Alloys

Question 1 What is an alloy?

Question 2 Give two examples of alloys?

Question 3 How are the properties of an alloy different from those of the constituent metals?

Question 4 What elements are present in steel?

Question 5 What are the constituents of stainless steel?

Question 6 State an alloy of copper?

 Question 7 Give the constituent of brass?

Question 8 Name an alloy of tin and lead?

Question 9 How is an alloy made?

Question 10 What is an amalgam?

Question 11 How many carats is pure gold?

Question 12 Why is pure gold not suitable for making ornaments?

Question 13 What is meant by 22 carat gold?

Alloys

The various properties of metals can be improved by mixing other metals in it. The homogeneous mixture of two or more metals is called alloy.

Duralumin is an alloy of Al, Cu, Mg, Mn

Steel is an alloy of C, Fe

Pure iron is very soft and stretches when hot but with c it forms steel which is hard and strong.

Stainless steel is a mixture of Fe, Cr, Ni. It is very strong and do not rust. It is used in making cooking utensils, surgical instruments, dairy industry etc.

Brass is a mixture of Cu and Zn.

Bronze is a mixture of Cu and Tin. It is tough, resistant to corrosion, used to make statues, coins, medals, utensils.

The properties of alloys are different from the properties of constituent metals.

1) Alloys are stronger than the metal which they are made.

2) More resistant to corrosion.

3) Have lower melting point .

4) Have lower electrical conductivity.

An alloy is prepared by mixing various metals in molten state in required proportion and then cooling their mixture to the room temperature.

Amalgam

An alloy of mercury metal with one or more other metal is called amalgam. Solution of sodium metal in liquid mercury is called sodium amalgam. Purity of gold is expressed in carats. Pure gold is 24 carats.It is very soft due to which it is not suitable for jewellery. 22 carats of gold consist of 22 parts of gold and 2 parts of copper.