Science Chemistry

Question 1

What is a chemical reaction?

Answer 1

New substance(s) formed

Question 2

Indications of a chemical reaction

Answer 2

Release of light or sound.
Formation of new gas
Formation of a new solid
Change in colour
Disappearance of a solid
Change in temperature.

Question 3

What is an atom?

Answer 3

Smallest part of an element

Question 4

What is a molecule?

Answer 4

A group of atoms bonded together

Question 4

What is a chemical bond?

Answer 4

An attractive force that holds two atoms together

Question 5

What is a mixture?

Answer 5

A combination of substances that can be physically separated.

Question 6

What is an element?

Answer 6

Any basic substances of the periodic table. Made up of only one type of atom.

Question 7

What is a compound?

Answer 7

Made up of two or more different types of atoms bonded together.

Question 8

What is a reactant?

Answer 8

A role in a chemical reaction. Substances that react with each other.

Question 9

What is a product?

Answer 9

A role in a chemical reaction. New substance formed by reaction.

Question 10

What are chemical equations?

Answer 10

Used to describe what is happening during a chemical reaction.
Formed through the use of a series of common symbols.
All have the same structure.

Question 11

What is the structure of a chemical equation?

Answer 11

Reactants –> Product

Question 12

What are the chemical equation state symbols?

Answer 12

Indicate the state of matter the reactants and products are in at room temp and show chemical changes of substances.
(s) = solid
(l) = liquid
(aq) = aqueous solution
(g) = gas

+ means ‘reacts with’
–> means ‘produces’

Question 13

What are the types of equations

Answer 13

Word equations: use the name of chemicals
Formula equations: use chemical symbols

Question 14

What is the atomic number for an element?

Answer 14

Number of protons

Question 15

What is the atomic mass for an element?

Answer 15

The number of protons + neutrons

Question 16

What is a chemical bond?

Answer 16

An attractive force that holds two atoms together.

Question 17

What is the law of conservation of mass?

Answer 17

Mass is conserved and is never lost or gained in a chemical reaction.

Question 18

What must you do to balance chemical equations?

Answer 18

obey the ‘law of conservation of mass’
Equations are balanced by adding coefficients which multiply every atom in the molecule.

Question 19

What is combustion?

Answer 19

Reaction where a fuel reacts with oxygen and releases energy.

Question 20

What are the 4 types of reactions?

Answer 20

Composition
Decomposition
Single displacement
Double displacement

Question 21

What is a composition reaction?

Answer 21

Multiple reactants join to form one product.
A + B –> AB

Question 22

What is a decomposition reaction?

Answer 22

One reactant breaks down into multiple products.
AB –> A + B

Question 23

What is a single displacement reaction?

Answer 23

One element is substituted for another compound.
AB + C –> CB + A

Question 24

What is a double displacement reaction?

Answer 24

The exchange of ions between two reactants to form two new compounds. AB + CD --> AD + CB

Question 25

What is an exothermic reaction?

Answer 25

Reaction that releases energy (usually heat but sometimes light and sound)

Question 26

What is an endothermic reaction?

Answer 26

Reaction that absorbs energy (absorb heat)

Question 27

What is activation energy?

Answer 27

Energy required to break bonds.

Question 28

What are the two steps of a reaction?

Answer 28

1. Breaking bonds (requires energy from surroundings) 2. Making bonds (Releases energy back into surroundings)

Question 29

What is chemical energy?

Answer 29

Energy stored in the chemical bonds of a substance.

Question 30

What is an energy level diagram?

Answer 30

Representation of changes in chemical energy during a chemical reaction.

Question 31

What is the energy released?