If a chemical reaction occurs, the properties of substances before and after the substances interact must be

different

Explanation:

A chemical reaction may be defined as the process or method by which a substance undergo a change in their structure chemically when reacting with some other substance and acquiring the property of both or sometimes forms a new substance. It leads to the chemical transformation of the chemical substance to some another substance.

The properties of the new substance formed is different form the parent substance before the reaction.

Thus, when chemical reaction occurs, the properties of the substances before the reaction and after the reaction takes place is different.

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.

he uptake of drugs from the intestine is often strongly influenced by diffusion. for example, consider a water-insoluble steroid for treating inflammation that is solubilized in aggregates of detergent molecules, called micelles. these micelles, aggregates of 80 soap molecules, have a molecular weight of 24,000, a diameter of 2.6 nm, and a charge of -27. the positively charge ions (counterions) in this system are na".