Solved Exercise Chapter 02 Chemistry Class 10th FBISE– Questions and Answers
Q1: Why does the temperature stay constant during the phase change from ice to liquid water?
A: Because the energy is used to break intermolecular bonds instead of increasing temperature.
Q2: What term is used when a solid changes directly into a gas?
A: This process is called sublimation.
Q3: How do evaporation and boiling differ from each other?
A: Evaporation occurs at any temperature; boiling happens at a specific boiling point.
Q4: Explain the heating curve of water and highlight the major phase transitions.
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A: The heating curve shows phase changes at constant temperatures: melting and boiling points.
Q5: What happens to the pressure of a gas in a sealed container when the temperature increases?
A: Pressure increases due to more frequent and energetic collisions of gas particles.
Q6: In what way does an increase in external pressure affect a liquid's boiling point?
A: It raises the boiling point.
Q7: How does the molecular mass of a substance impact the rate of diffusion?
A: Heavier molecules diffuse more slowly than lighter ones.
Q8: Provide an example of sublimation and describe how it is applied in real life.
A: Dry ice sublimates; it is used in fog machines and for cooling items.
Q9: Why do gases diffuse more quickly at higher temperatures?
A: Because gas particles move faster at higher temperatures.
Q10: What is the relationship between Avogadro’s law and the volume and number of moles of a gas?
A: Volume is directly proportional to the number of moles at constant temperature and pressure.
Long Questions
Q1: Explain the kinetic particle theory and describe how it accounts for the processes of melting, freezing, boiling, and condensation.
A: The kinetic particle theory explains that
- matter is made of constantly moving particles.
- During melting and boiling, particles gain energy and move more freely.
- During freezing and condensation, particles lose energy and become more ordered.
- Energy changes affect the arrangement and movement of particles, leading to phase changes.
Q2: Describe and interpret a cooling curve, emphasizing the importance of the flat sections on the graph.
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A: A cooling curve shows
- how a substance loses heat over time.
- Flat sections represent phase changes, like freezing or condensation.
- During these stages, temperature remains constant while particles lose energy.
- The curve helps visualize how matter transitions from one state to another and highlights the importance of energy exchange during phase changes.
Q3: Discuss how diffusion occurs in gases and explain the key factors—such as molecular mass and temperature—that influence its rate.
A:
- Diffusion in gases happens as particles spread out to fill available space.
- Lighter molecules diffuse faster than heavier ones.
- Higher temperatures increase particle speed, boosting diffusion rates.
- Factors like pressure and concentration gradient also influence diffusion.
- The kinetic energy of gas particles determines how quickly they move and mix.
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