Chemical Reactions

Question 1

What is a chemical reaction?

Answer 1

The rearrangement of atoms to form one or more new substances.

Question 2

What is a physical change? Examples.

Answer 2

No new substances formed, only a change in physical properties e.g. position, shape, state, and size.

Question 3

What is a chemical change? Examples.

Answer 3

New substances formed e.g. changes in temperature, the release of sound or light, formation of new gas or solid, change in colour, or the disappearance of solid.

Question 4

What is an element?

Answer 4

Basic substances on the periodic table are made of only one type of atom.

Question 5

What is a compound?

Answer 5

Two or more different types of atoms are chemically bonded together.

Question 6

What are reactants?

Answer 6

Substances that react with each other.

Question 7

What are products?

Answer 7

New substances formed by a chemical reaction.

Question 8

Reactants are _______ of the arrow in a chemical equation and products are to the ________

Answer 8

Left and right.

Question 9

The arrow in a chemical equation represents what?

Answer 9

A chemical change.

Question 10

What happens in a chemical reaction?

Answer 10

Chemical bonds are broken, atoms rearrange and then new bonds are formed.

Question 11

Why are the same elements present after a reaction?

Answer 11

Atoms can neither be created nor destroyed.

Question 12

What is an analogy for the rearrangement of atoms?

Answer 12

Salsa dancers whirl around with linked arms, swapping partners.

Question 13

What does pH stand for?

Answer 13

Potential hydrogen.

Question 14

What does pH refer to and what does it measure?

Answer 14

Whether a product is acid, alkali (basic) or neutral. It is the measure of hydrogen (H+) and hydroxide ions (H-).

Question 15

What does a pH scale measure?

Answer 15

The strength of the acid or base from 0-14.

Question 16

Acids have more ________, alkaline have more __________ and neutral has _____________.

Answer 16

Hydrogen ions, hydroxide ions, an equal no. of both ions.

Question 17

What is a pH below 7 is considered?

Answer 17

Acids

Question 18

What is a pH above 7 considered?

Answer 18

Alkali (basic)

Question 19

What is a pH equal to 7 considered?

Answer 19

Neutral

Question 20

What do we use to measure pH?

Answer 20

Indicators, papers or liquids, change colour depending on the pH they are exposed to.

Question 21

What is a solution?

Answer 21

A mixture where one substance dissolves into the other.

Question 22

What does corrosive mean?

Answer 22

Able to break down or destroy substances by reacting with them.

Question 23

Common properties of an acid? (7)

Answer 23

• conduct electricity
• turn blue litmus paper red
• corrosive
• reacts to metal and produces hydrogen gas leaving the salt behind
• sour taste
• solution (compound dissolved in water)
• neutralised by bases producing water and a salt

Question 24

Common properties of a base? (7)

Answer 24

• conduct electricity
• turn red litmus paper blue
• caustic
• bitter taste
• slippery, soapy feel
• If compound is soluble in water, it is considered alkali
• neutralised by acids producing water and a salt

Question 25

What is the conservation of mass?

Answer 25

Matter can neither be created nor destroyed.