- Begin the lesson by gathering students’ knowledge and ideas about water, ice, the process of freezing, melting, or evaporating. In a discussion, ask:
- What are the differences between running water and ice?
- How does an ice cube melt?
- How does water turn into ice?
- What happens when you boil water?
- As students share their ideas, record their thoughts before moving on to the experiments. An example chart for recording students’ theories is provided in Appendix A.
- The intent of this chart is to provide the educator an opportunity to understand what students understand so far about these concepts. While facilitating the discussion, it is important to encourage students to listen to one another’s theories, and agree/disagree or build upon the shared ideas. The educator may wish keep a personal record of what students share to help contribute to the development of their knowledge. For example, if a student theorizes that an ice cube melts because when the sun directly shines on it, return to this comment when conducting experiments to determine whether the student has built upon their knowledge.
- Ask students if they have ever seen a completely frozen pond or lake. Encourage them to think about how long it takes to freeze and what conditions are required.
- Ask how they think the time it takes to freeze a pond or lake compares to the time it takes to freeze a small ice cube?
- Introduce the experiment you’ll be conducting today:
- Four transparent containers will be filled with different amounts of water. The level of water will be marked on the container with a marker, so students can compare how the water level changes after freezing.
- Students will take the containers to a freezer (or to an outside space in winter) to start the freezing process.
- While the water is freezing, students will use the chart in Appendix B to record their predictions. Ask: Will the ice take up more or less space once all the water is frozen? How will that differ between containers? Which container will freeze faster? Will they all freeze fully?
- Students will then check the containers throughout the process. Note: It will usually take no more than a few hours for a full litre of water to freeze and will be even quicker for smaller amounts. Plan the check-ins accordingly so students can observe different stages of the process.
- When the water in all four containers has frozen, the containers can be taken out of the cold and into the classroom for discussion.
- Ask students what they notice about the space taken up by the ice: Does the ice take up more or less space than the liquid water? Why do you think this is the case?
To end this part of the activity, ask students to reflect on which predictions matched what they had anticipated, and what was different than what they expected. Ask them to update their pictures or words to represent what they observed throughout the experiment.
- For this part of the activity, students will sit on the carpet while the teacher does the demonstration at the front.
- Introduce the idea of water vapour and evaporation. Ask students to think about why we observe bubbles in the water when we heat it up to cook or why we see steam coming out of a hot bath or pool. Encourage them to think about heat or temperature and how that affects evaporation.
- In this kettle experiment, students will visualize how water transforms from one state to another.
- The teacher will add water to a kettle, showing students how much water there is. The teacher will then turn on the kettle.
- While the water is boiling, ask students to give ideas about what is happening to the water. Ask them to predict what they will see inside the kettle once the boiling is done.
- Keep boiling the water until a good amount of it has evaporated and the students can clearly see that the amount of water left over has reduced in quantity.
- Ask students to explain what they observe in the kettle: How much water is left over? Where did the rest of the water go? Could you see the water vapour leaving the kettle? Where did the vapour go? Where is it now?
- Ask the students to draw a picture to explain the kettle experiment and give labels to show what happened (see Appendix C).