Introduction: (Initial Observation)
Heat energy is required in many different aspects of our lives. Heating systems and refrigeration both rely on this type of energy to function; they function by adding or removing heat energy from an object or area to control its temperature. This transfer of energy can occur by three methods: conduction, convection or radiation.
Conduction is the most direct transfer of energy, as it requires two objects to directly contact one another. Thermal energy moves from particle to particle throughout a material as heat is conducted.
Conduction takes place when water heats on a stove top, or when a person takes a warm bath, or when a hot pan is cooled by running it under cold water.
In this project we will compare different metals to see which one is a better heat conductor.
Adult supervision is required
Information Gathering:
Find out about heat conduction and how it works. Read books, magazines or ask professionals who might know in order to learn about different metals and their physical properties such as conductivity. Keep track of where you got your information from.
Different kinds of metals have different physical properties. They are different colors, some are stronger than others, some conduct electricity better than others, they have different melting temperatures and they all conduct heat differently. You will test the heat conductivity property of different metals in this project.
Question/ Purpose:
We want to test the heat conductivity of some popular metals such as copper, aluminum, steel to see which one is a better heat conductor.
A question you could ask might be, “Which metal conducts heat most efficiently?”
Identify Variables:
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.
Type of metal is an independent variable. (It means we select the type of metal)
Heat conductivity is a dependent variable. (It depends on the3 type of metal)
Hypothesis:
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.
This is a sample hypothesis:
Among copper, stainless steel and aluminum metals, copper conducts heat the best.
Your hypothesis may be different.
Experiment Design:
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 1:
In this experiment we will compare the heat conductivity of three different metals.
Procedure:
Go to the hardware store and buy as many different thickness’ of copper, stainless steel and aluminum bare metal wire as you can find. Get a package of plain white candles, some matches and a watch with a second hand. Carefully melt some wax from a candle, rolling the warm wax into balls of the same size – about a quarter of an inch in diameter. You may have to increase the diameter of the wax balls, depending on thickness of the thickest wire you were able to find because in the next part of the experiment you’re going to skewer the wax balls on the end of the wires. Carefully measure your different wires into lengths of the same size – 6 inches long would be good – and ask the adult helping you to cut them for you.
Next light a candle and, holding your wire with a wax ball on the end with some tongs, put the end of the wire opposite the wax ball into the candle flame, hold it there until the wax ball melts off the wire and time on the watch how long it takes for the wax ball to melt off. Carefully note on a data collection sheet, for each piece of wire: whether it was copper, aluminum or stainless steel, how thick it was, how long the piece was and how long it took for the wax to melt off it.
Summarize your results and compare them with your hypothesis – did the wax ball fall off the copper wire fastest? What effect did the differing thickness’ of the wire have on the melting time? Write up your results and comparison of results with the hypothesis in a conclusion either supporting or disproving your hypothesis.
Note: If you don’t want to see the effect of thickness in heat transfer, it’s better to get wires with the same diameter.
Experiment 2:
In this experiment we compare the heat conductivity of a metal and a non-metal such as a cork. The question is which one conducts heat better? Copper or cork?
Procedure:
- Cut the copper wire into 3 pieces: one piece 10 cm long and two pieces 4.5 cm long.
- Push the longer copper piece through the middle of one cork so that the cork is at its midpoint. BE VERY CAREFUL DOING THIS!!
- Push the smaller pieces into either end of the second cork, but not touching inside.
- Light the candle or burner.
- Hold the end of one wire in the flame (See diagram).
- Note the approximate time until the heat can be felt on the opposite end of the wires. As soon as the wire feels warm, remove it from the flame.
- Record which wire heated faster. wax and quarters
Experiment 3:
In this experiment we will test the heat conductivity of 3 different spoons. You may select spoons made of stainless steel, aluminum and copper. You may also use this method to compare the heat conductivity of metal strips, rods or pipes.
Procedure:
- Press a small piece of warm candle wax from Part I into the handle of each of the three spoons (see diagram). Push the quarters into the wax so that they are attached to the spoons.
- Fill the beaker with 300 mL water and place the beaker on a hot plate.
- Place the three spoons in the water so that the quarters come out of the top of the beaker.
- Turn on the hot plate and allow the water to warm. Observe the quarters and note the order in which they fall from the spoons.
More advanced experiment
Jut for your review
Six rods of identical size, but made of different materials, are covered with heat-sensitive paint. One end of each rod is inserted into a pipe through which steam can pass. Thermal conductivity of each rod is indicated qualitatively by the extent of the color change. (The rods are made of copper, aluminum, zinc, tin, Iron and lead).
Directions: Wait until the water is almost boiling before attaching the hose to the end of the pipe. (Wear hand protection in case steam begins to emerge prematurely.) Point out the different color change rates as the process continues.
Applications: Conduction rates determine often what materials are used as insulators.
If you are using a MiniScience heat conductometer, insert wax in the holes at the ends of the rods. Hold the center of conductometer on flame of an alcohol burner. Watch for melted wax to drop from the ends of the rods. Record the type of metal and the time for the first drop of each rod.
Materials and Equipment:
List of material can be extracted from the experiment section and varries based on your final experiment design. Following is a sample list of material.
- 19 cm long, stiff copper wire
- Metal spoon
- 2 small corks
- 3 quarters
- Matches
- 600 mL beaker
- Candle
- 300 mL water
- Wooden spoon
- Hot plate
- Plastic spoon
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.
Your experiment result must have answer to these questions.
Experiment 1:
| Type of Metal | Minutes took for the wax to melt |
| Copper | |
| Iron | |
| …. |
Experiment 2:
1. In which wire was heat felt first? How much of a difference was there in the time it took the two wires to heat?
2. Explain the difference in the rate of heating of the two wires.
3. From your observations, do you think cork or copper is a better conductor? What properties make one material more conductive than the other?
Experiment 3:
1. In what order did the quarters fall from the spoons? Explain this based on heat conductivity.
2. Identify and explain a kitchen item made of each plastic, metal and wood. Distinguish the uses of these items based on heat conductivity.
3. Explain energy transfer through heat conductivity in your own words.
Calculations:
No calculation is required for this project.
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.
Conclusion:
Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.
Of copper, stainless steel and aluminum wire, ……….. conducts heat the best. …………… is the second best conductive and …………… has the lowest conductivity.
After you write the conclusion, write some additional information to show that you really learned the subject. This is an example:
Some materials are naturally good conductors of heat, while others are poor. Metals usually conduct heat extremely well, which explains the use of iron and copper in cooking utensils. Materials such as plastic, glass or wood do not conduct well; therefore, it is a better idea to use a wooden spoon than a metal spoon when cooking.
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.
Possible Errors:
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.
