# Changes in Matter - Let's Get Physical

A substance is a type of matter. For example, water is the substance that you add to cocoa to make hot chocolate. Hot chocolate is a substance that you drink on cold winter mornings.

A property is a characteristic of a substance. For example, a property of water is that at room temperature it is a liquid that it freezes at zero degrees Celsius, and at sea level it will boil at 100 degrees Celsius. Properties of hot chocolate are its warm temperature and sweet taste.

What a state!

One way to describe the physical properties of a substance is to identify its form, or state. The three states (or forms) of matter are:

• solid
• liquid
• gas

The air we breathe is a gas. The water we drink is a liquid. The desk you sit at is a solid. Many types of matter can exist in more than one state. Water is a unique substance because on Earth it naturally exists in all three states.

Each form or state of matter is different. The molecules in a solid, liquid and gas move at different speeds and are “packaged” differently. For example, the molecules in a solid are tightly packed together, while the molecules in a gas move about much more freely.

Explore this by dragging your mouse over each picture below. You will see a model of how the particles of each state of matter are moving. Watch closely for differences!

 Solid Liquid Gas

Home Activity

Changing the state of matter ...or making ice cream

Materials

• 2 cups of sugar
• 4 cups half and half
• 2 teaspoons of vanilla
• 1/2 teaspoon of salt
• Milk
• Plastic gallon jug with a lid
• Crushed ice
• 1/4 cup salt
• Spoons
• Cups
• One large re-sealable bag
• One small re-sealable bag

Note: This activity is more fun when done with a family member or friend

Procedure:

1. Put the sugar, half and half, vanilla, and the salt in the gallon jug. Place the lid on the jug and shake well to make sure all of the ingredients mix.
2. Put some of the mixture in your small re-sealable bag. Be sure to seal the bag well and do not overfill.
3. Now take your large re-sealable bag and fill it half way full of ice.  Put your small bag full of the ice cream mixture inside of the large bag with the ice.
4. Place the 1/4 cup of salt over the ice and then seal the large bags.

*STOP*  It is time to make a hypothesis. How long do you think it will take to freeze the ice cream? (In other words, how long will it take for the liquid ice cream mixture to change state to a solid?)

1. Slowly move the large bag back and forth in your hands. (Watch out ... this is COLD!)
2. When the ice cream is frozen, remove it from the bags.
3. Serve and enjoy!