Changes of State3.2

Think about this•What happens to a puddle of water on a warm day?•What happens to ice if left outside on a warm day?•What happens to a pond during very cold temperatures?

Changes between Solid and Liquid

•States of matter depend on molecular motion.•Matter changes states when thermal energy is added or taken away.

• (((O)))(((O)))= O O•Solids become a liquid by getting so much energy they move faster and faster then are broken free from their fixed position.•When a solid changes to a liquid we call this MELTING.• How do we know when a solid gets too much

energy and will break free from their fixed position?• Melting point- a certain temperature that will

cause a solid’s particles to break free. • SOLID TO LIQUID= MELTING

Changes between Liquid and Solid

The opposite of melting is ____________? •Freezing- the change from a liquid to a solid.• When a substance freezes the particles in a

liquid move so slowly that they begin to take on fixed position, freezing. Or becoming a solid.

•In order to make something freeze, or become a solid you must take awayENERGY.

How do you do this? By placing a substance into a freezer, and the freezer slows down the particles by taking away energy and turning liquids into solids. •Melting and freezing are reversible, and are NOT chemical changes.

Think about this• Liquids do not only freeze at low temperatures.

• Name solids that melt at room temperature (about 20˚ Celsius)

• What happens when these materials cool from a liquid state?

• *Becoming a solid is the same as freezing even when it occurs at room temperature* (candle’s FREEZE)

Changes between Liquid and Gas

Vaporization- takes place when the particles in a liquid gain enough energy to move independently, forming a gas.

Two types of Vaporization1. Evaporation- when a liquid vaporizes only on the top surface

of a liquid.

2. Boiling- when a liquid changes into a gas from below and on the surface.

• Boiling Point- the temperature at which a liquid boils.

Opposite of Vaporization:CondensationCondensation – is the change in state from a gas to a liquid.

• Ex: Breathing into a mirror.

• When the warm water vapor from your breath reaches the cool surface of the mirror the water vapor condenses into liquid droplets.

What happens?

During condensation gas particles lose enough thermal energy to form a liquid.

As the gas travels through the air it loses some of it’s thermal energy

• For condensation to occur temperatures must drop.

Changes between Solid and Gas?

Sublimation- occurs when surface particles of a solid gain enough energy that they form a gas. • During sublimation particles of a solid do not pass

through the liquid state as they form a gas. • As dry ice changes states it absorbs thermal

energy.

• Typically this occurs in colder climates where there is snow, and usually the temperature will remain below 0 Celsius but still lose snow from the ground.

• How does the motion of the particles change during sublimation?

Think about this

Energy

((0)) ((0)) ((0))particles go crazy

Energy

O Oparticles go crazy

Melting

Vaporization

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