States of Matter!

First of all, what is matter?

Matter is anything that occupies space and has mass. If you can see, touch, taste, smell, or feel it then it's matter.

There are three main states of matter...

Solid, liquid, and gas (or vapor)

The arrangement of the molecules and how they behave determine the state of the substance.

Molecule - a group of atoms bonded together

Atom - small building block or unit of matter

The molecules within a substance are attracted to one another which keeps them close, but each of those molecules has energy associated with how much they move about within the substance. The amount of movement of the molecules and the distance between the molecules within the substance determine its state.

Solid - molecules are tightly packed together and don't move about much within the substance; ex. ice, wood, and metal

A solid has a fixed structure, a definite shape. Its shape and volume do not change. Its molecules are packed closely together in a particular pattern and cannot move about freely. Molecules are able to vibrate back and forth in their places, but they cannot break the rigid structure.

Liquid - molecules are some distance apart and can move about and bump into one another within the substance; ex. water, oil, and blood

A liquid is a substance that flows freely. It does not have a defined shape, but it does have a fixed volume. The energy movement of its molecules causes them to overcome the attractive forces between them. This allows the liquid to take the shape of the container that holds it. Although the particles do move freely, they are still relatively close to one another.

The speed at which molecules move in a liquid is called viscosity. 

Viscosity - the resistance to flow, sometimes referred to as the friction between the molecules of the fluid

Gas - molecules are far apart and can move about freely within the substance; ex. air, stream, and smoke

A gas is composed of molecules that are spread far apart. Gas (or vapor) does not have a fixed shape or volume. Its volume and shape are dependent on its container. Unlike a liquid, a gas will expand to fill up the entire container in which it is placed. Gas molecules have relatively high kinetic energy, which means that they move quickly and are able to overcome the attraction between them and separate.

Compressibility - measures the change in volume resulting from applied pressure

A state of matter is not always permanent. The changes in temperature or pressure affecting matter are called phase changes, such as these...

Melting - occurs when solid turns into liquid

The melting point is the temperature at which the solid melts. Heat increases the kinetic energy (movement) of the molecules inside the solid. The increased energy and movement break the attraction between the molecules and allows them to move away from one another.

Freezing - is what happens when a liquid becomes solid

This is caused by reducing the temperature. As the temperature decreases, the molecules inside the liquid have lower kinetic energy (movement). When the molecules can no longer overcome their attraction to each other, they form an ordered structure or a solid. The point at which a liquid becomes a solid is called the freezing point.

At standard atmosphere pressure, above 100 degrees Celcius, water is a gas (or vapor). Between 0 degrees Celcius and 100 degrees, water is a liquid. Below 0 degrees Celcius, water is a solid.

Vaporization - occurs when a liquid turns to vapor (gas)

Vaporization or evaporation happens when molecules break the surface and are in contract with the air. For example, sweat is a liquid that forms on your body to regulate your temperature when you are hot. If you don't wipe it off, it will dry. The liquid (sweat) has absorbed energy from your body and then vaporized or evaporated into the air. When you boil water, some of the liquid turns into steam. That is because the heat increases the kinetic energy of the molecules and they move faster and then farther apart, resulting in vaporization.

Condensation - the opposite of vaporization; it occurs when a gas turns into a liquid

 When a gas cools, the molecules slow down, attract each other, and then move closer. They stick together and becomes a liquid. For example, if you place a lid on a pot of boiling water, you would see drops of water form on the inside of the lid. That is condensation. The hot steam hits the colder lid and turns the steam back to liquid.

Sublimation - when a solid becomes a gas, without ever becoming a liquid

Normally, states go from solid to liquid to gas, but sublimation skips a step. It is rare because it requires specific conditions to occur, such as the right temperature and pressure. For example, dry ice sublimes when the solid carbon dioxide turns from ice directly into CO2 gas.

When a gas/vapor changes to a solid, it's called deposition. For example, frost on a cold winter morning or snow forming within clouds.

Phase diagram - a way to show the changes in the state of substance as it relates to temperature and pressure

A phase diagram is usually set up so that the pressure in the atmosphere is plotted against the temperature in degrees Celsius or Kelvin. The diagram is divided into three areas representing the solid, liquid, and gaseous states of the substance. Every point in the diagram indicates a possible combination of temperature and pressure for the substance. The regions separated by the lines show the temperature and pressure that will most likely produce a gas, liquid, or solid. The lines that divide the diagram into states show the temperature and pressure at which two states of the substance are in equilibrium.

Another way of showing what happens during a phase change is to use a heating or cooling curve. This graph shows the temperature of the substance vs the amount of heat absorbed at a constant pressure. As substances heat, they absorb energy and change state.