Questions on Boiling
20 Multiple-Choice Questions on Boiling
1. Boiling occurs when:
A) A liquid freezes
B) Vapor pressure equals atmospheric pressure
C) Condensation begins
D) Surface tension increases
E) The temperature falls below freezing
2. What happens to the boiling point of a liquid at higher altitudes?
A) It increases
B) It stays the same
C) It decreases
D) It becomes zero
E) It doubles
3. Which of the following will raise the boiling point of water?
A) Decreasing temperature
B) Increasing altitude
C) Adding a non-volatile solute
D) Decreasing atmospheric pressure
E) Stirring the water
4. Boiling involves:
A) Only surface evaporation
B) Only heating from below
C) The formation of vapor bubbles inside the liquid
D) Sublimation of the solid phase
E) Ionization of molecules
5. The normal boiling point is defined as the temperature at which a liquid boils at:
A) 0 atm
B) 1 atm
C) 2 atm
D) Room pressure
E) Any pressure
6. Boiling is different from evaporation because:
A) Evaporation requires higher temperature
B) Boiling occurs only in solids
C) Boiling happens throughout the liquid
D) Evaporation is faster
E) Boiling does not involve vapor
7. During boiling, the temperature of the liquid:
A) Increases continuously
B) Decreases rapidly
C) Remains constant
D) Doubles
E) Drops to 0°C
8. A volatile substance will:
A) Have a low boiling point
B) Boil only at high pressure
C) Not evaporate
D) Be solid at room temperature
E) Have strong intermolecular forces
9. Adding salt to boiling water will:
A) Lower the boiling point
B) Raise the boiling point
C) Stop boiling
D) Freeze the water
E) Cause sublimation
10. Why does water boil at 100°C at sea level?
A) It's a universal constant
B) The vapor pressure equals atmospheric pressure
C) It is the melting point of water
D) Because of hydrogen bonding
E) That’s when water evaporates
11. Which of the following has the highest boiling point?
A) Acetone
B) Diethyl ether
C) Water
D) Ethanol
E) Methane
12. A pressure cooker cooks food faster because:
A) It lets air escape
B) It reduces boiling point
C) It increases boiling point by increasing pressure
D) It removes water from food
E) It uses steam to freeze food
13. Why do bubbles form inside a liquid during boiling?
A) Condensation
B) High viscosity
C) Formation of vapor inside the liquid
D) Precipitation of salts
E) Surface reaction
14. The boiling point of a liquid is most directly affected by:
A) Its color
B) Its density
C) Intermolecular forces
D) Its pH
E) Number of atoms
15. Which condition will cause a lower boiling point for a liquid?
A) Increasing solute concentration
B) Decreasing altitude
C) Increasing pressure
D) Decreasing external pressure
E) Stirring the liquid
16. When a liquid boils, the added heat:
A) Raises its temperature
B) Converts liquid to solid
C) Increases its pH
D) Breaks intermolecular forces to change phase
E) Increases its density
17. What is a boiling chip used for in laboratory boiling?
A) To increase surface area
B) To cool the liquid
C) To prevent bumping and ensure smooth boiling
D) To remove impurities
E) To stir the liquid
18. Boiling point elevation occurs when:
A) The pressure is lowered
B) A solute is added to a solvent
C) The solvent is evaporated
D) The solution is diluted
E) The liquid is cooled
19. Which factor does not influence the boiling point of a liquid?
A) Atmospheric pressure
B) Intermolecular forces
C) Solute presence
D) Liquid volume
E) Altitude
20. The reason pressure affects boiling is because:
A) Vapor molecules stick together
B) Boiling point is independent of pressure
C) External pressure controls vapor pressure balance
D) Molecules expand at high altitudes
E) Temperature changes molecular shape
Answers with Explanations
1. B – Boiling occurs when vapor pressure equals atmospheric pressure.
2. C – At high altitudes, atmospheric pressure is lower, so boiling point decreases.
3. C – Adding a non-volatile solute increases boiling point (boiling point elevation).
4. C – Boiling includes vapor formation throughout the liquid.
5. B – The normal boiling point is defined at 1 atmosphere of pressure.
6. C – Unlike evaporation (only at the surface), boiling happens throughout the liquid.
7. C – During boiling, temperature remains constant as heat goes into phase change.
8. A – Volatile substances have high vapor pressure and boil at low temperatures.
9. B – Solutes like salt raise the boiling point (colligative property).
10. B – Water boils at 100°C at sea level because vapor pressure equals 1 atm.
11. C – Water has strong hydrogen bonds, leading to a relatively high boiling point.
12. C – Pressure cookers increase pressure, raising boiling point and cooking faster.
13. C – Bubbles form as vaporized liquid inside the boiling liquid.
14. C – Boiling point is directly related to strength of intermolecular forces.
15. D – Lower external pressure = lower boiling point.
16. D – During boiling, heat is used to break intermolecular forces (not raise temperature).
17. C – Boiling chips promote smooth boiling by providing nucleation sites.
18. B – Solutes reduce vapor pressure, requiring higher temperature to boil.
19. D – Volume of liquid does not affect its boiling point.
20. C – Boiling point depends on the vapor pressure matching external (atmospheric) pressure.
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