THE THREE STATES OF MATTER

The states of matter are solid, liquid and gaseous. Each state has different properties.

-SOLIDS: have a fixed volume and shape. For example, if we put a ball in a bag, the shape of the ball stays the same.

-LIQUIDS: have a fixed volume, but not a fixed shape. Liquids take the shape of their container. For example, if we pour water into a glass, the water takes the shape of the glass.

- GASES do not have a fixed volume or a fixed shape. For example, if a ballon bursts, the air escapes and expands into the room. It acquires the volume and shape of the room.

Liquids and gases are fluid. They flow through openings in solid bodies. They can be transported through pipes.

CHANGES OF STATE

Matter can change from one state to another.

This change of state sometimes occurs when the temperature changes.

- MELTING: A solid changes into a liquid. For example, snow melts when it is warm.

- SOLIDIFICATION: A liquid changes into a solid. For example, water changes into ice when it is very cold.

- BOILING: A liquid changes into a gas. For example, water boils when it is very hot: one hundred degrees centigrade ( 100º C).

- EVAPORATION: A liquid changes into a gas. For example, water in a pond evaporates.

- CONDENSATION: A gas changes into a liquid. For example, water vapour in the air forms condensation on car windows when it is very cold.

- SUBLIMATION: A solid changes into a gas. For example, solid air fresheners change into a gas when they mix with air.

ACTIVITY "CHANGES OF STATE"

COMPLETE THE MISSING WORDS:

- ........... a solid changes into a liquid.
- ........... a liquid changes into a solid.
- .......... a liquid changes into a gas.
- .......... a liquid changes into a gas.
- .......... a gas changes into a liquid.
- .......... a solid changes into a gas.

UNDERSTANDING THE CONCEPT OF DENSITY

HANDS ON

DECANTATION

- Pour some oil into a container and add water.

- Quickly cover the container and shake it to mix the liquids.

- Let the container stand and answer:

- What is going to happen?

- Which liquid will be on top?

- Which is less dense, the oil or the water?

CHANGES IN MATTER

There are two types of change in matter:

- Physical changes: The object or substance changes, but the matter remains the same. When water freezes, it is still water.

- Chemical changes: The original matter changes into a different substance. When paper burns, it changes into ashes and gases.

PHYSICAL CHANGES

- Movement: The object changes position, but the matter remains the same.

- Expansion: When the temperature of an object increases, it gets bigger. If the temperature rises, mercury expands in a thermometer.

- Contraction: When the temperature of an object decreases, it gets smaller. If a balloon filled with air is put in a refrigerator, the air contracts: the balloon gets smaller.

- Changes of state: When the temperature rises, the state changes. If water is heated, it changes into steam.

- Fragmentation: The object is divided into small pieces. If a glass breaks, the pieces are still made of glass.

CHEMICAL CHANGES

- Oxidation: one substance changes into another when it reacts with oxygen. For example, iron changes into rust.

- Combustion: when an object or substance is burned, it changes into another subtance. For example, when wood burns, it changes into ashes and gases.

- Putrefaction: this occurs when a living thing decomposes. For example, when an apple decays, its appearance, colour, smell and taste change.

Chemical industries use chemical reactions to manufacture substances. Some substances, such as plastic, are artificial. Plastic is made from petroleum.

MASS

Mass is the amount of matter in an object. Some objects have more mass than others.

For example, a football has more matter than a pencil. The football´s mass is greater.

The unit of measure for mass is the kilogram ( kg ), or kilo. One kilo is equal to 1.000 ( one thousand ) grams ( g ). 1.000 ( one thousand ) kilos are equal to one ton ( t ).

VOLUME

Volume is the amount of space which an object occupies. For example, a football has more volume than a pencil. It takes up more space.

The unit of measure for volume is the litre ( l ). One litre is equal to 1.000 ( one thousand ) cubic centimetres . 1.000 ( one thousand ) litres are equal to one cubic metre.

DENSITY

Density is mass per volume. To calculate density, divide the mass of a substance by its volume.

Each object or substance has its own density:

- Water has a density of one kilo per litre of water: 1 kg/l. This means that one litre of water has a mass of 1 kilo.

- Iron has a density of 7.9 kilos per litre of iron: 7.9 kg/l. This means that one litre of iron has a mass of 7.9 kilos.

ACTIVITY "THE PROPERTIES OF MATTER"

MATCH
1. Mass                                                a. mass per volume.

2. Unit of measure for mass                   b. the kilogram

3. Volume                                             c. the litre

4. Unit of measure for volume                d.the amount of matter in an object.

5. Density                                             e.the amount of space which an object occupies.

MATTER

Everything in the universe is made of matter. The Sun, rocks, plants, human beings and manufactured objects are all made of matter.

Matter is made up of tiny particles called atoms. Atoms are extremely small. They are invisible to the human eye.

There are approximately one hundred different types of atoms. When they are combined in different ways, they make up all the substances in the world.

- An element is matter which consists of only one type of atom.

- A compound is matter which consists of more than one kind of atom.

TYPES OF MATTER

Matter can be classified into two groups:

- Pure substances are made up of a single type of element or compound. For example, gold, iron and salt are pure substances.

- Mixtures are made up of several pure substances. For example, sea water is a mixture which is formed by water and salt.

PROPERTIES OF MATTER

We can classify properties into two types:

- General properties: All matter has general properties like mass and volume. Everything which is made of matter has mass and takes up space.

- Characteristic properties: Properties like odour, colour, shininess and density are characteristics. They are different for each substance.

ACTIVITY "MATTER"

TRUE OR FALSE: Read the following sentences and write if they are true or false. If they are false, they correct them.

1. Matter is made up of tiny particles called atoms.
2. Atoms are visible to the human eye.
3. There are about 100 similar types of atoms.
4. An element is matter which consists of only one type of atom.
5. Salt is a pure substance.
6. Sea water is a pure substance.
7. All matter has mass and volume.