this is very useful for class 7

2.  Sour in taste
 Produce H+(hydrogen ions)
 Turns blue litmus red
 Acids+ metals salt+ hydrogen gas conduct
electricity are corrosive(acid rain)
 pH less then 7

3.  Vinegar
 Lemon juice
 Orange juice
 Curd
 Tamarind
 Amla
 Black tea
 Apple juice
 Unripe mango
 grapes

4. curd, lemon juice, orange juice and vinegar
taste sour. These substances taste sour
because they contain acids. The chemical
nature 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.  hydrochloric stomach acid
 sulfuric acid car batteries
 nitric acid explosives
 acetic acid vinegar
 carbonic acid sodas
 phosphoric acid flavorings Common Acids
 Formic acid ant’s sting
 Citric acid lemons, oranges etc.
 Lactic acid curd
 Oxalic acid spinach
 Ascorbic acid amla, citrus fruits
 Tartaric acid tamarind, grapes, unripe
mangoes, etc.

6.  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

7.  Detergent
 Baking soda
 Drain cleaner
 Antacid base
 Ammonia sops(hand, dish)
 Lime water
 Milk of magnesia

8. 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. The
nature of such substances is aid to be basic.

9.  sodium hydroxide - soaps, drain cleaner
 magnesium hydroxide - antacids
 Aluminum hydroxide - antacid, deodorants
 Calcium hydroxide - lime water
 Ammonium hydroxide - window cleaners
 Magnesium hydroxide - milk of magnesia
 ammonium hydroxide - “ammonia” Common
base

10.  Weak base :
potassium carbonate,
sodium carbonate
ammonia
 Strong Bases:
sodium hydroxide;
sodium phosphate;
barium hydroxide;
calcium hydroxide

11.  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
litmus paper.

12.  Litmus (paper/solution)
 Turmeric
 China rose
 Phenolphthalein (ph)

13. 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)