Chemical reactions introduction

Question 1

Chemical vs. Physical Changes

Answer 1

A physical change is a change of state only, no new substance is formed, easy to reverse.
A chemical reaction is a result of a chemical reaction, new substance is formed, difficult if not impossible to reverse.

Question 2

What is the reactant in a chem reaction?

Answer 2

Reactants are the original substances found at the start of a chemical reaction.

Question 3

What is a product in a chem reaction?

Answer 3

Products are new substances formed at the end of a chemical reactions.

Question 4

There are six signs that a chemical reaction may have occurred:–

Answer 4

a gas may be released;
a colour change may occur;
An odour is produced;
A temperature change may occur (either hotter or colder);
Light and/or sound may be produced; and,
A precipitate (often seen as cloudiness) may be formed (a precipitate is a solids that forms when two liquids are mixed).
Another way is when one of the reactants disappears as it is used up in the reaction.

Question 5

what is the Law of conservation of Mass

Answer 5

Law of Conservation of Mass” states that matter can neither be created nor destroyed in a chemical reaction.

The mass of the reactants equals the mass of the products.