-There are three states of the matter:

1- Solid state: such as sugar, salt, Iron, Copper and wood.

2- Liquid state:such as water, oil, milk, benzene, Kerosene and Alcohol.

3- Gaseous state:such as oxygen, nitrogen, carbon dioxide and water vapour.

Matter consists of small building units called molecules or particles.

Its properties:

1-Its molecules are packed very closely together.

2- It has a definite shape and volume.

1. Put a piece of stone and marble in a test tube.

2. Compare between the shape and volume of each body in the test tube and its real shape and volume.

Observation: shape and volume of each body don't change.

Conclusion: Solid matter has a definite shape and volume.

Its properties:

1-Its molecules are far from each other (the distance between molecules is larger than that of solids).

2- It has a definite volume and an indefinite shape.

1-Put 100 cm3 of water in a conical flask and pour them in cylindrical flask.

Observation: The volume of water doesn't change but its shape changes taking the shape of its container.

Conclusion: liquids have a definite volume and an indefinite shape (they take the shape of its container).

Its properties:

1-Its molecules are very far from each other (the distance between molecules is larger than that of liquids).

2-It hasn't a definite shape or volume.

1- Blow air in a balloon and tie it with a thread.

2- Press on the balloon with your hand.

Observation: The shape and volume of air changes by pressing on the balloon.

Conclusion: Gases always take the shapes and volumes of their containers (they don't have a definite shape or volume).

-In oxygen and butagas cylinders the gas is compressed inside them where its shape and volume is changed.