Experiment 4.
Specific Heat of a Metal

LEARNING OBJECTIVES

The students will be able to learn
 

  1. The concept of conservation of
  2. That heat flows from a hot object to a cold
  3. That metals are good conductors of heat. Metals have low specific heat; for a given energy input to a given mass, the temperature rise of metals will surpass the temperature rise of non-metals.

 
 

BACKGROUND

The First Law of Thermodynamics states that energy can neither be created nor destroyed; it can only be transformed to a different form of energy, e.g. in batteries, the chemical energy is converted into electrical energy and in automobile engines, where the gasoline is burned, the chemical energy is converted into kinetic energy. Basically, the energy of the Universe is a constant. The Universe is composed of a System (in this experiment, the calorimeter) and its Surroundings (everything else).
 
Heat energy is measured in terms of calories or Joules. One calorie is the amount of heat energy required to increase the temperature of 1.00 gram of water by 1.00 ᵒC. Specific Heat is a physical property of a substance. It is defined as “the amount of heat energy required to increase the temperature of 1.00 g of any substance by 1.00 ᵒC. Therefore, substances with low specific heat require less heat energy to raise their temperatures.
 
 
4.18 joules
Specific heat of water, c                            o
1.00 g 1.00 C
 
The unit of the specific heat is J/(g×ᵒC). There are two parts in this experiment:

  1. Determination of the specific heat of metallic
  2. Determination of the specific heat of an unknown

 
In Part A of these investigations, you will determine the specific heat of metallic copper. Then, in Part B, you will determine the specific heat of an unknown sample and identify it by using the specific heat value provided in the Table 1.
You will use a calorimeter to determine the specific heat of the metal. The calorimeter (in Greek calor means heat) is a device that measures the specific heat of a metal using the temperature changes of the metal and the water (see Figure 1).
 
The amount of heat energy needed to increase the temperature of an object is given by the following formula:
Q = m × c × ΔT                                                         Eq. 1
 
Q = heat energy (Joules) m = mass of the metal (g)
c = specific heat of the metal J/(g.ᵒC) ΔT
= change in temperature (ᵒC)

 
 
Assuming an ideal calorimeter, no heat escapes from the cup (the heat is not lost to the surroundings) and the heat is exchanged between the hot metal and the cool water:
 
 
DRY LAB SIMULATION: http://www.chemfiles.com/flash/calorimeter.swf
 
Now, using the First Law of Thermodynamics, we will write the following expression: Heat lost by the hot metallic object = Heat gained by the water
 
In this experiment, the metal will be heated in a test tube immersed in boiling water that is contained in a beaker. Then, the metal will be dropped into the calorimeter (doubled Styrofoam cups originally containing water at room temperature).
 
Qlost by the metal = Qgained by the water                                                        Eq. 2 mmetal × cmetal × (Tmetal – Tfinal) = mwater × cwater × (Tfinal  – Twater)               Eq. 3
where
 
mmetal = mass of the metal used (grams)
cmetal = specific heat of the metal (for copper c = 0.38 J/(g×ᵒC) Tmetal = temperature of the boiling water (100ᵒC) mwater  = mass of the water in the calorimeter (grams) cwater = specific heat of water; c = 4.18 J/(g×ᵒC)
Twater = the initial temperature of the water in the calorimeter (ᵒC)
Tfinal = the temperature of the water and the metal in the calorimeter (ᵒC)
 
 
 
PRE LABORATORY WORKED EXAMPLE
 
Example. A 50.00 g sample of copper at 99.0ᵒC is dropped into a calorimeter containing 170.00 g of water at 22.0 ᵒC, producing a maximum resulting temperature of 24.0ᵒC. Calculate the specific heat of the copper sample.
 
Solution:                                 Qlost by the metal = Qgained by the water
 
mmetal × cmetal × (Tmetal – Tfinal) = mwater × cwater × (Tfinal – Twater)
 
(50.00 g) × (ccopper) × (99.0 – 24.0 ᵒC) = (170.00 g) × (4.18)(J/g×ᵒC) × (24.0 – 22.0 ᵒC)
 
 
 
MATERIALS
3750 × ccopper = 1421.2 J ccopper = 0.38 J/(g×ᵒC)
 
 
100-mL graduated cylinder, 250-mL and 400-mL beakers, weighing dish, large test tube, heaterstirrer, utility clamp, ring stands, Styrofoam coffee cups, thermocouples (2), Labquest®, centigram balance, deionized water, copper shots, unknown metals, and boiling chips.
 
