Year 9 Chemistry

Question 1

Physical Change

Answer 1

A physical change involves only a change to the physical property of a substance such as its shape, state or temperature. A physical change can usually be reversed as no new substance is formed.

Question 2

Chemical Change

Answer 2

With a chemical change, one or more new substances are formed. The change is called a chemical reaction and the new substance(s) has different physical and chemical properties from the old substance.

Question 3

Example of a physical change

Answer 3

For example, when water freezes to ice its properties change. It is now a solid - but it is still water. And it can be easily changed back to liquid water.

Question 4

Example of a chemical change

Answer 4

For example, when hydrogen and oxygen react, they bond to form water.

Question 5

All chemical reactions involve what?

Answer 5

Reactants and products.

Question 6

Rusting is a chemical reaction in which iron reacts with oxygen in the air to form iron oxide. The reactants are?

Answer 6

Iron and oxygen

Question 7

How many hydrogen atoms are there in each molecule of ammonia, NH3?

Answer 7

3

Question 8

Electrical charge of a proton

Answer 8

Positive

Question 9

Electrical charge of a neutron

Answer 9

Neutral

Question 10

Electrical charge of a electron

Answer 10

Negative

Question 11

Which subatomic particle is not found in the nucleus?

Answer 11

Electron

Question 12

The mass of the neutron is approximately equal to the mass of the?

Answer 12

Proton

Question 13

Which subatomic particles are found in the nucleus?

Answer 13

Proton and neutron

Question 14

Most of an atom’s volume is made up of what?

Answer 14

Empty Space

Question 15

Where is most of the mass of an atom located?

Answer 15

Inside of the nucleus

Question 16

Overall the nucleus has a _______electrical charge

Answer 16

Positive

Question 17

What is a chemical element?

Answer 17

A substance made up of only one type of atom

Question 18

Calcium is an element. What type of atoms is it made out of?

Answer 18

Calcium Atoms

Question 19

Ammonia is a colourless gas that is used to make fertilizers, cleaners and medicines. A chemist heats up some pure ammonia to very high temperature and finds that it breaks down into two other gases.
Is ammonia an element?

Answer 19

No, because it is made up of multiple types of atoms.

Question 20

Like helium, argon is a noble gas. What structure would you expect argon to have?

Answer 20

Single Atoms

Question 21

Phosphorus is an element in which the atoms often bond together in groups of four. What is each group called?

Answer 21

A molecule

Question 22

T/F? A chemical bond is an attractive force that binds molecules to other molecules.

Answer 22

True

Question 23

Difference between a mixture and compound

Answer 23

Compounds are substances formed by the chemical combination of two or more elements. Mixtures are substances formed by physically mixing two or more substances together

Question 24

Endothermic reactions:

Answer 24

Absorb energy, causing a decrease in temperature

Question 25

Breaking chemical bonds:

Answer 25

Requires energy

Question 26

Making chemical bonds:

Answer 26

Releases energy

Question 27

T/F? All chemical reactions absorb energy and release energy.

Answer 27

True

Question 28

Activation energy is:

Answer 28

Needed to break the bonds in the reactant molecules

Required for both exothermic and endothermic reactions

Question 29

Activation Energy

Answer 29

The minimum amount of energy that is required to activate atoms or molecules to a condition in which they can undergo chemical transformation or physical transport.