Preparatory 2 Science – English

Interactive Exam: Chemical Reactions

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Interactive Exam: Chemical Reactions

Unit 2: Matter and Chemical Reactions

Test your knowledge with this interactive exam!

Student Name:
Class:
Date:
Time Allowed: 75 minutes
Total Marks: 100
Instructions:
  1. Click on options to select answers for multiple choice questions.
  2. Type your answers in the text areas provided.
  3. Drag and drop items to classify them as physical or chemical changes.
  4. Use the “Check Answers” button to see how you’re doing.
  5. Click “Submit Exam” when you’re finished to see your final score.
  6. Your progress is tracked automatically – see the progress bar above.
SECTION A: BASIC CONCEPTS (25 marks) 0/5
1 Define the following terms: What is Meant By [4 marks]
a Chemical reaction
b Physical change
c Chemical change
d Precipitate
2 Explain the mechanism of a chemical reaction. Use the reaction between baking soda and vinegar as an example in your explanation. Give Reason [5 marks]
3 List FOUR ways we can tell when a chemical reaction occurs (detect its occurrence). Complete [4 marks]

Drag and drop the correct indicators into the box below:

Color change
Formation of a precipitate
Evolution of gas
Emission of light or heat
Change in state only
Dissolving in water
Change in size only

Drop correct indicators here (4 items)

4 Classify the following changes into physical changes (P) or chemical changes (C): Complete [8 marks]

Click on each item to toggle between P (Physical) and C (Chemical):

a) Dissolution of sugar in water:
b) Conversion of milk to yogurt:
c) Combustion of wax:
d) Melting of wax:
e) Rusting of an iron nail:
f) Burning of bread in the oven:
g) Limewater turning milky with CO₂:
h) Universal indicator changing color near ammonia gas:
5 What happens if you leave an orange to rot? Is this a physical or chemical change? How can you tell? What Happens If [4 marks]
SECTION B: ACTIVITY-BASED QUESTIONS (35 marks) 0/6
Activity 1: Reaction of Baking Soda and Vinegar
Materials: Baking soda (sodium bicarbonate), Vinegar (dilute acetic acid), Empty bottle, Balloon, Spoon

Procedure: Baking soda is placed in a balloon, vinegar in a bottle. The balloon is secured over the bottle mouth, then baking soda is allowed to fall into the vinegar.

Reactants
Baking Soda (NaHCO₃)
Vinegar (CH₃COOH)
Products
Sodium Acetate
Water (H₂O)
Carbon Dioxide (CO₂)
6 Based on Activity 1, answer the following: [6 marks]
a What happens to the balloon during this activity?
b Is a new substance formed in this reaction? Explain.
c Is this change physical or chemical? Give TWO reasons for your answer.
Reasons:
Activity 2: Formation of Precipitate
Materials: Sodium chloride solution, Silver nitrate solution, Test tube, Dropper

Observation: Adding silver nitrate solution to sodium chloride solution causes formation of a white precipitate of silver chloride.

AgNO₃ (aq) + NaCl (aq) → AgCl (s) + NaNO₃ (aq)
7 Based on Activity 2, write the chemical equation for this reaction and explain why the formation of a precipitate indicates a chemical reaction. Give Reason [5 marks]
a Chemical equation:
b Explanation:
8 Table Completion: Based on Activity 6 observations: Complete [8 marks]
Reaction Properties Before Properties After Chemical Reaction? (Yes/No) Indication
Sugar burning
Reaction of oil with caustic soda
SECTION C: MULTIPLE CHOICE QUESTIONS (40 marks) 0/5
9 Which of the following expresses a chemical change?
a Iodine sublimation
b The conversion of charcoal to ash
c The heating of an iron rod
d The melting of ice
10 The combustion (burning) of table sugar is indicated by the formation of:
a a solid matter and evolution of smoke
b a white precipitate and evolution of smoke
c green solution and reddish brown gas
d white powder and bright light
11 The following reactions were carried out:
(1) Burning a strip of magnesium
(2) Adding hydrochloric acid to magnesium
(3) Adding sulphuric acid to baking soda
Which of these reactions is accompanied by the release of gas?
a (1) only
b (2) only
c (1), (3)
d (2), (3)
12 Soap is formed by the reaction of:
a oil with solid sodium hydroxide
b oil with sodium hydroxide solution
c oil with hydrochloric acid
d oil with silver nitrate solution
13 All chemical reactions are accompanied by the following, except:
a breaking down the bonds between the molecules of the reactants
b forming bonds between the molecules of the products
c the formation of new substances
d the release of heat
14 BONUS: Apply the concept of chemical reaction to the production of ammonia gas (NH₃) from nitrogen gas (N₂) and hydrogen gas (H₂). Give Reason [10 marks]

Build the chemical equation by dragging the correct coefficients:

1
2
3
4
N₂ +
1
2
3
4
H₂ →
1
2
3
4
NH₃
b Explain the bond breaking and forming during this reaction:
Time Remaining: 75:00