SAFETY INFORMATION

  1. NO EATING or DRINKING IS ALLOWED IN CHEMISTRY

 
 

  1. OBTAIN and WEAR EYE GOOGLES AT ALL
  2. NOTIFY YOUR INSTRUCTOR IF YOU HAVE ANY QUESTIONS OR ALLERGIES TO THE METALS.
  3. CLEAN UP WASH YOUR HANDS BEFORE LEAVING THE

 
 
 
 
 
 
 
 
 
 
 
 

PRELAB QUESTIONS                    NAME:                                         

  1. Identify the specific heat equation. Provide the names and identify the units of all the

 
 
 
 
 

  1. An unknown metal is dropped into 127 grams of water. The temperature of the water has beenraised from 25OC to 28O Using the specific heat of water found on page 54 determine the amount of heat gained by the water.

 
 
 
 
 
 
 
 
 

  1. A 20.0-gram piece of metal at 88OC is cooled by a sample of water to 25O The amount of energy (energy given off by the metal is = energy absorbed by the water) is 320 Joules. Determine the specific heat of the unknown metal.

 
 
 
 
 
 
 
 

  1. Identify the material based upon the specific heat calculated and the published values found within Table 1 of this

 
 

PART A: Specific heat of metallic copper PROCEDURE:

  1. Obtain a ring stand, a heater, and a utility clamp and assemble them according to Figure

 
 

  1. Obtain a 400-mL beaker, drop a couple of boiling chips in it, and fill it with about 250 mL of tapwater.

 
 

  1. Place the 400- mL beaker on the heater. Start heating the

 
 

  1. Obtain a test tube and place about 50 g of copper pieces in it. Place one of the thermocouples inthe test

 
 

  1. Insert the test tube, suspended by the utility clamp, into the water and continue to heat the wateruntil the water starts to

 
 

  1. Continue to boil the water while heating the metal. Record the temperature when it reaches aconstant value (about 98 to 100ᵒC).

 
 

  1. Assemble the Styrofoam cups, the beaker, cardboard cover, thermocouple, and the Labquest®according to the Figure

 

  1. Using a 100-mL graduated cylinder, measure 100.0 mL of deionized water, and place it in thecalorimeter. This equals to 100.0 g of water since the density of water is 1 g/mL. Measure the temperature (from LabQuest, first thermocouple) of the water in the calorimeter and record

 
 

  1. Read the temperature of the metal sample (from LabQuest, second thermocouple), record it, andusing the utility clamp as a test tube holder, rapidly transfer the sample into the calorimeter and stir the contents of the calorimeter with the thermocouple (first thermocouple).

 
 

  1. Observe the temperature rise and record the highest temperature. Your instructor will guide youon how to setup the time-based data acquisition using the LabQuest®.

 
 

  1. Empty and dry the calorimeter with a paper towel. Replace the water, weigh another sample(make sure it is dry), and do another trial. Record the maximum temperature. Compute the average value.

 
 

  1. Empty the calorimeter again. Dry the sample with a paper towel, and return the sample to thedesignated container.

 
 

MATERIAL Specific heat J/(g×ᵒC)
Aluminum 0.900
Brass 0.380
Copper 0.387
Silver 0.234
Gold 0.129
Iron 0.448
PVC 1.34
Marble Chips 0.860
Tin 0.210
Sand 0.830
Steel 0.120
Water 4.18

Table 1: Specific heat of some common materials.

PART B: Specific heat of unknown metal PROCEDURE:

  1. Obtain a ring stand, a heater, and a utility clamp and assemble them according to Figure

 

  1. Obtain a 400-mL beaker, drop a couple of boiling chips in it, and fill it with about 250 mL of tap water.

 

  1. Place the 400- mL beaker on the heater. Start heating the

 

  1. Obtain a test tube and place about 50 grams of unknown metal pieces in it. Place one of the thermocouples in the test tube.

 
 

  1. Insert the test tube, suspended by a utility clamp, into the water and continue to heat the water until the water starts to

 

  1. Continue to boil the water while heating the metal. Record the temperature when it reaches aconstant value (about 98 to 100 ᵒC).

 

  1. Assemble the Styrofoam cups, the beaker, cardboard cover, thermocouple, and the Labquest®according to Figure

 

  1. Using 100-mL graduated cylinder, place exactly 100.00 mL (assume a density of 1 g/1 mL) of deionized water in the calorimeter. Measure the temperature (from LabQuest) of the water in the calorimeter and record

 

  1. Read the temperature of the metal sample (from LabQuest, second thermocouple), record it, andusing the utility clamp as a test tube holder, rapidly transfer the sample into the calorimeter and stir the contents of the calorimeter with the thermocouple (first thermocouple).

 

  1. Observe the temperature rise and record the highest temperature. Your instructor will guide you on how to set up the time-based data acquisition using the LabQuest®.

 

  1. Empty and dry the calorimeter with a paper towel. Replace the water, weigh another sample (make sure it is dry), and do another trial. Record the maximum temperature and compute the average reading.

