Answer Show
Hint:We will start answering this question by knowing a basic idea about liquids. We know that when you heat a liquid, the particles gain more energy and move quicker and faster, expanding the liquid. We will later explain the effects of temperature on this liquid. Complete answer: Hence when a liquid is heated, it transforms into a gas (or converted into vapour). Additional information: Note:All materials have a certain temperature at which they boil when exposed to normal atmospheric pressure. The temperature at which something starts to boil is known as the "boiling point."Remember that you have to mention both points that it boils as well as converts into a vapour state. Thus phase change takes place when any liquid is heated. You can also give an example of water. Lesson Overview for TeachersView the video below to see what you and your students will do in this lesson. ObjectiveStudents will be able to explain that cooling water can change it to ice and that heating ice can change it back to liquid water. Students will be able to explain that this process can also happen to other substances. Students will also be able to explain that heating a substance makes its molecules move faster and cooling a substance makes its molecules move slower. The lesson can also be used to lay a foundation for learning about changes in state and chemical changes which can be further developed in later grades. Key Concepts
NGSS Alignment
Summary
EvaluationDownload the Student Activity Sheet (PDF) and distribute one per student when specified in the activity. The activity sheet will serve as the Evaluate component of the 5-E lesson plan. SafetyBe sure students wear properly fitting goggles. Materials for each group
ENGAGE1. Show a time lapse video of water freezing and ice melting to introduce the idea that cooling and heating can cause a change in a substance.Ask students:
Explain to students that when water freezes, it changes from a liquid to a solid. Show the time lapse video Water Freezing. Note: Tell students that this is a special type of video in which something that takes a long time can be shown in a much shorter time. The freezing of the water in the glass probably took at least six hours. The video was taken for the whole six hours but is shown speeded up so that the freezing process can be shown in about 1 minute. Tell students that this type of video is called “time lapse”. Ask students
Show the time lapse video Ice Melting. Explain that warming ice makes it change from solid ice to liquid water. Note: Students may not realize that the ice is being warmed just by being at room temperature. They may expect to see the ice put on the stove or held over a candle flame. Explain to students that the ice is being warmed because it is at normal room temperature and that room temperature is warmer than the temperature of the ice. Normally ice needs to be in a freezer at a low temperature or outside in cold weather (32 °F or 0°C or lower) to stay frozen as ice. If it is placed on a surface in a room at normal temperature, it is actually being warmed. Explain to students that water can be cooled to make ice and then the ice can be warmed to make liquid water again. Cooling and heating water in this way can make the changes go back and forth. Give each student an Activity Sheet (PDF). EXPLORE2. Have students investigate what happens when butter is heated.Question to Investigate: How does butter change when you warm and cool it?Materials for each group
Have students come to the front of the class. Show students a stick of butter at room temperature. Use a popsicle stick to show that it is soft and can be cut easily. Ask students
Explain to students that when scientists have a question they do an investigation to try to find the answer. Tell students that they can be the scientists and do an investigation to find the answer to the question. Procedure
Note: Tell students that while they heat the butter and stir it, you will stir the same amount of butter in the same type of cup but not heat it. Explain that you want to see if anything happens to the butter from just stirring it, or if it’s the heat that really causes the melting. Ask students:
Note: Let students know that the butter you stirred without heating didn’t change much at all. The change must have been caused by the heat and not just the stirring. 3. Have students investigate what happens when the liquid butter is cooled.Ask Students:
Ask students:
EXPLAIN |