Introduction: (Initial Observation)
While looking at the thermometer on the wall, I noticed that a red liquid goes up and down the glass tube as the temperature changes. I was wondering what is this red liquid inside the thermometer and what makes it move?
It was not hard to learn that this thermometer is known as an alcohol thermometer as opposed to a mercury thermometer like those we use to measure our body temperature.
But why alcohol? What type of alcohol?
Both mercury and alcohol thermometers are also known as bulb thermometers.
Bulb thermometers rely on the simple principle that a liquid changes its volume relative to its temperature. Liquids take up less space when they are cold and more space when they are warm. All bulb thermometers use a fairly large bulb and a narrow tube to accelerate the change in volume. This observation gave me the idea of comparing the expansion and contraction of liquids. I am wondering if we can use drinking water as the liquid inside a thermometer.
Adult supervision and support is required.
Information Gathering:
Find out about expansion and contraction of material. Read physics books, magazines or ask professionals who might know in order to learn about the effect of expansion and contraction on different material. Keep track of where you got your information from.
Learn how a thermometer is made and prepare yourself to build your own bulb thermometer using water or any other liquid.
Decide what liquids you want to test. Choose liquids that are not harmful, can be found at home or obtained locally. Gather information about physical properties of liquids that you want to test. I suggest to test water, mineral oil, isopropyl alcohol.
| The coefficient of volume expansion ß is defined as the ratio of the fractional change in volume to the change in temperature (at constant pressure): If you determine ß of a liquid you need to fill it into a container of some sort, and this container will expand, too. Since the coefficient of volume expansion of liquids is about 100 times that of solids it may be neglected, especially when using quartz glass. Though most materials expand when heated, water between 0 and 4 °C is an important exception. its volume is minimum, and therefore the density is maximum, at 4 °C. This property is called the anomaly of water and has important consequences for the ecology of lakes. At temperatures above 4 °C, the water in a lake becomes denser as it cools and sinks to the bottom. But at temperatures below 4 °C, the water becomes less dense as it cools, so it stays at the surface. Ice therefore forms first at the surface of a lake, and being less dense than water, it remains there and acts as a thermal insulator for the water below.
Changes in Volume |
Question/ Purpose:
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.
Lower grades will do this project as a display project. In this case you will only have a purpose like this:
The purpose of this project is to build a bulb thermometer in order to display or demonstrate the expansion and contraction of liquids caused by changes of temperature.
Higher grades may want to do this project as an experimental project. In this case you will start with a questions like this:
Compare the thermal expansion of liquids (Include at least 3 specific liquids such as water, 20% salt water, alcohol, corn oil, mineral oil,…). Which liquid has the highest thermal expansion coefficient?
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.
Skip this section if you are doing this project as a display project.
Independent variable (also known as manipulated variable) is the type of chemicals that you test. Possible values are: (water, corn oil, Isopropyl alcohol, 10% saltwater, 20% saltwater)
Dependent variable (also known as responding variable) is the rate of thermal expansion. (Thermal coefficient of expansion)
Controlled variables are experiment procedures and equipment.
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.
Skip this section if you are doing this project as a display project.
This is a sample hypothesis:
Among water, mineral oil and Isopropyl alcohol, I think alcohol has a higher expansion rate. My hypothesis is based on the fact that isopropyl alcohol has a lower boiling point. In other words it expands to gas, while before water and oil, so it must have a higher expansion rate.
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:
Introduction:
In this experiment you connect a narrow plastic or glass tube to a bottle filled with some liquid. When the liquid expands in the bottle, it will go up the tube.
By the amount that the liquid travels up the tube, you can measure the temperature or the expansion rate of the liquid.
Material:
- A bottle, preferably with lead and narrow mouth
- A drill or a hammer and a large nail
- Some silly putty, plumbers putty, caulk or chewing gum
- A drinking straw or any other narrow plastic or glass tube. (Glass may break and cause injury.)
- Some food coloring (optional)
- Water and other optional liquids such as vegetable oil and isopropyl alcohol.
- Thermometer (used to calibrate the thermometer that you make)
Procedure:
Drill or punch a hole in the lid of your jar. The hole should be as close to the diameter of the straw as possible. If the mouth of the bottle is narrow, you may skip this step.- Insert the end of the straw into the hole, and then seal around the hole with your silly putty both on the inside and the outside of the lid. When you get done, it may look something like this:
Fill your jar with cold water. You can do this either by filling it with water and leaving it in the refrigerator overnight, or by making some ice water in a pitcher and then pouring the ice water into your jar (straining the ice out in the process — all you want is water in the jar). Add food coloring if you desire and shake it up.
Put the jar on the table to keep it steady — you want the jar filled to the brim with cold water, as full as you can get it without overflowing.
Put the lid on the jar as shown in the picture. When you screw on the cap, a little water may spill out the sides, and a little water may be visible in the straw. That’s okay.- It is important that the cap be sealed. If it leaks, your thermometer will not work.
- Place the jar in your kitchen sink, plug the sink and run hot water into the sink until the sink is about half full.
Watch the level of the liquid in the straw and a very unusual thing will happen: You will SEE the water in the jar expanding right before your eyes! As the water in the jar gets warmer, it will expand and rise up the straw. This sort of expansion happens every day, but we don’t really notice it because the amount of expansion is fairly small. Here, because we have routed the expanding water into a narrow straw, it is much more obvious. We can actually see it happening.
We used a plastic 1 mL pipette as a narrow tube and hot melt glue instead of putty.
Your bulb thermometer is ready now. You can calibrate it and use it to measure your room temperature.
