the ice in this experiment, it lowered the freezing point of the water. This decrease in temperature allowed the milk to freeze quickly, making ice cream.

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