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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.

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

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

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

2. Melting point

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

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: 304


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IV.The boiling point is the temperature at which a substance begins to change from the liquid into the gaseous state. | A molecule consists of atoms.
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