 

  1. Empty the calorimeter again. Dry the sample with a paper towel, and return the sample to the designated container.

 
NOTE: ALL MEASUREMENTS WILL HAVE TWO DIGITS AFTER THEIR DECIMAL POINTS.
 
 
DATE:                             
DATA TABLE FOR SPECIFIC HEAT OF COPPER
NAME:                                            
 
 

  Known Object: COPPER
  Trial 1 Trial 2
1. mass of the weighing dish                             g                      g
 
2. mass of weighing dish + copper		  
                            g		  
                     g
 
3. mass of copper: (line 2) – (line 1)		  
                            g		  
                     g
 
4. mass of water in the calorimeter		  
                            g		  
                     g
 
6. temperature of metal		  
                            ᵒC		  
                     ᵒC

 
 

7. initial temperature of water                             ᵒC                      ᵒC
 
8. final temperature of water (in the calorimeter)		  
                            ᵒC		  
                     ᵒC
 
9. heat gained by water		  
                          J		  
                     J
[(100) × (4.18) × (line 8) – (line 7)]
10. heat lost by the copper# [-(line 9)]                                    J                      J
11. specific heat of copper                           J/(g×ᵒC)                      J/(g×ᵒC)
(solve for c using (line 10) / [(line 3) x ((line 8) – (line 6))]  

 
 

  1. average specific heat of copper J/(g×ᵒC)

 
 
 
 
# Denotes heat lost is negative.
 
 
 
 
 
 
 
 
 
DATE:                                                                                     NAME:                                            
 
DATA TABLE FOR SPECIFIC HEAT OF UNKNOWN METAL
 

  Unknown Object:                           
  Trial 1 Trial 2
1. mass of the weighing dish                             g                      g
 
2. mass of weighing dish + metal		  
                            g		  
                     g
 
3. mass of metal: (Line 2) – (Line 1		  
                            g		  
                     g

 
 

4. mass of water in the calorimeter                             g                      g
 
6. temperature of metal		  
                            ᵒC		  
                     ᵒC
 
7. initial temperature of water		  
                            ᵒC		  
                     ᵒC
 
8. final temperature of water (in the calorimeter)		  
                            ᵒC		  
                     ᵒC
 
9. heat gained by water		  
                          J		  
                     J
[(100) × (4.18) × (Line 8) – (Line 7)]    
 
10. heat lost by the metal#		  
                                   J		  
                     J

[-(Line 9)] EHFDXVHWKHWHPSHUDWXUHFKDQJHLVQHJDWLYH
 
 

  1. Temperature change of the metal                           ᵒC                                            ᵒC Line(8) – Line(6)

 

  1. specific heat of metal                         J/(g×ᵒC)                      J/(g×ᵒC)      solve for c using line

(10) / [Line (3) x Line (11)]
 

  1. average specific heat of unknown metal                    J/(g×ᵒC) # Denotes heat lost is

 
 
 
POST-LAB QUESTIONS                 NAME:                                       
(Observe the significant figures rules in your calculations).
 

  1. The specific heat of water is 4.18 J/(g×ᵒC). How much heat energy is required to raise thetemperature of 70.00 g of water by 00ᵒC?

 
 
 
 
 
 
 
 

  1. How much is heat required to raise the temperature of 50.00 grams of copper from 25.0ᵒC to 45.0ᵒC? The specific heat of copper is 0.387 J/(g×ᵒC).

 
 

  1. For a given energy input, which material will have the greater temperature rise: a sample of

10.0 gof water or a sample of 10.0 grams of copper? Why?
 

ADDITIONAL POST-LAB QUESTIONS.

  1. A 150.0 g sample of aluminum, c = 0.90 J/(g×ᵒC), is heated to 250.0ᵒC and rapidly dropped into acalorimeter containing 100.0 g of water, c = 4.18 J/(g×ᵒC), at 22.0ᵒC. What is the final temperature of water in the calorimeter? Assume no heat escaped from the

 
 
 
 
 
 
 
 
 

  1. A 50.0 g sample of zinc is heated, then placed in a calorimeter containing 100.0 g of water. Thetemperature of water increases from 22.00oC to 24.50o The specific heat of zinc is 0.390 J/(g×oC). What was the initial temperature of the zinc metal sample? (final temperatures of zinc and water are the same and no heat escapes from the calorimeter).

 
 
 
 
 
 
 
 
 

  1. A 15.0 g sample of gold is heated, then placed in a calorimeter containing 100.0 grams of water. The temperature of water increases from 29.0oC to 32.0o The specific heat of gold is 0.130 J/(g×oC). What was the initial temperature of the gold metal sample? (Assume no escape from the calorimeter).

 
 
 
 
 
 
 

  1. A 30.0 g sample of metal is heated to 109.0oC, then is placed in a calorimeter containing 50.0 g of water. The temperature of water increases from 21.0oC to 23.0o What is the specific heat of sample?

 

Chem Exp 4
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