Define the following chemical reaction and give an example of it.
Decomposition reaction
Important Questions on Physical And Chemical Changes
Out of the following, the number of properties which change during a physical change is:
Shape, size, state, chemical composition.
Among the following, the total number of methods that can be used to prevent rusting is:
Dipping in water, painting the surface, greasing the surface, galvanisation, alloying, heating the iron.
Among the following, the total number of chemical changes is:
Melting of ice, crushing of paper, rusting of iron, burning of magnesium, ironing of clothes, cooking of rice, burning of LPG, photosynthesis, digestion of food.
The number of changes from the given list that cannot be reversed are:
(i) Breaking of an earthen pitcher
(ii) Freezing of ice-cream
(iii) Falling of trees during storm
(iv) Filling of bucket with water
(v) Rusting of a bicycle
(vi) Digestion of food
All of the following processes involve a separation of either a mixture into its components, or a compound into elements. For each, decide whether a physical process or a chemical reaction is required.
(i) Sodium metal is obtained from the substance sodium chloride.
(ii) Iron filings are separated from sand by using a magnet.
(iii) Sugar crystals are separated from sugar syrup by evaporation of water.
(iv) Fine crystals of silver chloride are separated from a suspension of the crystals in water.
(v) Copper is produced when zinc metal is placed in a solution of copper (II) sulphate, a compound.
Observe the given figure carefully.
Read the given passage and fill in the blanks by selecting an appropriate option.
In the given figure, (i) reaction takes place, which is a chemical change. (ii) being more reactive than (iii), produces gas 'X' which is (iv) and it burns with a (v).
