Physics · Thermal Properties Of Matter · NEET
In an insulated system no heat escapes to the outside. So all the heat that the hot body gives out is taken in by the cold body (and by the calorimeter). We write this as: heat lost by hot body = heat gained by cold body. Using Q = m c dT for each body, this becomes m1 c1 (T1 - Tf) = m2 c2 (Tf - T2), where Tf is the final common temperature. This one equation lets you find any unknown.
Yes, if the question gives its mass and specific heat. The metal cup (calorimeter) also warms up or cools down, so it absorbs or releases heat too. Then: heat lost by hot body = heat gained by water + heat gained by calorimeter. In NCERT Example 10.3, heat from the hot aluminium sphere is set equal to heat gained by water plus heat gained by the copper calorimeter.
Water equivalent (w) of a body is the mass of water that would absorb the same amount of heat for the same temperature rise. It is w = m c / c_water. It is a shortcut: you replace the calorimeter (mass m, specific heat c) with an equal 'water mass' w, so you only deal with water in the equation. Its unit is kg or g, same as mass.
No. Specific heat c is per unit mass (J per kg per K). Heat capacity C is for the whole object: C = m c (J per K). In the principle of mixtures you can write heat as C dT directly. This matters in the 2016 NEET question, which compares two bodies by their heat capacities, not their masses.
So that no heat leaks to the surrounding air. The principle 'heat lost = heat gained' is only exactly true when the system is isolated. If heat escapes, the measured final temperature is lower than the true value and your calculated specific heat is wrong. That is why a real calorimeter sits inside a wooden box with an insulating lid and a stirrer to mix evenly.
Two bodies have different thermal (heat) capacities. One of them is at 100 C and the other at 0 C. If the two are brought into contact in an isolated system (no heat loss to surroundings), and the body at 100 C has the larger heat capacity, the final common temperature will be:
Try the real previous-year questions from this chapter — each with the answer and a full solution.
In an insulated system, heat lost by the hotter body equals heat gained by the colder body, so total heat is conserved.
Q = m c dT, where m is mass, c is specific heat capacity, and dT is the change in temperature. For the whole mixture, set total heat lost equal to total heat gained.
Usually a metal vessel (copper or aluminium) with a stirrer of the same metal, placed inside an insulating box so heat does not escape to the surroundings.
Joule per kilogram per kelvin (J per kg per K). For water it is about 4186 J per kg per K, or 4.186 x 10^3 J per kg per K.
It depends on the product m c (the heat capacity) of each body, not on mass alone. The body with the larger m c pulls the final temperature closer to its own starting temperature.
