NCERT 8th Class (CBSE) Science: Metals And Non-Metals

Question: How will you prove the nature of rust or the ash obtained from burning magnesium ribbon?

Answer: This can be easily proved in laboratory. Take some rust and dissolve it in water (a few drops). Now take a red litmus paper turns blue.

When the red litmus paper turns blue it means solution is basic in nature. So the rust is basic in nature. We can similarly check the nature of ash obtained by burning a magnesium ribbon. It will also turn red litmus paper blue proving its basic nature.

Question: How do different metals react with water?

Answer: Different metals react differently with water, hydrogen being a common end product.

Sodium metals react vigorously with water to form sodium hydroxide and hydrogen gas.

2Na              +             2H₂ O           →           2NaOH             +            H_{2
 Sodium                                 Water                            Sodium hydroxide                 Hydroden}

Magnesium only react with hot boiling water to form magnesium oxide and hydrogen.

Mg                +               H₂ O           →            MgO                 +             H_{2 
Magnesium                          Water                            Magnesium oxide                  Hydroden}

Red hot iron react with steam to form iron oxide any hydrogen copper. Silver and nickel do not react with water.

Question: What are the different uses of metals ?

Answer: Metals are very useful to us. Some of uses of common metals are following:

• Copper and aluminium metals are used to make electric wires. This is because copper and aluminium are good conductor of electricity.
• Copper, aluminium and iron metals are use for making utensils and other domestic things. These metal are also used to make various factory items. This is because, all these metals are good conductor of heat.
• Iron is used t make heavy machinery and also used in construction of building because it is very heavy and strong.
• Thin foils of aluminium are used in packing food material and medicines etc.
• The liquid metals mercury is used in thermometers.

Question: What are the different uses of non metals?

Answer: Following are the uses of non-metals:

• Non material is used  in crackers.
• Oxygen is used by plant and animal for respiration. Oxygen also supports the process of combustion in factories, houses, aeroplanes and missiles.
• Compound of nitrogen provide nutrients to soil and plant. Fertilizers made by using nitrogen are extensively used in agriculture practices.
• Chlorine is used to disinfect the drinking water as it has ability to kill germs.