Physical And Chemical Changes

Question 1

What is a chemical change?

Answer 1

When a transformation changes the molecules in matter

Question 2

True or false?

chemical changes are reversible.

Answer 2

False, chemical changes are irreversible

Question 3

What are the different indicators of a chemical change

Answer 3

Formation of a gas 
Formation of a solid
Change of a colour
Change in temperature 
Emission of light

Question 4

What are the types of chemical changes and explain what they are

Answer 4

Synthesis: reaction where 2 or more substances combine to make a new substance
Decomposition: when a substance breaks down into two or more simpler substances
Oxidation: chemical reaction between a substance and the oxygen in the air
Combustion: when a substance reacts with the oxygen in the air and releases a lot of heat

Question 5

Oxidation can either be Rapid or slow

Give an example of each

Answer 5

Rapid: a fruit browning
Slow: rust on a building or penny

Question 6

Which two types of chemical changes are opposites

A) oxidation and combustion
B) synthesis and decomposition
C) decomposition and oxidation
D) synthesis and combustion

Answer 6

B) synthesis and decomposition

Question 7

Give an example of each type of chemical change

Answer 7

Oxidation: rust
Synthesis: photosynthesis
Combustion: wood burning
Decomposition: cellular respiration

Question 8

Which is the right definition of a physical change

A) happen on a molecular level when you have two or more molecules that interact.
B) changes affecting the chemical composition but NOT the chemical substance
C) changes affecting the form of a chemical substance, but NOT its chemical composition

Answer 8

C) changes affecting the form of a chemical substance, but NOT it’s chemical composition

Question 9

Give some examples of physical changes

Answer 9

crushing a can
melting an ice cube
breaking a glass
shredding paper
chopping wood

Question 10

Name and explain the type of chemical change
A) Fireworks
B) Iron and oxygen combine to create rust
C) Hydrogen molecules combine with oxygen to create water
D) Hydrogen peroxide breaks down into hydrogen and oxygen.

Answer 10

A)combustion because the substance is reacting with the air.
B) oxidation because rust is forming
C) synthesis because Hydrogen molecules and oxygen are combining to make water
D) decomposition because the hydrogen peroxide is breaking down into two substances.