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Quiz Chapter 5: Thermochemistry

10 questions · Form 3 Science Bab 5: Thermochemistry

Question 1 of 10Score: 0

In a laboratory experiment investigating heat changes, why are polystyrene cups often used as reaction vessels instead of glass beakers?

Full Question List & Answer Key

Prefer reading to quizzing? All 10 questions are listed below with the answer and explanation under each one.

1. In a laboratory experiment investigating heat changes, why are polystyrene cups often used as reaction vessels instead of glass beakers?

  1. Polystyrene is a good heat conductor
  2. Polystyrene is a good thermal insulator that minimizes heat loss or gain to surroundings
  3. Polystyrene reacts with acid to give a clearer color
  4. Polystyrene increases the speed of chemical reactions
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Answer: B

Polystyrene acts as an insulator, reducing heat exchange with the external surroundings to ensure accurate temperature change measurements.

2. Why does cellular respiration count as an exothermic reaction?

  1. It absorbs carbon dioxide and heat from the environment
  2. It breaks down glucose to release energy for body activities
  3. It requires sun light to break chemical bonds in blood
  4. It converts heat energy into solid carbohydrates
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Answer: B

Respiration breaks down glucose in the presence of oxygen to release metabolic energy and heat, making it exothermic.

3. Which of the following daily phenomena involves an exothermic chemical reaction?

  1. Baking a cake in an oven
  2. Evaporation of sweat from skin
  3. Burning a candle
  4. Thermal decomposition of limestone
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Answer: C

Burning a candle is a combustion reaction that releases heat and light energy into the surrounding environment.

4. Which chemical compound is commonly used in instant hot packs?

  1. Ammonium nitrate
  2. Ammonium chloride
  3. Anhydrous calcium chloride
  4. Potassium nitrate
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Answer: C

Anhydrous calcium chloride dissolves in water exothermically, releasing heat energy which makes it suitable for instant hot packs.

5. Which of the following pairs of substances will undergo an exothermic reaction when mixed together?

  1. Water and ammonium chloride
  2. Water and anhydrous copper(II) sulfate
  3. Ethanoic acid and sodium hydrogen carbonate
  4. Water and ammonium nitrate
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Answer: B

Dissolving anhydrous copper(II) sulfate in water is an exothermic reaction that releases heat energy.

6. When solid ammonium chloride is dissolved in water in a beaker, the beaker feels cold. What type of reaction has occurred?

  1. Exothermic reaction
  2. Endothermic reaction
  3. Neutralisation reaction
  4. Combustion reaction
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Answer: B

Dissolving ammonium chloride absorbs thermal energy from the surroundings (including the container and solution), making the beaker feel cold.

7. Which application is suitable for treating an athlete's acute muscle sprain on the field?

  1. Instant hot pack to increase swelling
  2. Instant cold pack to reduce pain and swelling
  3. Rubbing ethanol to burn the skin surface
  4. Applying baking soda and vinegar
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Answer: B

Instant cold packs absorb heat, constricting blood vessels and helping to reduce pain and swelling in acute sports injuries.

8. A student mixes baking soda with vinegar in a cup and notices the temperature drops from 28°C to 21°C. What can be concluded?

  1. The reaction is exothermic because heat is generated
  2. The reaction is endothermic because heat is absorbed from the solution
  3. The reaction destroyed energy entirely
  4. The mixture undergoes physical condensation
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Answer: B

A decrease in temperature indicates that heat energy was absorbed from the solution/surroundings into the reaction, confirming an endothermic process.

9. What is observed on a thermometer when placed in a beaker where a neutralisation reaction between hydrochloric acid and sodium hydroxide is taking place?

  1. The temperature reading decreases
  2. The temperature reading increases
  3. The temperature reading drops to 0 degrees Celsius
  4. No change in temperature reading
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Answer: B

Neutralisation is an exothermic reaction, so heat energy is released, causing the thermometer reading to rise.

10. How does the total energy content of reactants compare to products in an exothermic reaction?

  1. Total energy of reactants is higher than products
  2. Total energy of reactants is lower than products
  3. Total energy of reactants and products are equal
  4. Reactants have zero energy content
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Answer: A

In exothermic reactions, reactants hold higher chemical potential energy than products; the difference is released as heat energy.

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