To explore what happens to water as it goes from solid to liquid and back again; to use observation, measurement, and communication skills to describe change.
This lesson is the first in a three-part series that addresses a concept that is central to the understanding of the water cycle—that water is able to take many forms but is still water. This series of lessons is designed to prepare students to understand that most substances may exist as solids, liquids, or gases depending on the temperature, pressure, and nature of that substance. This knowledge is critical to understanding that water in our world is constantly cycling as a solid, liquid, or gas.
In these lessons, students will observe, measure, and describe water as it changes state. It is important to note that students at this level "...should become familiar with the freezing of water and melting of ice (with no change in weight), the disappearance of wetness into the air, and the appearance of water on cold surfaces. Evaporation and condensation will mean nothing different from disappearance and appearance, perhaps for several years, until students begin to understand that the evaporated water is still present in the form of invisibly small molecules." (Benchmarks for Science Literacy, pp. 66-67.)
In this lesson, students explore how water can change from a solid to a liquid and then back again.
In Water 2: Disappearing Water, students will focus on the concept that water can go back and forth from one form to another and the amount of water will remain the same.
Water 3: Melting and Freezing allows students to investigate what happens to the amount of different substances as they change from a solid to a liquid or a liquid to a solid.
Begin this lesson by dividing the class into pairs. Assign each student a role: writer or illustrator. Students will exchange roles during the course of the lesson.
Distribute an ice cube in a clear plastic cup to each group. Have the illustrator draw a picture of what he/she sees. Have the writer write a sentence or word to describe the properties of the ice cube. Guide students' observations with questions such as the following:
- What is in the cup?
- Describe the ice. What does it look like? Feel like?
- What is the ice made of?
- How is ice made?
- Pour the ice into a container of a different shape or size. What does it look like now? Does it look the same or different? Has the shape of the ice changed? Why do you think that is?
- What will happen if we leave the ice out on the desk/table? Why? How do you know?How long might this take?
Tell students that they will be asked to observe the ice over time to see what changes take place. Set a timer or note 15-minute intervals on the clock. (Please note: The appropriate time interval will vary depending on the size of the ice cube, amount of sunlight, temperature in the room, etc. Choose the interval appropriate for your time constraints, number of students, age range. Although the activity could require an hour to fully complete, other activities are being conducted simultaneously.) Ask students to repeat the above recording procedures after each time interval.
While this activity is taking place, you may wish to read Amazing Water by Melvin Berger, or I am Waterby Jean Marzollo.
When the ice has completely melted, allow students to draw their final journal entry. You can post the students’ pictures of the ice in a line on the wall, so that students will have a visual representation of the change that has occurred.
- What happened to the ice? Why?
- What is in the cup?
- How is it like the ice? How is it different from the ice?
- Describe the water. What does it look like? Feel like? Pour the water into a container of a different shape or size. What does it look like now? Does it look the same or different? Has the shape of the water changed? Why do you think that is?
- Did the ice change its shape when you poured it into this container? Why or why not?
- Can you think of something else that we can pour in that will take the shape of the container?
- Return the water to the glass. Is there any way that we could change this water back to ice? How? How long might this take?
Have students place one or more of the cups of water in a freezer. If possible, repeat the procedure used above to observe change in the melting ice. Allow students to check on the water at regular intervals of your choice. When the water has frozen and the final illustration has been made, you can place a finished series of drawings up on the wall, in sequence, so that students can see the change in water temperature.
- Change is happening all around us. There are some changes that happen so quickly or slowly that we cannot see them. Did the change in the water happen slowly or quickly?
- How long did it take for the ice to turn into water? Do you think that there is any way to speed up this change? How? If time permits, allow students to share and test their ideas. (Students might suggest and test blow dryer, fan, sunlight, different spots in the room, radiator, salt, stirring it, different container, etc.)
- Is there any way to slow down this change? (different container, insulator, different location in the room, place in the shade, put a fan on it, etc.) How can we compare the rate of change? (Time it, use ice in a plastic cup as a control.)
- Can you think of anything else that changes from one form to another? In the kitchen? In the bathtub? How might soap change?
In groups or as a class, create a Venn Diagram comparing water in solid form and water in liquid form. How are they alike? How are they different?
Have students answer the questions below in their journal, using words and/or pictures. Allow students to explain their answers verbally.
- How can we make water go from water to ice?
- How can we make water go from ice to water?
- Give two examples of where you would see water going back and forth from one form to another.
- Does the water ever "get tired?" Would we ever get to a point where we couldn't get this change to happen?
Follow this lesson with the other lessons in the Water series: