### Year 9 Matter

Learning outcomes:

On completion of this unit students should be able to:

• group everyday substances according to the states of matter
• identify properties of different states of matter
• understand and link these properties to particle arrangement
• understand and demonstrate how to use a bunsen burner safely
• identify changes of state in everyday situations
• describe the changes that occur during the water cycle
• describe dissolving and understand how solutions are created
• define mixtures and describe techniques to separate different types of mixtures

Time allocation: 5 weeks            Assessment: written test

### What is matter?

Matter is everything we know about that has mass and takes up space..
Matter includes all the things we can see and all of the things we can't.
For example, water is a tricky substance to hold in our hands but ice is not, it just makes them cold!

### States of matter

We can group matter into three states - solids, liquids and gases.

Solid - This is the state of matter where the particles are really close together in neat rows. There is not much space between the particles, and they cant move past each other. Because of the particles are so close, solids do not change shape. A desk is solid. It does not change it's shape.

List five other examples of solids.

Liquid - The particles in a liquid are not close together as in solids. There is some space between the particles so it is easier for them to move. Because the molecules are able to move liquids are able to change shape. A liquid will take the shape of its container. If you were to fill a cup or a bowl with water, the water would take the shape of the cup or the bowl.

List five other examples of liquids.

Gas - The particles in gas have heaps of space between them. Gas particles move around very quickly. They do not stay close together. Particles of gas will spread out to fill the room. If the window or door is open, the gas will move out of the room. The air we breathe is a mixture of gases.

List five other examples of gases.

### Properties of matter

Solids. liquids and gases have a number of different properties.

Solids:

• can have a fixed or flexible shape
• may be crystalline
• can be dense
• cannot be squashed or compressed
• cannot be poured
• have a fixed volume
Liquids:

• take the shape of the container
• do not have crystals
• are dense
• are not able to be squashed or compressed
• can be poured
• have a fixed volume
Gases:

• take the shape of their container
• do not have crystals
• are not dense
• are able to be squashed or compressed
• can be poured
• have differing volumes

Physical properties of matter

Physical properties are all the properties of matter that do not involve chemical reactions:

• state
• mass
• colour
• temperature
• conductivity
• density
• volume
• boiling point
• melting point
• freezing point
Define each of these physical properties.

### Particle arrangement

Scientists believe that all atoms are made of particles. This is referred to as the particle theory of matter.

1. Matter is made up of tiny particles that are too small to see.
2. The particles have spaces between them.
3. The particles are attracted to each other by a force. The further apart they are, the smaller the force.
4. The particles are always moving.
5. At high temperatures the particles move faster than they do at low temperatures. This is because they have more energy.
Solids

The particles in a solid are close together in a fixed pattern. There are strong forces holding them together so they cannot change their positions. They only vibrate on the spot.

Draw a diagram to show the arrangement of particles in a solid.

Liquids

The particles in a liquid can move around past each other. They are still close together but are not in a regular pattern. The forces that hold them are weaker than in a solid.

Draw a diagram to show the arrangement of particles in a liquid.

Gases

The particles in a gas are really far apart, and they move very quickly. There are almost no forces holding them together. They collide with each other, the walls of their container and bounce off randomly in any direction.

Draw a diagram to show the arrangement of particles in a gas.

The particles of matter may be:

1. Independent atoms.
2. Groups of atoms called molecules.
3. Large, rigid networks of atoms called crystal lattices.
Draw a diagram and give an example for each of the three arrangements described above.

The movement of particles and the attractive forces between them can be used to explain the physical properties of solids, liquids and gases.

 Solids Liquids Gases Give example here: Ice Give example here: Give example here: Describe the particle model: The particles in a solid are packed tightly in a fixed pattern. There are strong forces holding them together so they cannot leave their positions. The only movements they make are tiny vibrations to and fro. Describe the particle model: Describe the particle model: Example of property: Example of property: As particles are held close together, liquids have a fixed volume and cannot be compressed Example of property: Example of property: Example of property: Example of property: As particles move freely, gases have no fixed shape

Copy and complete the table shown above.

Use this information to write several paragraphs comparing and contrasting solids, liquids and gases.

### Using a bunsen burner safely

In the science laboratory a Bunsen burner is used to heat things.

Draw and label a diagram of a Bunsen burner.

As the gas flows through the rubber hose and into the burner, air is drawn in through the air hole. This mixture of gas and air is then ignited using a lit match placed at the top of the barrel to produce a flame. The temperature of the flame can be controlled by turning the metal ring or collar. As the collar turns the air hole is either opened or closed, which changes the amount or air mixing with the gas. The more open the air hole, the more air is drawn in and the hotter the flame.

Air hole closed - yellow safety flame This yellow safety flame is easy to see.

