What is a physical change?

A physical change is a changes that changes the form of an object without changing the state of matter

How matter changes state

If you read my post on Matter, there are three common states of matter: solid, liquid, and gas.

Changes of state

• Solid to Liquid(melting)
  • When a solid melts into a liquid, the particles in a solid move faster and become less dense. It then turns into a liquid.
• Liquid to gas(evaporating)
  • The particles in a liquid move around faster and become less dense to form a gas
• Gas to liquid(condensing)
  • the particles in a gas move around less and become less dense to form a liquid
• Liquid to solid(freezing)
  • the particles in a liquid stop moving to form a solid.

What is Sublimation?

Sublimation is when a solid object turns directly into a gas without turning into a liquid first. An example of this is dry ice, which sublimes at room temperature.

When matter changes state

Matter changes state only when the temperature is high enough.

The boiling point is the temperature at which a substance boils or evaporates. The boiling point of water is 100°C.

The melting point is the temperature in which the substance melts. The melting point of water is 0°C.

The freezing point is the temperature in which the substance freezes. The freezing point of water is 0°C.

What are Thermal Expansion and Thermal Contraction?

Thermal expansion is when the volume of an object increases because of a gain in heat. This is because the particles start to move around faster.

Thermal contraction is when the volume of an object decreases because of a loss of heat. This is because the particles start to slow down.

How are expansion and contraction used?

This ability is used in thermometers. The alcohol inside of it expands if there is heat and becomes higher. The alcohol decreases if there is less heat and becomes lower.