Acids, Bases and pH

Content type

User Generated

Subject

Chemistry

Type

Lab

Uploaded By

ehaare

Pages

Acid and Bases

by Mrpotpot |

CONTENTS

Introduction

Cautions

A chemical reaction

Acids, Bases and pH

Measuring the pH

Red cabbage juice

Determining the pH of some substances

The color scale of the red cabbage

Is it magic?

Acid-Base Indicators

How acid is that vinegar?

The pH of soaps

Searching for natural indicators

Conclusion

Bibliography

INTRODUCTION

This time, we will do some simple chemistry experiments to begin learning about acids and

bases. We will see how the acidity of substances is measured; we will learn about some acid-

base indicators; we will produce pH indicating papers; we will do a titration of vinegar; we will

search for natural indicating substances and we will determine the color scale of them. In most

cases, we will use household substances. We will use also some substances and devices

bought especially for our experiments. The experiments we will describe are suited to be

performed not only in schools, but also at home and for your own personal interest. Their

difficulty differs from one case to another, and it is up to the teacher or parent to choose the

experiment to be performed and to adapt the explanations to the level of preparation of his or

her students.

CAUTIONS

Never use dangerous substances. Do not use strong acids or bases. Do not put dangerous

chemicals in containers for food use (i.e: cups, glasses, bottles) because they could be

mistaken for beverages or foods. Never leave dangerous chemicals around the house; work

instead in a room like a laboratory, a cellar, or a garage. At the end of the experiments, empty

the beakers and wash them. Place the containers of the remaining substances which you want

to preserve in suitable places, out of reach of children. Write on the containers their contents

and dangerousness. While using ammonia, work in the open air or in an airy room with open

windows. As soon as you have taken the amount of ammonia you need, close its container.

Boys and girls should keep at least 2 m distant, and upwind. An adult must always be present

during these experiments. In any case, we do not assume any liability. As for the safety issues

and the responsibilities involved, we recommend that you read our Warning page. You can buy

the chemicals and the laboratory equipment for these experiments in stores which sell chemical

laboratory items. Often, these stores are located near universities. Be safe and have a good

time!

A CHEMICAL REACTION

This first experiment serves to introduce the concept of chemical reaction and can be performed

in an elementary school also. It is useful to help children understand how acid substances react

with basic ones. 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 (figure 2). What happened? A chemical

reaction occurred between the baking soda (a basic substance) and vinegar (an acid

substance). These two 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

CH3COOH

NaHCO3

CH3COONa

H2O

CO2

Acetic acid

Baking soda

Sodium acetate

Water

Carbon dioxide

Figure 2 - Chemical reaction between vinegar and baking soda.

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Acid and Bases by Mrpotpot | CONTENTS Introduction Cautions A chemical reaction Acids, Bases and pH Measuring the pH Red cabbage juice Determining the pH of some substances The color scale of the red cabbage Is it magic? Acid-Base Indicators How acid is that vinegar? The pH of soaps Searching for natural indicators Conclusion Bibliography INTRODUCTION This time, we will do some simple chemistry experiments to begin learning about acids and bases. We will see how the acidity of substances is measured; we will learn about some acid-base indicators; we will produce pH indicating papers; we will do a titration of vinegar; we will search for natural indicating substances and we will determine the color scale of them. In most cases, we will use household substances. We will use also some substances and devices bought especially for our experiments. The experiments we will describe are suited to be performed not only in schools, but also at home and for your own personal interest. Their difficulty differs from one case to another, and it is up to the teacher or parent to choose the experiment to be performed and to adapt the explanations to the level of preparation of his or her students. CAUTIONS Never use dangerous substances. Do not use strong acids or bases. Do not put dangerous chemicals in containers for food use (i.e: cups, glasses, bottles) because they could be mistaken for beverages or foods. Never leave dangerous chemicals around the house; work instead i ...
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