JAMB and WAEC Physics questions: Change of state

23 questions with answers and explanations. Tap an option to check yourself.

1. Question 1· Change of state· JAMB

   Adding salt to ice

   • Alowers its melting point
   • Braises its melting point
   • Chas no effect on its melting point
   • Dturns it into steam

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   Explanation and discussion

2. Question 2· Change of state· JAMB

   Increasing the pressure on water

   • Aremoves its latent heat
   • Braises its boiling point
   • Cdoubles its volume
   • Dchanges its colour

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   Explanation and discussion

3. Question 3· Change of state· WAEC

   The flat part of a cooling curve shows that the substance is

   • Againing heat
   • Bcooling fastest
   • Cat room temperature
   • Dchanging state

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   Explanation and discussion

4. Question 4· Change of state· WAEC

   While water is boiling its temperature stays constant because the heat supplied

   • Ais used to overcome the forces between molecules
   • Bescapes to the surroundings
   • Craises the kinetic energy of the molecules
   • Dis changed into light

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   Explanation and discussion

5. Question 5· Change of state· WAEC

   How much heat is needed to melt 0.2 kg of ice at 0 °C? [specific latent heat of fusion = 3.36 × 10⁵ J/kg]

   • A6.72 × 10⁴ J
   • B3.36 × 10⁴ J
   • C1.68 × 10⁶ J
   • D6.72 × 10⁵ J

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   Explanation and discussion

6. Question 6· Change of state· JAMB

   Wet clothes dry faster on a windy day because wind

   • Aadds water
   • Braises the boiling point
   • Cremoves the vapour and speeds up evaporation
   • Dcools the sun

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   Explanation and discussion

7. Question 7· Change of state· WAEC

   Boiling differs from evaporation because boiling

   • Atakes place at all temperatures
   • Btakes place at a definite temperature throughout the liquid
   • Coccurs only at the surface
   • Dproduces no vapour

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   Explanation and discussion

8. Question 8· Change of state· JAMB

   Evaporation causes cooling because

   • Aheat flows into the liquid
   • Bthe liquid absorbs cold from the air
   • Cthe liquid's mass increases
   • Dthe faster molecules escape, lowering the average kinetic energy of those left

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9. Question 9· Change of state· WAEC

   Food cooks faster in a pressure cooker because

   • Athe pressure lowers the boiling point
   • Bthe higher pressure raises the boiling point of water
   • Csteam escapes quickly
   • Dless heat is needed to melt it

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   Explanation and discussion

10. Question 10· Change of state· WAEC

    Evaporation differs from boiling because evaporation

    • Aoccurs throughout the liquid
    • Btakes place only at 100 °C
    • Ctakes place at all temperatures from the surface of the liquid
    • Dneeds no heat

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11. Question 11· Change of state· JAMB

    While a pure liquid is boiling, its temperature

    • Arises and falls
    • Brises steadily
    • Cfalls steadily
    • Dremains constant

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    Explanation and discussion

12. Question 12· Change of state· WAEC

    Heat required to melt 0.5 kg of ice at 0 °C (latent heat 3.4 × 10⁵ J/kg) is

    • A6.8 × 10⁵ J
    • B1.7 × 10⁵ J
    • C3.4 × 10⁵ J
    • D3.4 × 10⁴ J

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    Explanation and discussion

13. Question 13· Change of state· WAEC

    Find the heat needed to change 2 kg of water at 100 °C to steam. (Specific latent heat = 2.26 × 10⁶ J/kg)

    • A4.52 × 10⁶ J
    • B2.26 × 10⁶ J
    • C1.13 × 10⁶ J
    • D9.04 × 10⁶ J

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    Explanation and discussion

14. Question 14· Change of state· JAMB

    A pressure cooker cooks food faster because

    • Asteam is a poor conductor
    • Bit lowers the boiling point of water
    • Cit uses less water
    • Dthe increased pressure raises the boiling point of water

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    Explanation and discussion

15. Question 15· Change of state· WAEC

    The heat absorbed when a solid changes to a liquid without a change in temperature is called

    • Alatent heat of vaporisation
    • Blatent heat of fusion
    • Cspecific heat capacity
    • Dheat of combustion

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    Explanation and discussion

16. Question 16· Change of state· WAEC

    The change of a substance directly from solid to vapour is called

    • Acondensation
    • Bevaporation
    • Csublimation
    • Dmelting

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    Explanation and discussion

17. Question 17· Change of state· JAMB

    The specific latent heat of fusion of a substance is the heat needed to

    • Araise 1 kg of it by 1 K
    • Bchange 1 kg of it from solid to liquid without a change of temperature
    • Cboil 1 kg of it
    • Dmelt any amount of it

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    Explanation and discussion

18. Question 18· Change of state· WAEC

    Evaporation differs from boiling in that evaporation

    • Aoccurs at all temperatures from the surface
    • Boccurs at a fixed temperature
    • Cproduces bubbles
    • Dneeds no heat

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19. Question 19· Change of state· JAMB

    How much heat is given out when 0.2 kg of steam at 100 °C condenses to water at 100 °C? (L = 2.26 × 10⁶ J/kg)

    • A4.52 × 10⁵ J
    • B2.26 × 10⁵ J
    • C1.13 × 10⁷ J
    • D4.52 × 10⁶ J

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    Explanation and discussion

20. Question 20· Change of state· JAMB

    Find the heat needed to melt 2 kg of ice at 0 °C. (Specific latent heat of fusion = 3.36 × 10⁵ J/kg)

    • A6.72 × 10⁵ J
    • B3.36 × 10⁵ J
    • C1.68 × 10⁵ J
    • D6.72 × 10⁶ J

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    Explanation and discussion