ACIDS

ANJANA P S

B. ED PHYSICAL SCIENCE, Reg No : NOAUTPN003

LITMUS PAPER

• Litmus paper is to test whether a solution is acidic or basic.

​

• They are available in red and blue colors.

​

• In acidic condition blue litmus paper turns red.

​

How to make litmus paper ?check out the

video....

�Let us do an experiment.....�

1

2

3

ACIDS

FOOD SUBSTANCE THAT CONTAIN ACIDS

ACIDS

Litmus paper is red in acid. All acids have sour taste . Acids present in food substance are weak.

• BUTTER MILK
• VINEGAR
• TAMARIND
• LEMON
• APPLE

• LACTIC ACID
• ACETIC ACID
• TARTARIC ACID
• CITRIC ACID
• MALIC ACID

FOOD SUBSTANCE

ACID PRESENT

ACIDS AND METALS

REACTION OF ZINC WITH HCL

REACTION OF ZINC WITH HCl

Zn + HCl ZnCl₂ + H₂

​

HYDROGEN IS INFLAMMABLE

HENRY CAVENDISH (1731-1810)

Hydrogen gas was first identified by the British scientist, HENRY CAVENDISH.

It was LAVOISIER who named this gas as hydrogen.

The meaning of the word hydrogen is “water producing”

Why are metal stoppers not used to store acids ?

EGG SHELL IN ACID

+

CARBONATE

• Egg shell, chalk and marble contain calcium carbonate.
• When acids react with carbonates, carbon dioxide is produced.
• Carbon dioxide is a gas which extinguishes fire.

pH VALUE

• pH paper is used to examine whether a substance is acidic or alkaline.
• If pH value is 7, it indicates neutral substance.
• When pH value is greater than 7, the substance alkaline.
• When it is less than 7, it is acidic.

The pH value of pure water is 7

How to check ?

FOLLOW UP ACTIVITY

When ants bite you,

why it pains?