1. Acids and Bases
Science 10

2. Examples of Acids
Lemons
Stomach acid
Acid rain
Battery acid
Vinegar

3. Characteristics of Acids
Sour taste
Can burn the skin
Conducts electricity
Neutralizes a base
Can dissolve in water

4. Examples of Bases
Bleach
Baking soda
Soap
Windex
Tonic water

5. Characteristics of Bases
Bitter taste
Slippery texture
Can burn skin
Conducts electricity
Neutralizes acids
Can dissolve in water

6. Acids, Bases, Ions and Indicators
In 1884, Svante Arrhenius, a Swedish chemist defined an acid and base.

7. HCl (aq)  H+(aq) + Cl- (aq)
Acid
In an aqueous solution, acids produce hydrogen H+ ions
Example: hydrochloric acid, HCl, which is found in our stomachs. In water the acid will produce H+ and Cl- ions.
HCl (aq)  H+(aq) + Cl- (aq)

8. NaOH(aq)  OH- (aq) + Na+(aq)
Bases
In an aqueous solution a base produces hydroxide OH- ions
Example: sodium hydroxide (NaOH). In water this base produces Na+ and OH- ions.
NaOH(aq)  OH- (aq) + Na+(aq)

9. Acid or Base? H2CO3 (aq) → H+ (aq) + CO32- (aq) acid
Ca(OH)2 (aq) → Ca2+ (aq) + OH- (aq)
base

10. Most acids and bases are clear and colorless
Most acids and bases are clear and colorless. You need an indicator to tell them apart.
Indicator: a chemical that changes color as the concentration of H+ or OH- changes.
There are many different indicators such as Litmus, phenolphthalein and even cabbage juice!

11. Litmus Test Red and blue litmus paper
Acids turn blue litmus paper red.
Bases turn red litmus paper blue
Neutral substances will not change the colour of red OR blue litmus paper.

12. Other Indicators Phenolphthalein Cabbage Juice
Turns bright pink in bases, at pH of 8.2 or higher
Will be clear in acids
Cabbage Juice
A homemade indicator
Turns a rainbow of colors based on various pH levels

13. To do: Read Pages 156-158 Notes – Acids and Bases Questions:
p. 161, #’s 11, 12, 15
p. 173, #’s 4, 5

14. pH scale pH: the measure of the acidity of a solution.
The scale ranges from 0 to 14.
pH  7 = acid (less then 7)
pH  7 = base (more then 7)
pH 7 = neutral

16. Acid, Base or Neutral?
H2O ↔ H+ (aq) + OH- (aq)
Neutral

17. Please note that the aforementioned indicators (litmus and Phenolphthalein do not give an exact pH, they only tell you if your solution is an acid or a base)

18. pH Paper You compare the colour with a given chart
Instead of telling you whether something is an acid or a base it gives you the exact pH.
Source:

19. pH meter

20. Acid or Base? milk (6.6) Baking Soda (8.7) Pure water (7.0)
Acid (H+ > OH-)
Baking Soda (8.7)
Base (H+ < OH-)
Pure water (7.0)
neutral (H+ = OH-)

21. To Do: Read pages 159-160 Notes – pH scale Questions:
p. 161, #’s 13, 16
p #’s 9, 11

22. Neutralization Reactions
An acid and a base react together to form a new compound (a salt) and water. It’s a double replacement reaction!
The general equation is:
Acid + Base → Salt + Water
Example: HCl + NaOH → NaCl + H2O

23. So the pH of the new products is close to 7 (neutral).
Examples of neutralization
Antacids
Calcium carbonate is added to acidic lakes.

24. Practice
Video – Acids and Bases
Notes
Practice Sheet