This activity 1.4 helps students understand the reaction between calcium oxide and water. When water is added to calcium oxide, a vigorous chemical reaction takes place. This activity demonstrates both combination reaction and exothermic reaction.
Activity 1.4 Class 10 Science
Objective
To
observe and demonstrate the chemical reaction between calcium oxide with water.
Materials Required
1. Calcium oxide (Quick lime)
2. Water
3. Beaker
Procedure
· Take a small amount of calcium oxide in a beaker.
· Slowly add water to the beaker.
· Observe the reaction carefully.
· Touch the outer surface of the beaker carefully and note any change in the temperature.
Observation
· A vigorous reaction takes place.
· The beaker becomes hot due to the release of heat.
· A hissing sound is heard during the reaction. Bubbles may be observed.
· After cooling a white suspension of calcium hydroxide (slaked lime) is formed.
Chemical reaction involved in the activity
CaO(s)
+ H2O(I) → Ca(OH)2(aq)
Explanation
When water
is added to calcium oxide, a vigorous reaction takes place and calcium hydroxide
is formed and a large amount of heat is released, that’s why beaker becomes
hot.
Since heat is released during the reaction, it is called an exothermic reaction.
In
this activity, two reactants combine to form a single product so it is called a
combination reaction.
Types of Chemical Reactions
1. Combination reaction: A reaction in which two or more substances combine to form a single product is called a combination reaction.
2. Exothermic reaction: A reaction in which heat is released is called an exothermic reaction.
Conclusion
The
activity 1.4 demonstrates the vigorous reaction between calcium oxide and
water. This is an exothermic reaction.
As CaO
combine with water to form Ca (OH)2 only so this is a combination
reaction.
Precautions
· Add water slowly to calcium oxide.
· Perform the activity under the supervision of a teacher.
· Avoid direct contact with calcium oxide and the reaction mixture.
· Use clean apparatus.
· Do not touch the reaction mixture directly as it becomes hot.
Viva
Questions and Answers
Q1. What
is the common name of calcium oxide?
Answer
Quick lime
Q2. What
is the common name of calcium hydroxide?
Answer
Slaked lime
Q3. What
happens when water is added to calcium oxide?
Answer
A vigorous
reaction takes place and calcium hydroxide is formed.
Q4. Why
does the beaker become hot?
Answer
Because
heat is released during the reaction so the beaker becomes hot.
Q5. Which
type of rection is demonstrated in this activity.?
Answer
Combination
reaction and exothermic reaction
Q6. What
is the chemical formula of calcium hydroxide?
Answer
Ca(OH)2
Q7. Why
is this called a combination reaction?
Answer
Because
calcium oxide and water combine to form a single product.
Key Learning Points
· Calcium oxide reacts with water to form calcium hydroxide.
· A large amount of heat is released during the reaction.
· The reaction is vigorous in nature.
· Calcium hydroxide is known as slaked lime.
· The reaction is both combination and exothermic.
Multiple
Choice Question
Q1. What is the common name of calcium oxide?
a. Slaked lime
b. Quick lime
c. Limestone
d. Gypsum
Correct
answer - b. Quick
lime
Q2. What is formed when calcium oxide reacts with water?
a. Calcium carbonate
b. Calcium chloride
c. Calcium hydroxide
d. Calcium sulphate
Correct
answer - c. Calcium
hydroxide
Q3. What is the common name of calcium hydroxide?
a. Quick lime
b. Slaked lime
c. Lime water
d. Chalk
Correct
answer - b. Slaked lime
Q4. Why does the beaker become hot during the reaction?
a. Heat is absorbed
b. Heat is released
c. Water evaporates
d. Oxygen is produced
Correct
answer - b. Heat is released
Q5. Which type of reaction is represented by CaO(s) + H2O(I) → Ca(OH)2(aq)
a. Decomposition reaction
b. Double displacement reaction
c. Displacement reaction
d. Combination reaction
Correct
answer - d. Combination reaction
Q6.This reaction CaO(s) + H2O(I) → Ca(OH)2(aq) is also classified as:
a. Endothermic reaction
b. Exothermic reaction
c. Neutralization reaction
d. Oxidation reaction
Correct
answer - b. Exothermic
reaction
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