changes from heat reflect One winter day, you sit by a window inside your warm home. You watch the snow pile up on the ground. You see small animals slide across a frozen pond in your backyard. You can see their hot breath as steam clouds in the cold air. You are drinking a cup of cocoa. You see steam rising from the mug, and you know it is too hot to drink. So you add an ice cube to the cup and wait for the melting ice to cool your cocoa. Solids, liquids, and gases are all around you. The solid ice in the pond, the liquid cocoa, and the steamy air are different states of matter. What is matter? How are solids, liquids, and gases different? Why did the solid ice cube melt into liquid when you put it into your cocoa? What are the three states of matter? Matter is the stuff all things are made of. It is a word that describes everything. Trees are made of matter. The Sun is made of matter. Even you are made of matter. Although trees, the Sun, and your body are made of different stuff, it is all matter. All matter is made up of tiny particles. You cannot see them with your eyes, but scientists know they are there. These particles act differently if they are in a solid or a gas. Matter comes in three different forms, or states. Matter can be solid. In solids, the particles are packed close together. They don’t move much. Because of this, a solid has a shape and size that doesn’t easily change. Solids are often hard and sturdy. Ice is a solid. There are many other solids in the world. Some solids you might see in your classroom are desks, the floor, windows, paper, and yourself. If you put a solid in a bowl, it keeps the same size and shape it had outside of the bowl. That is a good way to remember a solid. Matter can also be liquid. In liquids, the particles move around more than a solid. However, the particles are still close together. You can pour liquids. A very common liquid on Earth is water. The drinks you have with your meals are liquids, too. If you put a liquid in a bowl, it doesn’t keep its size and shape from before. It will spread out and fill the bowl from the bottom. Think of pouring a glass of milk. It takes the shape of whichever glass you choose.

Can you find solid, liquid, and gas forms of matter in this picture?

The third state of matter is gas. In gases, the particles are very far apart and move around a lot. A gas has no shape and no size. It spreads out until it cannot spread anymore. Air is made of gases. Even though you can’t see many gases, you can often smell them. Have you smelled a hot pizza from across the room? Have you caught the scent of baking cookies in the oven? The smells are gases reaching your nose.

© 2013-2014 Accelerate Learning - All Rights Reserved

7

changes from heat what do you think? Take a look at these pictures of different types of matter. Which picture shows a solid? Which picture shows a liquid? Which picture shows evidence of a gas?

How does heating cause matter to change state? Matter can change from one state to another by heating or cooling. When matter changes state, it does not change what it is. For example, ice is solid. When it is heated it becomes liquid. Although the ice has changed to a liquid, it is still water. Ice is the solid form of water. When you heat something, you add energy to it. This causes the particles to move faster and farther apart. Heating solids turns them into liquids. Turning a solid into a liquid is called melting. Ice melts into liquid water. Any solid can melt into a liquid if it is heated enough. Some solids melt if they are at room temperature. Ice melts if it is sitting outside the freezer. You may have seen butter melt on hot popcorn or ice cream melt in the warm sun. Sometimes a lot of heat is needed to melt a solid. To melt metals like gold and iron, you must heat them to very high temperatures. When they are liquids, they can be poured into different shapes for jewelry, coins, or furniture. The liquid cools and the metal becomes solid again. If you add heat to a liquid, it becomes a gas. A pot of water on the stove bubbles when it boils. Bubbles are proof that liquid is turning into gas. Bubbles are full of air. The gas form of water is called water vapor. This is related to the word evaporation. Evaporation is when a liquid turns into a gas.

8

© 2013-2014 Accelerate Learning - All Rights Reserved

changes from heat try now Find a partner. Then, try to change solid ice to liquid water by adding heat. For this activity, you will need: • 3–5 ice cubes

• 1 cup warm water

• 3 plastic cups

• stopwatch/timer

• 1 spoon 1. Fill a cup with warm water, about ¾ full. 2. Place one ice cube in the water. Start the timer. 3. One partner stirs the ice water with the spoon. The other partner times how long it takes the ice to melt. Write down the time. 4. Next, put an ice cube in an empty cup. Set it outside in the sunlight. 5. Time how long it takes the ice cube to melt. Write down how long it takes. 6. Have one partner hold an ice cube in their hands. The other partner times how long it takes to melt. Write down the time. 7. Compare how long it took each ice cube to melt. Which way melted the ice cube the fastest? Why do you think this way worked best? Suggest another way that you could change ice into water. How does cooling cause matter to change state? A solid can turn into a liquid, but can a liquid turn into a solid? Can gas become liquid? Certainly! Matter changes states in this direction by cooling. When a liquid cools, the particles pack closer together. Eventually, the liquid becomes a solid. This is called freezing. You can make popsicles or ice cubes by freezing liquid juice or water. Liquids are poured into ice cube trays and put in the freezer. The cold air in the freezer causes the particles in the liquid to pack closely together and freeze into a solid. A similar thing happens when a gas becomes a liquid. The fastmoving gas particles slow down when they cool. They move close together and form a liquid. This is called condensation. Have you seen water droplets form on the outside of a glass of ice water? If so, then you have seen condensation happen. The water on the glass came from the air. Water vapor in the air touched the side of the cold glass. When it did, the gas particles slowed down. The water vapor changed into a drop of liquid water.

