Materials Included In Kit

Additional Materials Required

Prelab Preparation

Each of the five lab stations should be set up to have three sets of the materials listed on each Lab Station Instruction Sheet, three copies of the instruction sheet and one or more thermometers. Each set of equipment can be noted as “A,” “B” and “C” and the Lab Station Instruction Sheets should be labeled accordingly. This stations laboratory activity can be set up so three groups can work at any one lab station at the same time. Pairs of students may be assigned the letters “A,” “B” and “C” and should use the appropriately labeled set of equipment at each lab station. Assemble the sling psychrometers by following the instructions given.

Sling Psychrometer Assembly

1. Construct a wet-bulb thermometer by slipping a small piece of cotton wick over the bulb of one of the thermometers. The other thermometer is the dry-bulb thermometer.
2. Attach the two plastic-backed thermometers together back-to-back using a small rubber band (see Figure 7).
   {13525_Preparation_Figure_7}
3. Slide both of the thermometers onto the screw through the hole used to hang the thermometers.
4. Twist the screw carefully into the end of the plastic handle (with the predrilled hole) until 3 mm to 4 mm of the screw’s shaft remains above the handle.
5. Place the rubber cap on the bottom end of the psychrometer handle.

Safety Precautions

Exercise extreme caution when using a scalpel. Calcium chloride is slightly toxic. Ammonium nitrate is a strong oxidizer and may explode if heated under confinement. It is also slightly toxic by ingestion and it is a body tissue irritant. Hydrogen peroxide is a severely corrosive to skin, eyes and the respiratory tract. It is a very strong oxidant and a dangerous fire and explosion risk. Do not heat this substance. Wear chemical splash goggles, chemical-resistant gloves and a chemical-resistant apron. Wash hands thoroughly with soap and water before leaving the laboratory. Please consult current Safety Data Sheets for additional safety, handling and disposal information.

Disposal

Please consult your current Flinn Scientific Catalog/Reference Manual for general guidelines and specific procedures, and review all federal, state and local regulations that may apply, before proceeding. All liquid waste may be disposed of according to Flinn Suggested Disposal Method #26a, flushed down the drain. The potato may be disposed of according to Flinn Suggested Disposal Method #26b, in the regular trash.

Lab Hints

• Enough materials are provided in this kit for 30 students working in pairs or for 15 groups of students. The five stations in this learner-center, stations laboratory activity can reasonably be completed in one 50-minute class period, as long as the students rotate every 7–10 minutes. The prelaboratory assignment should be completed before coming to lab, and the Post-Lab Questions can be completed the day after the lab.
• In a 50-minute period, allowing students seven to eight minutes at each station will allow for additional time to revisit a station that was not completed in the allotted time. If this occurs at the first station, it will give students an opportunity to work on their time management skills as they complete the remaining stations knowing that they will only have time to return to one station in the end.
• Laminate the Lab Station Instruction Sheets to avoid damage during laboratory investigations. As an alternative to lamination, additional copies could be used to replace damaged Lab Station Instruction Sheets.
• Use the following mnemonic device to gain a better understanding of temperature in the Celsius scale: “Thirty is hot, twenty is nice, ten is chilly, and zero is ice.” Or “When it’s zero it’s freezing, when it’s ten it’s not, when it’s twenty it’s warm, and when it’s thirty it’s hot.”

Teacher Tips

• Basic temperature measurement is a must for every science discipline and is essential in addressing the National Science Education Standards. This station-based learner-center laboratory approach may be used to teach the techniques and equipment vital to measuring temperature throughout the science curriculum.
• Teach basic temperature measurement in conjunction with the history curriculum to provide a historical overview of the International System of Units, the scientists and agencies involved, and the history of the historical and natural phenomena associated with the kelvin, degree Celsius and temperature measurement.

Answers to Prelab Questions

1. What is the base SI unit for temperature?

   Kelvin (K) is the base SI unit for temperature. Although an SI unit, degrees Celsius (°C) is a derived unit and not a base unit.

2. Temperature is based on changes in state of what substance? Explain.

   Temperature is based on the changes in state of water. The melting point of water is 0 °C or 273.15 K, the boiling point is 100 °C or 373.15 K and the triple point is 0.01 °C or 273.16 K.

3. Why is it inappropriate to stir a solution using a spirit- or mercury-filled thermometer?

   Students’ answers will vary, but may include that the glass thermometer may break causing injury to a student, the thermometer fluid may contaminate the experiment or the environment, or the fluid may catch fire if exposed to a flame, along with the obvious—that this is not what a thermometer is designed to do.

