C4: Indicators and pH

Question 1

Acids all taste…

Answer 1

sour

Question 2

Alkalis all feel…

Answer 2

soapy

Question 3

Vinegar, oranges and lemons all contain an acid or alkali?

Answer 3

Acid

Question 4

Toothpaste, soap and bleach all contain an acid or alkali?

Answer 4

Alkali

Question 5

What are the main hazard linked to acids?

Answer 5

They are corrosive / irritants (will burn your skin or eyes)

Question 6

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

Answer 6

Wear safety glasses Wear gloves

Question 7

Which type of acid is found in your stomach?

Answer 7

Hydrochloric Acid

Question 8

What is the scientific name for acid particles?

Answer 8

H+ (hydrogen ions)

Question 9

What is the scientific name for alkali particles?

Answer 9

OH- (hydroxide ions)

Question 10

What is an indicator?

Answer 10

Something that tells us if a substance is an acid or alkali.

Question 11

How do indicators work?

Answer 11

They contain a dye which changes colour in acidic and alkaline conditions.

Question 12

You add blue litmus paper to an unknown solution and it turns red.

You add red litmus paper to an unknown solution and it stays red.

The substance is…

Answer 12

Acidic

Question 13

You add red litmus paper to an unknown solution and it turns blue.

You add blue litmus paper to an unknown solution and it stays blue.

The substance is…

Answer 13

Alkaline

Question 14

You add blue litmus paper to an unknown solution and it stays blue.

You add red litmus paper to an unknown solution and it stays red.

The substance is…

Answer 14

Neutral

Question 15

If you want to know exactly how acidic or alkaline a substance is then we use which indicator?

Answer 15

Universal Indicator

Question 16

pH1 =

Answer 16

Strong acid (red)

Question 17

pH3 =

Answer 17

Strong acid (orange)

Question 18

pH5 =

Answer 18

Weak acid (orange)

Question 19

pH6 =

Answer 19

Weak acid (yellow)

Question 20

pH7 =

Answer 20

Neutral (green)

Question 21

pH9 =

Answer 21

Weak alkali (blue)

Question 22

pH10 =

Answer 22

Weak alkali (purple)

Question 23

pH12 =

Answer 23

Strong alkali (purple)

Question 24

pH14=

Answer 24

Strong alkali (purple)

Question 25

Give an example of useful neutralisation reactions.

Answer 25

Toothpaste is alkaline to neutralise the acids produced by bacteria that cause acid erosion of teeth

Indigestion tablets neutralised excess stomach acids to prevent heartburn/indigestion.