Heat Capacity:

Heat Capacity, C, of a body is defined as the amount of heat (Q) required to raise its temperature (θ) by one degree, without going through a change of state. 

• Amount of heat needed to raise the temperature of an object depends on the mass of the object.
• Heat capacity also depends on the material of the object. Some materials are harder to heat up than others. In order to record 1°C increase in temperature, liquids would require more heat energy than solids.
• SI. unit of heat capacity is joule per kelvin (J K^-1) or joule per degree Celsius (J °C^-1).

C=QΔθ
 , where
C = heat capacity (JK^-1, J°C^-1)
Q = heat or thermal energy absorbed or released (J)
Δθ = change in temperature (K or °C)

 Specific Heat Capacity: 

Specific heat capacity, c, of a body is defined as the amount of heat (Q) required to raise the temperature (θ) of a unit mass of it by one degree, without going through a change in state.

• When the mass of an object is greater, the object will contain more atoms or molecules than a less massive object made up of the same material. Hence, when the temperature of the objects are raised, the more massive object will require a larger thermal energy than the less massive object. (Analogy: The more massive object has more “mouths” to feed) It is thus more common to consider the heat capacity per unit mass or specific heat capacity of the body.

SI unit of specific heat capacity is joule per kilogram per kelvin (J kg^-1 K^-1) or joule per kilogram per degree Celsius (J kg^-1 °C^-1)
Q=mcΔθ

 

 

Thermal Energy and Temperature

Thermal Energy:
 Thermal energy is a form of internal energy. Thermal energy is possessed by all material matter and manifest as the random motion of atoms and small particles. The amount of thermal energy depends on the temperature of the matter.

Temperature:
Temperature is a measure of the degree of hotness or coldness of a body.

Transfer of Thermal Energy:
Thermal energy may be transferred from one region to another as a result of a difference in temperature via thermal:

1. conduction 
2. convection 
3. radiation 

Thermal energy flows from a higher temperature object to a lower temperature object. However, this heat exchange will cease when both objects reach thermal equilibrium (same temperature).
Important:
Temperature is not the equivalent of the total energy contained in a body. The total energy contained in a body is comprised of other forms of energy as well.

...determining Density

DENSITY

The density, or more precisely, the volumetric mass density, of a substance is its mass per unit volume. The symbol most often used for density is ρ (the lower case Greek letter rho), although the Latin letter D can also be used. Mathematically, density is defined as mass divided by volume:

where ρ is the density, m is the mass, and V is the volume. In some cases (for instance, in the United States oil and gas industry), density is loosely defined as its weight per unit volume, although this is scientifically inaccurate – this quantity is more specifically called specific weight.

• SI unit of density is kilograms per metre cube (kg m^-3). It is a scalar quantity.
• Another common unit of density is g cm−3. 1000 kg m−3=1 g cm−3

ρ=The density of a substance does not change as you move from place to place as the mass and volume does not depend on the gravitational acceleration of the point that the object is at.

Qtn: Why does the cork float and the rock sink in water?
Ans: The density of a substance determines whether it will float or sink in different liquids (or gases).
The cork is less dense than water → it floats in water.
The rock is denser than water → it sinks in water.