Materials Included In Kit

Additional Materials Required

Prelab Preparation

Experiment 1. Conductometer

1. Use a razor blade, if necessary, to cut out five small (approximately 0.3 cm³) pieces of wax. The wax tends to be brittle and may crumble. If the wax crumbles, gather the small pieces and press them together with your index finger and thumb.
2. Place the wax pieces into a plastic weighing tray or watch glass.

Experiment 2. Specific Heat

1. Identify the metal specimens included. Use Figure 5 as a reference.
   {13474_Preparation_Figure_5}
2. Prepare a hot-water bath by filling a 600-mL beaker ¾-full with water and placing it on a hot plate (or Bunsen burner equivalent). Add several boiling stones to the bottom of the beaker.

Assembly

3. Any thermometer may be used with the foam calorimeters. However, it is best to use a razor blade to cut a small hole or slit in the foam lid about the same size as the width of the thermometer. Do not make the hole too large. The foam will shape itself around the thermometer shaft, forming an airtight seal, when the thermometer is inserted into the lid (see Figure 6).
   {13474_Preparation_Figure_6}

Experiment 4. Relative Humidity and Dew Point

1. Use scissors to cut the cotton wick into ½" pieces for use. Extra wick is included as a surplus supply.

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).
   {13474_Preparation_Figure_7}
3. Slide both of the thermometers onto the screw through the hole used to hang the thermometers.
4. Use a screwdriver to carefully twist the screw into the end of the plastic handle (with the predrilled hole it it) until 3 or 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

Burns are one of the most common laboratory accidents. Review proper safety precautions with your students and teach them how to use the back of their hand to “feel” for heat. To avoid burns, use extreme caution while using heating equipment in these experiments. Students should wear safety glasses and heat-resistant gloves when performing these experiments. Please follow all normal laboratory safety guidelines. Experiment 1: Take extra care when heating with a Bunsen burner. Instruct students how to properly use a Bunsen burner before the experiment. Do not touch the hot Conductometer. Allow it to cool on a heat-resistant ceramic fiber square for at least 10 minutes after the experiment. Use caution when cutting wax with a razor blade. Do not cut in the direction of anyone. Experiment 2: Use tongs and allow the boiling water to cool before pouring it down the drain to prevent steam burns. Wear heat-resistant gloves when performing this experiment. Experiment 3: Infrared lamps get very hot and can cause burns. Do not leave lamps unattended. The Radiation Cans may also become very hot and should be handled carefully. Experiment 4: Be sure that the thermometers are securely attached to the plastic handle before swinging. The instructor should inspect the assembled sling psychrometer prior to use. Be careful not to drop or break the thermometers. Demonstration: Take extra care when heating with a Bunsen burner. Do not touch the hot Ball and Ring Apparatus. Allow it to cool on a heat-resistant ceramic fiber square.

Disposal

The materials from each lab should be saved and stored in their original containers for future use. Allow the Conductometer to cool completely before storing. Make sure metal specimens are cool and dry before storing to prevent corrosion. Empty and dry the radiation cans before storing. Wax can be placed into normal trash. Use a paper clip to scrape out any solid wax from inside the dimples.

