Can somebody describe to me, how can we find the heat capacity of substances in liquid state?

Question

What values are needed to find the heat capacity.??

thx for the help...

Answer 1

You need a scale, a thermometer, a calorimeter, the substance's molecular weight, and quantifiable source of heat (like a heated block of metal).

Weigh the liquid. Use it's molecular weight to calculate the number of moles. Place the liquid in the calorimeter, and use the thermometer to find the initial temperature. Weigh the metal block. Heat the metal block to some high temperature (I would suggest at least 40°C above the temperature of the liquid, but below the boiling point - DO NOT DO THIS WITH A FLAMIBLE LIQUID!) and place it immediately into the liquid. Wait for the temperature to stop rising and record that temperature.

Now, for the calculations:
Calculate the amount of energy released from the metal block: mass of the block * specific heat capacity * (final temp - initial temp). When something is cooled (the metal), the energy will be negative.
The negative of that is the energy released into the liquid.
Calculate the heat capacity of the liquid: energy / (moles of liquid * (final temp - initial temp)).

Example:
You have 100 g of an unknown liquid with a molecular weight of 50 g/mol. The initial temperature is 20°C. You heat a 50 g block of copper to 100°C and place it in the liquid. The final temperature is 50°C.
The number of moles of the liquid is 2 mol (100 g / 50 g/mol)
The specific heat capacity of copper is 0.385 J / g / K
50 g copper * 0.385 J/g/K * (50°C - 100°C) = -962.5 J
So, 962.5 J is released into the liquid.
The heat capacity of the liquid is 962.5 J / (2 moles * (50°C - 20°)) = 16.04 J / mol*K

If you don't know the molecular weight, you can find the specific heat capacity of the liquid, just using the number of grams in place of the number of moles in that last equation (ie: 962.5 J / (100 g * 30°C) = 0.3208 J / g*K

Good luck!

Answer 2

The heat capacity of a substance is the change in heat (added) divided by the change in temperature.

For liquids, a calorimeter is usually used. A small amount of heat is added to the liquid in the calorimeter and the temperature change is measured.

The heat capacity divided by the mass is called the specific heat capacity.

Answer 3

teh formula to use woould be mass x specific heat capacity of liquid x temperature difference = energy in KJ

this is KS4 chemistry so any website would have this in chemistry notes
specific heat capacity of liquid can be found in tables