Properties and uses of Alkali

Lesson Plan of Properties and uses of Alkali s

General Science Grade VIII

Students’ Learning Outcomes

·         Define the term alkalies in their own words.
·         Describe the properties of alkali s.
·         Explain the uses of alkali s in daily life.

Information for Teachers

·         The word alkali comes from the Arabic word for ashes.
·         Alkali is now used as another word base.
·         Alkali mater reacts with water.
·         A chemical substance which gives hydroxide ions (OH) in water is called alkali.
·         Alkali s have bitter taste & turn red litmus blue.
·         Alkali have soapy feel.
·         Alkali dissolves in water to form solutions which conduct electricity.
·         Alkali s react with acids to form salt & water (neutralization).
·         They are good electrical conductors in solutions. They have pH more than 7.
·         Household cleaner: NH4OH to remove grease from window.
·         Soap making:  Na Oh+Oil (Any soap).
·         Detergent making: KOH.
·         Industries: medicines (milk of magnesia).

Concept Map

Material / Resources

Soap, bar, water, soap solution detergent solution and household cleaner solution, pH papers, vegetable such as ginger, garlic, onion

Worm up activity

·         Write the ideas given by the students about alkali s on board.



Activity 1

·         Divide students in pairs; give three types of solutions (detergent, soap and household cleaner) in separate bottles and red litmus papers.
·         instruct the students to:
o   Dip red litmus paper in soap, detergent and household cleaner solutions separately and observe what happens to the color of red litmus paper.
·         Now, ask these questions:
o   Did you see any change in the color of red litmus paper?
o   What does the change in the color of red litmus paper indicate?
·         After getting students responses tell them that red litmus paper changes into blue in basic solutions thus indicating that detergent, soap & housecleaned solutions are basic in nature.
·         Teacher can also provide students with vegetables such as ginger garlic onion and ask them to find their nature. Students will find out that these vegetables are alkaline in nature.

Activity 2

·         Teacher can provide students with small amounts of quick lime; it can be obtained from pan shop/hardware shop.
·         Ask students to:
o   Dissolve it in water.
o   Then dip the strips of pH paper in quick lime solution.
·         Ask students:
o   Did you notice any change in the color of pH paper?
o   If yes, what does it indicate?
o   Decide quick lime solution is an alkali or a base?
·         After taking student’s responses tell them that pH value more than 7 indicates that solution is basic in nature. The color ranges from dark green to dark blue which is an indication of basic solutions.

Activity 3

Group discussion
·         Divide students in groups and ask them to discuss the following points.
o   Discuss the properties, sources and uses of bases in daily life.
o   Write main points on the board and ask students to give a presentation to compare properties of acid and alkali s. 
·         Ask following questions to further elaborate the importance of alkalizes in our daily lives.
o   A compound is found to react with fats to form soap and causes red litmus to turn blue. Would the compound be classed as an acid, or a base? Why?
(Expected response: The compound would be a base as it turns red litmus o blue).
o   Doctor has diagnosed stomach ulcer for Bilabial. She was advised to reduce acidity level in the stomach. She was prescribed such medicines that lower the acidity in the stomach. Can you guess what would be the nature of chemicals found in the medicines? Why do you think so?
(Expected response: The medicines used will be alkaline in nature. They neutralized the acidic affect and are called “antacids”.

Sum up / Conclusion

·         Conclude lesson by telling children that they have learns:
o   All alkali s are bases but all bases aren’t alkali s.
o   They have pH value greater them.
o   Alkali s are widely used for cleaning purpose in soap and detergent making.


·         Ask the following questions to recap the lesson and also to assess students understanding of the taught concepts.
o   Why is it dangerous to identify alkali s by tasting or touching them?
(Expected response: Alkali s are corrosive and cause skin burns). 
o   What would we do immediately if we accidentally touch an alkali?
(Expected response: We should treat the effected part with a mild acid to neutralize the effect of alkali).

Follow up

·         Ask students to:
o   Prepare a poster about the uses of common alkali s in our daily life.
o   the poster should contain objects (empty bottles of cleaners, detergents and soap wrappers)and it must be eye catching.

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