What could be the final temperature of a mixture of 100 g of water at 90 C and 600g of water at 20 C ans 30 C?

Calorimetry is an experimental method that allows one to calculate the heat change in a chemical process.

calorimeter is just a reaction vessel. It could be a foam cup, a soda can, or a commercially available bomb calorimeter like http://www.parrinst.com/products/oxygen-bomb-calorimeters/1341-plain-jacket-bomb-calorimeter/.

Basically, you have a certain amount of water surrounding a reaction. You measure the temperature change in that water, and you use that to calculate the heat gained or released during a process. That equation usually takes a form:

#-q_(rxn) = q_(cal) + q_(water)#

Where q represents the heat change in the reaction, the calorimeter and the water. Since you are only measuring temperature, you will need to calculate the heat using it.

The change in heat of the calorimeter is given by:
#q_(cal) = CDeltaT# where C is the heat capacity of the calorimeter.

The change in heat of the water is given by:
#q_(water) = c_(p)mDeltaT# where #c_p# is the specific heat of water, which is 4.184 J/gC, m is the mass of water in the calorimeter in grams, and delta T is the change in temperature.

The video discusses how to solve a sample calorimetry calculation.

Video from: Noel Pauller

See here for more sample calculations:
http://www.chem.ufl.edu/~itl/2045/lectures/lec_9.html

Another video on calorimetry:

Calorimetry is the measurement of heat flow.

Heat energy flows from a substance that has a higher temperature to a substance that has a lower temperature. The heat will continue to flow until both substances reach the same temperature, known as the final temperature.

A device called a calorimeter is used to measure heat flow. It consists of nested styrofoam cups. In a high school chemistry class we generally study the heat exchange between hot metals and water or water samples at different temperatures. The nested styrofoam cups are insulators so that all the heat is transferred from the warm object to the cooler one.

The equation for heat, q = m x #C_s# x #deltaT# is used for calorimetry. The heat lost by the warm object is equal to the heat gained by the cooler object: Q lost by the hot material = Q gained by the cold material We can set up the following equation to solve for any part of the heat calculations

[ Mhot x #C_s#hot x (#T_f# - #T_bhot)] - [Mcold x C_s# cold x (#T_f# -#T_b#cold)] = 0