NCERT CLASS 10-2021- METALS AND NON METALS -CHAPTER-3-PART 1-PHYSICAL PROPERTIES OF METALS AND NON METALS

 

CLASS 10 METALS AND NON METALS -CHAPTER-3-PART 1-PHYSICAL PROPERTIES OF METALS AND NON METALS

PHYSICAL PROPERTIES OF METALS

Think about some metals which you use and find in daily life like iron, silver, gold, aluminium, copper and also some non-metals which you see in daily life like carbon and oxygen.

Let us discuss the physical properties of the metals just by performing certain activities.

• METALLIC LUSTRE

 Take some pieces of iron, copper, aluminium, magnesium, lead and zinc. Rub these metals with sandpaper and see what happens.

What do you see? You will find that these metals have a shining surface. This shining surface which the metals have is called metallic lustre. So it is a peculiar property of the metals. Metals have metallic lustre or metals have shining surfaces.

METALLIC LUSTRE

• HARDNESS

 You must have seen that most of the metals are very hard and strong. But there are certain exceptions also. Some metals like sodium and potassium are very soft and if you want to cut these metals with a knife you will be able to cut it.

• PHYSICAL STATE

 Metals are generally solids. Think about the metals like silver, gold, copper or aluminium. All are solids, but there is an exception- mercury is a metal which is a liquid at room temperature.

• MALLEABILITY

An activity can be performed. Take some metals like aluminium, copper, silver or gold.  Place it on an iron block and hammer it. What do you see? You will get a sheet on hammering and this property is called malleability. So malleability is an ability of the metals to be beaten into thin sheets. Most of the metals can be beaten into thin sheets.

You must be very fond of eating the sweets and have you ever noticed the silver foils over the sweets. So these are made of silver. Silver can be beaten into thin foils. Aluminium foil is used for packing the foods. Gold and silver are the most malleable metals.

aluminium package

• DUCTILITY

You must have seen the wires of aluminium and copper.  Ductility is the ability of the metals to be drawn into thin wires. That is why metals are used to make the wires because they can easily be drawn into thin wires. From one gram gold about two kilo meter long wire can be drawn. Most ductile metal is gold. 

•  CONDUCTORS OF HEAT

An activity can be performed to study the next property of metals. This activity can be performed in the lab.

Fix a metal wire with the help of a stand and fix a pin with the help of wax.  Place a burner at one end of the wire and heat the wire.  What do you observe?  You will find that this pin falls down.  Why? The heat is being conducted to this and off the wire due to which the wax melts and the pin falls down. What does it show?  It shows that metals allow the heat to pass through them. So most of the metals are good conductors of heat.

You have seen the cooking utensils in the house. What is the material used to make the cooking utensils? Generally cooking utensils are made of metals because metals are good conductors of heat. Best conductors of heat are silver and copper. Lead and Mercury are poor conductors of heat.

• CONDUCTORS OF ELECTRICITY

Another activity can be performed next. Take a battery and connect it to a conducting wire and a bulb is placed in the circuit. There is a switch and the metal which is to be tested is inserted in the circuit.  Different metals are taken and they are tested. When all these metals copper, aluminium iron, silver and gold are placed in this space to complete the circuit, it is found that the bulb grows.  What does it show?  The glowing of the bulb shows that all these metals allow the current to pass through them.

 All the metals are good conductors of electricity. That is why the metals are used to make electric wires .

copper wire and insulated wire

You must have seen the electric wires which are used in the houses. They are generally coated by a layer of either rubber or PVC poly vinyl chloride because you must be very well aware of this that rubber and PVC are insulators. They do not allow the electric current to pass through them and so a person who is handling these electric wires can be saved from electric shock.

• SONOROUS

You must have seen the bell in your school. On hitting it with a hammer it produces a ringing sound. This property is known as sonority and the metals are said to be sonorous. The metals that produce a sound on striking a hard surface are said to be sonorous.

• HIGH MELTING POINT AND BOILING POINT

Metals have very high melting points and boiling points. They melt at very high temperature except for sodium and potassium. Another exception is gallium and cesium which melt on taking over the palm.

• DENSITY AND COLOUR

Metals have very high densities except sodium and potassium.

Now let us see the colour of the metals. You must have seen that most of the metals are either silver or grey in colour but there are certain metals which have different colours. copper is reddish brown in colour and gold is shining yellow in colour.

 

PHYSICAL PROPERTIES OF NON- METALS

Collect various samples of different non-metals which you can easily get and study their physical properties as you studied the properties of the metals. You can collect non-metals like graphite, sulphur and phosphorus.

Non-metals do not possess lustre. The lustre is present only in the case of metals. They do not possess a shining surface. Observe the surface of the nonmetals you will find that the non-metals do not possess a shining surface like metals. Non-metals have a dull surface except diamond and iodine, which have a lustrous surface.

Non-metals cannot be beaten into thin sheets nor can be drawn into thin wires. So non-metals are neither malleable nor ductile. If you beat them with the hammer non-metals will break into pieces. Non-metals are brittle.

Non-metals are neither good conductors of heat nor good conductors of electricity. But there are exceptions like graphite which is a good conductor of electricity. Graphite contains carbon. It is used to make  batteries. So graphite conducts electricity very well.

 Non-metals are soft. Unlike metals which are very hard, nonmetals are soft. But there are exceptions like diamond.  Diamond is the hardest substance.

diamond

Diamond and graphite both are forms of carbon. They are called allotropes of carbon.  They are different physical forms of carbon with different physical properties but same chemical properties.

 Most of the non-metals are solids or gases. Oxygen is a gas, hydrogen is a gas, sulphur is a solid, graphite is a solid,but bromine is a liquid.

Unlike metals, non-metals have low melting points and boiling points except diamond which has a high melting point.

Non-metals have low densities.

The colour also varies in the case of non-metals. They have different colours. Sulphur is yellow in colour, phosphorus is white or red colour,  graphite is black in colour and bromine is orange in colour.

Do you want to learn the chemical properties of metals?

YOU CAN ALSO READ: PART -2- METALS AND NON -METALS