Heat and Matter

Once students have modeled an atom, they investigate how the motion of atoms changes when heat is added to or removed from a substance. In this lesson, students carry out an experiment to observe how heat affects the movement of liquid molecules.

• Water is a kind of matter because it is made up of atoms.
• Water is found throughout Earth in all three states, and it is a sign of life for scientists who are exploring Mars because it is necessary for life as we know it.
• Water molecules change their motion depending on the amount of heat present. It is the amount of heat present that determines whether water is found as ice, liquid water, or water vapor (a gas)
• Heat makes liquid water molecules move faster and spread out more.

• Why is water considered matter?
• What would happen to the water in a lake if all of the water molecules were removed?
• What do solid ice, liquid water, and water vapor all have in common?
• What are the properties of ice?
• What would happen to a piece of ice if it were left outside on a hot day?
• How can water vapor that is in the atmosphere, which we cannot see, be made up of the same molecules that make up liquid water and ice?
• What is an example from everyday life of water changing from liquid water to water vapor?

Misconception:  Only Earth has gravity.

Fact: All matter has gravity. All objects near Earth’s surface are pulled on by Earth’s gravity because Earth is the most massive object near us.

Misconception: Earth doesn't move in the solar system. 

Fact: The sun’s gravity keeps Earth and the other planets in orbit.

Misconception: If an object is at rest, no forces are acting on it.

Fact: Forces are constantly acting on objects both at rest and in motion. 

Atom : the smallest piece of matter that has the properties of an element; a combination of three subatomic particles: protons, neutrons, and electrons

Cause and Effect : a relationship between events or things, where one is the result of the other

Force : a push or pull that acts on an object, changing its speed, direction, or shape

Gravity : a force of attraction between all matter

Mass : a measure of the amount of matter that makes up an object; a property of matter

Matter : everything that has mass and takes up space

Pattern : something that happens in a regular and repeated way

Scale :the size, extent, or importance (magnitude) of something relative to something else

Science : all knowledge gained from experiments

Earth is unique. Unlike on Mars, water molecules are found almost everywhere on Earth, in all three states. Water molecules make up the ice found in glaciers. They make up the liquid water in the oceans. Water molecules also make up the water vapor gas that mixes with air.

Ice is water’s solid state. A solid has its own shape until something changes it by force. Solids such as ice hold their shape because the atoms that make them up are packed tightly together. They do not have enough energy to move past one another.

Liquid water has no shape of its own. It takes the shape of its container. This is because the atoms in a liquid are close together but can slide past one another. This is why liquids flow.

Water vapor is water’s gas state. A gas takes the shape of whatever it is in. It will spread out to fill all of the space it is in, no matter how big the space is. This is because the atoms in gasses are far apart and move with a lot of energy.

Changing States

Water isn’t the only molecule that can be a solid, liquid, and gas. Every atom and molecule can be turned into a solid, liquid, or gas when the right amount of heat is added or taken away. Matter changes state because of the amount of heat present. Heat causes the motion of atoms to change.

When you add enough heat to a solid, it will become a liquid. When you add enough heat to a liquid, it will become a gas. If you take away enough heat from a gas, it will become a liquid. If you take away enough heat from a liquid, it will become a solid.

In this lesson, students conduct an experiment to answer the question: “How does heat affect the movement of liquid water molecules?” Students compare the height of liquid water in a straw before and after it is heated. Then, they use the data they gathered in the heat and matter experiment as evidence to support the claim that the behavior of atoms determines the properties of matter.