137. Acids, Bases and Salts - Physical and Chemical Reactions -

Exploring Acids, Bases, and Salts through Physical and Chemical Changes

Introduction:

Welcome to our DIY activity blog post designed specifically for high school teachers and homeschooling parents! In this article, we will provide you with engaging and hands-on activities to teach and demonstrate the concepts of acids, bases, physical changes, and chemical changes. These activities are designed to make the learning process interactive and memorable for your students. Let's dive in!

Definition: Physical changes are changes that affect the form of a substance, but do not change its

chemical composition. This change may be reversible or non reversible.

Reversible Physical Change: A physical change that does not change the form of a substance permanently is a reversible physical change.

Example: As camphor changed to gas and again back to solid its a reversible physical change.

Non-reversible physical Change: A Physical change that changes the form of a substance permanently is a Non-reversible Physical Change.

Example: Bursting of a balloon (Try it at home)

Activity 1: Exploring Physical Changes

Materials Required:

Candle
Metal cup
Plastic glass
Camphor
Tripod stand

Procedure:

Light the candle using a match or a lighter.
Observe and discuss the changes that occur as the candle burns (e.g., melting wax, release of heat and light).
Place the metal cup and the plastic glass near the flame. Observe any physical changes that occur due to the heat.
Crush a small piece of camphor and place it on a tripod stand. Ignite the camphor and observe the physical changes that occur.

Definition: A change in which a substance either combines with another to form a new substance or decomposes into two or more different substances. These changes may be reversible or non-reversible.

Non-reversible Chemical Change: A Chemical change that forms substance / substances that cannot be converted back to the original is a Non-reversible chemical change Reversible Chemical Change: A Chemical change that forms a substance / substances that can be converted back to the original is called a Reversible chemical change.

Example :

2NaCl + CaCO3

Na2 CO3+ CaCl2

Activity 2: Investigating Chemical Changes

Materials Required:

Metal cap
Camphor
Tripod stand

Procedure:

Place a metal cap on the tripod stand.
Ignite the camphor and carefully place it inside the metal cap.
Observe and discuss the chemical changes that occur (e.g., flame, release of gases).
Emphasize the difference between physical changes and chemical changes.

Activity 3: Exploring Non-Reversible Chemical Changes

Materials Required:

Baking soda, Test tube, Rubber band, Vinegar, Balloon

Procedure:

Fill a test tube with vinegar.
Secure a balloon over the mouth of the test tube using a rubber band.
Add a small amount of baking soda into the test tube.
Observe the inflation of the balloon as a non-reversible chemical change takes place due to the reaction between vinegar and baking soda.

Acids and Bases Important guidelines
Acids:
Acids are substances that taste sour. Chemicals or substances having the property of an acid are said to be acidic.
Examples: acetic acid (in vinegar), sulphuric acid (used in car batteries), and tartaric acid (used in baking).
Bases:
A base in chemistry is a substance that can accept hydrogen ions. They are bitter in taste and feel soapy on touching.
Examples: Calcium Hydroxide – Lime Water, Sodium Hydroxide used in soaps

What’s Happening?

As BAKING SODA (NaHCO3) is mixed with VINEGAR (CH3COOH) the following reaction occurs:-
CH3COOH + NaHCO3 → CH3COONa + H2O + CO2
vinegar Baking Soda Sodium acetate Water Carbon dioxide Acetic Acid Sodium bicarbonate

The CO2 is seen foaming and bubbling in this reaction that gets collected in the balloon.

Physical changes:

Chemical changes:

Activity 4: Testing Acids and Bases with Litmus Papers

Materials Required:

Citric acid
White wash
Red and blue litmus papers
2 cups and spoons

Procedure:

Prepare two cups containing equal amounts of water.
Dissolve citric acid in one cup and white wash in the other.
Dip a red litmus paper into the citric acid solution and observe the color change.
Repeat the process with blue litmus paper, this time using the white wash solution.
Discuss the results and classify the liquids as either acidic or basic.

Salts:
They are ionic compounds that result from the neutralization reaction of an acid and a base that results in the formation of salt and water.
Example: Common salt (NaCl) formed by reaction between NaOH (sodium hydroxide) and HCl (Hydrochloric acid) CUP 1 Add 10 ml water to the cup using syringe Add a pinch of Citric acid
Indicator.
Definition: A substance the changes its color when in either an acid or a base is called an indicator.

Activity 5: Turmeric as an Indicator

Materials Required:

White wash, Turmeric powder, Boric acid, Citric acid, 2 x 2ml syringes, 1 x 5ml syringe, 8 measuring cups, 3 plastic glasses

Procedure:

In each plastic glass, prepare separate solutions of white wash, turmeric powder, boric acid, and citric acid.
Use the syringes to measure precise amounts of each solution into the measuring cups.
Add a few drops of turmeric powder solution to each of the other solutions and observe the color changes.
Discuss how turmeric acts as an indicator, changing colors in the presence of acids and bases.

Activity 6: Testing Acid Strength through Titration

Materials Required:

Acids from Activity 5
Dropper or pipette
Water
Burette (if available)
Phenolphthalein indicator

Procedure:

Prepare a dilute solution of one of the acids from Activity 5 by adding it to water.
Add a few drops of phenolphthalein indicator to the acid solution.
Using a burette or dropper, slowly add the other acid solution drop by drop until the color change occurs.
Measure the amount of acid solution required for the color change.
Compare the amounts used for different acids and determine which acid is stronger based on the volume required.

Step by Step Instruction video on Acids & Bases

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Conclusion:
By engaging in these DIY activities, high school students will gain a deeper understanding of the concepts of acids, bases, physical changes, and chemical changes. These hands-on experiences will not only enhance their knowledge but also make learning enjoyable. Have fun exploring the fascinating world of chemistry.