Change of State
Physics ⇒ Heat and Thermodynamics
Change of State starts at 8 and continues till grade 12.
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See sample questions for grade 11
A 0.3 kg sample of a substance at its boiling point requires 90,000 J to completely vaporize. What is its specific latent heat of vaporization?
A 250 g sample of a substance requires 50,000 J to change from solid to liquid at its melting point. What is its specific latent heat of fusion?
A beaker contains 100 g of water at 100°C. How much heat is needed to convert all the water to steam at 100°C? (Latent heat of vaporization = 2,260,000 J/kg)
Calculate the amount of heat required to convert 500 g of ice at 0°C to water at 0°C. (Latent heat of fusion of ice = 334,000 J/kg)
Define latent heat of fusion.
Describe what happens to the arrangement and movement of particles during melting.
During the boiling of water, what happens to the temperature of the water?
During which change of state does a substance absorb energy but does not increase in temperature?
Explain why ice at 0°C is more effective in cooling than water at 0°C.
Explain why sweating helps to cool the body.
If 150,000 J of heat is supplied to 0.5 kg of a substance at its melting point, what is its latent heat of fusion?
Is freezing an exothermic or endothermic process?
State the difference between evaporation and boiling.
State the law of conservation of energy as it applies to changes of state.
What is the SI unit of latent heat?
A 0.4 kg block of a substance at -10°C is heated until it becomes steam at 100°C. The specific heat capacity of the solid is 2,000 J/kg·K, the specific heat capacity of the liquid is 4,200 J/kg·K, the latent heat of fusion is 330,000 J/kg, and the latent heat of vaporization is 2,260,000 J/kg. Calculate the total heat required for this process.
A 200 g sample of a substance at its melting point is supplied with 66,000 J of heat, and only 150 g of it melts. What is the specific latent heat of fusion of the substance?
Describe how the energy distribution among particles changes during the process of evaporation and how this affects the temperature of the remaining liquid.
Explain why the latent heat of vaporization is generally much higher than the latent heat of fusion for the same substance.
Explain, at the molecular level, why the temperature of a substance does not change during a phase transition, even though energy is being supplied.
