Which of the following quantities increases when a liquid at room temperature
becomes a gas at its boiling point?
A The average kinetic energy of the molecules
B The molecular size
C The total number of molecules
D All of these
Mr Khanna had a pond in his garden, filled with all kinds of aquatic plants. He wanted to prevent mosquitoes from breeding in the pond without harming the plants in any way. He could __________.
(i) Add salt into the water
(ii) Add some goldfish into the pond
(iii) Spray a film of oil on the surface of the pond
A (i) only
B (ii) only
C (iii) only
D (i), (ii) and (iii)
B is correct. As goldfish eat the mosquitoe's eegs
While building a new house, which of the following things should be taken care of to keep house clean and free of germs?
AThere should be proper ventilation, so that clean air can enter the house.
BThere should be good drainage system in bathrooms and kitchen.
CWindows and doors should have wire mesh to avoid flies and mosquitoes from entering into house.
DAll of these