Question

Which of the following is a common sign that a chemical change has occured?
A. a chemical has changed in size
B. a chemical has changed to a different state of matter
C. a chemical has become a different shape
D. a chemical combines with another to form a new compound

Answer 1

Answer:

According to me it should be opt (D). a chemical combine with another to form a new compound

Explanation:

because all the other options are not common to all type of reactions!

Answer 2

The common sign that a chemical change has occurred is D. a chemical combines with another to form a new compound.

Explanation:

• Chemical change is defined as a change where new substance is formed and their is change in chemical composition.

• Chemical change is mainly observed when there is change in chemical composition of molecules involved and when there is change in chemical bonds.

• Change is size, change in different states of matter or change in shape of the substance can result even without any change in composition of molecules. So, it is not a sure sign for a chemical change. These are all physical changes.

• When a new compound is formed, then there are new chemical bonds that are formed which results in change in chemical composition and so it is a sure sign of chemical change.