Heating Matter and Changes in State

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Observe how the particle behave and the change in state that occurs when matter is heated. Head to ngscience.com for a range of related resources for use in the classroom and at home.

Most matter changes state when it is heated or cooled. Some matter requires large increases or decreases in temperature before it changes state. Gold is a solid at room temperature. It needs to be heated to over 1,000oC (1,832oF) before it begins to melt. Other matter can change state more easily.

On Earth, water exists in three states – as solid ice, liquid water and as the gas water vapor. Let’s take a look at the temperature changes that must take place for water to change from one state to another.

At room temperature, water is in a liquid state. When water is cooled to 0oC (32oF), it begins to change into solid ice. This process is called freezing and the temperature at which this occurs is called its freezing point. So, the freezing point of water is 0oC.

At temperatures below 0oC, ice will remain in its solid state. If ice is heated, it can change from a solid to a liquid. The process in which matter changes from a solid to a liquid is called melting. The temperature at which this begins to occur is called the melting point. The melting point of matter is the same as its freezing point. So ice has a melting point, 0oC (32oF).

When water is heated it changes from a liquid into the gas water vapor. This process, called evaporation, occurs more rapidly the more water is heated. At 100oC (212oF), water begins to boil. Boiling is the process by which a liquid rapidly changes into a gas. When water boils, it changes into an invisible gas called steam. The temperature of a boiling liquid does not increase, even when more heat is added.

Have you ever noticed water droplets form on the side of a cold glass of water? The droplets of water form when water vapor in the air cools as it comes in contact with the cold glass. This process of changing from a gas to a liquid is called condensation. Condensation can occur at any temperature.

What Is Matter?
Inflate a balloon by blowing air into it. Notice that the balloon gets bigger. The amount of space the balloon takes up – its volume – increases. The air in the balloon, the balloon and even you are matter. Matter is anything that has mass and volume.

Mass is the amount of matter an object has. Mass is measured using a scale or balance and is commonly measured in kilograms, grams, ounces or pounds.

Volume is how much space the matter takes up. The foam ball and the baseball are both made of matter. Volume is commonly measured in cubic units, milliliters or liters.

Observe the foam ball and the baseball on the balance. Notice that the foam ball takes up more space than the baseball – it has a greater volume. However, the baseball has a greater density and greater mass.

Matter is made up of tiny particles, called atoms. They are the basic unit of all matter. Atoms are so small they can only be seen with special high-powered microscopes.

Matter typically exists in three forms or states – solids, liquids or gases. The state matter is in depends on the arrangement of its atoms.

Matter comes in three different states – solids, liquids and gases. Each state of matter has unique properties.

The objects around you, such as your desk, chair, books and pencils are solid matter. Solids are matter that have a fixed shape and volume. The particles that make up solid matter are tightly packed together. This gives solid matter its rigid shape.

The shape and volume of a solid does not change when it is placed in different containers. If you take a solid and move it between different containers, its shape and volume does not change.

As the particles in sold matter are not free to slide past each other or move about, solid matter cannot be compressed.

Water, fruit juice and cooking oil are examples of matter in a liquid state. Like solids, liquids have a fixed volume. This means the amount of space taken up by a liquid always stays the same. Like solids, liquids cannot be compressed.

Compared to a solid, the particles that make up a liquid are less tightly packed together. They are free to slide past each other. This property allows liquids to flow and change shape.

A liquid will spread out to take the shape of the container it is in. When you pour some milk from a carton or bottle into a glass, the shape of the milk changes, but the volume of the milk remains the same.

Like solid matter, liquids cannot be compressed.

Gases are matter that can change in both shape and volume. You can’t always see gases, but they are all around you. The air you breathe is a gas. The water vapor released from a boiling kettle is also a gas.

If you take a balloon filled with air and squeeze it gently, you will notice that the shape of the balloon changes.