Reversible and irreversible changes
Reversible and irreversible changes

Reversible and irreversible changes

I can construct an argument that some changes caused by heating or cooling can..

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Students learn about the difference between reversible and irreversible changes.


NGSS: 2-PS1-4

Learning objective

Students will be able to construct an argument using evidence that some changes caused by heating and cooling can be reversed and some cannot.


As a class, ask students to classify the given pictures as pictures that show either heating or cooling.


Explain to students that as matter is heated, molecules move faster and that when matter is cooled, molecules move slower. Explain further that with enough heat, solids can become liquids, and liquids can become a gas. In a similar way, with enough cooling, a gas can become a liquid and a liquid can become a solid. It is important to understand how this works because heating and cooling are happening on Earth and all around us. Some of these changes are permanent and others can still be changed. Explain to students that a reversible change is temporary and can be undone and give some examples of reversible change within heating or cooling. Give more extended examples of reversible change with melting ice-cubes and then challenge students to turn and talk about what they would think with the given cooling example. Continue by defining irreversible change to students and emphasize that with irreversible change, the original substance has been changed into a new substance, it cannot be turned back. Give some examples of irreversible change within heating and cooling. Discuss examples of irreversible change with the students. Have students form pairs and ask them to decide if the given change is reversible or irreversible. Why? What evidence do they have to prove their idea? Discuss their ideas as a class. Ask them to switch partners and decide if the given change is reversible or irreversible- and that they must come up with evidence. Discuss their ideas as a class. Check their understanding by asking the students to drag reversible or irreversible to the images shown.


Students are asked a set of true/false questions about key concepts of the lesson. They must also decide if given situations are reversible or irreversible and answer multiple-choice questions about heating and cooling.


Discuss the learning goal with the students. Be sure the emphasize that coming up with evidence why a change is reversible or irreversible is required when you make an argument about it. Why is it important to know which changes are reversible and irreversible? Close the lesson with a game. Show an image on the interactive whiteboard. If the change is reversible- ask them to hold up 1 finger. If the change is reversible- ask them to hold up 2 fingers.

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