Hot and Cold
Lesson 9 of 10
Objective: SWBAT collect data on how some changes caused by cold or heat are irreversible and some are not.
The purpose of this lesson is to help students gather evidence that some changes caused by heating and cooling can be reversed and some can not.
For this lesson you will need access to a heat source (hot plate, oven, or microwave for heating), and access to a freezer for the freezing parts of the lesson.
Students will need to collect data over the course of 2 days to allow for things to freeze, or harden after they are heated, and to melt after being frozen.
Materials: water, butter, cup of instant - just add water- soup, popcorn (unpopped), chocolate chips
I Can and the Test Question
I invite students to read the I Can statement with me. It says, "I can test to see if things that change with heat or cold, can go back to the way they were when the hot or cold is gone."
I ask, "what do you think that might mean?" I let students share their ideas on what we will be doing.
I say, "When we start an experiment, what is the first thing we need?" (a question). "Good, can anyone suggest a question they might be wondering now that they have read the I can statement?"
I listen to several suggestions and write them on the board. Our Working Question I say to students, "we want to come up with a question that will help us to figure out if things that change when we heat or make them cold can go back the way they were without the hot or cold. Does anyone want to suggest how one of these questions on the board, or several of them together, might be our best question for our investigation?" I let students share their ideas until we have formulated a single question. I ask students to copy the question into their science journal.
Planning the Investigation
"You have just copied the question into your journal. What do we do next if we are going to work as scientists?" (Write our hypothesis. Say what we think will happen.) "I want each of you to write your hypothesis in your journal. Do you think it is possible to turn something back to the way it was after heating or cooling it and why?" I give students 3 - 4 minutes to write their hypothesis in their journals. Writing the Hypothesis
"Now we have a question and a hypothesis what do we need before we start our investigation?" (a procedure)
"I am going to show you the materials and we will talk about whether these things should be heated, cooled or both and how we might do that."
I put out water, butter, cup of instant - just add water- soup, popcorn (unpopped), chocolate chips. I hold up each object one at a time and ask do you want to heat this or cool it or both? I put a chart on the board for us to fill in. I say, I would like you to write each material in your journal under the heating or cooling headings as we have on the board and then put a check next to each one that you think we can change back to just what we have here when we have heated or cooled it.
"Now we need to write the steps that we will use when we heat or cool each object and then try to change it back by doing the opposite. In other words, we have to try to heat an object and see if it changes and then if we cool it, see if it will change back. Remember that we want to know if something can change back if it changes when we heat or cool it." I want students to come away with the knowledge that some things can be changed back when heated or cooled, but others can not. Some changes that we make to materials are permanent. This is part of the basic understanding of how things are made, and how the materials matter, that second graders should begin to grasp. Creating A Procedure
"Please write a set of steps you might take to test each of these materials. I will give you 5 minutes to record the steps you think you need to take." I want students to try to come up with their own procedure and then we will work with their suggestions to write a class set of procedures.
I circulate around the room looking at student procedures and making comments as appropriate such as, why might you take that step before this one.
"Now that everyone has a set of procedures, I would like you to work as a table to revise your procedures so that you have 1 set for your table. Each person will be given 4 colored cubes. You will need to comment on each person's ideas by suggesting one of their steps to keep, or to change the order of, or to skip. You can contribute a cube to the group tower each time you share. At the end of the shares, your table should have 1 set of procedures to share with the class."
I listen in as the groups discuss the procedures and what needs to be done in the investigation.
When all groups have had a chance to share I invite all students to come to the rug. I collect the group's procedure sheets.
I compare them quickly and then read any differences and as a class we decide which parts to keep and in what order. When we have a final set of steps I say, "we could have followed any of the procedures that you wrote alone or at your tables, but now we have a class procedure that we will work with today."
Carrying Out the Procedure
I ask students to return to their seats. I say that because of our materials, today's investigation will be mostly demonstration.
I begin with the first step of the procedure which is to heat the soup. I say, "you have checked in your journals whether you think the soup can be changed back after it is heated. First we will heat it and you will need to record what you see. I pour boiling water into the cup - o - soup and ask students to record any changes they notice. I say, " what do you think will happen when we cool the soup off? Will it look like it started? Why or why not" I give students a chance to discuss and record their observations.
I set the soup aside and take out the butter and a small hot plate. I ask for a student to add the butter to a pan and we let it get warm. After the butter melts I ask students to record what happened after the butter was heated. Again we discuss what might happen when it cools. I set it aside.
I repeat the process with the popcorn, chocolate chips Predicting Change In Melting Chocolate, and the water.
When we have recorded all the things that happen with heating, I tell students that we now want to cool all of these things and see if they change back. I have several children take all of the items and place them in a refrigerator.
We will check on all of the cooled items in an hour (or the next day depending on your schedule). Students will record what they observe in their journals.
Drawing conclusions is an important step in the scientific process. Comparing Before and After I ask students to look back over their results.Chart of Results What do they notice? Did everything change back to the way it was before it was heated? Did anything change back? Why do they think this happened?
" You have thought about your results. I want you now to write the conclusions. Conclusion Remember that when we write conclusions, we go back to the original question. Did we prove it to be true always, sometimes or never? What in your results makes you decide this? I want you to write down your thoughts about whether we proved that things can always, sometimes or never be changed back when they are heated. "
I give students time to write their thoughts.
Drawing conclusions is important to the scientific process. I want students to be able to write about their scientific reasoning by formulating these conclusions.