4. Explain the difference between an endothermic reaction and an exothermic reaction.

   An endothermic reaction absorbs heat so the surroundings (container) feel cold to the touch. An exothermic reaction releases heat, therefore, the surroundings (container) feel warm to the touch.

5. Convert SI temperature values.
   1. Convert the following average temperatures from degrees Celsius to kelvin.
      1. 37 °C body temperature

         273.15 + 37 = 310.15 K

      2. 22 °C room temperature

         273.15 + 22 = 295.15 K

   2. Convert the following temperature from kelvin to degrees Celsius.
      1. 273.15 K ice freezes (or melts)

         0 °C

      2. 373.15 K water boils (or condenses)

         100 °C

      3. 273.16 K triple point of water (exists in all three states of matter)

         0.01 °C

Sample Data

Station 1

Station 2 Station 3 Station 4 Station 5

Answers to Questions

1. Which box actually had the highest temperature in the activity at Lab Station 1, and why?

   The black box had the highest temperature because the black color absorbs more radiant heat than either the white box or the red or blue box.

2. Did adding salt to ice in the activity at Lab Station 2 increase or decrease the temperature? Based on this result, what is the effect of salting icy streets?

   Adding salt to the ice lowers the freezing point, therefore decreasing the temperature of the solution. Salting icy roads lowers the freezing point of water, which results in the ice melting.

3. The dissolution of which substance at Lab Station 3 could be used to make a cold pack? Which one could be used to make a heat pack?

   Ammonium nitrate is endothermic when dissolved in water and could, therefore, be used to make a cold pack. Calcium chloride is exothermic when dissolved in water and could, therefore, be used to make a heat pack.

4. Use the following Relative Humidity Table to determine the relative humidity of the classroom from the wet-bulb and dry-bulb temperature readings taken at Station 4.

   Relative Humidity Table in Percent (%)

   {13525_Answers_Table_7}
   Students’ answers will vary. Check their results using the Relative Humidity Chart. The sample data results in a relative humidity value of 54%.
5. What gas is given off in the decomposition of hydrogen peroxide at Lab Station 5?

   The equation for the decomposition of hydrogen peroxide is
   2H₂O₂ → 2H₂O + O₂
   Therefore oxygen is the gas given off in the decomposition reaction.

Introduction

All students must learn basic measurement techniques to be successful in any science class. Become measurement-savvy students with this introduction to basic temperature measurement. Five lessons are provided in a stations approach to teach the concept of temperature measurement and the tools involved.

Concepts

• Catalyst
• Heat absorption
• SI prefixes
• Endothermic
• Relative humidity
• Temperature measurement
• Exothermic

Background

Temperature affects all living organisms. The temperature of an area determines what kinds of plants and animals will be present and also dictates various events in their lifecycles such as blooming, hibernation, or aestivation. People depend on temperature in many ways, including the range of temperature for food, water, and air that keep people comfortable or alive. In the United States, temperature is most often stated in degrees Fahrenheit (°F), a scale named after Daniel Gabriel Fahrenheit (1686–1736). Degree Fahrenheit is a customary or English unit.

Absolute temperature (T), the measure of the kinetic energy of molecules, in the International System of Units (SI) is measured in kelvin (K), named after William Thomson, 1st Baron Kelvin (1824–1907). Kelvin is defined as 1/273.16 of the thermodynamic temperature at the triple point of water. Absolute zero, or 0 K, is the temperature at which all molecules’ kinetic energy equals zero.

In 1887, the International Bureau of Weights and Measures (BIPM) in Sèvres, France, adopted the constant-volume hydrogen scale for measuring temperature. On this scale, 0 °C is the freezing point of water and 100 °C is the boiling point, at standard atmospheric conditions. In the original scale the °C was referred to as “degree centigrade” and the name was changed to “degree Celsius,” in honor of Anders Celsius (1701–1744) in 1948. The upper and lower limits of the scale, how to extrapolate temperatures, and what instrument to use outside the acceptable range for a traditional thermometer have been debated since 1898. First, a helium constant-volume scale was developed, then a helium constant-pressure scale was adopted, followed by a low-temperature scale. In 1954, a proposal originally made by William Thomson, in 1854, was adopted as the International Practical Temperature Scale. It was defined as the interval between absolute zero and a fixed point. The fixed point was the triple point of water, the point at which water exists in all three phases of matter (solid, liquid, and gas) at the same time. The unit for the scale was °K (degree Kelvin). In 1968 this practical scale was determined to be identical to the thermodynamic scale for temperature and the unit was renamed kelvin (K). The value of the triple point of water is exactly 273.16 K and, as adopted in 1990, is the defining point in the scale instead of the freezing point of water, which is 273.15 K. Kelvin and degrees Celsius are both units of the International Temperature Scale of 1990.