Lab Hints

Experiment 1. Conductometer

• Enough materials are provided in this kit for two student groups to work at the same lab station. This laboratory activity can reasonably be completed in one 30-minute class period.
• Two groups can perform this experiment at once. Alternatively, one Conductometer can be used while the other one is allowed to cool. The Conductometer can be alternated for each group.
• One wax block has enough material to perform the experiment at least 30 times. Ordinary candle wax may be used as a replacement.
• Caution students not to place the Conductometer directly in the Bunsen burner flame. Maintain a height of approximately 10 cm above the flame.
• The melting point for the wax is approximately 55–60 °C.
• Some Conductometers may have a stainless steel (SS) spoke instead of a nickel–alloy steel spoke. Nickel–alloy steel and stainless steel have nearly identical thermal conductivity. Stainless steel will be the last to melt the wax. It may take eight to ten minutes for the nickel–alloy and stainless steel spokes to get hot enough to melt the wax.
• (Advanced information for teacher) For transition metals, the d-orbital electrons are at the highest energy level and con¬tribute significantly to the electron overlap. So, it might be expected that the more d-orbital electrons there are, the greater the thermal conductivity. This trend is observed in the first row of transition metals, where the thermal conductivity trend shows that iron (Fe) < nickel (Ni) < zinc (Zn) (see Table 1 in the Background section). Copper is an exception however (as is silver in the second row of transition metals). This exception can be explained by referring to the electron configuration of copper and silver {Cu = [Ar]3d¹⁰4s¹; Ag = [Kr]4d¹⁰5s¹}. Copper and silver have completely filled d-orbitals, and partially filled 4s and 5s orbitals, respectively. Therefore, copper and silver have the same number of high-energy d-orbital electrons as zinc and cadmium, respectively. However, since there is one less positively charged proton pulling on the overlapping electrons (compared to zinc and cadmium, respectively), there is less resistance to the motion of the mobile electrons. The higher mobility of the ten d-orbital electrons in copper and silver give them significantly higher thermal conductivities compared to the other transition metals in the same row.

Experiment 2. Specific Heat

• Enough materials are provided in this kit for five student groups of students to work at the same lab station. This laboratory activity can reasonably be completed in one 40-minute class period.
• Three experiment options are possible with the materials in this experiment. The metal specimens provided in this set are labeled for easy identification. Students may know the identity of the metal and its specific heat before the experiment, and then compare the experimental specific heat values to the theoretical values, or students may know the identity of the metal and then determine the specific heat for a grade. And finally, students can determine the identity of the metal by determining the specific heat and them comparing it to the values in the table.
• If students know the specific heat of the metal, they should calculate the heat lost by the metal and then compare it to the heat gained by the water. If the values are not equal, where might the missing heat have gone?
• Digital thermometers work well for this experiment.
• Enough water must be used to cover the metal specimen completely. For the long aluminum specimen, it requires approximately 220 mL. For the smaller specimens, less water may be used to obtain a larger temperature change.
• Do not fill the foam calorimeters with organic solvents.
• Tongs may be used instead of string to pull the metal samples from the boiling water. This can be a tricky task so students should practice the technique in cold water before attempting to pull the metal sample from hot water.

Experiment 3. Radiation Cans

• Enough materials are provided in this kit for four student groups of students to work at the same lab station. This laboratory activity can reasonably be completed in one 40-minute class period.
• Digital thermometers work well for this experiment.
• Infrared heat lamps must be used for this experiment. “Normal” 110-W incandescent lightbulbs will not work.
• Empty the water from the cans and allow them to air dry before storing them.
• The infrared lamp available from Flinn Scientific (Catalog No. AP5371) may be clamped to the lab bench or the back of a chair so that it is at the proper height for the cans.

Experiment 4. Relative Humidity and Dew Point

• Enough materials are provided in this kit for four student groups of students to work at the same lab station. This laboratory activity can reasonably be completed in one 40-minute class period.
• Relative humidity and dew point values are given for temperature ranges between 32 and 94 °F. Plan this activity accordingly.
• The sling psychrometers may be assembled ahead of time by the instructor or in class by the students. Be sure to inspect the psychrometers before each use.
• This activity may be done over an extended period of time to study the long-term relative humidity and dew point trends.
• Have students compare their calculated values to values reported by a local weather station or the National Weather Service (http://weather.gov).
• As an interesting side note, the heights of cumulus cloud bases can be calculated using the dew point temperature and the surface air temperature. Height of cumulus cloud bases (in feet) = 222 [temperature of air (°F) – dew point temperature (°F)].
• Dew point values may also be calculated using the air temperature (°F), relative humidity values and the dew point calculation chart found in the Supplementary Information section.
• The psychrometers are fragile. Care should be taken as to how vigorously the psychrometer is spun.

