6. 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.

7. 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		M aking jewellery

Explain why:

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

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

1. 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.

2. Explain why:

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

……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….

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.

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

3. 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.

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

4. What’s meant by:

1. Matter

………………………………………………………………………………………………………………………………………………………………………………….……………………………

2. Melting point

……………………………………………………………………………………………………………………………………………………………………………………..…………………………

3. Electric conductivity

…………………………………………………………………………………………………………………………………………………………………………………………………………

5. Write the scientific term:

The temperature at which a substance changes from the liquid state to the gaseous state.
Substances which don’t allow heat to pass through them.

o

A molecule is the smallest particle of matter that exists freely & it carries the properties of the substance.

pen 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:

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

• Observation:

The colour spreads in the water

• 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..

• Observation:

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

• 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

E xplain why: