Year 8 Science | Acids and Alkalis

Question 1

Recall the six signs of a chemical reaction

Answer 1

1) Odour (smell) 2) colour change, 3) precipitate formed, 4) temperature change, 5) gas produced, 6) light emitted

Question 2

What is a chemical reaction?

Answer 2

A change in which a new substance is made, atoms are rearranged.

Question 3

What is a physical change?

Answer 3

A change in which all of the substances remain themselves

Question 4

Name some physical changes

Answer 4

Changes of state (melting, freezing, condensing, evaporating, boiling), dissolving

Question 5

Is water changing into ice a chemical or a physical change?

Answer 5

Physical - the particles are the same they are just moving differently

Question 6

Is paper burning a physical or chemical change?

Answer 6

Chemical - new substances are made

Question 7

Give an example of an acid from everyday life?

Answer 7

Citric acid (fruit), vinegar

Question 8

Give an example of an alkali from every day life?

Answer 8

Soap, sodium bicarbonate (in baking powder), toothpaste

Question 9

How do acids taste (not all are safe to taste!)?

Answer 9

Sour

Question 10

How to alkalis feel and taste?

Answer 10

Soapy, taste bitter

Question 11

Some acids and alkalis are dangerous. What problem can they cause?

Answer 11

Chemical burns to skin and eyes

Question 12

What hazard sign do dangerous acids and alkalis have?

Answer 12

Corrosive (eats away at materials)

Question 13

What hazard sign is found on acids and alkalis that might cause swelling or redness to skin?

Answer 13

irritant

Question 14

What safety precautions do we take when working with acids and alkalis?

Answer 14

wear safety goggles, avoid skin contact

Question 15

How can an acid be made safer?

Answer 15

It can be diluted with water

Question 16

Which is more dangerous? Strong acid or strong alkali?

Answer 16

Equally dangerous

Question 17

What is the difference between concentrated and dilute ?

Answer 17

A concentrated solution has more of the substance particle in a given volume.

Question 18

What do we call a substance that changes colour in acid or alkali?

Answer 18

Indicator

Question 19

What colour would universal indicator turn in a strong acid?

Answer 19

Red

Question 20

What colour would universal indicator turn in a weak acid?

Answer 20

Orange

Question 21

Name 2 examples of indicators

Answer 21

Litmus paper and universal indicator

Question 22

Why is universal indicator moe useful than litmus?

Answer 22

It doesn’t just say whether something is acid or alkali, it shows how strong they are

Question 23

What is a neutral solution?

Answer 23

One that is neither acid nor alkali

Question 24

What is the formula for hydrochloric acid?

Answer 24

HCl

Question 25

What colour would universal indicator turn in neutral substance?

Answer 25

Green

Question 26

What colour would universal indicator turn in an alkali?

Answer 26

Purple

Question 27

What is the pH of a strong acid?

Answer 27

pH 1-3

Question 28

What is the pH of a weak acid?

Answer 28

pH 4-6

Question 29

What is the pH of a neutral substance?

Answer 29

pH 7

Question 30

What is the pH of a weak alkali?

Answer 30

pH 8-10

Question 31

What is the pH of a strong alkali?

Answer 31

pH 11-14

Question 32

What is the formula for sodium hydroxide

Answer 32

NaOH

Question 33

Define "neutralisation"

Answer 33

The reaction of an acid with an alkali to form a neutral salt and water

Question 34

What is a base?

Answer 34

A substance that neutralises an acid

Question 35

What is an alkali?

Answer 35

A base that dissolves in water

Question 36

Give two uses of neutralisation?

Answer 36

Getting the right pH in soil for farming, treating lakes affected by acid rain, toothpaste neutralising acids in mouths

Question 37

How can you use neutralisation to work out how strong an acid is?

Answer 37

See how much alkali is needed to neutralise it

Question 38

What is a salt ?

Answer 38

A substance that forms when an acid reacts with metal or with an alkali

Question 39

Recall the general equation for a neutralisation reaction

Answer 39

Acid + alkali -> salt + water

Question 40

Recall the general equation for an acid reacting with a metal

Answer 40

Acid + metal -> salt + hydrogen

Question 41

Which salt is produced when hydrochloric acid is used?

Answer 41

Metal chloride

Question 42

Which salt is produced when sulphuric acid is used?

Answer 42

Metal sulphate

Question 43

Which salt is produced when nitric acid is used?

Answer 43

Metal nitrate

Question 44

How can you collect the salt crystals from a neutralisation reaction?

Answer 44

Evaporate the water