Phase Change LabName:

Period:

Purpose:

Hypothesis: What will happen to the temperature of a substance during phase changes?

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PROCEDURE:

  1. Set up your equipment as directed by your teacher. Make a diagram below.
  2. Fill a beaker full of ice and add about 100mL of distilled water.
  3. Add 2-3 boiling chips to your liquid in the beaker.
  4. Make sure the bulb of the thermometer is always just below the surface of the liquid, but is not touching the bottom of the beaker
  5. PUT ON YOUR SAFETY GOGGLES AND APRONS
  6. Turn on the Bunsen burner. Continually stir the ice water using a stirring rod while heating.
  7. Record the temperature every thirty secondsuntil all ice is melted.
  8. Once the ice has melted you may turn up the heat and heat the liquid to a boil. Continue to record the temperature every 30 seconds. (you may need to extend your data table)
  9. CONTINUE TO BOIL AND RECORD THE TEMPERATURE OF THE LIQUID UNTIL THE TEMPERATURE HAS REMAINED THE SAME FOR AT LEAST FIVE READINGS.
  10. Plot a time verses temperature graph, with time on the horizontal axis and temperature on the vertical axis. Be sure to give your graph a title and label its axes.

Time(sec) / Temp (°C) / Time(sec) / Temp (°C) / Time(sec) / Temp (°C)
0
30
60
90
  1. What is the melting point of the ice? What happens to the temperature while the ice is melting?

2. What is the boiling point of this liquid? What happens to the temperature while the liquid is boiling?

  1. Why doesn’t the temperature continue to rise even though you continue to heat the liquid? What is happening to that heat energy?
  1. Does the boiling point or melting point depend upon the amount of substance used?
  1. What are three changes of state you observed during this investigation?
  1. Can a substance be both a liquid and a gas at the same temperature? (HINT: Think of what happens as the liquid boils)
  1. Compare your results to those of some of your classmates. What is similar about your graphs? What is different?

8. Could an unknown substance’s melting point be use to help determine its identity?

9.Could an unknown substance’s boiling point be use to help determine its identity?

10. Do phase changes produce changes in the physical properties of

matter or the chemical properties of matter?

11.Assume you had an unknown liquid and after boiling it and plotting a

time vs. temperature graph you determined that there were two different boiling points. What would this information tell you about the unknown liquid?