Lesson Plan of Properties and uses of Salt General Science Grade VIII

Lesson Plan of Properties and uses of Salt

General Science Grade VIII

Students’ Learning Outcomes

·         Define the term salt.

·         Describe the properties of salts.

·         Explain the uses of salts in daily life.

Information for Teacher

·         A salt is a compound formed by the neutralization reaction between an acid and a base.

·         Salts of calcium, present in our bones are responsible for strengthening of bones.

·         Potash alum is used for the purification of water.

·         Salts of iodine are needed for the proper functioning of thyroid gland. they are also used for the treatment of goiter.

·         salts ionize in water e.g., Na CI dissociates into Na’& CI

Uses of Salts

Sr.	SALT	USE
1	Ammonium Chloride	In torch batteries
2	Ammonium Nitrate	In fertilizers
3	Calcium Chloride	As Drying Agent
4	Iron Sulfate	In Iron Tablets
5	Magnesium Sulfate	In Medicine
6	Potassium Nitrate	In Gunpowder etc.
7	Silver Bromide	In Photography
8	Sodium Chloride	Making Na OH
9	Sodium Stearne	In Making Soap

·         Salt solutions are also used as electrolytes and as fertilizers.

·         Salts are used for seasoning food.

·         Salts such as baking soda are used to soften bread & cake.

 

Properties of Salt
Name of Compound	Sodium Chloride
Chemical Formula	Na CI
Formula weight	58.443
Color	Colorless or white when pure; colored splotches       (e.g. Blue, purple) when impure.
Luster	Vitreous
Physical form	Transparent to translucent cubic crystal; also powder or granules
Mos hardness	2  1/2
Density at O* C(32*f)	2.17 g/cm
Melting point	801* C (1,474*F)
Boiling point	1,465* C (2, 669* F)
Solubility	Water (S)*;  glycerol  (S); alcohol (SS) hydro chloride acid

Concept Map

Material / Resources

Vinegar, sodium hydroxide, beakers, pH papers, burner/spirit lamp

Worm up activity

·         Write the word “salts” on the board & ask students to give their ideas about it. write students ideas on the board.

·    

Development

Activity 1

·         divide students in small groups and instruct them to:

o   Take small amount of sodium hydroxide in beaker A.

o   Add few drops of phenomenological to it. Solution will turn pink.

o   Take vinegar in beaker B and add it drop wise to beaker A until it becomes colorless.

o   Dip pH paper after each addition and then evaporate the solution mixture to dryness.

·         Ask students to write answers of following questions in their journals.

o   What is the name of process when alkali is added in acid?

(Expected response: Neutralization)

o   What did you get after solution mixture is evaporated?

(Expected response: Salt crystals)

o   Can you name the solid product obtained after evaporation?

(Expected response: Sodium acetate)

Activity 2

·         Divide students in small groups & instruct them to:

o   Dissolve washing soda (Sodium carbonate) in water in beaker A.

o   Dissolve baking soda baking soda (sodium bicarbonate) in water in beaker B.

o   Dissolve common salt in water in beaker C. dip pH paper in all the three solutions.

Observation:

o   What change in color of pH paper is observed in all the three solutions?

o   What is the nature of the solutions in beaker A, B and C?

·         The beaker ‘A’ will give value of pH more than 7. (Basic salt) the beaker ‘B’ will give value of pH less than 7. (acidic salt) the beaker ‘C’ will give value of pH equal to

Sum up / Conclusion

·         Conclude the lesson by telling students:

o   Salts are formed as a result of neutralization reaction between an acid and base.

o   Salts are of great use and are also found in human body.

o   Salts are crystalline and soluble in water.

Assessment

·         Assess students’ Learning by asking these questions:

o   Explain the role of baking soda in the process of baking?

(Expected response: Baking soda produces carbon dioxide which raises the baking material.

o   Which salts are used as fertilizers in different crops?

o   Calcium phosphate, DAP or ammonium sulfate.

Follow up

·         Visit the Khewra Mines:

Read the situation below and give appropriate answers to the, “ Khewra Mine Guide”, question based upon your recently developed knowledge about salts.

A group of students visited Khewra mines, where the guide told them few interesting facts about mine:

Fact 1:

·         There are small ponds. if anyone jumps into the water, he/she will never drowned. Can you tell the reason?

A1: the person will not drown but can suffer from severe dehydration. 

Fact2:

·         If you come in winter, you will never feel cold. What you think, why is it so?

A2: Salts are bad conductors of heat.

Solve the mystery

·         One morning a watchman’ body was found lying on the floor of a warehouse. Nader was suspected murdering the watchman. Police found white powder in his socks. They said it was slaked lime from ware house where his body was found. But Nader insisted that he has been accused wrongly as he was on the salty beach last night. The powder in his socks was salt. What tests would you carry out to find out if Nader was telling the truth?

Answer: pH of salt and slaked lime could be checked. salts are neutral while slaked lime is highly basic.