For many applications in the science classroom, temperature (t) is measured in °C (degrees Celsius). Celsius is also an SI unit; however, it is a derived unit and not a base unit. In other words, it is derived from the base unit for temperature, kelvin. Therefore, t = T – T₀, where T₀ = 273.15 K (the freezing point of water, not the triple point). Each Celsius degree is equal in magnitude to one kelvin. Therefore, to convert from kelvin to Celsius add 273.15 to the kelvin temperature value. To convert from Celsius to kelvin subtract 273.15 from the Celsius temperature value.

Adding SI prefixes to kelvin creates the following multiples and submultiples

Note: While SI prefixes may be used with °C, they are typically only applied to kelvin.

Temperature measurements are conducted with thermometers. Thermometers quantitatively measure temperature by using materials that change in some way when they are heated or cooled. In spirit- or mercury-filled thermometers, the liquid expands with an increase in temperature and contracts with a decrease in temperature. The expansion and contraction of the liquid in the thin-walled glass tube changes the level of the liquid; it is the level of the liquid that is read against a scale of numbers to determine the temperature. Because the amount of expansion or contraction is the same for each degree of temperature change, the scale on the thermometer is linear—each temperature division is an equal distance apart.

There are limits to the range of temperature each instrument can measure. In fact, BIPM specifically defines approximately four ranges of temperature measurements based on the capability of the instrumentation. For mercury- and spirit-filled thermometers, the limits are dependent on the boiling and freezing point of the substance and the ability of the container to withstand the pressure exerted. With spirit-filled thermometers, the temperature ranges that can be measured include temperatures as low as approximately –30 °C and as high as 260 °C, depending on the substance used. Mercury-filled thermometers can measure a range of temperatures from –35 °C to approximately 350 °C (the freezing point of mercury is –38.9 °C and its boiling point is 356.6 °C). For temperatures outside these ranges, scientists use electrical thermocouples called thermoelectric thermometers. The platinum resistance thermometer can measure temperatures from –260 °C to 1235 °C.

Experiment Overview

Using learner-centered stations, learn the basic concept of temperature measurement. Rotate through each of five stations every 7–10 minutes. Each station provides an activity that allows you to practice temperature measuring skills using the appropriate tools.

Lab Station 1
Does the color of an object have any effect on the ability of the object to absorb or reflect heat? Try this activity to discover the answer!

Lab Station 2
Will adding salt to ice increase or decrease the temperature (alter the freezing point)?

Lab Station 3
Dissolve two salts in water to determine their heat of solution. Does either of the two salts going into solution take in heat (endothermic) or give off heat (exothermic)?

Lab Station 4
Does a wet-bulb thermometer give a different reading than a dry-bulb thermometer? Use the sling psychrometer, an instrument used to measure the relative humidity of the air, to measure the difference in the temperature readings between a wet-bulb and dry-bulb thermometer. The dry-bulb thermometer measures the temperature of the surrounding air and the wet bulb thermometer measures the cooling effect that takes place when the water evaporates from the cotton wick on the bulb. The temperature difference between those two readings is a direct function of the percent humidity in the air at the given temperature.

Lab Station 5
Hydrogen peroxide releases heat when it decomposes into oxygen and water. By adding the enzyme catalase from a potato to hydrogen peroxide, the reaction speeds up and this makes it possible to measure any temperature change resulting from the heat that is released. Note: This is this same process that makes hydrogen peroxide bubble when placed on a cut.

Materials

Prelab Questions

1. What is the base SI unit for temperature?
2. Temperature is based on changes in state of what substance? Explain.
3. Why is it inappropriate to stir a solution using a spirit- or mercury-filled thermometer?
4. Explain the difference between an endothermic reaction and an exothermic reaction.
5. Convert SI temperature values.
   1. Convert the following average temperatures from degrees Celsius to kelvin.
      1. 37 °C body temperature
      2. 22 °C room temperature
   2. Convert the following temperature from kelvin to degrees Celsius.
      1. 273.15 K ice freezes (or melts)
      2. 373.15 K water boils (or condenses)
      3. 273.16 K triple point of water (exists in all three states of matter)

Safety Precautions

Exercise extreme caution when using a scalpel. Calcium chloride is slightly toxic. Ammonium nitrate is a strong oxidizer and may explode if heated under confinement. It is also slightly toxic by ingestion and it is a body tissue irritant. Hydrogen peroxide is a severely corrosive to skin, eyes and the respiratory tract. It is a very strong oxidant and a dangerous fire and explosion risk. Do not heat this substance. Wear chemical splash goggles, chemical-resistant gloves and a chemical-resistant apron. Wash hands thoroughly with soap and water before leaving the laboratory.

