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 12
A 250 g block of ice at 0°C is placed in 500 g of water at 30°C. Calculate the final temperature of the mixture. (Assume no heat loss, specific heat of water = 4.18 kJ/kg·K, latent heat of fusion = 334 kJ/kg)
A 500 g sample of water at 100°C is converted to steam at 100°C. If the latent heat of vaporization is 2260 kJ/kg, how much heat is required?
A sample of water is heated from 20°C to 100°C and then converted to steam at 100°C. List the energy changes involved in this process.
A scientist observes that dry ice (solid CO₂) disappears at room temperature without forming a liquid. What process is occurring?
Calculate the amount of heat required to convert 200 g of ice at 0°C to water at 0°C. (Latent heat of fusion of ice = 334 kJ/kg)
Describe the difference between evaporation and boiling.
Describe what happens at the molecular level during condensation.
During the melting of ice, the temperature of the system does not change even though heat is being supplied. Explain why.
Explain why ice floats on water.
Explain why sweating helps to cool the human body.
If 100 g of steam at 100°C is condensed to water at 100°C, how much heat is released? (Latent heat of vaporization = 2260 kJ/kg)
State the effect of pressure on the boiling point of a liquid.
State the law of conservation of energy as it applies to changes of state.
A 100 g sample of a substance requires 42 kJ of heat to change from solid at its melting point to liquid at the same temperature. What is the latent heat of fusion of the substance in kJ/kg?
A 300 g sample of a substance at 20℃ is heated until it completely melts at its melting point of 80℃. The specific heat capacity of the solid is 0.8 kJ/kg·K, and its latent heat of fusion is 250 kJ/kg. Calculate the total heat required for this process.
A sealed container holds 2 kg of water at 100℃ and 1 atm pressure. If the pressure inside the container is suddenly increased to 2 atm, what will happen to the boiling point of water? Explain your answer.
Describe how the concept of dynamic equilibrium applies to a closed container containing both liquid and vapor at the boiling point.
Explain, using the concept of entropy, why the melting of ice is a spontaneous process at temperatures above 0℃.
