Unit 3: Considering the Influence of Light and Thermal Phenomena on Local Weathe
Unit 3: Considering the Influence of Light and Thermal Phenomena on Local Weather
III. Developing Central Ideas Based on Evidence
Unit 2 developed the central idea that heat and temperature are different ideas. The next exploration extends this development to examine what happens when water changes state.
A. Exploring the difference between heat and temperature during changes in states of matter
Question 3.2 What happens when ice melts, liquid water warms, and the liquid water eventually boils?
To explore changes in state, assemble:
- rice cooker, pot and hot plate, or pot and stove
- tray of ice cubes
- thermometer
- large binder clip.
We use a digital temperature probe connected to a computer that displays a continuous record of the temperature (see https://www.vernier.com/product-category/?category=temperature-sensors). We set the duration for 1800 seconds (30 minutes) and the temperature scale from about -5 °C to about 110°C. A regular bulb and tube thermometer will work if the scale ranges at least from a little below the freezing point of water (0°C) to a little above its boiling point (100°C).
- In the Before section of your physics notebook page, predict how the temperature of water changes when a container of ice cubes is placed on a heater and the ice melts, the liquid water warms, and then boils. Sketch a graph of temperature versus time to illustrate your prediction.
- What happens when ice melts, warms, and boils?
- Put some ice and a little water in a container that can be heated such as in a rice cooker or in a pot on a hot plate or on a stove. Place a thermometer or temperature probe connected to a computer in the ice.
- You can use a binder clip to keep the temperature probe or thermometer from touching the bottom of the pan as shown in Fig. 3.2.
- Turn on the heat source and keep its level constant throughout this exploration so that energy is flowing at a constant rate into the system of the pot and the frozen, liquid, and finally boiling water.
- In the During section of your physics notebook page, record what happens to the temperature when you heat the ice.
- Be sure that the thermometer or temperature probe is not resting on the bottom of the rice cooker or pot but is measuring the temperature of the melting mixture of ice and liquid water. Stir occasionally to be sure the temperature is the same throughout the mixture of melting ice and liquid water.
- Leave the temperature probe in the warming liquid water, stirring as needed, and for a few minutes while the liquid water is boiling.
- If using a regular thermometer, stir and record the temperature repeatedly while the ice melts, the liquid water is warming, and boils.
- Draw and interpret a graph of the recorded temperatures as the ice melts, liquid water warms, and eventually boils.
- Discuss with your group members what the relation is between the energy flowing into the system and the temperature of the water in its various phases and phase changes. Formulate your insi