© 2013-2014 Accelerate Learning - All Rights Reserved

Water vapor in the air condenses on the outside of this cold glass.

9

changes from heat look out There is no such thing as “adding” cold. Cold is the absence of heat. In order to cool an object, heat is removed from it. The heat moves somewhere else. So the object is left cold. For example, if you hold an ice cube in your hand your hand gets cold. Heat is being removed from your hand. But where does the heat go? As the heat moves out of your hands, the ice cube warms up and starts to melt. The heat is moving into the ice cube. Scientists in the Spotlight: Anders Celsius (1701–1744) Every type of matter will change from a solid to a liquid at a certain temperature. This temperature is called the melting point. The melting point of ice is 0°C. Every type of matter will also change from a liquid to a gas at a certain temperature. This temperature is called the boiling point. Water’s boiling point is 100°C. The °C in these values stands for “degrees Celsius.” The Celsius scale is used to measure temperature. It is named after Anders Celsius. He was a Swedish scientist who invented the scale. He based it on the melting and boiling points of water. These round numbers—0 and 100—make the Celsius scale easy to use. In comparison, the Fahrenheit scale measures the melting point of water at 32°F, and the boiling point of water at 212°F. The Celsius scale is always used for scientific measurement and commonly used by most countries around the world. Only a few countries including the Cayman Islands, Belize, and the United States still use the Fahrenheit scale. What predictions can we make about the changes in states of matter? You have learned that matter can change states between solid, liquid, and gas. You have also learned heat is either added or removed to make those changes. Knowing this, you can make predictions about changes in states of matter. For example, what do you predict will happen if you leave a container of frozen yogurt out on the kitchen counter for a couple of hours? If you predicted heat from the air would melt the frozen yogurt, then you are correct. What do you predict will happen to a puddle of water on a hot, sunny day?

10

© 2013-2014 Accelerate Learning - All Rights Reserved

changes from heat what do you think? Look at the table below. Column A shows objects in one state of matter. Column C shows the same object in a different state of matter. In Column B, write whether heat was added or heat was removed to cause the first object (Column A) to become the second object (Column C). The first one has been done for you as an example. Here’s a hint: Think of whether each object in Column A was heated or cooled. Column A Lake in winter

Column B Heat is added.

Column C Lake in summer

Chocolate sauce

Chocolate pieces

Stick of butter

Melted butter

© 2013-2014 Accelerate Learning - All Rights Reserved

11

changes from heat What Do You Know? Matter changes states between solids, liquids, and gases. Adding or removing heat causes these changes to happen. 1. Decide if each picture shows melting, freezing, evaporation, or condensation. 2. Then, describe the change of state taking place. 3. Finally, decide whether heat is added or removed in the process.

1. This shows

.

2. The change is from

2. The change is from to

.

. .

1. This shows

.

3. Heat is

.

2. The change is from

12

.

to 3. Heat is

3. Heat is

1. This shows

1. This shows

.

2. The change is from to

to

.

. .

3. Heat is

.

© 2013-2014 Accelerate Learning - All Rights Reserved

changes from heat connecting with your child Changes from Cooking To help your child learn more about changes from heat, cook with them in the kitchen. Prepare a few simple dishes that involve changing food into different states of matter. For example, a simple pasta dinner includes several opportunities to observe changes from heat. Help your child boil water for pasta. Encourage them to predict what will happen when heat is added to the liquid water. Then have them observe and describe what they see. Point out that the bubbles in the water indicate gas is forming through evaporation. Also, if there is a lid on the pot, point out the condensation occurring on the inside of the lid when the hot vapor touches the cooler lid.

Here are some questions to discuss with your child: • How does cooking cause a change of state? • Which changes of state required heat to be added? Which needed heat removed? • Where else can we observe melting, freezing, condensation, and evaporation around the house or in our daily lives?

To learn more about freezing, make juice popsicles for dessert. Have your child pour juice into ice cube trays, cover them with foil, and then poke a toothpick into each square for the handle. Place the trays in the freezer to solidify. Have your child check on the popsicles as they freeze, and observe how they gradually become solidified. Before eating the popsicles, have your child predict what will happen when you eat them. Encourage them to describe the changes of state that occur in our mouths when we eat frozen foods and how heat is transferred between the cold food and our warm tongues.

© 2013-2014 Accelerate Learning - All Rights Reserved

13