Give reasons for the followings.
(a) Why do we see water droplets collected on the outer surface of a glass container, containing
ice?
(b) Why is it advisable to use a pressure cooker at higher altitudes?
(c) Why is water liquid at room temperature?
(d) Why are solids generally denser than liquids and gases?
(e) Why do people perspire a lot on a hot humid day?
(f) Liquids generally have lower density as compared to solids, but ice floats on water. Find out, why.
(g) Why should we wear cotton clothes during summer?
(h) Why does a desert cooler cool better on a hot dry day?
(i)Why do people sprinkle water on the roof after a hot sunny day?
(j) Why does ice at 0°C appear colder than water at same temperature?
(k) Why mixture does not have a fixed melting point or a fixed boiling point? Give two reasons?
(l)Why does our palm feel cold when we put some acetone or petrol or perfume on
(m) Give reason to explain why it takes longer time to dry wet clothes in humid
(n) Cotton is solid but it floats on water. Why?
Answers
Answer:
a. due to condensation of the water particles around the glass tumbler
b. to increase the boiling point of the food articles inside the pressure cooker as increase pressure increases boiling point of a substance
c. because it's boiling point is 100°c and freezing point is 0°c
d. due to greater force of attraction between the molecules of a solid
e. because air gets saturated with humidity, decreasing the rate of evaporation
f. because of inter-particular gap between liquids is more than that in solids and still more in gases
g. because they have pores,letting in the exchange of sweat from inside and air from the outside and it reflect most of the sun's energy, thus keeping us cool
h. because there is less humidity on a hot dry day
I. so that roof gets colder due to the evaporation of water, as the evaporating water absorbs heat from its surrounding I. e. the roof
j.because of the greater density of solid ice
k. 1.because it constitutes of two different substances with different melting or boiling poins.
2.the particles constituting the mixture are not in chemical bond but only in a physical bond
l. because the acetone or alcohol have low melting point and thus evaporate,absorbing heat from the palm of our hands
m. evaporation from the clothes lessens because the air is already saturated with water particles
n. because it has pores which contains air in it and thus its relative density becomes less than that of water.
I have answered all the questions on the basis of my knowledge but if you are eligible to please check for yourself