Another Sample:
In another experiment I came across a very narrow glass tube known as capillary tube. It is apparently used in laboratories. I also found a small bottle with a hard plastic screw cap.
After making a hole in cap (using a drill), I inserted the capillary tube in the cap and sealed it with hot melt glue.
Hot melt glue is good for hard plastic and glass, however it can melt soft plastic and plastic straw.
Then I filled up the bottle with cold colored water and placed the cap on the bottle.
| To see how does the temperature affect the expansion, I placed the bottle in a cup of warm water. Warm water expanded the colored water and water climbed the tube all the way to the top and then started to overflow.Other small bottles that can be used for this experiment are perfume bottles and some medicine bottles. Plastic tubes from empty pens have also been used for this experiment with success. |
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Notes:
- Because the working fluid is water, it cannot measure temperatures below 32 degrees F / 0 degrees C (the water would freeze). It also cannot measure temperatures above 212 degrees F / 100 degrees C (the water would boil).
- Because the “bulb” (the jar) is so large, it takes a long time for the thermometer to reach the same temperatures as the object it is measuring — perhaps an hour.
- Because the top of the tube is open, the water can evaporate and pick up dust and debris.
How to calibrate the thermometer?
Place your bottle in ice-water for a while. Wait until the level of water declines to the lowest possible. Mark the level of water as 0ºC or 32ºF.
Keep your bottle in room temperature for a while. Wait until the level of water climbs to the highest possible. See the actual temperature of the room in another thermometer. Mark the level of water with the room temperature. For example if the room temperature is 70ºF, mark the new level of water with 70ºC.
Divide the space between these two markings in equal distances and mark them every 10 degrees.
For example if your markings are at 32ºF and 70ºF, divide the space between the two markings by 38 equal segments. Each segment represents one degree Fahrenheit. Attach a piece of cardboard to the tube for your markings.
Experiment 2: Only for higher grades. (optional)
Introduction: This is an experiment to test your hypothesis. In this project you will make three identical bulb thermometers with three different liquids. The purpose of this experiment is to see which liquids expand or contract more by changing the temperature.
Procedure: Make three bulb thermometers with three different liquids; however use identical size of bottle and tube as the first experiment. Use the same procedures as experiment one in building your thermometers.
Mark thermometers with the name of liquid that is used to make them.
Place all three thermometers in cold water. Wait a few minutes until the level of liquid remains unchanged for at least one minute. Mark the level of liquid in all thermometers using a tape or marker. Record the actual water temperature using a thermometer.
Remove all three thermometers and place them in warm water. Wait a few minutes until the level of liquid remains unchanged for at least one minute. Mark the new level of liquid in all thermometers using a tape or marker. Record the actual water temperature using a thermometer.
Measure the distance between two marks in all three liquids.
Record the results in a table like this:
| Water | Alcohol | Mineral oil | |
| Low temperature | 5ºC | 5ºC | 5ºC |
| High temperature | 55ºC | 55ºC | 55ºC |
| Change in liquid level | 3.5 cm |
If you are using a pipette as a tube, you can also add another row to the above table and write the changes in the volume of liquids as well.
Materials and Equipment:
- A bottle, preferably with lead and narrow mouth
- A drill or a hammer and a large nail
- Some silly putty, plumbers putty, caulk or chewing gum
- A drinking straw or any other narrow plastic or glass tube. (Glass may break and cause injury.)
- Some food coloring (optional)
- Water and other optional liquids such as vegetable oil and isopropyl alcohol.
- Thermometer (used to calibrate the thermometer that you make)
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.
Calculations:
No calculation is required. You may optionally want to calculate the coefficient of volume expansion for each of your test liquids in the experiment number 2. In this case you have to use a graduated tube such as a pipette and then use the following formula for your calculations.
Changes in Volume
ß = —————————————
initial Volume * changes in Temperature
Summery 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.
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.
References:
List of References
http://www.sciencebyjones.com/expansion-contraction.htm
http://www.teachervision.com/lesson-plans/lesson-4131.html?for_printing=1
http://webpages.marshall.edu/~bady/RICK/expcon2.txt
http://scienceworld.wolfram.com/physics/ThermalExpansionCoefficient.html
http://irc.swan.ac.uk/Thermal-Expansion/
George D. Nickas. “A Thermometer Based on Archimedes’ Principle.” Am. J. Phys. 57 (9), September 1989.
H-018: “Liquid Xtal-Galileo’s Thermom.” DICK and RAE Physics Demo Notebook.
Ha-2: Freier and Anderson, A Demonstration Handbook for Physics.
James Evans and Brian Popp. “Pictet’s experiment: The apparent radiation and reflection of cold.” Am. J. Phys. 737, Vol. 53, No. 8 (August 1985).
John H. Moore, Christopher C. Davis, Michael A. Coplan. “Expansion Thermometers.” Building Scientific Apparatus 2nd Edition. pp. 510-511.
Martin Gardner, “Two Stunts with a Bottle,” TPT 35, 53 (1997).
Philip Gash. “So You Thought a Glass Thermometer Measured Temperature.” TPT 40, 74 (Feb. 2002).
Shawn Carlson. “Home-Made Precision Thermometer.” The Amateur Scientist. (March, 1999).
Tik Liem, “The Rising Juices,” Investigation to Science Inquiry, pp. 211.
Tik Liem, “Withdrawing Juices,” Investigation to Science Inquiry, pp. 212.
Volker Thomsen. “Response Time of a Thermometer.” TPT 36, 540 (Dec. 1998).
