Specific Heats

IMPORTANT

Specific Heats: Overview

This topic covers concepts, such as, Specific Heat Capacity of Water, Heat Capacity, Variation of Specific Heat Capacity of Water with Temperature & Water Equivalent of Calorimeter etc.

Important Questions on Specific Heats

MEDIUM
IMPORTANT

The molar heat capacity of water at constant pressure is  75J K1 mol1. When 1kJ of heat is supplied to 100g of water, which is free to expand, the increase in temperature of water is

                               

MEDIUM
IMPORTANT

In a certain system of units, the fundamental unit of mass is taken as 2 kg, unit of length is taken as 12 m, unit of time taken as 4 s and unit of temperature is taken as 2 Kelvin. In this system. 1 unit of specific heat capacity will be (specific heat capacity is given by s=Qm×ΛT. Where Q is heat, m is mass and ΔT is change in temperature) :-

HARD
IMPORTANT

Four different liquids, each of mass 1 kg, are separately heated at the same rate The initial temperatures of the liquids are all 20°C. The boiling points (b.p.), specific heat capacities (s.h.c.) and latent heat (L.h.) of the liquids are shown below. Which one of them will completely evaporate first?

EASY
IMPORTANT

During an adiabatic process, the pressure of a gas is found to be proportional to the cube of its absolute temperature. The ratio CPCV  for the gas is x2. Find x.

MEDIUM
IMPORTANT

A U-tube, made of heat- insulating material, is shown in figure. One limb is closed by a non- conducting cork, the temperature is T0=300 K. How much heat (in multiples of 100 Joule) is required to be given by the coil so that the air rises to a temperature T=510 K? The thermal expansion of mercury is negligible. (Take:
Area of the tube as 0.1 m2,ρHg=13.6 g cc-1; Patm=75 cm of Hg,R=253 SI units). Neglect the heat flow through the mercury.

HARD
IMPORTANT

A fuse made of a lead wire with a cross-section of 0.2 mm2 is incorporated into a circuit of copper wire with a cross-section of 2 mm2. On short circuiting the current reaches 30 A. The temperature of wires before short circuiting is T0=20°C. Neglect the loss of heat due to thermal conductivity and radiation. Take the specific heat of lead and copper as constant and equal to C1=0.032cal gm-1°C and C2=0.091cal gm-1°C respectively. Given that resistivity and density of lead are ρ1=22×10-6ohm-cm and d1=11.34gm cm-3 and for copper ρ2=1.7×10-6ohm-cm and d2=8.9gm cm-3. The melting point of the lead is T1=327°C. Let  "t0" is the time when the lead fuse begins to melt after the short circuit occurs and Δt is the rise in temperature of copper wire during this time. Then mark the CORRECT option(s) up to three significant figures after decimal

MEDIUM
IMPORTANT

An ideal gas which undergoes through a process V=aT2; starting at T0 and ends at 2T0. a is a constant. The molar heat capacity of the gas if it is monoatomic is n2R; What is n ?

EASY
IMPORTANT

The SI unit of specific heat is Jkg K.

MEDIUM
IMPORTANT

Amongst object A and B, if the specific heat of object A is less than of object B, then 

EASY
IMPORTANT

The specific heat capacity of any substance is the amount of heat required to raise the temperature of one unit substance by hundred degree.

EASY
IMPORTANT

The amount of heat required to increase the temperature of one kilogram of a material, by 1 °C is called latent heat.

EASY
IMPORTANT

The time taken for a calorimeter containing 75 g of water at 62°C to cool to 58°C is 9 minutes. When the calorimeter contains 105 g of water, it takes 12 minutes to cool from 62°C to 58°C. The water equivalent of the calorimeter is

MEDIUM
IMPORTANT

The specific heat capacity of water is less than that of steam.

MEDIUM
IMPORTANT

The specific heat capacity of water is less than that of ice.

MEDIUM
IMPORTANT

A cube of lead of 500 g at 25 °C is supplied with a 3225 J heat. Find the final temperature (in degree Celsius) of the lead cube. (Take, specific heat of lead is 0.129 Jg °C

EASY
IMPORTANT

The specific heat capacity of water is less than that of aluminium.

MEDIUM
IMPORTANT

Calculate the heat energy (in joules) to raise the temperature of 5 kg of water from 20 °C to 100 °C. (Take specific heat of water, sw=4.2×103 J kg-1 K-1)

EASY
IMPORTANT

Explain the specific heat capacity of water.

MEDIUM
IMPORTANT

A container has 4.2 litres of water at 40 C°. Heat required to boil water in kJ is

MEDIUM
IMPORTANT

The amount of heat required to raise the temperature of 1 kg mass of water through 1 K is called its