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Chemistry LAB name:

Specific Heat of a Metal Lab Labs Section

Date

Background:

In class, we have discussed some introductory characteristics of thermodynamics. In your background section, some topics to consider and write about or define include: energy, heat, heat capacity, and specific heat capacity.

Purpose:

Calculate the specific heat of an unknown metal and use this number along with the density of the metal to correctly identify the metal.

MATERIALS:

1 hotplate 1 crucible tongs Boiling stones

400-mL beaker 2 Styrofoam cups Metal sample

100-mL graduated cylinder 1 thermometer Distilled water

Procedure: Determining the Specific Heat of a Metal

1. Add a few boiling stones and 250-mL of tap water to a 400-mL beaker; heat the water until the water is boiling gently using the hot plate (DO NOT turn the hot plate to max. heat).
DO STEP 2 WHILE WAITING FOR WATER TO BOIL

2. Obtain a piece of metal from your teacher.

3. Record the mass of your metal.

4. Using tongs, carefully place your metal in the water that is gently boiling on the hot plates. Allow the metal to heat up for approximately 5 minutes. Continue to the next steps while you wait.

5. Setup a makeshift calorimeter using 2 styrofoam cups (one as the base, one as the top, which has a small hole in the top for the thermometer).

6. Measure around 250.0 mL of cool distilled water in a graduated cylinder and pour this water into your calorimeter. Record the exact amount (nearest 0.1 mL) as the mass of your water (since the density of water = 1.0 g/mL, the volume = mass. EXAMPLE, 50.0 mL = 50.0 grams of water).

7. Measure the temperature of the water in the Styrofoam cup calorimeter. Record this as the initial temperature of the water in your data table.

8. Check the thermometer of the hot water bath and record this temperature as the initial temperature of the metal. (Since the metal has been in there for 5 minutes we can assume it is the same temp as the boiling water)

9. DO THIS STEP QUICKLY: Using tongs, remove metal from hot water and immediately place it in the calorimeter.

10. Monitor the temperature of the water in the calorimeter. Carefully use the thermometer to gently stir the water. Record the highest temperature as the final temperature of the metal and as the final temperature of the water in your data table.

11. Remove the metal from the cup, dump the water from your calorimeter, dry the metal and calorimeter, and repeat steps 4-10 two more times.

12. Clean your designated lab area, return all materials, and check in with your teacher before returning to your desks.

Pre-Lab Questions:

1.  (1 pts) A sample of water changes temperature from 80.0 °C to 20.0 °C. Calculate ∆T.

2.  (2 pts) How much energy is required to raise 57.1 grams of water from atemperature of 36.5 °C to 66.9 °C? (the specific heat of water = 4.184 J/g ºC)

3.  (3 pts) What mass of magnesium is present if 250 J raises the temperature from 25.0 °C to 27.0 °C? (specific heat of magnesium = 1.05 J/g ºC)

DAta Table: (4 points: must have units, correct number of sig figs for measurements, complete)

Trial: / 1 / 2 / 3 /
AVG
Mass of metal (MASS OF METAL WILL NOT CHANGE)
Mass of water in Styrofoam cup (record the volume to ONE DECIMAL PLACE and just change mL to grams of water)
Initial temperature of water in Styrofoam cup
Initial temperature of metal (same as the temp. of the boiling water the metal is in)
Final temperature of the metal and as the final temperature of the water (MAXIMUM temperature reached by metal + water combination)

Calculations (show work for full credit):

1. (2 points) Determine the change in temperature for the water and the metal respectively. Use the same final temperature for both the metal and the water.

Metal: ΔT = Tf - Ti

Water: ΔT = Tf - Ti

2. (2 pt) Calculate the heat gained by the water. Use q =mc∆T, solving for q (heat) and inserting m (mass of water), c (specific heat of water = 4.184 J/g ºC), and ∆T (change in temperature for water).

3. (2 points) Since the heat gained by the water is equal to the heat lost by the metal, we can use this value to determine the specific heat of the unknown metal. q = mc∆T

Use q (answer from #2), m (mass of your metal), and ∆T (change in temperature for the metal) to solve for c (specific heat of the unknown metal).

4. (1 point) Use the included table of specific heats and your answer to the metal’s specific heat from CALCULATION #3 to determine the identity of your unknown metal.

Your metal:

Metal / Specific Heat (J/g ºC)
Aluminum / 0.91
Iron / 0.46
Lead / 0.13
Silver / 0.23
Tin / 0.21
Titanium / 0.54
Zinc / 0.39
Water / 4.18

5. (2 points)
Your metal was actually LEAD.
Calculate the percent error for this experiment. Use your value from calculation #3 as the experimental and the value in the table for lead as the accepted value (0.13 J/g°C).

RECORD ANSWER TO ONE DECIMAL PLACE

% error = |(accepted value - experimental)| x 100

accepted

6. (5 points) A beaker contains 125.0 grams of water at 22.0 °C. A small piece of metal with a mass of 38.2 grams is hanging in another beaker of boiling water, measured at 102 °C. When the metal is removed and added to the cooler water, the final temperature is 23.3 °C. What is the specific heat of the metal?

7. (2 pt) Using the table of specific heats above, list the 5 metals (aluminum, lead, tin, zinc, iron) and water in order of increasing specific heat.

8. (2 pt) If you have 50.0 g samples of each of the 5 metals and water, and you add 100 J of energy to each, which substance will have the largest resulting temperature change? Which substance will have the smallest temperature change?

9. (3 points) Identify 3 sources of error in your experiment to help explain your percent error.