1. UNIT 9 – PART 6: ACIDS & BASES
MEASUREMENT
REACTIONS

2. ACIDS & BASES INTRODUCTION
The sour and spicy tastes are properties of acidic substances
The bitter taste is a
property of basic
substances

3. ACIDS & BASES INTRODUCTION
Your own body produces acids and strong bases
The stomach secretes hydrochloric acid, which attacks the food to extract nutrients
The pancreas secretes bicarbonate (base) to neutralize the effect of acid when the food is in the small intestine

4. ACIDS & BASES INTRODUCTION
Some insects ( bees , wasps and some ants ) produce a highly acidic venom to defend themselves
When one gets stung or bitten , the venom of the acid reacts with the water in skin cells.
You can use baking soda in water (base) to relieve the burning or the sting

5. ACIDS & BASES INTRODUCTION
Some plants, such as poison ivy, produce a basic substance for defense
When the water in the skin comes into contact with this substance, we feel a violent irritation.
A slightly acidic substance may be used (vinegar or lemon juice) to relieve the itching.

6. ACIDS & BASES INTRODUCTION

7. ACIDS & BASES MEASUREMENT
HOW DO WE MEASURE ACIDS & BASES
Measurement: pH level (0 – 14)
The pH level indicates whether the substances are very or somewhat acidic or very or somewhat basic. An indicator is used to measure the acidity or basicity of a substance.
Indicator: A substance which changes color in the presence of acids or bases (Red or Blue)

8. ACIDS & BASES MEASUREMENT

9. ACIDS & BASES MEASUREMENT
Acid Neutral Base

10. ACIDS & BASES MEASUREMENT
Each degree of the pH scale represents a factor of 10 (multiplied by 10)
Ex. The pH of an apple = 3 and the pH of a lemon = 2.
The Lemon is 10 times more acidic
than the apple.

11. ACIDS & BASES MEASUREMENT
Universal pH paper changes color to each degree of acidity or alkalinity.
It gives a more accurate
pH level when compared
to the color chart that
measures the different
levels of pH.

12. ACIDS & BASES MEASUREMENT
The pH meter is an electronic device that directly gives the value of pH of a substance.
It uses the ability of liquid substances to conduct an electrical current.
The more substance is acidic
or basic , the better it conducts
electricity.

13. ACIDS & BASES MEASUREMENT
1) LITMUS PAPER – only indicates whether or not the substance is an ACID or BASE
2) UNIVERSAL pH PAPER – indicates the level of ACIDITY or ALKALINITY
3) pH METER – digital reading pinpointing levels of ACIDITY or ALKALINITY

14. ACIDS & BASES REACTIONS
REACTIONS TO INDICATORS
LITMUS PAPER – colour changes depending on acidity or alkalinity of substance
COBALT CHLORIDE PAPER – colour changes depending on presence or absence of water
LIMEWATER – indicates presence or absence of gaseous carbon dioxide
GLOWING WOOD SPLINT – indicates the absence or presence of  combustible substance
BURNING WOOD SPLINT – indicates the absence or presence of an explosive substance
OPEN FLAME – colour changes depending on the presence of certain substances
ACIDS & BASES REACTIONS

15. ACIDS & BASES REACTIONS
Some flowers are natural indicators; they change color depending on the acidity or alkalinity of the soil.
Ex. Hydrangeas
Lichen, red cabbage juice , tea and grape juice also change color in the presence of acids or bases
BASE SOIL
ACID or NEUTRAL SOIL

16. ACIDS & BASES REACTIONS
Indicator: Litmus Paper
The litmus paper is available
in two colors: red and blue
If the Litmus Paper is
soaked in a liquid:
1) Blue paper turns red
in the presence of ACID.
Blue Red = ACID
2) Red paper turns blue
in the presence of BASE.
Red Blue = BASE
ACIDS & BASES REACTIONS

17. ACIDS & BASES REACTIONS
LITMUS PAPER
BLUE LITMUS
RED LITMUS
ACIDIC SUBSTANCE
WILL TURN RED
WILL REMAIN RED
BASIC SUBSTANCE
WILL REMAIN BLUE
WILL TURN BLUE
NEUTRAL SUBSTANCE

18. ACIDS & BASES REACTIONS
The Litmus Paper does not indicate whether a substance is very or somewhat acidic or basic.
The pH scale classifies substances according to their degree of acidity or alkalinity (base).
It goes from
Acids: pH < 7
Neutrals: pH = 7 (neither acid nor alkaline)
Bases: pH > 7
ACIDS & BASES REACTIONS