Demonstration: Ball and Ring Apparatus

• This demonstration can also be used as a safety and instructional lesson for the proper use of Bunsen burners. Perform the demonstration at the same lab station as the Conductometer so students can obtain a quick review of how to properly light and use a Bunsen burner.
• This activity is presented as a demonstration due to its quick nature. The four hands-on labs take time, whereas this activity can be completed in less than five minutes. Also, the Ball and Ring Apparatus needs time to cool down and presenting it as a demonstration helps to prevent downtime for students. It works best as a demonstration while students are working on the Conductometer experiment. It also serves well as an instructional demonstration for the proper use of Bunsen burners.
• Allow the Ball and Ring Apparatus to cool before performing the next demonstration.
• An alternate method to demonstrate size changes due to temperature changes is to plunge the ring into an ice-water bath to cause it to shrink in size. Allow the ring to cool for a minute or two before attempting to slide the ball through the ring.

Teacher Tips

• Set up each lab station accordingly before class. Students should leave the stations as they find them before they move on to the next lab station.
• Before class, prepare copies of the student worksheets for each student. The Background information for each experiment can also be copied at the instructor’s discretion.

  Experiment 2. Specific Heat

• Several of the metals are similar in color and size. The following descriptions may help distinguish and identify tin, zinc, and steel. Zinc: Dull, silver gray, surface is slightly cratered or pockmarked. Tin: Light silver, shiny and reflective, pockmarked. Steel: Silver or gray, polished or smooth metal surface.

Further Extensions

Sample Data

Experiment 1. Conductometer

Experiment 2. Specific Heat Experiment 3. Radiation Cans Experiment 4. Relative Humidity and Dew Point Results Table: Relative Humidity Calculation

Answers to Questions

Experiment 1. Conductometer

1. Describe the process of thermal conduction in metals.

   See Background information.

2. Which metal conducted heat the fastest?

   Copper conducted heat the fastest.

3. Which metal conducted heat the slowest?

   Nickel-alloy steel conducted heat very slowly. The wax did not even begin to melt after 8 minutes of heating.

4. Explain why some metals conduct heat slower and others conduct it fast.

   See Background information.

5. Which metal would lose heat the fastest? Explain.

   Copper should lose its heat the fastest because it is the best heat conductor. Copper will lose its heat to the air faster than the other metals.

Experiment 2. Specific Heat

1. Define specific heat.

   em>See Background information.

2. Calculate the heat gained by the water using the mass of the water, the temperature change of the water in °C, and the specific heat of the water. (Hint: Use Equation 1.)

   If a 57.9 g sample of metal at 100.0 °C is placed into a calorimeter containing 215.1 g of water at 20.5 °C, the temperature of the water increases to 22.0 °C.
   q (gained by water) = m (water) x C_p (water) x ΔT (water)
   q (gained by water) = (215.1 g) x (1.00 cal/g•°C) x (1.5 °C) = 323 calories

3. Determine the identity of the unknown metal by calculating its specific heat using Equation 3. (Note: Remember that the heat gained by the water equals the heat lost by the sample.) Compare the value to a list of published values given in Table 2.

   m (water) x C_p (water) x ΔT (water) = –[m (metal) x C_p (metal) x ΔT (metal)]
   (215.1 g) x (1.00 cal/g•°C) x (1.5 °C) = –[(57.9 g) x C_p x (–78 °C)]
   C_p = 0.071 cal/g•°C
   Using the table of specific heats, the metal is zinc (the metal is also silver in color).

4. Describe any sources of error that may have affected the results of this experiment.

   Removing the metal specimen from the hot water and transferring it to the water in the calorimeter cup results in some heat loss into the air. The air inside the colorimeter cup also removes heat from the specimen as well as the water. The calorimeter is a good insulator but it is not perfect. Some heat is also lost to the glass (or metal) of the thermometer.

5. When are two objects considered to be in thermal equilibrium?

   Two objects are considered in thermal equilibrium when they are at the same temperature. Energy transfer only occurs between objects of different temperatures.

6. Calculate the amount of energy needed to heat up 240 mL (8 oz) of ice-cold water (0 °C) to body temperature (37 °C) after drinking it. 1 mL of water is 1 gram. Compare this value to the energy spent by a 75-kg person walking up five flights of stairs (or 30 meters). (PE = mgh, where m = mass, g = 9.81 m/s², h = height).

   Energy expended to heat water:
   (240 g) x (4.184 J/g•°C) x (37 °C) = 37,000 J
   
   Energy expended to climb stairs:
   (75 kg) x (30 m) x 9.81 m/s² = 22,000 J
   
   It requires more heat energy to heat up a cup of ice-cold water than it does to climb up five flights of stairs!

