Changing States Changing States of Matterof Matter

PART ONEPART ONE

What states of matter do you know?

We are going to analyse just three of them, the main ones:

SolidLiquidGas

Now, name at least two examples for each of the three states.

Materials can be changed from one state to another by adding ...

energyenergyAnd what's the easiest energy around?

Probably heat!

But matter changes if you take away heat from it, too.

Adding energy is

HEATING

Taking away energy is

COOLING

HeatingHeat can change solids into liquids or gases.

Most solids melt into liquid when they are heated.

A liquid evaporates into a gas when it is heated.

Let's see what happens to water.

If ice (solid) is heated, it changes to water (liquid). This change is called

melting.

Water (liquid) can change to water vapour (gas). This is called

evaporation.

If water (liquid) is heated until it boils, it changes to water vapour (gas) very quickly.

Cooling

Cold can change gases and liquids.

Gases may change to liquids. This change is called

condensing.

Liquids may change to solids. This change is called

freezing.

Cooling

If water vapour (gas) is cooled, it changes to water (liquid). This change is called

condensing.

If water (liquid) is cooled, it changes to ice (solid). This change is called

freezing.

Different solids melt at different temperatures, some high, some low. These

are called their...

melting points.

Different liquids freeze at different temperatures.

Scientists use something called a freezing point to measure when that liquid turns into a solid

Finally, different gases turn to liquids at different condensation points.

Sublimation: · This is when a solid, on heating, directly

changes into a gas without melting, AND the gas on cooling re-forms a solid directly without

condensing to a liquid. They usually involve just a physical change

BUT its not always that simple!

Chemical vs. Physical Changes

It is important to understand the difference between chemical and physical changes.

The two types are based on studying chemical reactions and states of matter. Physical changes are about

energy and states of matter.

Chemical changes happen on a molecular level.

When you melt an ice cube you have forced a physical change (adding energy).

That example caused a change in the state of matter.

You can cause physical changes with forces like

motion, temperature,

pressure.

Now, we know matter can change from one state to another.

But what happens inside matter when such changers occur?

Pressure

Let's start it all over agian...

What is a solid?

Solids are usually hard because their molecules have been packed together.

The closer your molecules are, the harder you are.

Solids also can hold their own shape. A rock will always look like a rock unless something

happens to it.

Even when you grind up a solid into a powder, you will see little tiny pieces of that solid under a microscope.

Liquids will move and fill up any container.

Solids like their shape.

In the same way that a solid holds its shape, the

atoms

inside of a solid are

not allowed to move around too much.

This is one of the physical characteristics of solids.

Atoms and molecules in liquids and gases are bouncing and floating around, free to move

where they want.

The molecules in a solid are stuck.

The atoms still spin and the electrons fly around, but the entire atom will not change position.

The second state of matter we will discuss is a liquid.

Solids are hard things you can hold. Gases are floating around you and in bubbles.

What is a liquid? Water is a liquid.

Liquids are an in-between state of matter. They can be found in between the solid and gas

states.

They do not have to be made up of the same compounds. If you have a variety of materials in a

liquid, it is called a solution.

One characteristic of a liquid is that it will fill up the shape of a container.

It fills the bottom first because of gravity. The top part of a liquid will usually have a flat

surface. That flat surface is because of gravity too.

A special force keeps liquids together. Solids are stuck together and you have to force them apart. Gases bounce everywhere and they try to spread themselves out. Liquids actually want to stick together.

There will always be the occasional evaporation where extra energy gets a molecule excited and the molecule leaves the system.

Overall, liquids have cohesive (sticky) forces at work that hold the molecules together.

A special force keeps liquids together.

Solids are stuck together and you have to force them apart.

Gases bounce everywhere and they try to spread themselves out.

Liquids actually want to stick together. There will always be the occasional evaporation where extra energy gets a molecule excited and

the molecule leaves the system.

Overall, liquids have cohesive (sticky) forces at work that hold the molecules together.

PART TWO: AFTER THE SIMULATIONPART TWO: AFTER THE SIMULATION

All matter is made up of tiny particles called atoms.

These particles are always moving and are attracted to one another. A

material's state of matter is determined by the movement of the particles.

The more energy they have, the further apart they want to get from each other.

SolidsA solid is the state of matter that has the least

amount of energy. It has a definite shape and volume.

The particles of a solid are packed close together.

The particles of a solid are moving, vibrating back and forth, but they don't have enough energy to

break away from one another.

A liquid is matter that has a definite volume but no definite shape.

A liquid takes the shape of its container but keeps the same volume.

The particles in a liquid move more freely than those in a solid, but do not have

enough energy to move apart from one another

Gas is matter that does not have a definite shape or volume.

The particles in a gas are far apart and move quickly in all directions.

A gas can expand or be compressed much easier than a liquid and a solid.

Think of a balloon filled with air. What happens if you squeeze the air into a smaller part of the

balloon? The gas particles or random groups of atoms, get

closer together. Most gases are invisible, such as the air you

breathe.

Plasma, the 4th state of matter, only happens at very high temperatures. Plasma

is a lot like a gas, except for the fact that electrons get stripped from neutral atoms

of the element. It does not occur naturally on Earth, but can be found in neon signs, fluorescent lights,

plasma tv's, and lightening. Most of the visible universe is in the state of plasma, such as stars, which are big balls of

gases (hydrogen & helium) at really high temperatures.

What happens when I add energy to a solid?

Physical ChangeA Physical Change is a change in the way an object looks, but not in what the object is made of. Changing of state, such as a

pond freezing in the winter is an example of a physical change. The appearance of the pond has changed, but the composition of the water has not changed, it is still made

of hydrogen and oxygen. Changing shape is also a physical change. Like crumpling

paper, cutting a banana, or slicing an apple are all examples. When you cut, tear, grind,

or bend matter, you cause a physical change.

Dissolving sugar in iced tea is a physical change, which is often misconceived as a chemical

change. Salt in water is also another example. When you not sure whether it is physical or

chemical you can always ask yourself did the substance change composition after the change.

Chemical ChangeIn a Chemical Change substances are

changed into different substances. Fireworks are a prime example of a

chemical change. The explosions and colors are evidence of changes in compostion. Chemical changes are often hard to spot,

but there are some signs to look when determining if it is a change in

compostion. The easiest to spot is a color change. Have you ever seen an apple slice

turn brown? A chemical change occurs when an apple reacts with oxygen in the air. This occurs with other fruits as well.

Leaves changing colors in the fall is also a good example. Energy is another sign of a chemical change. Many substances must

absorb energy to have a chemcial change. For example, what do you add to pancake

batter to make it turn into a pancake? Energy in the form of heat is added. The

energy is absorbed by the pancake batter as it undergoes a chemcial change and a

solid pancake is the result.

Conservation of MassThe Law of Conservation of Mass state that the total mass of matter is the same before and after physical or chemical changes. So,

matter cannot be created or destroyed.