Question

1. what must occur for a change to be a chemical reaction?

a. there must be a change in physical properties.
b. there must be a change in chemical properties.
c. the change must involve a change in volume
d. the change must involve a change in mass.

1. which of the following is a chemical change?

a. fermenting of cheese
b. mixing two cheeses in a bowl
c. grating cheese
d. melting cheese

1. which of the following changes to a metal is a chemical change?

a. polishing
b. bending
c. rusting
d. melting

1. which of the following involves a chemical change?

a. grinding
b. melting
c. decomposing
d. mixing

1. which of the following processes involves a change in physical properties?

a. fermenting
b. boiling
c. burning
d. rusting

1. a chemical change occurs when a piece of wood

a. is cut.
b. is painted.
c. decays.

Explanation:

Question 37

A chemical reaction involves the formation of new substances, which means a change in chemical properties (since chemical properties relate to a substance's ability to undergo chemical changes). Physical property changes (option a) can happen in physical changes too. Volume (option c) and mass (option d) changes aren't essential for a chemical reaction (mass is conserved in chemical reactions, and volume change can be physical). So the correct answer is b.

Fermenting cheese (option a) involves the action of microorganisms, leading to the formation of new substances (like acids, flavors), so it's a chemical change. Mixing two cheeses (b), grating (c), and melting (d) are physical changes as no new substances are formed.

Rusting (option c) of a metal (like iron rusting to form iron oxide) is a chemical change as a new substance (rust) is formed. Polishing (a), bending (b), and melting (d) are physical changes (no new substance).

Answer:

b. There must be a change in chemical properties.

Question 38