Experiment 3. Radiation Cans

1. Graph the temperature versus the time for the data in Data Table 1. Use a different coded line (or different color) for each can.
2. How did the temperature vary in each can over time? Explain the variation.

   The temperature of the water in the silver can did not change much over 10 minutes. The temperature in the black can changed by 2 °C in 10 minutes. The black can absorbed more heat energy from the infrared light than the silver can.

3. On a sunny winter day what coat—black or white—might be warmer? Why?

   A black coat would tend to be warmer because it absorbs more heat energy than a white coat.

4. On a sunny summer day what shirt—black or white—might be cooler? Why?

   A white shirt would be cooler because it reflects the light instead of absorbing it.

5. On a separate graph, graph the temperature versus the time for the data in Data Table 2. Use a different coded line (or different color) for each can.
6. How did the temperature vary in each can over time for Experiment 2? Explain the results.

   The temperature of the water decreased in each can, but the temperature decreased more rapidly in the black can compared to the silver can. The black can acted as more of a heat conductor compared to the silver can.

7. Do the results of this experiment affect your answers to Questions 3 and 4?

   Students’ answers will vary.

8. Would shining a heat lamp on the cans affect the results of Experiment 2? Why?

   Yes, because the heating will affect the water in the black cans more than in the silver cans. The heating and cooling rates in both cans will probably balance enough so that the cooling rate for each can will be approximately equal. They would both cool with a rate similar to the original silver can in Experiment 2.

Experiment 4. Relative Humidity and Dew Point

1. Convert the dry-bulb temperature and the dew point temperature from the Data Table from Fahrenheit to Celsius using Equation 4. Record these values in the Results Table.
   {13474_Answers_Equation_4}
2. Calculate the saturation vapor pressure by using Equation 5 (assuming standard atmospheric pressure). Record this value in the Results Table.
   {13474_Answers_Equation_5}
3. Calculate the actual vapor pressures using Equation 6 (assuming standard atmospheric pressure). Record these values in the Results Table.
   {13474_Answers_Equation_6}
4. The relative humidity values can then be calculated using Equation 7. Record this value in the Results Table.
   {13474_Answers_Equation_7}
5. Define dew point.

   See Background section.

6. Define relative humidity.

   See Background section.

7. Compare the relative humidity calculation to the measured relative humidity found using the sling psychrometer.

   Student answers will vary.

Demonstration: Ball and Ring Apparatus

1. Which object had the greatest change in size, the ball or the ring?

   The ring appears to change in size more than the ball. It required less heating for the ball ring to increase in size enough to allow the ball to fit through the opening.

2. A long, narrow iron bar is heated uniformly. Which dimension, the length or the width, will expand the most? Explain.

   em>The length will expand the most because linear expansion is proportional to the original length. Since the length is greater than the width, the bar will expand more in the longer length than the width.

Discussion

Demonstration: Ball and Ring Apparatus

Procedure

1. Set up a Bunsen burner at the same lab station as the Conductometer, or use the Bunsen burner at the Conductometer lab station.
2. Show students the cool, room-temperature Ball and Ring Apparatus. (The ball should easily fit inside the ring.) Students should record their observations in the data table.
3. Ignite the Bunsen burner and heat the ball in the flame for approximately 30 seconds to one minute.
4. Remove the ball from the flame and attempt to insert it into the ring. (If the ball fits inside the ring, heat the ball for another minute in the flame.) Students should record their observations in the data table.
5. Heat the ring in the Bunsen burner flame for approximately 30 seconds to one minute.
6. Remove the ring from the flame and attempt to insert the ball into the ring. (If the ball does not fit inside the ring, heat the ring for another minute.) Students should record their observations in the data table.
7. Place the Ball and Ring Apparatus on a heat-resistant ceramic fiber square and allow it to cool before the next demonstration.

References

Bonnet, R. L.; Keen, G. D. Earth Science—49 Science Fair Projects; TAB Books, USA, 1990; pp 124–126.

