CLASS 7 SCIENCE

1. ACIDS,BASES AND SALTS
CHEMISTRY

2. ACIDS
.

3. ACIDS
• SOUR IN TASTE
• PRODUCE H+(HYDROGEN IONS)
• LITMUS BLUE=RED
• ACIDS+METAL SALTS+HYDROGEN GAS CONDUCT ELECTRICITY ARE
CORROSIVE(ACID RAIN)
• PH LESS THAN 7

4. ABOUT ACID
• curd, lemon juice, orange juice and vinegar taste sour.
• These substances taste sour because they contain acids.
• The chemicalnature of such substances is acidic.
• The word acid comes from the Latin word acere which mean sour.
• The acids in these substances are nature acids.

5. ACIDS AND FOUND IN :

6. BASES
.

7. BASES
• Base bitter to taste
• Soapy to touch
• Water soluble base are called alkalis. All
• alkalis are bases but all bases are not alkalis.
• Turns red litmus blue
• Ph greater then 7

8. EXAMPLES OF BASES
• Detergent
• Baking soda
• Drain cleaner
• Antacid base
• Ammonia sops(hand, dish)
• Lime water
• Milk of magnesia

9. ABOUT BASES
• baking soda taste sour? What is its taste?Since, it does not taste sour it
means, that it has no acids in it.
• It is bitter in taste.
• If you rub the solution between fingers, it feels soapy on touching are know
as base.
• Then nature of such substances is aid to be basic

10. BASES AND FOUND IN :

11. WEAK BASE VS STRONG BASE
• Weak base :potassium carbonate, sodium carbonate ammonia
• Strong Bases: sodium hydroxide; sodium phosphate; barium hydroxide;
calcium hydroxide

12. NATURAL INDICATORS
.

13. NATURAL
INDICATORS
Litmus: A natural indicator
The most commonly used indicator
is litmus.
It is extracted from lichens. It has a
mauve (purple) colour in distilled
water. When added to an acidic
solution, it turns red and when
added to basic solution it turns blue.
It will be in the form of solution or in
the form of strips of paper, known as
litmus paper. Generally, it is
available as red and blue

14. EXAMPLES OF INDICATORS
• Litmus (paper/solution)
• Turmeric
• China rose
• Phenolphthalein (ph)

15. NEUTRALISATION

16. NEUTRALISATION
• When an acidic solution is mixed with a basic solution, both the solutions
neutralise the effect of each other. the reaction between an acid and a base
is known as neutralisation. Salt and water are produced in this process with
the evolution of heat.
• Acid+ base salt+water (heat is evolved)
• Hydrochloric acid (HCl)+sodium hydroxide
• (NaOH) sodium chloride (NaCl)+ water
• (H2O)

17. LITMUS ADDED TO
.

18. WHAT HAPPEN IF BASE ADDED TO LITMUS
PAPER ?
PURPLE LITMUS +BASES =BLUE
LITMUS PAPER TURNS BLUE WHEN BASE IS ADDED TO IT.

19. WHAT HAPPEN IF ACID IS ADDED TO LITMUS
PAPER
• PURPLE LITMUS +ACID = RED
• LITMUS PAPER TURNS RED WHEN ACID IS ADDED TO IT.

20. THANK YOU
.