Acids and Alkalis

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By the end of this chapter, you should be able to:

1. recognize that locally available materials and substances are either acidic or alkaline.
2. understand the concept of ph as a measure of the strength of acids and alkalis.
3. understand the reaction between acids and alkalis

Introduction

Have you ever eaten raw mangoes, oranges or lemons, or tasted aloevera, okra or neem leaves? What did they taste like?

To many people, the word “acid” is associated with the liquid used in car batteries, that is known to recharge the battery and cause skin burns. The word acid comes from the Latin word “acidus”, which means sour. In this chapter, you will appreciate the properties and importance of acids, alkalis/bases and salts in our daily life

Acids and alkalis are found in our day to day life. They are found in our environment, and some are man-made.

Some acids that occur naturally in plants and animals include; methanoic acid in bee and ant stings, citric acid in raw oranges and lemons, lactic acid in sour milk and carbonic acid in rain water. Sometimes, we add vinegar to food as a preservative’ because it contains ethanoic acid. Vinegar is obtained from rotting fruits; for example, pineapples.

Proteins are made up of amino acids, while apples contain vitamin C which is an acid, called ascorbic acid.

All acids contain at least one hydrogen atom, which is released as hydrogen ic~s •.vhen the acid is dissolved in water. It is these hydrogen ions in an aqueous solution that make the substance acidic.

Most vegetables, such as spinach, Hibiscus canabinus (locally known as malakwang), and amaranthus (dodo), contain alkalis. Toothpaste is an example of an alkali. It is used for brushing teeth because it neutralises the acid produced by bacteria that ^emain in the teeth.

All alkalis release hydroxide ions when dissolved in water. It is the hydroxide ions that make a substance behave like an alkali in an aqueous solution

Note: An alkali is a soluble base.

A base is a substance that reacts with an acid to form salt and water only.

Activity (a): Classifiying substance as either acids or alkalis / bases

In this activity, you will work in groups, What you need

• lemon                                 * okra
• beakers                                • baking soda
• raw mangoes                    • African eggplant
• sour milk                            * aloe vera
  What to do

1. Wash the raw mangoes, African eggplant, aloe vera and okra provided.

Bite into each of the fruits provided and taste them.

for more about Acids click here.

Identify whether it is an Acid or Alkaline/base