Introduction

This all-in-one Heat and Temperature Kit is designed to give students the opportunity to explore the fundamental properties of heating objects and measuring temperature. Four hands-on lab stations and one demonstration can be arranged so student groups can experiment with different aspects of heat conduction, heat expansion, specific heat, calorimetry and relative humidity.

Concepts

• Thermal conductivity of metals
• Specific heat
• Heat capacity
• Calorimetry
• Absorption
• Reflection
• Electromagnetic radiation
• Kirchoff’s law of radiation
• Relative humidity
• Dew point
• Water vapor
• Evaporative cooling

Background

Experiment 1. Conductometer
Thermal conductivity is a measure of how well a substance transfers thermal energy (heat) through itself, and to other matter. The higher the thermal conductivity of a substance, the faster heat transfer will take place. Many metals conduct thermal energy well because they have a large number of mobile electrons. These mobile electrons help with heat conduction because as the metal heats up, the mobile electrons gain kinetic energy and have the ability to travel throughout the metal at a faster rate. The fast-moving electrons “bump” into neighboring slow-moving “cooler” electrons and transfer some of their energy to these slower electrons. The energy transfer continues from regions of high thermal energy to areas of low thermal energy until the metal is in thermal equilibrium.

Alloys, or homogeneous metal mixtures, typically have much lower thermal conductivities compared to the pure metals that compose them. Electron mobility and energy transfer are impeded due to the structural differences that result when two or more different atoms mix together to form a homogenous solid. See the Thermal Conductivity of Metals Table.

*Approximate values at room temperature (25 ºC). Thermal conductivity is temperature dependent.

Experiment 2. Specific Heat
Transfer of heat or heat flow always occurs in one direction—from a region of higher temperature to a region of lower temperature—until some final equilibrium temperature is reached. The transfer of this heat energy can be detected by measuring the resulting temperature change, ΔT, calculated by subtracting the final temperature from the initial temperature.

In this experiment, heat is transferred from a hot metal sample to a colder water sample. Each metal causes the temperature of water to increase to a different extent. This means that each metal must have a differing ability to absorb energy and then release energy to the water causing the temperature to rise. The ability of any material to contain heat energy is called that material’s heat capacity. The measure of heat capacity, or the quantity of heat needed to raise the temperature of one gram of a substance by one degree Celsius at constant pressure is termed specific heat, and is represented by the symbol, C_p. The SI units for specific heat are given in J/g•°C and the non-SI units are cal/g•°C. (Note: 1 calorie = 4.184 Joules).

In general, larger metal atoms have lower specific heat. Part of the reason for the variation of specific heats is that substances composed of larger atoms have fewer atoms for the same amount of material as a substance with smaller atoms. For example, the mass of each copper atom is larger than the mass of each aluminum atom. Therefore, a given mass of copper has fewer atoms than the same mass of aluminum. When heat is added to copper and aluminum, fewer atoms need to be put in motion in copper, and thus less heat is needed to increase the kinetic energy of the atoms in the copper. Therefore, the specific heat of copper is lower than the specific heat of aluminum. Notice in Post-Lab Question 3 that copper and zinc have identical specific heat values. This is due to the similar mass of the atoms. Compare the heat capacities of wood and the metals in general. Wood—with its relatively high specific heat value—is able to absorb more heat than metal before its temperature rises, and therefore does not feel hot to the touch. Metals, on the other hand, will heat up more quickly and feel hot to the touch due to their relatively low heat capacities. The amount of heat delivered by a material (q) is equal to the mass (m) of the material delivering the heat multiplied by the specific heat of the material (C_p) multiplied by the temperature change associated with delivering the heat (ΔT). The equation can be written as follows: To make accurate measurements of heat transfer and to prevent heat loss to the surroundings, an insulating device called a calorimeter is used. A calorimeter is a device used to measure heat flow, where the heat given off by a material is absorbed by the calorimeter and its contents (often water or other materials whose heat capacities are known). The heat gained by the water in the calorimeter must be equal in magnitude (and opposite in sign) to the heat lost by the sample, or Or Equation 3 may be used to calculate the specific heat of an unknown metal sample.

