SCIENCE
CHEMISTRY
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Physical Change
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Chemical Change
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Either A or B
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None of the above
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Detailed explanation-1: -You forgot to dry the bread knife when you washed it and reddish brown spots appeared on it. Chemical because water + metal = rust. A new substance was formed.
Detailed explanation-2: -Rusting is an example of a chemical change.
Detailed explanation-3: -The appearance of reddish-brown spots is a chemical change. The bread knife reacted with moisture thus forming reddish-brown spots. This change is indicative of rusting of the knife. The presence of moisture causes rusting of iron.
Detailed explanation-4: -Explanation: Physical changes change the shape, size or phase of a substance. Crumpling paper, getting a haircut, dissolving salt in water, melting wax, making ice cubes, chopping veggies for tossed salad, growing crystals from a supersaturated solution, grinding metal and slicing bread are all physical changes.
Detailed explanation-5: -It is a chemical change. The transformation of flour into gluten chains creates a new substance with different properties, and an altered chemical composition. The gluten chains cannot become flour again. It is an irreversible change.