Procedure

Preparation 

1. Become familiar with reading the supplied thermometer.
2. Follow any special instructions given by the teacher for the proper use of the thermometer and any other laboratory equipment used at each station.

General Procedure

1. Proceed to one of the lab stations (1–5) as directed by the teacher.
2. Follow the instructions for each lab station.
3. Record the appropriate measurements and observations on the Temperature Measurement Worksheet as instructed at each lab station.
4. Rotate to the next lab station in numerical order when the teacher signals. This should be approximately every 7–10 minutes. Note: Students at station 5 should rotate to station 1.
5. Consult your teacher for appropriate disposal procedures.

Lab Station 1

1. Place all three boxes in direct sunlight or under a lamp.
2. Allow the boxes to sit in the light, undisturbed, for at least 3 minutes.
3. In the meantime, predict which box will have the highest temperature, lowest temperature or whether all the boxes have the same temperature?
4. Using the thermometer, measure the temperature under the white box (see Figure 1).
   {13525_Procedure_Figure_1}
5. Record the temperature measurement on the Temperature Measurement Worksheet.
6. Repeat steps 4 and 5 for the remaining boxes.

Lab Station 2

1. Will adding salt to an ice–water mixture decrease the temperature? Record the prediction on the Temperature Measurement Worksheet.
2. Fill the beaker with ice to approximately the 200 mL mark (see Figure 2).
   {13525_Procedure_Figure_2}
3. Fill the beaker with distilled water to about the 200 mL mark.
4. Using a thermometer, measure the temperature of the ice–water mixture and record the measurement on the Temperature Measurement Worksheet.
5. Add a spoonful of sodium chloride (approximately 10 g) to the ice–water mixture and stir with a stir rod to dissolve.
6. Using a thermometer, measure the temperature of the salt–ice–water mixture and record the measurement on the Temperature Measurement Worksheet.
7. Lab Station 3
   1. Fill the beaker with 200 mL of distilled water.
   2. Using the thermometer, measure the temperature of the water (see Figure 3).
      {13525_Procedure_Figure_3}
   3. Record the initial temperature on the Temperature Measurement Worksheet.
   4. Add 20 g of ammonium nitrate and stir to dissolve.
   5. Take a temperature reading every 30 seconds for the next 2 minutes and record the measurement on the Temperature Measurement Worksheet.
   6. Dispose of the waste solution as instructed by the teacher.
   7. Rinse the beaker with water.
   8. Repeat steps 1–7 for 10 g of calcium chloride.

Lab Station 4

1. Using a Beral-type pipet, place a few drops of water on the cotton wick of the wet-bulb thermometer (see Figure 4).
   {13525_Procedure_Figure_4}
2. Hold the plastic handle and slowly rotate the thermometers around the screw. The spinning motion will accelerate the evaporation rate of the water.
3. Spin the thermometers on the sling psychrometer for thirty seconds or until the temperature on the wet-bulb thermometer drops to a point where it remains constant.
4. After the time has elapsed, immediately record the temperature of both thermometers on the Temperature Measurement Worksheet. Determine the difference between the dry-bulb and wet-bulb thermometers. Record this value on the Temperature Measurement Worksheet.
5. Repeat steps 1–4 two more times.

Lab Station 5

1. Using a graduated beral-type pipet, place 2 mL of hydrogen peroxide into the test tube.
2. Using a thermometer, measure the temperature of the hydrogen peroxide (see Figure 5).
   {13525_Procedure_Figure_5}
3. Record the temperature measurement on the Temperature Measurement Worksheet.
4. Cut a 1 cm³ square piece of potato.
5. Score the potato as shown in Figure 6 to increase the surface area.
   {13525_Procedure_Figure_6}
6. Place the potato cube into the test tube with the hydrogen peroxide.
7. Measure the temperature of the catalyzed decomposition of hydrogen peroxide every minute for five minutes. Note: The equation for the decomposition of hydrogen peroxide is 2H₂O₂ → 2H₂O + O₂.
8. Record the temperature measurements on the Temperature Measurement Worksheet.

Student Worksheet PDF

13525_Student1.pdf