Experiment 3. Radiation Cans
“Hotness” is a property of an object called temperature—the factor that is measured with a thermometer. Temperature is a property of matter meaning it does not depend upon the number of particles in the object. Temperature only depends upon the average kinetic energy of the particles in the object. When light strikes an object, the motion of its internal particles will speed up as various wavelengths are absorbed. We detect this “average” increased speed of particle motion as an increase in temperature. The more energy that is absorbed results in greater kinetic motion and higher resulting temperature. Objects that absorb more energy tend to be warmer than objects that reflect energy.

The absorption or reflection of light energy is greatly contrasted in the Radiation Can Set in Experiment 1. The black can absorbs energy more quickly and thus, the temperature of the water inside the can rises more quickly than the water in the silver can. The shiny silver can’s surface reflects most of the light energy and the water temperature rises at a much slower rate. The results of Experiment 1 will lead to the classic suggestions to wear black clothing on a sunny winter day and white clothing on a sunny summer day.

Experiment 2 illustrates a different set of concepts related to conduction of heat through an object. Kirchoff’s law of radiation states that “the emissivity of a body is equal to its absorbancy at the same temperature.” In other words, if a black can absorbs energy more quickly than a silver can, it should also lose heat more quickly than the silver can. The results of Experiment 1 and Experiment 2 should verify Kirchoff’s law. Combining the results of both experiments would seem to cast doubts on the wisdom of wearing black clothing in the winter. In fact, without other design variables involved in clothing materials, it would. In real-life clothing situations, the question is more related to the ability of the clothing to trap the energy and slow down its escape. In addition, body temperature and physiology each contribute to the “warmth” of various clothing materials and their ability to trap energy.

Experiment 4. Relative Humidity and Dew Point
Water vapor is the gaseous, invisible form of water in the atmosphere. It is better known as humidity. When the air in the atmosphere contains a large amount of water, the air feels very humid. The opposite is true when the air is relatively void of water vapor—the air feels very dry. Relative humidity is defined as the percentage of moisture that the air is holding compared to the maximum it can hold at a particular temperature. For clouds to form and rain to start, the air has to reach 100% relative humidity, at the site where the rain is originating. Rain will often fall from clouds, where the humidity is 100%, into areas of much lower humidity.

A sling psychrometer can be used to measure relative humidity and the dew point level. When water evaporates, a certain amount of heat is required to convert the water into vapor. Therefore, a cooling effect takes place when evaporation occurs. A sling psychrometer consists of two thermometers—a dry-bulb and a wet-bulb. The dry-bulb thermometer measures the temperature of the surrounding air while the wet-bulb thermometer measures the amount of cooling that is required for the water to evaporate at that specific temperature. If the air is very humid, the difference in temperature between the dry-bulb and wet-bulb thermometers will not be large because there is only a small amount of evaporation. However, if the air is arid or dry, a large amount of evaporation takes place (which causes a cooling effect on the wet-bulb thermometer) and the resulting temperature difference between the two thermometers will be much greater.

Dew point is defined as the temperature at which air must be cooled (at constant pressure and water vapor content) for saturation (dew formation) to occur. When the dew point is below freezing (32 °F), it is commonly referred to as the frost point. The dew point is an important measurement used to predict the formation of dew, frost, and fog. Since atmospheric pressure varies only slightly at the Earth’s surface, the dew point is a good indicator of the air’s water vapor content. High dew points indicate high water vapor and low dew points indicate low water vapor content. The difference between the air temperature and dew point indicates whether the relative humidity is low or high. When the air temperature and the dew point are dramatically different, the relative humidity is low. When the air temperature and the dew point are close to the same value, the relative humidity is high. When the air temperature and dew point are equal, the relative humidity is 100%.

Demonstration: Ball and Ring
Matter tends to expand when it is heated—the result of increasing vibration amplitudes of the atoms and/or molecules that compose the matter. This is true for solids, liquids and gases.

Thermal expansion is a physical property of matter. Every material has its own unique coefficient of thermal expansion, just as the specific heat of a substance is unique. Under a given temperature change, materials will expand or contract proportional to their original size. Therefore, a larger object will expand more than a smaller object of the same material.

