Metals

Question 1 Name one metal which has a low melting point?

Question 2 Name two metals which are malleable and ductile?

Question 3 Name one soft metal that can be cut with knife?

Question 4 Name the metal which is the poorest conductor of heat?

Question 5 Why copper and aluminium metals are used for making electric wires?

Question 6 Why copper and aluminium metals are used for making cooking utensils?

Question 7 Why metals are good conductors of electricity?

Question 8 Why metals lose their shine on keeping in air for a long time?

Question 9 Why metals are used for making bells?

There are 115 elements known at present.

All the elements are divided into two main groups

1) Metals

2) Non-metals

 

Metals

For Example: Iron, gold, silver, copper, aluminium, zinc, lead, mercury, potassium, calcium, sodium, magnesium.

Metals are the elements which form positive ions by losing electrons. They are electropositive elements because they can form positive ions by losing electrons.

Most abundant metals on earth crust are Al (7%), Fe (4%).

Physical Properties of Metals

1) Metals are malleable (can be beaten with hammer to form thin sheets)

For Example :Gold, silver, aluminium.

They are used in very thin sheets called foils.

Al foils are used for packing food items. Al sheets are used to make utensils.

Fe sheets are used to make buckets, boxes, water tanks etc.

2) Metals are ductile (Drawn into wires)

For Example: Cu, Al, Mg, Fe, Gold, Silver etc.

Cu and Al are used to make electric wires, Mg wires are used in laboratory, Tungsten metals are used to make filaments of electric bulb.

 

3) Good conductor of heat and electricity

They allow heat and electricity to pass through them easily.

For Example :Silver, Copper, aluminium, tungsten, gold etc.

Silver is the best conductor of heat.

Copper and aluminium are used in cooking utensils, water boilers.

Mercury and lead are poor conductors of heat.

Copper and aluminium wires are used.

Metals are good conductor of electricity because they contain free electrons. These free electrons can move easily through the metal and conduct electric current.

4) Metals are lustrous

This means they have shiny surface.

For Example :Gold ,silver, copper

The shiny appearance of metals makes them useful in making jewellery and decorative pieces.

The metals lose their shine on keeping in air for a long time and acquire a dull appearance due to the formation of thin layer of oxide, carbonate or sulphide on their surface.

5) Metals are generally hard except Na and k.

Fe, Cu, Al are hard and cannot be cut with a knife whereas Na and K can be easily cut with a knife.

6) Metals are solid at room temperature except mercury.

7) Metals have high melting and boiling point except Na and K.

8) Metals have high densities except Na and K.

9) Metals are sonorous i.e. make sound when hit with an object. That is why they are used for making bells, strings of musical instruments.

10) They have silver or grey colour except copper which is reddish-brown and gold is yellow in colour.