Temperature

Introduction: (Initial Observation)

How does the temperature change during the day? What time is usually the warmest? Can you construct your own thermometer to keep your own records?
By doing this project you will learn about the factors that affect the temperature of our environment.

Information Gathering:

Find out thermometers and other weather instruments. Read books, magazines or ask professionals who might know in order to learn about the factors affecting temperature of different locations. Keep track of where you got your information from. Following are some sample information that you may find:

What is Temperature?

Temperature of an object is what determines the sensation of warmth or coldness felt from contact with it.

When two objects of the same material are placed together, the object with the higher temperature cools while the cooler object becomes warmer until a point is reached after which no more change occurs, and to our senses, they feel the same.

The customary unit of temperature is the Centigrade degree, 1/100 of the difference between the temperature of melting ice and that of water boiling under standard atmospheric pressure. The Celsius temperature scale is a designation of the scale also known as the centigrade scale.

What is a Thermometer?

A thermometer is an instrument that measures the temperature. The easiest way to do this is to find a substance having a property that changes with its temperature.

For example, the element mercury is liquid metal in the temperature range of -38.9° C to 356.7° C (we’ll discuss the Celsius ° C scale later). As a liquid, mercury expands as it gets warmer, its expansion rate is linear and can be accurately calibrated.

The mercury-in-glass thermometer illustrated in the above figure contains a bulb filled with mercury that is allowed to expand into a capillary. Its rate of expansion is calibrated on the glass scale.

The Development of Thermometers and Temperature Scales

The historical highlights in the development of thermometers and their scales given here are based on “Temperature” by T. J. Quinn and “Heat” by James M. Cork.

One of the first attempts to make a standard temperature scale occurred by Galen, in his medical writings, proposed a standard “neutral” temperature made up of equal quantities of boiling water and ice; on either side of this temperature were four degrees of heat and four degrees of cold, respectively.

The earliest devices used to measure the temperature were called thermoscopes.

They consisted of a glass bulb having a long tube extending downward into a container of colored water, although Galileo in 1610 is supposed to have used wine. Some of the air in the bulb was expelled before placing it in the liquid, causing the liquid to rise into the tube. As the remaining air in the bulb was heated or cooled, the level of the liquid in the tube would vary reflecting the change in the air temperature. An engraved scale on the tube allowed for a quantitative measure of the fluctuations.

In 1641, the first sealed thermometer that used liquid rather than air as the thermometric medium was developed for Ferdinand II, Grand Duke of Tuscany. His thermometer used a sealed alcohol-in-glass device, with 50 “degree” marks on its stem but no “fixed point” was used to zero the scale. These were referred to as “spirit” thermometers.

Robert Hook, Curator of the Royal Society, in 1664 used a red dye in the alcohol . His scale, for which every degree represented an equal increment of volume equivalent to about 1/500 part of the volume of the thermometer liquid, needed only one fixed point. He selected the freezing point of water. By scaling it in this way, Hook showed that a standard scale could be established for thermometers of a variety of sizes. Hook’s original thermometer became known as the standard of Gresham College and was used by the Royal Society until 1709. (The first intelligible meteorological records used this scale).

In 1702, the astronomer Ole Roemer of Copenhagen based his scale upon two fixed points: snow (or crushed ice) and the boiling point of water, and he recorded the daily temperatures at Copenhagen in 1708- 1709 with this thermometer.

It was in 1724 that Gabriel Fahrenheit, an instrument maker of Däanzig and Amsterdam, used mercury as the thermometric liquid. Mercury’s thermal expansion is large and fairly uniform, it does not adhere to the glass, and it remains a liquid over a wide range of temperatures. Its silvery appearance makes it easy to read.

Fahrenheit described how he calibrated the scale of his mercury thermometer:

“placing the thermometer in a mixture of sal ammoniac or sea salt, ice, and water a point on the scale will be found which is denoted as zero. A second point is obtained if the same mixture is used without salt. Denote this position as 30. A third point, designated as 96, is obtained if the thermometer is placed in the mouth so as to acquire the heat of a healthy man.” (D. G. Fahrenheit,Phil. Trans. (London) 33, 78, 1724)

On this scale, Fahrenheit measured the boiling point of water to be 212. Later he adjusted the freezing point of water to 32 so that the interval between the boiling and freezing points of water could be represented by the more rational number 180. Temperatures measured on this scale are designated as degrees Fahrenheit (° F).

In 1745, Carolus Linnaeus of Upsula, Sweden, described a scale in which the freezing point of water was zero, and the boiling point 100, making it a centigrade (one hundred steps) scale. Anders Celsius (1701-1744) used the reverse scale in which 100 represented the freezing point and zero the boiling point of water, still, of course, with 100 degrees between the two defining points.

