To draw a graph between temperature and time when ice is converted into water and then to steam by slow heating

 

Abstract

This experiment aims to observe the phase changes of water by plotting a temperature vs. time graph as ice is slowly heated to become water and then steam. The experiment illustrates the concepts of latent heat of fusion and vaporization.

Introduction

The phase changes of water are essential physical chemistry concepts, demonstrating the energy changes associated with state transitions. This experiment uses controlled heating to track temperature changes as ice melts into water and water boils into steam, providing a visual representation of these changes through a graph.

Procedure

1. Begin with a measured amount of ice at 0°C in a beaker.
2. Set up a heating mechanism, such as a Bunsen burner, beneath the beaker.
3. Insert a thermometer in the beaker, ensuring it does not touch the bottom or sides.
4. Heat the ice slowly and record the temperature every minute until all ice is melted.
5. Continue heating the water and record the temperature until it starts boiling.
6. Keep the water boiling and record the temperature until all water turns to steam.
7. Plot these temperature readings against time on a graph to show the temperature plateau during phase changes.

Observations

Temperature readings show a plateau at 0°C as ice melts and another plateau at 100°C as water boils, demonstrating the latent heat of fusion and vaporization.

Conclusion

The experiment visually demonstrates that during phase transitions, the temperature remains constant despite continuous heat application, highlighting the concept of latent heat.

Short Questions with Answers

1. What is latent heat?
   Answer: Latent heat is the heat required to change the state of a substance without changing its temperature.
2. Why does the temperature stay constant during a phase change?
   Answer: The heat energy is used to break the intermolecular bonds, not to increase temperature.
3. What is the latent heat of fusion?
   Answer: It is the heat required to convert solid to liquid without temperature change.
4. What is the latent heat of vaporization?
   Answer: It is the heat required to convert liquid to gas without temperature change.
5. Why is slow heating important in this experiment?
   Answer: It ensures even heat distribution and accurate temperature measurements during phase changes.
6. How can you tell when the ice has completely melted?
   Answer: The temperature starts to rise above 0°C.
7. Why is it important to ensure the thermometer does not touch the sides of the beaker?
   Answer: To avoid heat conduction from the beaker, ensuring accurate readings of the water/ice.
8. What does a plateau on a temperature-time graph indicate?
   Answer: A phase change occurring at constant temperature.
9. How does the graph look before and after each plateau?
   Answer: It rises during heating, plateaus during phase change, and rises again after the change completes.
10. What safety precautions should be taken during this experiment?
    Answer: Handle the Bunsen burner carefully, use heat-resistant gloves, and ensure the setup is stable.

MCQs with Answers

1. What does the plateau in the temperature-time graph represent during the ice to water transition?
   1. Decrease in temperature
   2. Constant temperature
   3. Increase in temperature
   4. None of the above
   Answer: B. Constant temperature
2. What is the primary reason for the temperature plateau at 100°C?
   1. Condensation of steam
   2. Water boiling into steam
   3. Ice melting into water
   4. None of the above
   Answer: B. Water boiling into steam
3. Which phase change consumes the most energy?
   1. Ice to water
   2. Water to steam
   3. Water to ice
   4. Steam to water
   Answer: B. Water to steam
4. Why is it important to heat the ice slowly in this experiment?
   1. To prevent boiling over
   2. To save energy
   3. To ensure accurate temperature readings
   4. All of the above
   Answer: C. To ensure accurate temperature readings
5. What does a rising line after a temperature plateau indicate?
   1. The start of a phase change
   2. The end of a phase change
   3. No change in phase
   4. Temperature decrease
   Answer: B. The end of a phase change