Air hole open - blue heating flame This blue flame is hard to see and at times it is almost invisible. It can cause serious burns as it is very hot.

Lighting the burner:

1. Place the burner on the side bench. Connect the rubber hose to the gas tap.
2. Turn the collar so the air hole is closed.
3. Light a match, switch on the gas, and bring the match close to but not over the top of the barrel. The gas should ignite.
4. Observe the flame with the air hole closed.
5. Gradually open the air hole, noting carefully what happens to the flame.
Draw diagrams of the yellow safety flame and the blue heating flame. Use coloured pencils.

Rules for safe use of the burner:

1. Keep the burner away from books, and away from the edge of the bench.
2. Always light the burner with the air hole closed.
3. Switch to the yellow safety flame when not heating.
4. The barrel of the burner may get very hot. If you leave to move the burner, turn it off first. Hold it by the base or by the gas hose.
5. Check the gas is turned off properly when you have finished.

### Changes of state

The three states of matter are solids, liquids and gases. When you cool down or heat up a substance, a change of state may occur. These changes occur at a fixed temperature unique to the substance involved. When a substance is changing state, the temperature stays the same. We can use the particle theory to explain changes of state.

When a solid is heated, its particles gain more energy and vibrate more. This makes the solid get bigger. At the melting point the particles vibrate so much that they break away from their positions. When this happens the solid becomes a liquid.

When a liquid is heated, its particles have more energy and move faster. They bump into each other more energetically and bounce further apart. This makes the liquid expand. At the boiling point, the particles have enough energy to break free of the forces holding them together. They form a gas.

Not all the particles in a liquid have the same amount of energy. Even when a liquid is well below its boiling point, some particles have enough energy to escape and form a gas. This is what happens in evaporation.

List the five key points of the particle theory of matter.

Define the following terms:

• melting
• melting point
• freezing
• freezing point
• boiling
• condensing / condensation
• evaporating / evaporation
• sublimating / sublimation

Describe the two ways a liquid can change into a gas.

Check out this activity about changing states - what was your score in the quiz?

Draw and label a diagram to show the changes of state between solids, liquids and gases.

### The water cycle

All living things depend on water for their survival. Without water life would not exist. Water is more important than food. Water is the key to life on our planet and it is the reason that our planet is habitable. Through changes in state it keeps the creatures of our living world happy and healthy.

Think about when you leave a bowl of water out in the sun for some time, what happens to it?

The water disappears, it becomes vapour. This process is called evaporation. As the water evaporates it leaves behind any dissolved substances, such as salt, so only pure water goes up into the air. You can speed up the process by boiling the water. When the water vapour hits a cold surface, it changes back to liquid water. This process is called condensation.

The earth's water is always moving from one place to another, and changing from one form to another. The heat of the sun evaporates water from the soil and the surfaces of lakes, rivers and oceans. Water also enters the air from trees and other plants. This process is called transpiration. This invisible water vapour is carried about by the wind. As it rises it becomes much cooler and may condense to form clouds and perhaps rain, hail or snow.

Rain, hail and snow return the water to the land or ocean. The water that falls on the land flows into rivers and lakes, and eventually reaches the oceans. Some water seeps into the soil and rocks to become underground water, or groundwater

Other water evaporates from the land. Once the water reaches the streams, lakes and the oceans, the sun causes more evaporation, and the changes continue. These changes are known as the water cycle.

What happens to all the water?

Create a labelled diagram of the water cycle.
In your own words, write a paragraph to explain the water cycle.

### Dissolving and solutions

When a solid is mixed into a liquid and the solid then disappears, it is said to have dissolved. Dissolving is not the same as melting. When dissolving occurs, two different substances are mixed together, a solid and a liquid. When melting occurs, a solid turns into a liquid.

List three examples of dissolving.

When you stir sugar into a glass of water it seems to disappear into the water. We say it dissolves into the water. The sugar and water have mixed to form a solution. Solutions are very important to you. The food you eat is digested and dissolved in water. It is then carried around your body in your blood which is a solution.

A solution is a special mixture that behaves and looks like a single substance. It is made up of a solvent and solute which is evenly spread throughout the solvent. Consider what happens when instant coffee dissolves in hot water. The substance that dissolves (the coffee) is called the solute. The substance that does the dissolving (the water) is called the solvent. So the solute dissolves in the solvent forming a solution.

A substance that dissolves is said to be soluble. A substance that will not dissolve is insoluble. Some insoluble substances sink in water (settle out), and others float on top. If the solid present in a mixture settles when you let it stand for a while, then such a mixture is not a solution but a suspension. Muddy water is an example of a suspension, because the mud settles to the bottom when you let it stand.

Define the following terms:

• dissolve
• solution
• solute
• solvent
• soluble
• insoluble
• suspension

Two liquids can also form a solution. For example, the fuel for two-stroke motor mowers and outboard engines is a solution of oil in petrol.

