1. Acids and Bases

2. By the end of today’s class you should be able to:
Explain what an indicator is
Know that litmus paper is an indicator

3. An indicator
An indicator is chemical that changes colour if it is in an acid or a base
Litmus paper is an indicator.

4. How litmus paper works.. Red litmus stays red Red litmus turns blue
Blue litmus turns red
Red litmus turns blue
Blue Litmus stays blue
Red litmus stays red
Blue Litmus stays blue

5. Doing the litmus test Substance tested What happened to red litmus
What happened to blue litmus
Is it acid/ base or neutral

6. 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.

7. By the end of today’s class you should be able to:
Name some common AND lab acids and bases
Know what the pH scale is and how it works

8. What is an acid? Acids are a group of chemicals.
What do you know about acids? Are all acids dangerous?

9. Some common acids used in the laboratory are:
Hydrochloric Acid (HCl)
Sulfuric Acid (H2SO4)

10. What is a base? everyday alkalis
Bases are another group of chemicals. Examples…
everyday alkalis

11. Some common bases used in the laboratory are: Sodium hydroxide - NaOH
Limewater – Calcium hydroxide - Ca(OH)2
Bases that are soluble in water are called alkalis.

12. Can you… Explain what an indicator is?
Give an example of an indicator?
Use litmus paper to test a variety of solution and classify these as acidic, basic or neutral?
Name some common acids and bases?

13. Learning objectives for today..
What the PH scale is
How universal indocator
Learn what a neutralisation reaction is

14. Indicators: how acidic or basic?
Litmus will tell you whether a solution is acidic or basic: what it won’t tell you is how acid or basic.
Universal indicator is an indicator that tells us how strong an acid or base is.

15. Indicators: the pH scale
The pH scale is a scale that runs from 0 to 14 which tells you how acidic or how basic something is.
pH7 is neutral
pH 1 is strongly acid
pH14 is strongly basic 1 2 14 13 12 11 10 9 8 7 6 5 4 3
Strong acid
Neutral
Strong bases
Weak acid
Weak Bases

16. Doing the universal indicator test
Substance tested
What is its pH?
What type of substance is it?

17. What type of substance? 7 Are these substances acidic or alkaline?
Are they weak or strong?
Substance pH
Description of acid/alkali
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 alkali
weak alkali
strong acid
very strong alkali
weak acid
alkali
acid 1 2 14 13 12 11 10 9 8 7 6 5 4 3

18. The PH scale

19. Learning check: Can you.. Tell what universal indicator is used for?
Explain the difference between universal indicator and litmus paper?
Explain what the pH scale is?

20. What is the pH?

21. Learning objectives
To learn about what happens in a neutralisation reaction

22. ? What happens when an acid and an alkali are mixed?
Mixing an acid and a base causes a chemical reaction.

23. The chemical reaction between an acid and a base
is called neutralisation.
acid
base
a salt
water
The pH value of the reaction mixture will turn to 7

24. When an acid is mixed with a base they react with each other form a salt and water. This is called a neutralisation reaction.
The things that are made are called products
The things that react are called reactants
Acid + Base Salt + Water

25. Examples of neutralisation reactions
The vinegar neutralises the wasp sting!

26. Learning check.. What is a neutralisation reaction?
What is made during a neutralisation reaction?
What is the chemical formula of hydrochloric acid?
What is the chemical formula of sodium hydroxide?
Give one example of a neutralisation reaction

27. By the end of the lesson you should be able to:
Know what a burette and pipette are used for and how they are used
Learn the word equation and chemical equation for a neutralisation reaction between sodium hydroxide and hydrochloric acid
Know how to titrate HCl against NaOH and prepare a sample of sodium chloride salt.

28. A Neutralisation reaction:
The reaction in words (A word equation):
Hydrochloric acid + Sodium Hydroxide Sodium Chloride + Water
HCl NaOH NaCl H2O
The reaction in chemical formulas (A chemical equation):

29. Homework
Draw diagrams of the four main steps in the experiment into notes copy
Filling pipette,
Filling burette,
Titration,
Evaporating water to get salt

30. Measure out 25cm3 of sodium hydroxide into the conical flask. 2
Measure out 25cm3 of sodium hydroxide into the conical flask! 2. Add some indicator to the solution

31. 3. Fill up the burette with hydrochloric acid (HCl) to the zero level.

32. Start the titration!
Do the titration once roughly, twice more and then finally without an indicator.

33. Finally repeat the titration without using an indicator!

34. Evaporation will separate the salt and water!

35. Acids and Bases neutralisation
Acids react with bases called carbonates to produce a salt, carbon dioxide gas and water. This is also a neutralisation reaction.
Acid + Carbonate  Salt + Carbon dioxide + Water

36. A different type of neutralisation reaction
Acid + Carbonate  Salt + Water + Carbon dioxide
Hydrochloric acid + calcium carbonate 
Calcium chloride + Water+ Carbon dioxide
HCl + CaCO3  CaCl2 + H2O + CO2