Question

get a whiff of this
a fresh rose, a puddle of gasoline, or a trash bin of rotting garbage—you know it when you smell it. but where do smells come from? odors are chemicals found in tiny molecules that float in the air. anything with a smell, whether it is minty toothpaste or a moldy bathmat, sends off a mixture of these tiny molecules. when they reach your nose, you inhale and some of the chemicals reach nerve cells in your nasal cavity. nerves send the message to your brain: \something smells in here!\
not everyone reacts to smells in the same way. some people are very sensitive to specific smells, and others can hardly smell anything at all. researchers have discovered that our ability to detect odors is genetic, which means that it is passed on from parents to their children. every person recognizes smells differently.
strong smells linger because the chemicals do not change easily. one of the most pungent aromas known is that of a skunks spray. getting rid of the smell on a person or dog that has been sprayed can be quite difficult. some traditional methods, such as bathing in tomato juice, only mask the odor. other mixtures, such as a mixture of hydrogen peroxide and baking soda, work better because they actually change the chemical composition of the odor molecules. but they cant neutralize the smell completely. wetness can bring out a smell that you thought you had gotten rid of. so, a dog might smell ok when its fur has dried after a bath, but when it starts to rain, you might need to hold your nose again!
skill practice read each question. fill in the bubble next to the correct answer.

1. what causes smells?

a patterns of odor recognition
b mixtures of foods
c chemicals in the air
d nerves in the nasal cavity

1. why do people react differently to smells?

a some people have genetic diseases.
b peoples unique sensitivity to odors is genetic.
c levels of moisture change what they smell.
d peoples noses change chemicals differently.

1. why is tomato juice not effective in getting rid of the smell of skunk spray on a dog?

a it only neutralizes the smell temporarily.
b it only changes the color of the dogs fur.
c it only makes the smell worse.
d it only hides the smell.

1. what causes a smell to be neutralized?

a a chemical change in the odor molecules
b the odor entering the nasal cavity
c water interacting with the odor
d nerves in the nose detecting the odor
strategy practice explain which information in the passage is most important to understand for knowing how to deal with skunk spray.

Explanation:

1. The passage states that odors are chemicals in tiny molecules that float in the air. So, for the first question, the answer is based on this description.
2. It mentions that the ability to detect odors is genetic, which leads to different reactions.
3. Regarding tomato juice, it says "only mask the odor", which means it hides the smell.
4. When the chemical composition of odor molecules changes (as with hydrogen peroxide and baking soda mixture), the smell is neutralized.

Answer:

1. C. chemicals in the air
2. B. People's unique sensitivity to odors is genetic.
3. D. It only hides the smell.
4. A. a chemical change in the odor molecules