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States of matter
Chemistry
Useful for: OSSC RHT — Regular High School Teacher, OSEPA Upper Primary — Science, OSSC Science, OSSSC Govt TGT Science — CBZ, OSSSC Govt TGT Science — PCM, SSB Lecturer (Degree Colleges), SSB TGT CBZ, SSB TGT PCM
Overview
Matter exists as solid, liquid and gas (and plasma); the kinetic theory explains their properties and changes of state.
Key points
- Particles are closely packed in solids, less so in liquids and far apart in gases.
- Evaporation causes cooling and occurs at all temperatures; boiling occurs at a fixed temperature.
- Sublimation: solid to gas directly (camphor, naphthalene, dry ice).
- Boyle’s law: at constant temperature, PV is constant.
- Charles’s law: at constant pressure, volume is proportional to absolute temperature.
- Latent heat is absorbed or released during change of state without temperature change.
Explanation
- Pressure cookers raise the boiling point.
- Humidity slows evaporation.
- Plasma is ionised gas (stars, neon lights).
- Diffusion is fastest in gases.
- Temperature in gas laws must be in kelvin.
Step by step
- Identify the concept, method or fact asked.
- Recall the definition, thinker, year or rule.
- Apply it and eliminate extreme or mismatched options.
Examples
- Sweating cools the body → evaporation.
- Doubling pressure at constant temperature halves volume → Boyle’s law.
- Naphthalene balls shrink → sublimation.
Traps and advanced points
- Trap: Using °C in gas laws.
- Trap: Mixing evaporation and boiling.
- Trap: Calling sublimation melting.
Quick revision
- Kinetic theory.
- Boyle PV constant; Charles V ∝ T.
- Sublimation examples.
Practice MCQs
Evaporation causes —
- cooling
- no change
- freezing
- heating
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Answer: (a) cooling. Escaping molecules take energy.
Camphor changing directly into vapour is —
- sublimation
- condensation
- boiling
- melting
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Answer: (a) sublimation. Solid to gas.
Boyle’s law states that at constant temperature —
- P + V is constant
- PV is constant
- V/T is constant
- P/T is constant
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Answer: (b) PV is constant. Pressure × volume constant.
Charles’s law states that at constant pressure, volume is proportional to —
- density
- pressure
- absolute temperature
- mass
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Answer: (c) absolute temperature. V ∝ T (kelvin).
If pressure doubles at constant temperature, volume becomes —
- double
- half
- four times
- unchanged
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Answer: (b) half. Boyle’s law.
Latent heat is absorbed during a change of state —
- only in gases
- never
- with a rise in temperature
- without a change in temperature
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Answer: (d) without a change in temperature. Energy breaks bonds.
Diffusion is fastest in —
- gases
- all equally
- solids
- liquids
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Answer: (a) gases. Gas particles move freely.
Boiling occurs —
- only in vacuum
- at all temperatures
- at a fixed temperature for a given pressure
- only below 0 °C
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Answer: (c) at a fixed temperature for a given pressure. Boiling point depends on pressure.
Pressure cookers cook faster because they —
- raise the boiling point
- remove water
- add air
- lower the boiling point
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Answer: (a) raise the boiling point. Higher pressure raises the boiling point.
Gas-law calculations require temperature in —
- any unit
- °C
- kelvin
- °F
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Answer: (c) kelvin. Absolute temperature.
More topics in this chapter
Notes and questions are written by Kundali IQ for practice. They are not official papers; always check the latest official notification for the syllabus and pattern.