Which type of substance is made of only one kind of matter and has definite properties?
an atomic substance
a chemical substance
a molecular substance
a pure substance

it should be p1 v1 = p2 v2

r just means there's a number of carbon in teh chain. for example rcooh means that after x number of carbon, the chain ends with cooh.

explanation:

away from the curb

explanation:

the wheels would then hit the curb if it started to rolling, decreasing the chance of an accident.

answer : a model is often used to explain and make things easier to understand when any scientific topic needs to be demonstrated and explained.

as in this case where a scientist wants to use a model to present the results of his detailed scientific investigation. he should do it as it will him to make the audience understand the concept in a much better way. also, it can be changed according to new scientific understandings.