Which among the following are physical or chemical changes? i. Evaporation of petrol

 Cutting of trees → Physical change   Melting of butter in a pan → Physical change   Rusting of almirah → Chemical change   Boiling of water to form steam → Physical...

Following are Chemical changes.  (a)Growth of a plant  (b)Rusting of iron  (c) Cooking of food  (d)Digestion of food  (e) Burning of a candle.

(c) (i), (iii) and (iv)

(a) Evaporation produces cooling as the particles at the surface of the liquid gain energy from the surroundings and change into vapour thereby producing a cooling effect.  (b) Air around us...

(a) physical change     (b)chemical change    (c) physical change  (d)chemical change (e) physical change 

Physical Changes: (b) Dissolving sugar in water, (d) Melting of wax, (e) Beating Aluminium to make Aluminium foil. Chemical Changes: (a) Photosynthesis, (c) Burning of coal, (f) Digestion of food

Physical Changes: On heating, candle wax gets melted is a physical change. Since it again turns into solid wax on cooling. Chemical Changes: The wax near to flame burns and gives...

Renewable sources: wind, tides, Sun, biomass, hydro energy Non-renewable sources: coal, petrol, CNG

(i) and (iii) are physical changes (ii) and (iv) are chemical changes

Most of the processes are carried out in an open system i.e, at constant pressure.