UNIT 9 – PART 6: ACIDS & BASES MEASUREMENT REACTIONS

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

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

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

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.

ACIDS & BASES INTRODUCTION

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)

ACIDS & BASES MEASUREMENT

ACIDS & BASES MEASUREMENT Acid Neutral Base

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.

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.

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.

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

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

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

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

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

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 0 - 14 Acids: pH < 7 Neutrals: pH = 7 (neither acid nor alkaline) Bases: pH > 7 ACIDS & BASES REACTIONS