Go premium Contact About Us
Logo
Home › Grade7 › Grade 7 CBSE › Science › Acids, Bases and Salts › Acids, Bases and Salts Notes › Basic Substances

Basic Substances

BASIC SUBSTANCES

  • Basic substances are those which contain bases.
  • Some examples of bases are sodium hydroxide (NaOH), Potassium hydroxide (KOH), Calcium hydroxide [Ca (OH)2], Magnesium hydroxide Mg(OH)2 etc.

  • Bases also occur in plant and animal products such as corn starch, fresh egg white, etc.
  • Bases may have a strong irritating odour and should be used with caution as it can harm the skin and eyes.

 

Bases:

 

Properties of Bases:

Some of the characteristic properties of bases are:

  • Bases are bitter in taste: A bitter taste is characteristic of all bases.
  • Solutions of bases are soapy to touch: If we rub a drop or two of solution of detergents or baking soda between our fingers, we feel soapy.
  • Bases may or may not be soluble in water: Bases that can be dissolved in water are called alkalis.

Some examples of soluble bases or alkalis are sodium hydroxide, potassium hydroxide, and calcium hydroxide.

Like acids, bases can also be strong or weak.

Strong bases are very corrosive and can burn the skin. Caustic soda or sodium hydroxide (NaOH) and caustic potash or potassium hydroxide (KOH) are strong and corrosive bases.

 FACT

  • There are acids and bases in our body.

  • HCI is present in the stomach.

  • The saliva in our mouth is basic in nature.

On the other hand, Copper hydroxide Cu(OH)2, Zinc hydroxide Zn(OH)2, and Ammonium hydroxide (NH4OH) are weak bases.

 

Uses of Bases:

1. Calcium Hydroxide (Slaked lime) Ca(OH)2:

  • It is used to neutralize the acidity in soil.

  • It is a component of the Bordeaux mixture used for protecting crops from pests.
  • It is used in the preparation of dry mixes for painting and decorating.
  • It is an ingredient in whitewash and mortar.

 

2. Magnesium Hydroxide (Milk of magnesia) Mg(OH)­2

  • It is used as an antacid and helps to reduce excess acidity in the stomach.

 

3. Sodium Hydroxide (Caustic soda) (NaOH)

  • It is used in the manufacture of paper, textiles, detergents, soaps etc.

        

  • In homes it is occasionally used to unblock drains.
  • Drainex is a powerful basic compound, specifically formulated to clear blockages in drains caused by organic substances.

 

4. Ammonium Hydroxide and other Weak Bases:

  • Weak bases such as ammonia in dilute form are used as household cleaners.
  • Solution of ammonia with water (diluted form) is used as a fertilizer.