FOCUS QUESTION
1. Conduct an investigation to illustrate that some changes result in the formation of new materials and others do not.
2. Work cooperatively in groups
3. Predict the effects of heat on selected materials
4. Make careful observations of reversible change and record and explain this using scientific language.
Materials can undergo reversible or irreversible changes. Irreversible changes cannot be undone and form new materials. Reversible changes can be undone. Reversible and irreversible changes can be useful in every day life.
Substances can change their state by heating and cooling.
Melting, freezing, evaporation and condensation can cause materials to change state.
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The students in 6 B received a box of ice-cream from the past
principal of their school. By the time it reached their class, it was very
soft, however, the teacher starting sharing. This was a very difficult task
for her, so she sent it back to the tuck shop to be placed in the refrigerator. |
Students will discuss why the ice-cream was harder to share and why it was sent back to be placed in the refrigerator.
They will tell if all materials are like that. (can go back to their original state) They will discuss the changes that the ice cream had undergone. (this will lead to the concept reversible)
Students I need you to observe and record what happens when the following are done.
a. Heat a square of butter in hot water then allows it to cool
b. Inflate and then deflate a balloon
c. Cut a sheet of paper in four pieces then fit it back together
d. Boil water and place a mirror directly above the steam.
(They will make predictions of what will happen before the experiment is done}.
They will also watch Youtube video clip on reversible changes to glean additional information for reportingStudents will explain the changes that occurred in each case and state whether any new materials have been formed.
Students will write a simple description of the meaning of the term “reversible change” and share their discussions with class.
Individually, students will create a table to record frequent reversible changes they experience at home or seen at school daily. Eg.
|
Action (Before) |
Description of the change (After) |
Reversible Yes ¡ / No ¡ |
|
Placing water in freezer |
Water turned ice |
Yes ¡ / No ¡ |
EVALUATE
Answer questions of the types listed below.
1. Which of the following activities depicts a reversible change?
(a) Boiling an egg until hard (c) melting a cube of ice
(b) Burning an old rag (d) combining ingredients to make muffins for the family
2. Define the term “reversible”
3. Helen and Jane were both asked to provide examples of reversible changes. Helen’s response was “the burning of a piece of paper.” Jane’s answer was “melting of an ice cube”. Whose response was correct?
Justify your answer.
4. Provide two examples of a reversible change.
(a) (b)
5. For each of the following, indicate by shading under the column whether you agree or disagree with the statements about reversible changes.
Statement Agree Disagree
When a material is changed in a reversible way, a
new material is not made. ¡ ¡
Burning a piece of paper can be reversible. ¡ ¡
