Basics of Acids & Bases

Shubhangi Mishra
45mins
Critical thinking, Creative thinking
Remember, Understand, Application

Basics of Acids & Bases
1. Introducing the terms Acids, bases, salts, disassociation, reactions, pH to the students2. Making them understand that Acids and bases when react produce salt ,water and CO2
The objective of this activity is to explain students that Acids are substances which free hydrogen ions (H+), when they are mixed with water. Bases are substances which free hydroxide ions (OH-) when they are mixed with water.
Beaker, Water, Vinegar and Baking Soda, Lid to cover the beaker, Stirrer

Simple Experiment to Show how Acids & Bases React together- An introduction

Since Students are being introduced to the concept of Acids and Bases for the first time, it is best if  this experiment is shown to them to introduce the concept of chemical reaction between the two.

Step 1: In half a glass of water, put a few teaspoons of baking soda and mix in order to obtain a quite concentrated solution. In the same glass, pour a spoon of vinegar. As you can see, there will be an abundant production of foam.

Step2: Ask students What happened? Students would respond saying “A chemical reaction occurred between the baking soda  and vinegar.”

Step3: Explain to the students how the substances reacted with each other, producing a salt, water, and carbon dioxide. That is the gas which produced the little bubbles you observed. In general, acid and basic substances react with each other, producing a salt and often other substances like water and carbon dioxide. If you want make the reaction more lively, use warm (not hot) water. The salt produced by this reaction is sodium acetate:

CH3COOH + NaHCO3 = CH3COONa + H2O + CO2

Some Important Tips to be given to Students:

1.Acids are substances which free hydrogen ions (H+), when they are mixed with water.

2. Bases are substances which free hydroxide ions (OH-) when they are mixed with water.

3.This freeing of ions is called dissociation in both cases.

4. Reaction happening in Bases and Acids:

5.Free hydroxide ions react with the hydrogen ions producing water molecules: H+ + OH- = H2O. in this way, bases diminish the concentration of hydrogen ions.

6.A solution rich in hydrogen ions is acidic, a solution poor in hydrogen ions is basic.

7. Some acids dissociate only in part and they are called weak acids; others dissociate completely, freeing large amounts of hydrogen ions, and they are called strong acids. In the same way, the bases can be stronger or weaker. Diluted acids and bases are less concentrated and less aggressive in their actions.

8. The acidic or basic degree of substances is measured in pH units. The scale used spans from 0 to 14. Substances with pH lower than 7 are considered acids, those with pH equal to 7 are considered neutral, and those with pH higher than 7 are considered bases. Substances with low pH are very acidic, while those with high pH are highly basic.

Concentrated acidic and basic substances are very corrosive and dangerous

9. We use our bodies use acids and bases too. Our stomachs use hydrochloric acid to help digest foods. This strong acid also kills bacteria and helps to keep us from getting sick. Our muscles produce lactic acid when we exercise. Also, our pancreas uses a base called an alkali to help with digestion. These are just a few examples of how the chemistry of bases and acids help our bodies function.

1. http://www.ducksters.com/science/quiz/acids_and_bases_questions.php 2.http://www.helpteaching.com/questions/Acids_and_Bases/Grade_7 3. https://schools.aglasem.com/60221
1.Can you guess why when baking soda is added to a dish, it neutralizes sour or bitter dishes.
2.Can you tell why one of sodium bicarbonate's common uses was as a stomach antacid for many years.
3. What do you think will happen to a raw egg if its dropped in Vinegar? Explain the process
(Ans: The acid in the vinegar breaks down the calcium carbonate of the shell, a process which you can see starting almost immediately when bubbles begin to form on the surface of the egg as it releases carbon dioxide. A scum will develop on the surface of the liquid as the shell disintegrates, and after a few days you have a soft-boiled egg that has effectively ‘cooked’ in the acid, and will bounce if dropped)
Accurate, Clearly explained, Knowledgeable, Precise, Well crafted/ articulated, Informative

You can use questions in the practice sheet as home assignments to develop the HOTS among the children