Lab 5: Identification of 3 Metals Using Specific Heat
Problem: Can Specific Heat be used to identify unknown substances?
Background:
Specific Heat is a physical property of matter. Each substance has its own Specific Heat. Specific Heat
measures the about on heat a substance needs to absorb or release to change one gram of the substance one
degree Celsius. Specific Heat is influenced by the mass and the amount of matter being heated or cooled as well
as the overall change in temperature.
To calculate Specific Heat (C)
q = mCΔt
Where q is the amount of heat involved in Joules, m is the mass of the substance in grams, C is the
specific heat of the substance in J/g·°C and Δt is the change in temperature in °C.
In this experiment we will be transferring heat from one substance to another. Given enough time the
two substances will come to equilibrium. That is, the heat lost by the first substance will be equal to the heat
gained by the surroundings. This must be kept in mind when performing the associated calculations!
In this experiment the metal will be heated to the boiling point of water and then transferred into a
different sample of water. The metal and the water sample will begin to exchange heat right away, the metal
releasing heat and the water sample absorbing heat. The amount of heat lost by the metal is equal to the
amount of heat gained by the water!
Materials and Methods:
3 Metals Cylinders
50mL graduate cylinder
Hot plate
Aluminum-sided thermometer
250mL Beaker
Tongs
100mL Beaker
1. Set up a 250mL beaker, half filled with water on the hot plate. Dial the hot plate to setting “5”.
Allow the water to come to a boil (so what is the temperature of boiling water?). This larger
beaker and hot plate will be used to transfer heat to the metal cylinders.
2. Obtain a metal cylinder (one at a time) and make note of the color of the metal.
3. Using the electronic balance measure the mass of the slug.
4. Once the water bath is boiling, place the metal cylinder in the water and allow it to heat up for
at least 5 minutes. By doing this, it can be assumed that the metal will reach equilibrium with
the water, and the same temperature as its surrounding. This will be the initial temperature for
the metal cylinder (T1metal).
5. While the metal is in the water bath, measure exactly 50mL of water in a graduated cylinder and
place it in a 100mL beaker. This will be the water sample!
6. Place an aluminum-sided thermometer into the water sample and allow it to equilibrate. This
temperature is the initial temperature of the water sample (T1water).
7. When both initial temperatures have been measured the metal cylinder will be transferred from
the boiling water bath into the water sample. To do this, using tongs, CAREFULLY and QUICKLY
remove the metal cylinder and place it into the water sample so that the water does not spill or
splatter. Do NOT allow the metal to cool in the air (in other words this has to be done super fast
– no hesitating).
8. Using the thermometer stir the water sample and metal cylinder and observe the temperature.
Record the highest temperature the water is heated to. This is the final temperature of the
water (T2water) AND the metal cylinder (T2metal) (assuming they reach equilibrium).
9. Repeat for the other two metal samples.
Calculations:
Throughout this experiment there will be a number of calculations done in order to even come
close to the specific heat of the metal.
A. First, the water sample’s mass is not being measured directly. To determine the mass of the
water sample the density formula can be used. The density of pure water is 1g/cm3 or
1g/mL. Using that information and the volume of the water sample, what is the mass of the
water sample?
D = mass/volume
B. To calculate the specific heat of the metal, the amount of heat absorbed by the water must
be determined. Using the heat formula and knowledge about the specific heat of water
calculate the amount of heat absorbed by the water sample.
q = mCΔt
Where Δt is the final temperature of the water (T2water)– initial temperature of the water (T1water).
C is the specific heat of water (assuming it is pure).
C. Using this information, the amount of heat absorbed by the water is equal in value to the
amount of heat released by the metal. Calculate the specific heat of the metal using the
same formula as above:
q = mCΔt
Where Δt is the final temperature of the metal (T2metal)– initial temperature of the water (T1metal).
q is the amount of heat lost by the metal.
Data:
In your lab report there will be a total of 4 tables.
For each metal create a table modeled after the one below. Include all units.
Color of Metal
Mass of Metal
(g)
Initial
temperature
of metal (T1)
Final
temperature
of metal (T2)
Mass of water
sample (g)
Initial
temperature
of water
sample (T1)
Final
temperature
of water
sample (T2)
Below each table show calculations for:
1. The heat gained by the water.
2. The specific heat of the metal.
Once all calculations have been completed create a fourth table similar to the one below.
Color of metal
Measured specific heat
(C)
Accepted specific heat
(C)
Percent Error (%)
Below this table show your calculations for determining the percent error in specific heat values for each
metal.
Discussion Questions:
(Type both the question and the answer. Answer them thoroughly.)
1) Why was the q for water equal to – q for the metal?
2) What was the endothermic process vs. the exothermic process in this lab?
3) What was the relationship between metal mass and specific heat? What was the relationship
between temperature change and specific heat?
4) Research what is known to affect the specific heat of metals. (CITE IN THIS ANSWER.)