# STATES OF MATTER.

## Presentation on theme: "STATES OF MATTER."— Presentation transcript:

STATES OF MATTER

MATTER Affected by temperature and pressure
A change in temperature and/or pressure can change the state of matter of a substance

Kinetic Theory – Energy in Motion Three assumptions of how particles in matter behave
1. All matter is made of small particles - atoms, molecules and ions 2. These particles are in constant motion. The motion has no pattern. 3. These particles are colliding or crashing into each other and into the walls of their container.

Thermal Energy Thermal energy is the total energy of the particles in a material. Thermal energy includes kinetic energy and potential energy Solid particles do not appear to be moving but they are! Solid particles move slowly.

Absorb or Release Thermal Energy
When particles absorb thermal energy then Temperature increases or Temperature remains constant and particles transition to more energetic phase of matter When particles release thermal energy then Temperature decreases or Temperature remains constant and particles transition to less energetic phase of matter

Temperature Measure of the average kinetic energy of the vibrating or moving atoms or molecules of a substance Absolute zero = no movement Heat= the total kinetic energy of a substance

Pressure The force per unit area applied on a surface in a perpendicular direction These gas molecules are constantly moving in random directions. When a molecule hits the container wall (green), it exerts a tiny force on the wall. The sum of these tiny forces, divided by the interior surface area of the container, is the pressure.

One atmosphere is defined as the pressure caused by the weight of all the overlying air at sea level or 14.7 pounds per square inch (psi).

Solid Low Temperature and/or High Pressure Low Kinetic energy
Low Temperature and/or High Pressure Low Kinetic energy Definite pattern resulting in definite volume and definite shape Can be an atom, ion or molecule Usually in crystalline form, although some are glass

Itl.chem.ufl.edu/2045_s00/lectures/fg11_001.GIF

Liquid Less Pressure, More Kinetic Energy
Less Pressure, More Kinetic Energy Definite volume, no definite shape Melting point= the vibrations of the particles cause the forces holding the solid together to break These forces are called chemical bonds

Bonds Solid water has MORE H-bonds (4) than liquid water (~2 )

Itl.chem.ufl.edu/2045_s00/lectures/fg11_001.GIF

If solids are more compact and more dense due to high pressure, why does solid water float?
Most substances contract when temperatures decrease because the particles move closer together, but not water!

Why is solid ice less dense than liquid water?
Water expands when it freezes into ice because water is a polar molecule. The negative and positive charges are attracted to one another so when they line up that leaves empty space. Therefore water expands when it freezes or changes from a liquid to a solid.

Gas Least pressure, most kinetic energy
Least pressure, most kinetic energy No definite shape, no definite volume Evaporation (Liquid to Gas) is the boiling point of the liquid Gravity – prevents escape of gases Gas would escape to space if not for the Earth’s gravity

Itl.chem.ufl.edu/2045_s00/lectures/fg11_001.GIF

Plasma Hot ionized gas with energy temperatures above 5000°C
Violent collisions cause electrons to be knocked off Stars, lightning, neon signs, solar wind, auroras, comet tails, welding arcs, fireball made by nuclear weapons

Earth’s Plasma Fountain

Conservation of Matter and Energy
During an ordinary chemical change, there is no detectable increase or decrease in the quantity of matter. LAW Energy cannot be created or destroyed, it can only change form.

Condensation – Gas to a Liquid Releases Thermal Energy

Freezing - Liquid to a Solid Releases Thermal Energy
Freezing is an exothermic process

Melting - Solid to a Liquid Absorbs Thermal Energy
For water the temperature has to be a little over zero degrees Celsius. If you were salt, sugar, or wood your melting point would be higher than water.

Evaporation – Liquid to a Gas Absorbs Thermal Energy

Sublimation – Solid to a Gas Absorbs Thermal Energy
Skip a Phase: Solid to a Gas Carbon dioxide (dry ice), Naphthelene (moth balls) and snow sublime

*** Condensation & evaporation are opposite (type error)

Absorb or Release Thermal Energy?
Which phase is missing on this diagram?

Recap of Phase Changes Melting – Solid to Freezing – Liquid to
Evaporation – Liquid to Condensation – Gas to Sublimation – Solid to