The amount of expansion also depends on the state of the matter. Under the same temperature conditions, gases expand much more compared to liquids and solids of the same material. Solids typically expand the least. The property of thermal expansion is used in thermometers to indicate temperature. As the temperature rises, the volume of the mercury (or alcohol) inside the thermometer will increase. The glass column holding the mercury will also increase, but by a much smaller amount. Therefore, the increased volume of mercury fills up more of the glass column and the mercury rises in the thermometer.

Thermal expansion can wreak havoc on the material used to construct roadways and bridges. If the material expands too much, a great deal of stress could result and the material may crack or split. To prevent this from occurring, concrete roadways and sidewalks as well as bridges are segmented. Each segment is separated by a small gap to allow for expansion and contraction due to temperature changes.

Linear thermal expansion can be calculated using the following equation:

ΔL = change in length
α = coefficient of linear expansion
Lo = initial length
ΔT = change in temperature

Experiment Overview

Experiment 1. Conductometer 
Metals are generally considered to be good conductors of heat. However, some metals are better than others. Determine which metals conduct heat well, and which ones do not.

Experiment 2. Specific Heat
The purpose of this activity is to measure the specific heat of a metal using a calorimeter in order to identify the metal.

Experiment 3. Radiation Cans
Use this radiation can set to examine the differential absorption and reflection of infrared radiation by different surfaces.

Experiment 4. Relative Humidity and Dew Point
In this activity, determine the relative humidity and the dew point levels of air.

Materials

Safety Precautions

Take extra care when heating with a Bunsen burner flame in the Conductometer experiment. Do not touch the hot Conductometer. Allow it to cool on a heat-resistant ceramic fiber square for at least 10 minutes after the experiment. Use caution when cutting wax with a razor blade. Do not cut in the direction of anyone. To avoid burns, use extreme caution while using heating equipment in this experiment. To avoid burns, use extreme caution while using heating equipment in the Specific Heat experiment. Use tongs and allow the boiling water to cool before pouring it down the drain to prevent steam burns. To avoid burns, use extreme caution while using heating equipment in the Radiation Cans experiment. Infrared lamps get very hot and can cause burns. Do not leave lamps unattended. The Radiation Cans may also become very hot and should be handled carefully. Be sure that the thermometers are securely attached to the plastic handle before swinging in the Relative Humidity and Dew Point experiment. The instructor should inspect the assembled sling psychrometer prior to use. Be careful not to drop or break the thermometers. Wear safety glasses and heat-resistant gloves when performing this experiment. Please follow all normal laboratory safety guidelines.

Procedure

Experiment 1. Conductometer

1. Obtain a Bunsen burner and, if available, a support stand and clamp.
2. If a support stand and clamp are used, secure the Conductometer to the support stand with the clamp. Clamp as close to the wood handle as possible. If a support stand and clamp are not used, carefully hold the Conductometer above the Bunsen burner flame positioned as shown in Figure 1.
   {13474_Procedure_Figure_1}
3. Position the dimples on top and the spokes parallel to the tabletop (see Figure 1).
4. Obtain five wax pieces (or carefully cut small wax pieces using a razor blade).
5. Press one wax piece (clump) in the dimple at the end of each metal spoke. Brush off any excess wax with a paper towel.
6. Obtain a stopwatch or other timer with a second hand.
7. Light the Bunsen burner and adjust the flame height to approximately 8–10 cm.
8. Position the center hub of the Conductometer approximately 10–12 cm over the Bunsen burner flame, making sure the wax pieces are on top and the spokes are parallel to the tabletop. Caution: Hold the Conductometer only by the insulated wood handle.
9. As soon as the Conductometer is in position, begin timing. Measure the time it takes for the wax to melt completely in each dimple. Record the time measurements in the worksheet.
10. After 10 minutes, or when all the all the wax has melted (whichever is first), remove the Conductometer from the flame and place it on a heat-resistant ceramic fiber square and allow it to cool for at least 10 minutes. Do not place the hot Conductometer directly on the tabletop. It may scorch the finish or cause a fire.

