Introduction: (Initial Observation)
If you try to warm up equal amounts of water, vegetable oil and salt water with identical heat sources, you will notice that they don’t get warmed up at the same rate. One may get to a certain temperature after 5 minutes, while it takes 8 or 11 minutes for others to get to the same temperature.
Obviously the amount of heat that different material get in order to increase their temperature a certain amount varies among different material.
In this project we want to study this phenomena and compare this property of different material. We can test different metals or different liquids to see how much heat do they need to increase their temperature 1ºC.
Find out about physical properties of different material. Read books, magazines or ask professionals who might know in order to learn how different material vary in the amount of heat that they need to warm up a certain number of degrees. Keep track of where you got your information from.
Following are samples of information that you may find:
The property of a substance determining how much its temperature rises as a result of a certain amount of heat input is called specific heat, commonly denoted by C.
The specific heat (c) of a substance is the amount of energy required to raise the temperature of one gram of that substance by one degree Celsius. For example, one calorie of energy is required to raise the temperature of one gram of water one degree Celsius. So for water c =1cal/g. Thermal capacity is a measure of the amount of thermal energy that different substances have at the same temperature. To visualize this concept, think of a metal seat belt latch and a plastic door handle, both in a very hot car. They are both at the same temperature, but when they are touched, the seat belt latch feels much hotter because it contains so much more thermal energy than the plastic. (This is correct, but other factors are involved too. Plastic is less heat conductive. So the heat from plastic can not exit as fast. That is why we don’t feel the heat that much. Project Advisor)
Specific heats and molar heat capacities for various substances at 20 C
|Substance||c in J/gm||c in cal/gm||Molar C
|Ice (-10 C)||2.05||0.49||36.9|
The specific heat capacity of a solid or liquid is defined as the heat required to raise unit mass of substance by one degree of temperature. This can be stated by the following equation:
What do you want to find out? Write a statement that describes what you want to do. Use your observations and questions to write the statement.
The purpose of this project is to measure and compare the specific heat of several metals and liquids.
When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other.
The Independent variable is the type of material being tested. Possible values are Aluminum, Copper, Lead and iron.
Dependent variable is the specific heat.
Constants are method, procedures and instruments.
Controlled variables are weather temperature and pressure. (Do not perform your tests in different locations, different elevations or different weather conditions. We control these variables to make sure that they will not have any unwanted affect in our experiment results.)
Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis.
Following is a sample hypothesis:
Among aluminum, copper and lead, I think aluminum has a higher specific heat. My hypothesis is based on my observations of electronic boards that have a heat sync or coolers made of aluminum.
Note that a hypothesis does not have to be true. Your experiments later may support your hypothesis or not.
Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.”
Experiment : Measuring the Specific Heats of Solids (using a calorimeter)
Introduction/ summary: To find the specific heat of a solid substance such as copper, heat up a copper piece to 100 °C and then drop it in a calorimeter. Observe and record the temperature change in the calorimeter and then use it to calculate the specific heat of your sample.
Material and equipment:
- Calorimeter (MiniScience.com Part# CALMETGA)
- Glass test tube
- Test tube clamp
- Sample of the solid (must fit in test tube)
- Scale (digital or analogue, 0.1 gram or better accuracy)
1. Measure the mass of your solid and record it. It is best if the mass of your solid is about 100 grams.
2. Place the solid in a glass test tube
3. Place the test tube in a beaker half filled with water.
4. Place the beaker over a hot plate (electric stove) and let it boil for about 5 minutes.
5. Fill the inner cup of your calorimeter with 100 ml room temperature water. Close the lid and adjust the thermometer so the bulb of the thermometer will be in water.
6. Observe and record the temperature of water inside the calorimeter.
7. Temporarily open the calorimeter.
8. Carefully drop the solid into the calorimeter.
9. Close the calorimeter.
10. Stir the contents by moving the steering ring up and down.
11. Read the thermometer as the temperature rises. Temperature will get to a maximum and then start to drop slowly. Record the maximum temperature as the final temperature of calorimeter.
For this experiment, the calorimeter constant is assumed to be 0.00 j/ºC. This means that all the heat lost by the metal goes into heating the water. None of the heat is used to heat the calorimeter parts. This assumption is not too incorrect.
Using this assumption…..
Heat lost by the test piece = Heat gained by water
(Weight(metal))(Temperature loss(metal))(Sp Heat(metal)) = Heat Loss(metal)
(Weight(water))(Temperature gain(water))(Sp Heat(water)) = Heat Gain(water)
Since you know everything except the specific heat of the metal, you can solve for this as the unknown.
Also remember although the metal and the water start at two very different temperatures, they end up at the same temperature.
Because the Specific Heat of water is so high and the weights of water and metal used in this experiment are similar, the temperature rise of the water will be much less than the temperature fall of the metal.