In 1948 use of the Centigrade scale was dropped in favor of a new scale using degrees Celsius (° C). The Celsius scale is defined by the following two items that will be discussed later in this essay:
(i) the triple point of water is defined to be 0.01 C
(ii) a degree Celsius equals the same temperature change as a degree on the ideal-gas scale.

On the Celsius scale the boiling point of water at standard atmospheric pressure is 99.975 C in contrast to the 100 degrees defined by the Centigrade scale.

To convert from Celsius to Fahrenheit: multiply by 1.8 and add 32.

° F = 1.8° C + 32

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.

The purpose of this project is to see how does the temperature change in different hours of a day.

Problem statement:
The air temperature affect every aspect of our lives. Humans need to be aware of the air temperature so that they can adjust their activities based on the air temperature or control it (change it) to their comfort level.

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.

Independent variable is the time of the day. Dependent variable is the temperature. Controlled variables are all other environmental factors such as wind and light that may affect the temperature.

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.

Following are two sample hypothesis:

• Temperature will be low in the morning and goes up as sun rises. The warmest hour will be the noon because after that sun starts to decline. Temperature declines as sun declines.
• Mornings are cold. As sun rises, temperature starts to rise. Temperature increase will continue until the sunset. Before sunset is expected to be the warmest hour of the day. Temperature starts to drop after the sunset.

Note that the hypothesis does not have to be true. Your experiments may support or reject your hypothesis.

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:

Monitor temperature changes.

Introduction: You can measure and record the temperature in different hours of the day to see how does the temperature change in different hours.

What you need:

• One room thermometer
• One watch or clock
• Your notebook and a pen

Procedure:

1. Find a location in your backyard that is away from buildings and trees.
2. Place a table there and cover the table with a white blanket or with aluminum foil. This is needed so the table will not absorb extra heat from the sun.
3. Place a glass container on the table and put the thermometer in the glass container. Do not close the lead. Glass container is required to stop the wind.
4. Use an umbrella or any other way to keep your thermometer in the shade at all times.
5. Wake up early morning (5 or 6 A.M. and record the temperature.
6. Repeat this every hour at the top of the hour until about 10 p.m. (If you can not do it yourself, get help. Someone else can also read the thermometer and record it for you.)
7. Record your results in a table like this:
   

   Time	Temperature
   6:00 A.M.
   7:00 A.M.
   8:00 A.M.
   9:00 A.M.
   8:00 P.M.
   9:00 P.M.

    

You may write temperature in Centigrade or Fahrenheit degrees. When your results table is ready, use it to draw a line graph.

To draw the graph, mark one spot for each line of your results table. To do that find the hour in the horizontal line and from there draw a vertical line. Then find the temperature in the vertical line and draw a horizontal line from there. Put an X or dot where these two lines cross. Repeat this for all lines of your data table. Finally connect all dots or Xs.

Note:

• During your experiment, make sure that nothing such as watering plants will happen close to your experiment setup. You don’t want external factors affect your results.
• Numbers that we have used for temperature in the above graph are good for Celsius degrees. Fahrenheit degrees use different numbers.

Experiment 2:

Make a simple thermometer

Introduction: Many thermometers are constructed based on the expansion of liquids and gases by heat. In the following experiment we try to make a simple thermometer using colored water.

Procedure:

1. Pour equal parts of tap water and rubbing alcohol into the bottle, filling about 1/4 of the bottle.
2. Add a few of drops of food coloring and mix.
3. Put the straw in the bottle. DO NOT DRINK MIXTURE. Don’t let the straw touch the bottom.
4. Place the bottle in the refrigerator for about one hour.
5. Use the modeling clay to seal the neck of the bottle, so the straw stays in place.
6. Now hold your hands on the bottle and watch what happens to the mixture in the bottle.

This thermometer will not show the actual temperature, but it shows how can the temperature affect the expansion of gas and liquids, resulting the liquid climb the straw.

Materials and Equipment:

List of material can be extracted from the experiment section.

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.

You provide the results in the form of a table and a graph.

Calculations:

No special calculation is required for this project; however, it is good if you calculate the average temperature of the day. To do that add all temperatures and divide the result by the number of observations (number of result lines in result table). When you find the average temperature, you can write it somewhere around your graph or below your results table.

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.

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.
What other factors affect temperature change? Do plants and trees affect temperature?

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.energyquest.ca.gov/how_it_works/thermometer.html

http://www.allstar.fiu.edu/aero/Experiment9.htm

http://www.worldclimate.com/