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Natural sciences

Reactions that occur between different kinds of matter: acids and bases

Educator section

Memorandum

Leaner section

Content

Activity: to name well-known acids and bases and their functions [lo 2.1]

(A) ACIDS AND SOME OF THEIR FUNCTIONS

  • Hydrochloric acid

used for cleaning brickwork and cement;

reduces the pH levels of swimming pool water.

  • Nitric acid

used in artificial fertilisers, dyes and explosives;

present in plastics.

  • Sulphuric acid

probably the most important acid in South Africa;

an effective drying agent;

used in the preparation of fertilisers, dyes, paper and glue.

  • Phosphoric acid

used to flavour cold drinks;

used by dentists in dental cement.

  • Boric acid

used in many disinfectants;

an effective germicide.

  • Citric acid

the acid contained in oranges (citrus fruit).

  • Oxalic acid

the acid contained in tomatoes.

  • Tartaric acid

used in baking powder.

  • Acetylsalicylic acid

the acid in aspirin tablets.

  • Ascorbic acid

this is vitamin C.

  • Lactic acid

the acid formed when milk turns sour;

lactic acid is also formed in muscles, particularly after vigorous exercise.

(B) BASES AND SOME OF THEIR FUNCTIONS

  • Sodium hydroxide

used in the manufacturing of soap;

(also known as caustic soda)

used as a cleanser in drainage pipes.

  • Calcium hydroxide

present in milder soaps;

(lime water/whitewash)

used in the agricultural and building.Industries

  • Magnesium hydroxide

this is used as a purgative, as well as for other purposes (purgatives encourage the evacuation of the bowels).

  • Ammonia

is a general domestic cleaning agent;

is used as smelling salts (sal volatile) because of its pungent smell;

also is an ideal stain remover

Test:

Try to list at least eight acids and three alkalis and their uses (on a separate sheet of paper).

Assessment

Learning Outcome 2: The learner will know and be able to interpret and apply scientific, technological and environmental knowledge.

Assessment Standard 2.2: We know this when the learner categorises information.

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Source:  OpenStax, Natural sciences grade 7. OpenStax CNX. Sep 16, 2009 Download for free at http://cnx.org/content/col11077/1.1
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