Question

sometimes you might not be able to see a new substance forming, so be on the lookout for evidence that a chemical change has occurred. a change in smell and color can indicate that a new substance has formed. for example, caramelized onions have a very different smell than raw onions. they have a darker color, too. other physical properties about the onions change during caramelization, including their texture. the formation of bubbles can be evidence of a chemical change, but only if they indicate that a new gas is formed. if you heat a pot of water, the water will begin to boil. those bubbles are not any new substance forming. theyre just the same water you started with changing state from liquid to gas.
based on this passage, if you cannot see that a new substance has formed,
choose one option
a only a physical change could have occurred.
b a chemical change might have occurred.
c a change in state has always occurred.
d no change could have occurred.

Explanation:

The passage states that sometimes you can't see a new substance forming but should look for evidence like a change in smell, color, etc. This implies that a chemical change (which forms a new substance) might have occurred even if you don't see the new substance. Option A is wrong as it's not only physical change. Option C is incorrect as it's not always a change in state. Option D is wrong as changes can occur.

Answer:

B. a chemical change might have occurred.