Question

Which of the following is a physical change?

Select one:

freezing
cooking
All of the listed answers are correct
rotting
rusting
None of the listed answers are correct

Answer 1

Chemical change is any change that results in the formation of new chemical substances. At the molecular level, chemical change involves making or breaking of bonds between atoms. These changes are chemical:
iron rusting (iron oxide forms)
gasoline burning (water vapor and carbon dioxide form)
eggs cooking (fluid protein molecules uncoil and crosslink to form a network)
bread rising (yeast converts carbohydrates into carbon dioxide gas)
milk souring (sour-tasting lactic acid is produced)
suntanning (vitamin D and melanin is produced)

Physical change rearranges molecules but doesn't affect their internal structures. Some examples of physical change are:
whipping egg whites (air is forced into the fluid, but no new substance is produced)
magnetizing a compass needle (there is realignment of groups ("domains") of iron atoms, but no real change within the iron atoms themselves).
boiling water (water molecules are forced away from each other when the liquid changes to vapor, but the molecules are still H2O.)
dissolving sugar in water (sugar molecules are dispersed within the water, but the individual sugar molecules are unchanged.)
dicing potatoes (cutting usually separates molecules without changing them.)

Answer 2

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Answer 3

Cooking would be a chemical change because you can't uncook something. Physical changes are reversible. There is one up there that you are able to reverse

Answer 4

Think of it this way:
Can you uncook something? No you can't so it's a chemical change
Can you make something unrust? No therefore it is a chemical change
Can you make something unrot? No that is also a chemical change
Can you unfreeze something? Yes because it's a physical change you're not altering anything at a molecular level