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Three States, One Explanation
Every general-science paper opens somewhere near this chapter, and it looks so easy that most candidates skim it. Then the paper asks which process turns camphor straight into vapour, or why a desert cooler fails in the monsoon, or what the latent heat of fusion of ice is — and the easy chapter has quietly taken three marks.
The whole topic rests on one idea: matter is made of particles, and the state depends on how strongly those particles are held together and how much energy they carry. Heat the particles and they break free; cool them and they lock up again.
Get that single sentence properly, and the definitions, the naming of each change of state, the gas laws and the everyday examples all follow from it. Memorise them as separate lists and you will confuse sublimation with deposition in the hall — which is exactly what the paper is counting on.
1. Which change of state converts a solid directly into a gas without passing through the liquid state?
2. A temperature of 25 °C is equal to how many kelvin?
3. According to Boyle's law, at constant temperature the pressure of a fixed mass of gas is:
4. What is the latent heat of fusion of ice?
5. Which of the following does NOT increase the rate of evaporation of a liquid?
6. Which of the following is regarded as the fourth state of matter?
7. Why does a desert cooler cool a room much better on a hot, dry day than during humid monsoon weather?
8. At constant pressure, if the absolute temperature of a fixed mass of gas is doubled, its volume will: