Mixing Warm and Cold Water

 Heat can be defined as energy transferred between matter because of differences in temperature. The ability of matter to transfer heat depends on its mass and temperature. A calorimeter is an instrument used to measure changes in heat energy. You can make a simple calorimeter using a Styrofoam cup to contain water, a beaker for more insulation and support, and a thermometer to measure temperatures. The joule (J) is the SI unit for heat energy. An equation that can be used to calculate change in heat energy is  Q = m•Dt•C_p where Q = heat absorbed or released (in J), Dt = change in temperature (in °C), m = mass (in g), and C_p = specific heat capacity (4.185 J/g° C for water).

 OBJECTIVES
 In this experiment, you will
• mix cold and warm water
• determine heat lost by cooling water
• determine heat gained by warming water
• compare heat lost by cooling water and heat gained by warming water

 PROCEDURE

 1. Using a graduated cylinder get 50.0 mL (50.0 g) of cold water from the container supplied by the teacher. Be careful not to take any ice pieces. Pour the cold water into the calorimeter. Record the mass of the water. Record  the temperature of the water after leaving the thermometer in water for at least 15 seconds.

2..   Use graduated cylinder to get 50.0 mL (50.0 g) of warm water from the container supplied by the teacher (at teachers desk - hot water faucet). Record mass of water and temperature.

3.    After the first temperature readings have been made, transfer the warm water into the calorimeter. Stir to mix the warm water with the cold water. Record the final temperature reached.

 DATA

 Cold Water: __________g                             Warm Water: _________g

 Initial temp. ________________°C                                   Initial temp.   ______________°C

 Final Temperature of Mixture: ____________________°C          

 PROCESSING THE DATA

 1.        Calculate the temperature change, Δt, for the warming of cold water and the cooling of warm water by subtracting the initial temperature from the final temperature for the cold water and the warm water:

 cold water: _________°C                                                       hot water: __________°C

2.Calculate the heat gained by the cold water (in J). Use the equation: Q = m•Dt•C_p

 

 where Q = heat absorbed (in J), Dt = change in temperature (in °C), m = mass (use actual mass of cold water), and Cp = specific heat capacity (4.185 J/g° C for water).

 3.        Calculate the heat lost by the warm water (in J). (see number 2 above for formula)

 

4.    Calculate the percent difference using the formula

                          heat lost - heat gained
difference =                 heat loss                    X 100

 

 

 5. What are some factors that might have caused the difference determined in Step 4?

 EXTENSIONS

 1. Give design ideas for a better calorimeter that might reduce heat lost in this experiment.

 

 2. Suggest possible factors that might have contributed to error in the heat exchange.