Submission

Introduction

The purpose of this lab is to understand the process of measurement and recording using scales of units -- in this situation, calibrating an alcohol thermometer using degrees Celsius. A thermometer is a useful device for measuring the temperature of a gas or liquid. It functions through the expansion of liquids in response to the presence of heat. A glass bulb attached to a long, even tube is filled with a liquid such as mercury or alcohol. When placed in a substance, the liquid in the thermometer expands until it is of the same temperature as the substance that the thermometer is in. Different thermometers will have different sets of marks along the side, depending on what scale is used.

Materials

• Unlabeled alcohol thermometer taped to strip of plastic
• 250 mL beaker filled with 200 mL of distilled water
• 250 mL beaker with 100 mL of distilled water and 100 mL ice
• Hot plate
• Sharpie
• Ruler
• Calculator

Procedures

• Set hot plate to highest setting so that water boils and 100° C can be located on the thermometer.
• Put the 250 mL beaker of distilled water on the hot plate.
  
• When the water begins to boil, hold the thermometer in the water. Do not let the thermometer touch the glass, or else the reading will be thrown off.
• Mark where the alcohol expands to.
• Remove the thermometer from the heated water and place in it into the 250 mL beaker containing ice so that the temperature of the water approaches its freezing point and 0° C can be located.
  
• Mark where the alcohol expands to.
• Measure the distance between the two markings on the plastic strip with a ruler and use the calculator to find one twentieth of the distance.
• Use this value as the 5° C increment and mark each increment from 0° C (freezing point) to 100° C (boiling point) using the ruler.
  
• After the thermometer has been completed, it may be tested using an additional two preparations of water of temperatures not precisely located during the calibration -- for example, 27° C and 84° C.

Extension

1. The overall principle of using 2 known points and marking increments between them on some measurement tool is applicable in a variety of situations. For example, in calibrating a slab of wood for measuring length, one could use the height of an average piece of paper to mark 0 and 11 inches or approximately 28 cm.
2. Water was used to calibrate the thermometer because the boiling and freezing points of water (in degrees celsius) -- 100 and 0, respectively -- are generally well-known. Additionally, the water was distilled because regular tap water contains trace elements, which affect the boiling and freezing points.
3. There were a few sources of error in this experiment. One source could have been that the water wasn’t exactly at boiling temperature, so our top temperature could be a little low. The second possible source of error, similar to the first reason, could be that the ice and water that we put the thermometer in was greater than the freezing point of water because the preparation was not entirely frozen. As a result, our 0° C mark could actually have been greater. Finally. the thermometer may have touched the glass of the beaker and altered the data by giving us the temperature of the beaker instead of the water.
4. We chose to plot every 5° C on our thermometer so our data would be fairly precise. 5° C is a reasonably accurate interval and marking every 5° C between 0° C and 100° C does not require a great deal of time as would say, marking every 1° C.