Experiment 2. Specific Heat

1. Set up a boiling water bath with a 600-mL beaker of water on a hot plate. Turn on the hot plate to begin the heating process.
2. Weigh an unknown metal sample on a balance to the nearest tenth of a gram. Record this mass in the data table.
3. Cut approximately 10 cm of fine fishing thread.
4. Tie one end of the thread to the knob on the metal sample.
5. Measure the mass of the foam calorimeter cup and lid. Record this mass in the data table.
6. Fill the foam calorimeter with approximately 220 mL of tap water.
7. Measure the mass of the foam calorimeter cup, lid and water. Record this mass in the data table.
8. Once the water bath is boiling, carefully place the metal sample in the boiling water using the tied thread. Make sure the end of the thread hangs over the lip of the beaker. Allow the metal sample to sit in the boiling water for approximately 5 minutes so that its temperature reaches equilibrium with the water.
9. Measure the temperature of the water in the foam calorimeter in degrees Celsius. Record this value in the data table.
10. After 5 minutes, measure the temperature of the boiling water bath. Record this value in degrees Celsius in the data table.
11. Carefully insert the thermometer into the hole in the calorimeter cup lid.
12. Using the thread, quickly and carefully pull the metal sample from the boiling water, allow excess water to drip from the sample for a second or two and then place the metal sample into the foam calorimeter cup and fully submerge it under the water. Quickly place the lid with the inserted thermometer on the calorimeter cup and begin measuring the temperature changes.
13. Gently swirl the calorimeter cup occasionally to ensure thorough heating of the water in the calorimeter cup.
14. Measure the highest temperature that the water reaches (in degrees Celsius). Record this value in the data table.
15. Repeat steps 1–14 for a second trial.
16. If time permits, repeat the experiment using a different unknown metal sample (see instructor).

Experiment 3. Radiation Cans

Experiment 1

1. Fill each radiation can ¾-full with room temperature water.
2. Place a thermometer into the water in each can (see Figure 2). Measure the initial temperature of the water in each can. Record the values in °C in Data Table 1.
   {13474_Procedure_Figure_2}
3. Shine an infrared heat lamp on the sides of both cans, approximately 10 cm from each can, so that it shines with equal intensity on both cans. Be sure the lamp is equal distance from the outer surface of both cans (see Figure 3).
   {13474_Procedure_Figure_3}
4. Measure the temperature in both cans over the next 10 minutes. Record the values in Data Table 1.

Experiment 2

1. On a hot plate, heat approximately 500 mL of water in a 600-mL beaker to about 90–95 °C.
2. Wearing heat-resistant gloves, carefully fill both cans about ¾-full with the hot water.
3. Place a thermometer into the water in each can. Measure the initial temperature of the water in each can. Record the values in Data Table 2.
4. Measure the temperature in both cans over the next 10 minutes. Record the values in Data Table 2.

Experiment 4. Relative Humidity and Dew Point

Dew Point and Relative Humidity Measurement

1. Obtain a preassembled sling psychrometer (see Figure 4).
   {13474_Procedure_Figure_4}
2. Measure the temperature of the air using the dry-bulb thermometer. Record this value in °F in Data Table 1.
3. Use a Beral-type pipet and place a few drops of water on the gauze (cotton wick) of the wet-bulb thermometer.
4. Hold the plastic handle in your hand and slowly rotate the thermometers around the screw. The spinning motion will accelerate the evaporation rate of the water.
5. Spin the thermometers on the sling psychrometer for thirty seconds or until the temperature of the wet-bulb thermometer drops to a point where it remains constant.
6. After the time has elapsed, immediately record the temperature of the wet-bulb thermometer in Data Table 1. Determine the temperature difference between the dry-bulb and wet-bulb temperature measurements. This is the wet-bulb depression. Record this value in Data Table 1.
7. Use the dry-bulb temperature reading and the Dew Point Table to determine the dry-bulb factor. Record this value in Data Table 1.
8. Multiply the wet-bulb depression by the dry-bulb factor. Record this value in Data Table 1.
9. Subtract the value obtained in step 8 from the initial dry-bulb temperature. This is the Dew Point Temperature. Record this value in Data Table 1.
10.  Use the Relative Humidity Table to determine the relative humidity of the air. Record this value in Data Table 1.

 

Student Worksheet PDF

13474_Student1.pdf