Measuring the Specific Heats of Solids (using a home made calorimeter)
Introduction/ summary: To find the specific heat of a solid substance such as copper, heat up a copper piece to 100 °C and then drop it in a Styrofoam cup of water at room temperature. Water temperature will rise. Then use the change in water temperature to calculate the heat energy lost by the copper piece. To heat up a copper piece to 100°C, you can hang it by a string suspend it into hot (boiling) water, but a better method is placing the copper piece in a test tube and place the test tube in hot/ boiling water. In this way copper piece will not get wet and does not transfer some hot water with itself to the cup.
Styrofoam is a good insulator, so we use a Styrofoam cup as a calorimeter. We cover the cup with a cork or another Styrofoam piece. Thermometer will be inserted trough a hole until it reaches to the middle of water.
You will use a high precision thermometer to measure the temperature rise of water when hot metal is added.
Warning: when using the precision thermometer, support the Styrofoam cup in a 400 mL beaker as shown. The apparatus is less likely to tip over and break the thermometer.
1. weigh water in calorimeter (Styrofoam cup)
2. weigh metal in a test tube
3. heat tube with metal in boiling water bath.
4. record initial temperature of water
5. pour hot metal from tube into calorimeter
6. mix by swirling and record highest temperature.
You now have the data necessary to calculate the specific heats of all of these materials.
a. Transfer metal to calorimeter rapidly. It must not cool before it enters the water!
b. In swirling do not lose water or wet the cork.
a. Metals are excellent conductors of heat. If after removing the tube with metal from the boiling water bath, you hesitate before dumping the metal into the calorimeter, the metal will no longer be at the temperature of boiling water. Therefore the water in the calorimeter will be heated to a lower temperature.
b. If you lose water from the calorimeter by wetting the cork or even splashing it out before heat transfer from the metal to the water is complete, the remaining water will be heated to a higher temperature.
See the calculations section below.
Repeat the experiment with different material and report the results.
Specific heat of a liquid
By mixing an amount of water at one temperature with an amount of a different liquid at a different temperature, we can find the specific heat of the second liquid in essentially the same way. The procedure may appear to work best if the second liquid is miscible with water. But there may be a change in chemical energy when one substance is dissolved in another, so a less ambiguous result may be obtained for a liquid which is not miscible with water (e.g. oil). As a test of the potential role of chemical energy, you might check whether there is a change in temperature when salt or some other substance is dissolved in water when both are initially at room temperature.
Some of the liquids you may try for this experiment are:
Methyl alcohol (methanol), Ethyl alcohol (Ethanol), Isopropyl alcohol (rubbing alcohol), mineral oil, different vegetable oils, different solvents, Glycerin, Antifreeze (Ethylene Glycol).
Materials and Equipment:
- Calorimeter (or use a Styrofoam cup as calorimeter)
- Thermometer (it may come with your calorimeter)
- Aluminum cylinder or small cubes
- Copper cylinder or small cubes
- Lead cylinder or small cubes
- Boiling water
- Cool water
- Test tube.
- Test tube clamp
Calorimeter and metal samples (cylinders) are available at MiniScience.com.
Results of Experiment (Observation):
Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.
The energy lost by each metal ball and the antifreeze was gained by the cool water, so the energy balance is very straight forward. Use these two equations to find the specific heat of each metal ball.
DEnergyGainwater = (Masswater)*(Tcold-Teq)*cwater
Compare your answers with known values and calculate a % error.
Remember that an analysis consists of more than equations and numbers. You must interpret your data: tell what it really means. Write down your observations, explain what is going on in the experiment.
Summary of Results:
Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.
It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.
Using the trends in your experimental data and your experimental observations, try to answer your original questions.
Your conclusion should discuss, but is not limited to, the following topics.
Compare the specific heats of the samples with that of water.
What are some sources of unwanted heat gain or loss in this experiment?
Why is antifreeze a better engine coolant than water?
Related Questions & Answers:
What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.
If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.
If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.
Visit your local library and search the Internet to find articles related to the specific heat or heat capacity. Such information may be found in the physics section or the material science of your library. Find out how the heat capacity of different materials affect our decisions on selecting them for special uses.
- R. Bachmann, F. J. Disalvo, T. H. Geballe, R. L. Greene, R. E. Howard, C. N. King, H. C. Kirsch, K. N. Lee, R. E. Schwall, H. U. Thomas, and R. B. Zubeck, Heat capacity measurements on small samples at low temperatures, Rev. Sci. Instrum. 43, 205 (1972).
- Y. E. Volokitin, Electrons and phonons in nanocluster materials, Ph. D. Thesis, Leiden University (March 1997).
- J. S. Butterworth, C. R. Brome, P. R. Huffman, C. E. H. Mattoni, D. N. McKinsey, and J. M. Doyle, A demountable cryogenic feedthrough for plastic optical fibers, Rev. Sci. Instr. 69, 3697 (1998).