Open Question
What is the difference between a physical change and a chemical change?
3. Matter and Energy
Physical & Chemical Changes
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Which of the following represents a reversible change?
A
Melting a chocolate bar then re-solidifying it in the freezer.
B
Changing water vapor into oxygen and hydrogen gas.
C
Turning a potato into french fries.
D
Baking a cake from a recipe.
Verified step by step guidance1
Identify the concept of reversible and irreversible changes. A reversible change is a physical change that can be undone, while an irreversible change is a chemical change that cannot be easily reversed.
Examine the first option: Melting a chocolate bar then re-solidifying it in the freezer. This involves a physical change where the chocolate changes state from solid to liquid and back to solid, which is reversible.
Consider the second option: Changing water vapor into oxygen and hydrogen gas. This involves a chemical change (electrolysis) that is not easily reversible, as it requires specific conditions and energy input.
Analyze the third option: Turning a potato into french fries. This involves both physical and chemical changes (cutting and cooking), making it irreversible.
Evaluate the fourth option: Baking a cake from a recipe. This involves chemical changes (baking) that create new substances, making it irreversible.
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