Download Using Specific Heat to Determine the Identity of an

Using Specific Heat to Determine the Identity of an Unknown Metal
Specific heat is the energy needed to raise one gram of a substance by one degree Celsius. Since
this value is unique for every substance, it is possible to use specific heat to determine the
identity of an unknown substance. According to the law of conservation of energy, the heat
within a system must remain constant. Therefore, the heat lost by one part of the system must be
equal to the heat gained by the remainder of the system.
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Fill a 250 ml beaker about half full of water and begin to heat it
Obtain a metal sample and determine its mass
Place the metal sample in the water
Heat the water to boiling. Leave the metal I the water for at least two minutes after the
water boils, to assure that the metal is the same temperature as the water
Record the temperature of the boiling water
Weigh a Styrofoam cup and record the mass
Fill the cup with cold water and record the mass of the cup and the water
Record the temperature of the cold water in the cup
Transfer the metal from the hot water to the cup of cold water. Stir the water gently with
the thermometer and record the highest temperature reached by the water. This should be
the equilibrium temperature
Calculations:
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Calculate the ∆T for the water.
Calculate the ∆T for the metal (remember the final temperature of the water and the metal
are the same
Determine the specific heat of the metal
Identify the metal, based on its specific heat
Questions for further thought (include answers to these in conclusion):
1. Look up the specific heat values for Mg, Al and Zn. If equal masses of these metals are
exposed to the same amount of heat, which metal will reach the highest temperature?
Why?
2. 1500 calories of heat are added to 50.0 g of Mg at 25°C. What is the final temperature of
the Mg?
3. 500.0 calories are removed from 40.0g of a silvery metal at 80°C. the temperature falls to
30.0°C. Would the metal most likely be silver, tin or magnesium? How do you know?