Gases and Liquids

Lesson 4. Working on the authentic material
(Materiallar bilan ishlash)
Work on the text

Text “Gases and Liquids”

Another phase of matter-the gas phase-does not have a definite shape or a definite volume. A gas fills of the available space in a container, regardless of the size or the container. Although the particles of a gas tend to spread far out from one another, they can be pushed close together. When you pump air into a bycicle tire or blow up a party ballon, squeeze a large amount of gas into small volume. Fortunately, you can do this to the particles in a gas.

Just the opposite can also happen. The particles of a small amount of gas can spread out to fill a large volume.The smell of an apple pie baking in the oven in the kitchen will reach you in another room of your house,because gases given off by the pie spread out to fill the whole house. In fact, if they are allowed to, gases will expand without limit. If not for the pull of gravity, the gases that make up the atmosphere of the Earth would expend into deep space. Can you explain then why a small planet like Mercury has little or no atmosphere?Like liquids, gases have no definite shape. The particles that make up a gas are not arranged in any set pattern. So it is easy for gas particles to move around,either spread apart or moving close together.

LIQUIDS

Although the particles in a liquid are close together,they are not held as tighty together as are the particles in a solid. So the particles in a liquid are free to move.Thus a liquid has no definite shape.It takes the shape of its container. A liquid in a square container is square.The same liquid in a round container is round. Although liquids do not have a definite shape,they do have a definite volume. One liter of water is still one liter of water whether it is in a round container or a square one.And if that one liter of water is poured into a two – liter bottle,it will occupy only half the bottle’s volume. It will not fill the bottle.One liter of water does not spread out to fill a two –liter the bottle.What do you think would happen if you tried to pour that one liter of water into a half –liter bottle?Remember that the particles in a liquid are free to move. This movement is basically a flowing around one another.Some liquids flow more easily than others,however. The resistance of a liquid to flow is called viscosity (vihs-KAHS-uh-tee). Honey has a high viscosity compared to water. This means that honey flows more slowly than water. If you have ever poured honey from a jar, you are probably familiar with this fact. The oil you put in an automobile also has a high viscosity. This is important because the oil coats the moving parts in the motor and prevents them from rubbing together and wearing out.
True or False
Begin to work on exercise “True or False”. Write “T” for true and “F” for False. Correct the false sentences.

1.----Liquids and gases are also kinds of matter.

3.----We can see gases and define them quickly.
4.----- Like gases liquids have no definite shape.
5.----The particlesof a small amount of gas can spread out to fill a large volume.