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# VI.Thermal conduction

 Good thermal conductors Bad thermal conductors Definition They allow heat to pass through them. They dont allow heat to pass through them. Examples Metals such as copper, aluminium & iron. Wood & plastic. Uses Aluminum is used in making cooking pots. Wood & plastic are used in making handles of cooking pots.

VII. Rusting of metals:

When different metals are exposed to humid air for some time, some of them rust , others dont rust.

 The ability of the metal to react with oxygen(rust) in the presence of water High (active) Low (inactive) Examples Sodium Potassium Gold, silver platinum Uses Making jewellery

Explain why:

Metallic parts of bridges, cars & light posts are painted periodically.

Painting prevents the reaction between the metal & oxygen & protects them against rust.

I. Complete the following statements:

1. The unit of mass is .while the unit of volume is.

2. Density is the .of a unit volume of a substance & its unit is.

3. Some examples of good electric conductors are.& .

4. .doesnt conduct heat or electricity.

II. Explain why:

1. A piece of lead sinks in a basin of water while a piece of wood floats on the surface.

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2. A piece of ice which left at room temperature becomes water.

3. Metallic parts of bridges & light posts can stand for long time without rust.

III. Problems :

1. In the lab , the mass of a piece of iron was measured to be 87 g. When the piece was immersed in a graduated cylinder that contains 90 cm3 , water level increased up to 100 cm3. Calculate the density of iron.

2. The mass of an object is 8g. its density = 0.5 g/ cm3 . calculate the volume of the object.

IV. Whats meant by:

1. Matter

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2. Melting point

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3. Electric conductivity

V. Write the scientific term:

 1. The temperature at which a substance changes from the liquid state to the gaseous state. 2. Substances which dont allow heat to pass through them.

open a bottle of perfume the smell of the perfume spreads in the room indicating that the perfume consists of tiny particles called molecules . they have the smell of the perfume & spread in the air.

Activity 1:

With a dropper , put a drop of liquid colour in a beaker of water.

Ø Observation:

The colour spreads in the water

Ø Conclusion :

Molecules are in continuous motion.

Activity 2:

Measure 50 ml of water with a graduated cylinder.

Measure 50 ml of vinegar then pour it in the cylinder that contains water..

Ø Observation:

The volume of water & vinegar is less than 100 ml.

Ø Conclusion :

Some vinegar molecules occupy the spaces between water molecules.

Matter consists of molecules. The spaces between the molecules are called intermolecular spaces .

Attraction forces keep molecules together .

Comparison between the 3 states of matter.

 Points of comparison Solid state Liquid state Gaseous state Volume Definite Definite Not Definite Shape Definite Not Definite, they take the shape of their containers Examples Ice , iron , aluminiumm. Water, alcohol, oil Water vapour , oxygen , carbon dioxide intermolecular forces Very strong Weak Dont exist intermolecular spaces Tiny Bigger Very large Motion of molecules Limited More free Completely free

Explain why:

Date: 2015-12-24; view: 651

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