1. Acids produce H+ in solution,
example: HCl
Bases produce OH- in solution,
example NaOH

2. everyday acids laboratory acids
What is an acid?
Acids are a group of chemicals.
everyday acids
laboratory acids
Can you think of other examples of acids?

3. What is a weak acid? Strong acids cannot be touched and are corrosive.
Weak acids are safe to handle and have a sour taste.

4. What is a strong acid?
Some acids, like those found in the laboratory or a car
battery, are very dangerous (too dangerous to taste or touch).
These acids are said to be corrosive as they can damage
other materials by wearing them away! They are strong acids.
Why must strong acids always be handled very carefully?

5. everyday bases laboratory bases
What is a base?
Bases are another group of chemicals, the opposite of acids.
everyday bases
laboratory bases
Can you think of other examples of bases?

6. What is a weak base?
Bases are used for cleaning. Strong bases are caustic and cause redness on the skin.
Weak bases are soapy and safe to touch.

7. What is a strong base?
Some bases, like those in the laboratory or in cleaning
materials such as toilet cleaner, are too dangerous to touch.
These bases are said to be caustic because they can burn skin and damage other materials! They are strong bases.
Why must strong bases always be handled very carefully?

8. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 What is the pH scale? stronger acid
The strength of an acid or base is measured by the pH scale.
Each universal indicator colour is given a number called the pH value.
Universal indicator can tell you the pH of a solution.
stronger acid
stronger base
strongacid
weakacid
weak base
strongbase
neutral

9. What type of substance? 7 Are these substances acidic or basic?
Are they weak or strong?
Substance pH
Description of acid/base
soda water 6
car battery acid 1
soap 8
washing soda 10
stomach acid 2
oven cleaner 14
vinegar 4
very weak acid
very strong acid
very weak base
weak base
strong acid
very strong base
weak acid
base
acid 1 2 14 13 12 11 10 9 8 7 6 5 4 3

10. What is the pH?

11. Litmus is red in acid. Litmus is blue in base.
What is an indicator?
How can you test a liquid to find if it is an acid or an base?
An indicator is a special chemical that changes
to a different colour in an acid or an base.
Litmus paper and litmus solution are examples of indicators.
Litmus is red in acid.
Litmus is
blue in base.

12. Litmus test experiment
The results for the litmus tests are:
Tube 1. The solution is an alkali which turns blue when red litmus is added to it and remains blue when blue litmus is added to it.
Tube 2. The solution is an acid which remains red when red litmus is added to it and turns blue when red litmus is added to it.
Tube 3. The solution is water which remains red when red litmus is added to it and remains blue when blue litmus is added to it.

13. Litmus paper cannot distinguish between a weak acid and a strong acid (or weak base and strong base).
A better indicator is required…

14. What is universal indicator?
Litmus is used to show if a solution is acid or base.
Litmus does not show if the acid or base is weak or strong.
Universal indicator has a range of colours that indicate the difference between weak or strong acids or bases.
stronger acid
stronger base
strongacid
weakacid
weak base
strongbase
neutral

15. #1: Neutralization acid base a salt water
The GENERAL reaction between an acid and an base
is called neutralization.
acid
base
a salt
water
What happens to the pH value of the reaction mixture during neutralization?
The pH value of the reaction mixture becomes closer to 7.

16. #1: Neutralization H2O NaOH NaCl HCl
The EXAMPLE for the chemical reaction between an an acid and an base can be written as:
H2O
HCl
NaOH
NaCl

17. #1: Neutralization acid salt H2O CO2
The GENERAL reaction between an an acid and a carbonate can be written as:
acid
carbonate
salt
H2O
CO2

18. #1: Neutralization 2HCl Na2CO3 2NaCl H2O CO2
The EXAMPLE of a chemical reaction between an an acid and a carbonate can be written as:
2HCl
Na2CO3
2NaCl
H2O
CO2

19. General Reaction: #3: Metals with Acid acid salt hydrogen metal MgCl2
Example:
MgCl2
HCl Mg H2

20. #3: Metals with Acid

21. All acids, bases and salts dissolve in water.
Summary Chart
Property
Acid
Base
Salt
Definition
produce H+
produce OH-
ionic compound
Example
HCl, CH3COOH
NaOH, NH3
NaCl pH
1-2, 3-6
8 – 11, 12 – 14 7
red litmus
red
blue
stays red
blue litmus
stays blue
Universal indicator
red – yellow
ROY
blue – violet
BIV
green G
taste sour
vinegar,
lemon juice
corrosive
feel soapy
household cleaners
caustic
All acids, bases and salts dissolve in water.

22. Summary of Reactions #1: Neutralization acid + base  salt + water
#2: Carbonate with acid
acid + carbonate  salt + water + carbon dioxide
#3: Metal with acid
acid + metal  salt + hydrogen

23. Neutralization and indigestion

24. Why can bicarbonate of soda (pH 9) be used to treat a bee sting?
Neutralizing stings
A bee sting
is acidic.
A wasp sting
is alkaline.
Why can bicarbonate of soda (pH 9) be used to treat a bee sting?
Why can vinegar (pH 3)
be used to treat
a wasp sting?

25. Neutralizing soil
Soils in different places can be acidic, alkaline or neutral.
Many plants do not grow
well in acidic soil.
Why do farmers test soil
to check the pH?
Farmers often add an alkali to acidic soil to make their plants grow better.
How does the alkali help to treat the acidic soil?

26. Neutralizing acid rain
Gases emitted by cars, power stations and factories mix with rainwater in the atmosphere.
This rainwater has a pH <5.5.
Why is it called acid rain?
Acid rain can have a harmful effect on the environment killing trees, polluting lakes and damaging buildings.
How can the effects of
acid rain be prevented?

27. Glossary
acid – A chemical that has a pH less than 7.
base – A chemical that has a pH greater than 7 and dissolves in water.
indicator – A special chemical that changes into different colours in acid and base solutions.
neutral – A chemical with a pH of 7 that is not an acid or a base.
neutralization – The chemical reaction between an acid and a base.
pH scale – The range of values that shows how strong or weak an acid or base is.
universal indicator – The indicator that shows the pH value of a chemical.

28. Anagrams