# Physical Science: Session 7

## Melting Point of Ice; Delta Science Modules

Lesson at a Glance:
Curriculum: Delta Science Modules “States of Matter”
Topic: Melting Point of Ice

During the two weeks prior to the lesson seen in the video, the students had been studying various kinds of energy transfer with their teacher Gina Robertson. In this lesson, Paula asks the students to put a thermometer in a glass of ice and take a reading. They then remove the thermometer from the ice and place it in a glass of warm water. As the students watch the volume of the red liquid in the thermometer expand, they speculate that it is because it has absorbed “heat energy” from the warm water. Paula comments, “First I wanted to develop the idea that the same amount of matter, which is that red liquid, can somehow occupy two different amounts of space, and why that’s happening.”

The students then return the thermometer to the glass of ice and observe the red liquid contract again. “I hope we can get them to see that it is happening because there is heat being transferred into the molecules of the red liquid when it is in the hot water, and the transfer is out of the hot red liquid when you put it in the cool water. So it goes the opposite way and suddenly the matter takes up less space,” said Paula.

Later, the students pour some of the warm water into the glass of ice and carefully observe the red liquid in the thermometer. From this experiment, they were able to notice that there is a moment just before the ice begins to melt in which the temperature of the water is the same temperature that the ice was. Paula remarks, “This lesson is about the melting point of ice but, in actuality, what I am looking for is for them to develop ideas about the effect of energy on the change of state of matter, and the effect on the motion of molecules when energy comes in contact or transfers in or out of a state of matter, whatever that might be.”