Question

(i) Why does a bottle of soft drink cool faster when surrounded by ice cubes than by ice cold water, both at ${0^ \circ }C$?
(ii) A certain amount of heat Q will warm 1g of material X by ${3^ \circ }C$ and 1g of material Y by ${4^ \circ }C$. Which material has a higher specific heat capacity?

Answer 1

Hint: Heat is a type of energy, when absorbed by a substance, heat causes the inter particle bonds to weaken and break which leads to the change of state. Heat energy absorbed by a body depends upon the heat capacity Specific heat is defined as the number of calories required to raise the temperature of 1gm of a substance ${1^ \circ }C$
Formula used:
Specific heat capacity $ = \dfrac{Q}{{m\Delta T}}$

Complete answer:
(i) The bottle of soft drink cools faster when it is surrounded by ice cubes than when surrounded by ice cold water because 1g of ice at ${0^ \circ }C$ takes 336 J of heat energy from the drink to melt into water at ${0^ \circ }C$. Thus, the soft drink loses an additional 336 J of heat energy for 1g of ice at ${0^ \circ }C$than 1gm of ice-cold water at ${0^ \circ }C$. Therefore, cooling produced by 1g of ice at ${0^ \circ }C$is more than that produced by 1g of water at ${0^ \circ }C$.

(ii) Specific heat capacity or thermal heat capacity is defined as the amount of heat needed to increase the temperature of 1kg of a substance by 1 kelvin.
Mathematically it is given as,
Specific heat capacity $ = \dfrac{Q}{{m\Delta T}}$
Which means, Specific heat capacity $ \propto \dfrac{1}{{\Delta T}}$
According to the above relation we can conclude that the material X has a higher specific heat capacity.
Hence, (i) a bottle of soft drink cools faster when surrounded by ice cubes than by ice cold water because the soft drink loses an additional 336 J of heat energy for 1g of ice at ${0^ \circ }C$ than 1gm of ice-cold water at ${0^ \circ }C$.
(ii) Material X has a higher specific heat capacity.

Note:
There are several factors on which heat energy absorbed by a body depend which are: Heat capacity which is known as the body's ability to retain heat. More the heat capacity of a body, more will it absorb the heat energy. It also depends upon the colour of the body; dark colours absorb more heat. It also depends upon the temperature of the body, lesser is the temperature of the body, greater will be its ability to absorb heat.