What are Acids?

A substance is said to be acid when it taste sour, sharp, or biting to the taste. Acid came from the word “acidus” which is the Latin word for ‘sour’.

Not all acids are corrosive (destroys surfaces). Some are produced by animals while some by fruits. Acids produced by animals and plants are called organic acids.


1. Citric acid in orange and lemon

2. Ascorbic acid in fruits

3. Tartaric acid in grapes

4. Ethanoic acids in vinegar

5. Hydrochloric acid (HCL) in the stomach

6. Lactic acid in the muscle during exercise

7. Uric acid in urine

8. Methanoic acid in bee sting etc.


1. Acids have a sour taste

2. Acids dissolve in water to form solutions which conduct electricity (electrolytes).

3. Acids turn blue litmus paper red

4. pH value is less than 7

5. Acids dilutes in water

6. Acids react with base to form salt

7. Acids react with active metals to yield hydrogen gas.

8. Acids give off H+ (Hydrogen) ions in water;


Acid at pH 0-2 is a strong acid,

Acid at pH 3-6 is a weak acid


1. Hydrochloric acid (HCl) – stomach acid that aid digestion

2. Sodium hydroxide – for making soap

3. Nitric acid – fertilizer production and explosives

4. Aluminum hydroxide for fire extinguishers

5. Carbonic/phosphoric acid for carbonated drinks

6. Sulfuric batteries

7. Lactic acid – food additive

8. Ascorbic acid – vitamin C

9. Boric acid – food preservation and eyewash

What are Alkalis?

An alkalis is also known as a base when it dissolves (soluble) in water.

Alkalis has a bitter taste and slippery feeling when touched.

Alkalis came from the word “al-qaliy” meaning “ashes “


  1. Sodium hydroxide(NaOH)
  2. Potassium hydroxide(KOH)
  3. Calcium hydroxide(CaOH)
  4. Ammonia (NH3)
  5. Lime

Properties of Alkalis/Base

  1. It feels soapy
  2. It is corrosive (it can burn your skin away)
  3. pH scale is above 7.
  4. Highly soluble (can be dissolved) in water
  5. They have a bitter taste
  6. Turns red litmus paper blue
  7. Can conduct electricity due to the presence of ions


Alkalis at pH 12-14 is a strong alkalis,

Alkalis at pH 8-11 is a weak alkalis


  1. Sodium hydroxide is used in the manufacture of soap, in making medicines, paper, etc.
  2. Calcium hydroxide also known as lime used to neutralize acid in water supplies, manufacture of bleaching powder, as an antidote for food poisoning.
  3. Ammonium hydroxide is used to remove ink spots from clothes and to remove grease from window-panes. It is used in the cosmetic industry.
  4. Potassium hydroxide are used in alkaline batteries.


Neutralization is the reaction between an acid and a base to produce salt. Neutralization reaction is used to neutralize;

  1. Insect sting- Methanoic acid neutralized by soap
  2. Indigestion

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