LAB 3.1 CALIBRATION OF A THERMOMETER
BACKGROUND:
In the last unit, we visualized particles that we could not see in order to construct a model of matter that can be used to explain our observations. In the first unit, we investigated energy transfers involving objects that we could see. In this unit, we will use both our model of energy and our model of particles to explain our observation of temperature and heat.
Temperature is a measure of the average kinetic energy of particles colliding with a thermometer. Just as the objects transferred energy in collisions, particles also transfer energy in collisions, in the form of heat. The direction of heat transfer is from areas of higher temperature to lower temperature until they are the same temperature. When a thermometer is used to measure temperature, energy is transferred between the thermometer and the substance until they reach the same temperature and the red liquid stops moving.
In this lab, you will calibrate a thermometer in the Celsius Scale (˚C), also called a centigrade scale. The thermometer has no numbers on it, so your task is to determine where to place numbers on the thermometer. The freezing and boiling points of water will be used to determine the location of 0˚C and 100˚C.
PURPOSE: To investigate temperature and calibrate a thermometer.
PRE-LAB QUESTIONS:
1. In the last lab, heat from your hands was transferred to gas particles inside a flask. In this lab, when you put a thermometer in something hot, like boiling water, heat will be transferred to the liquid particles inside the thermometer.
a. Describe what will happen to the speed of the red-liquid particles in the thermometer.
b. What will happen to the spacing between the red-liquid particles?
c. What will happen to the volume of the red-liquid?
d. How is this change in volume observed by a person using the thermometer?
2. a. True or False? When a thermometer is placed into a substance, the substance will always transfer energy to the thermometer. (Hint: is the thermometer always warmer than the substance it’s in?)
b. Explain your thinking for your answer.
3. How is energy transferred between particles?
4. Thermometers measure temperature. Define temperature.
PROCEDURES:
A. The glass tube is filled with a red liquid (alcohol), but has no marks (gradations). In order to place numbers on the thermometer, either attach a wooden splint or trace the thermometer on a card.
Note: Procedures B – D may be done in any order.
B. Place the bulb of the thermometer in ice water. While the thermometer is still in the ice water, place your thumbnail where the alcohol stops moving. Remove the thermometer, but keep your thumbnail on the spot. Make a mark on the splint or card to record the level of alcohol. Label that spot “0” (zero). This is zero degrees Celsius (0˚C).
C. Place the thermometer in boiling water. Place your thumbnail where the alcohol stops moving and label as “100”. This is 100˚C.
D. Following the same process, make marks for each of the following:
(1) Some tap water from the faucet (pour some into a Styrofoam cup)
(2) Room temperature (Let the thermometer sit on the desk for a couple of minutes)
(3) Body temperature (Do not place it in your mouth!! Use your underarm or elbow)
(4) Some hot water from the coffee pot (pour some into a Styrofoam cup)
(5) Alcohol and ice bath or salt water and ice bath
E. There should be seven marks on the splint or card. Carefully trace the location of all the marks from your splint or card into your lab. Be sure to label each mark on your sketch. It is important that your sketch accurately reflects the measurements made with your thermometer.
INTERPRETATIONS:
1. a. Measure the distance in mm between the “0” and the “100” marks with a ruler.
b. Divide that distance in half. Measure this distance from the 0˚C mark. Make a line on your sketch at this halfway point. Label it as “50˚C”.
c. Estimate the placement of 4 equally-spaced marks between 0˚C and 50˚C. Mark these as 10˚C, 20˚C, 30˚C and 40˚C.
d. Estimate the placement of 4 equally-spaced marks between 50˚C and 100˚C. Mark these as 60˚C, 70˚C, 80˚C and 90˚C.
2. Copy the following table. Use your calibrated thermometer to complete the “measured temperature” column in the table. The teacher will provide the accepted temperatures.
Substance Measured / Estimated Temperature(from your thermometer) / Accepted
Temperature
(provided by teacher) / Error
(+ or –)
Body Temperature
Room Temperature
Hot water
Alcohol and ice bath or Salt water and ice bath
Tap Water
3. How was the zero mark determined for the thermometer?
4. How was the one hundred mark determined for the thermometer?
5. Why did we use water instead of any other liquid?
6. A thermometer is placed in a container of ice water.
a. Does the red liquid in the thermometer move up or down the thermometer?
b. What must be happening to the spacing between the red liquid particles?
c. Why does the spacing between the particles change? Hint: think about particle speed and collisions.
d. Does the thermometer transfer energy to the ice water, or does the ice water transfer energy to the thermometer?
e. Why does the red liquid eventually stop moving?
7. Recall that temperature is the average kinetic energy of particles in a substance. Based on the meaning of the word “average” in math/science, are all of the particles in a glass of tap water moving at the same speed?
8. The lowest temperature possible is called “absolute zero”, a temperature at which all particle motion stops. Is 0˚C truly “absolute zero”? Explain using observations from the lab.
CONCLUSION:
Write a paragraph describing how a thermometer measures temperature. Use terms such as: expansion, contraction, particle spacing, particle speed, particle collisions and energy transfer.