A particular substance may not dissolve in every solvent. For example, salt is soluble in water, but insoluble in alcohol.

Solubility

A cup of coffee is like any liquid solution. It comes in many different strengths. If you like your coffee stronger, you add more coffee powder. If you like it weaker, you add more water.

We use the terms dilute and concentrated to help us compare solutions. A dilute solution contains a small amount of solute in a given volume of solvent whereas a concentrated solution contains a large amount of solute. You may have used the terms weak or strong - but the correct scientific terms are dilute and concentrated.

The colour of solutions gives you some idea of their concentration. The darker the colour, the higher the concentration. Or, a more dilute solution will be lighter in colour. This is a general statement or generalisation - one that is true in most cases.

There is a limit to the amount of solute that will dissolve in a solution. When a solution will dissolve no more solute, it is said to be saturated. Until it reaches this point, it is unsaturated. If you add more solute to an unsaturated solution, it will dissolve.

Define the following terms:

• dilute
• concentrated
• generalisation
• saturated
• unsaturated
• kilogram
• litre
Draw and label diagrams to show the difference between dilute and concentrated soltuions.

### Mixtures

Different substances have different properties. To begin with, they can be either solids, liquids or gases. But there are also many other properties which allow you to know the difference between one substance and another. For example, you can detect sugar by its sweet taste. Glass is transparent (you can see through it). Lead is heavy. The list can go on.

List three other examples of substances with a property.

The materials around you can be grouped into pure substances and mixtures. Pure substances contain only one substance. Their composition and properties are fixed. Examples include sugar, gold, pure water and hydrogen gas.

List five other examples of pure substances.

Most materials around you are mixtures - several substances mixed together. Examples are custard, soft drinks, lipstick and the air we breathe.

Not all mixtures of the same substances have the same properties. The amounts of each part of the mixture (called their proportions) can vary widely. This changes the properties of the mixture.

The parts of mixtures can be solids, liquids or gases. For example, soft drink is a mixture of liquid water and carbon dioxide gas, plus sweetener, flavouring and colouring.

 Lipstick Custard Soft drink Air Contains:  castor oil beeswax carnauba esters antioxidant aloe mineral oil red dye No. 21 perfume Contains: Contains: Contains: Used for: Used for: Used for: Used for:

Copy and complete the table shown above.

### Separating techniques

Separating suspensions

Suppose you are in the kitchen and have boiled some potatoes in water, but you don't want the water. You gently tip the saucepan so the water runs out, leaving the potatoes in the saucepan. Pouring off liquid, while keeping the solid in the saucepan, is called decanting. It is a way of separating the liquid part of a suspension from the solid part.

If a suspended solid settles very slowly you can speed up the separation by using a centrifuge. This is a machine designed to separate mixtures by spinning them around.

Decanting is not a very good method for complete separation. Some liquid is usually left behind. Also, unless you are careful, you are likely to pour off some of the solid with the liquid. Yes, sometimes we lose a potato or two down the sink! A better way of separating suspensions is by filtering.

Suppose you have a suspension of a powder in water. The powder can be separated from the suspension through filter paper. The filter paper has tiny holes in it. the water passes through these holes, but the powder cannot. The solution that passes through the filter paper and collects in the beaker is called the filtrate. The solid material that remains in the filter paper is called the residue.

List three examples of where we use filters in our everyday lives.

Separating solutions

Once a solute has dissolved in a solvent to form a solution, we cannot separate it by filtering. The solution simply passes through the filter paper like the water does.

So how can we separate the solute and solvent?

If a solution consists of a solid dissolved in water, they can be separated by heating. The water evaporates and leaves behind the solid. During evaporation the liquid part of the solution escapes into the air.

List three examples of separating this type of solution.

How can we get the liquid part back?

If we want the liquid it needs to be trapped as it evaporates so we can condense it back to a liquid. This process is called distillation.

Separating solids

Sometimes we need to separate a mixture of solids from each other. The method used depends on the differences in properties of the solids.

1. If one solid is soluble in water and the other is insoluble, then add water.

When the mixtures is filtered, the residue in the insoluble solid. The filtrate contains the soluble solid in solution. It can be recovered by evaporation.

2. If one solid is attracted to a magnet and the other is not, then use magnetic separation.

This method is used in industry to separate the magnetic material in mineral sands.

3. If one insoluble solid floats on water and the other sinks, add water and skim off the floating solid.

4. If one solid is heavier than the other, use gravity separation.

A good example of this is gold panning. The water is swirled around in the pan, the heavy gold sinks and the lighter mud and sand are washed off the top.

Separating colours

Paper chromatography can be used to separate a mixture of coloured substances.

Gas chromatography is used in industry and scientific research to detect very small amounts of chemicals in mixtures.