Name:

Phase Change Lab

Question:

What is the temperature profile of the beaker contents as thermal energy is added?

Background:

The atoms of matter are in motion. This motion corresponds to the material's internal energy. We measure the amount of this motion (or internal energy) with a thermometer. The greater the material's internal energy, the higher the temperature of that material. Heat is the energy flow between objects of different temperature. Heat and temperature are NOT the same.

Hypothesis:

Written hypothesis with graph as defined below.

Equipment:

hot plate, 400 ml beaker, thermometer, scoopula, ice water.

Safety:

Be very careful with the hot plates. If you want to check if it is warm, put the top of your hand ABOVE it. Hot glass does not look any different from cool glass. Safety goggles must be worn at all times throughout the lab.

Procedure:

  1. Measure out approximately 200 ml of ice water in your beaker. Be sure there are ice cubes in your water sample.
  2. Verify your hot plate is off and cool. Make sure the bottom of your beaker is DRY. Place the beaker on the hot plate.
  3. Record the temperature of the ice water. Adjust the ring stand clamp holding the thermometer so only the bottom 4 cm of the thermometer is below the water surface. You may wish to stir the water with the scoopula, but be very careful NOT to touch the thermometer.
  4. After 30 seconds, measure and record the temperature again.
  5. Turn on the hot plate and set it to its maximum setting.
  6. Measure the temperature every 30 seconds until the water starts to boil.
  7. Take six more temperature readings (three more minutes) after the water is boiling.
  8. Turn off the hot plate and unplug it. Do NOT touch the beaker.

Data Table:

Manipulated variable:

Responding variable:

Controlled variables:

time (30 sec increments) temperature (°C)
0 s  
30 s  

Graph:

Graph the data you have gathered with the manipulated variable on the x-axis and the responding variable on the y-axis. Refer to the lab report format section on graphing. Looking at your graph:

  1. Can you tell from your graph when the all the ice was melted? Label that point on your graph.
  2. Can you tell when the water started to boil? Label that point on your graph.

Conclusion:

Refer to the lab report format and write a conclusion (in paragraph form on a separate sheet of paper) for this lab. Your instructor will display a graph of a typical data set (time vs. temperature readings). If your graph doesn't resemble the instructor's graph, be sure to address this in your error discussion.

Be sure to discuss:

  1. the water temperature while the ice was melting.
  2. the water temperature after the ice melted, but before it started boiling.
  3. the water temperature as the water was boiling.
  4. what do your answers above (a, b, c) mean in terms of the energy you were adding?