Q1.TemperatureEasy · 1m
Convert 25 °C into kelvin.
Answer: K = °C + 273 = 25 + 273 = 298 K.
Class 9 · Science · Important Questions
Matter in Our Surroundings — Important Questions
Q2.CharacteristicsEasy · 2m
State any two characteristics of the particles of matter.
Answer: Particles of matter have space between them and are continuously moving; they also attract each other.
Q3.StatesEasy · 2m
Why do gases have neither a fixed shape nor a fixed volume?
Answer: The force of attraction between gas particles is very weak and the spaces between them are large, so they move freely and fill the whole container.
Q4.SublimationMedium · 2m
What is sublimation? Give one example.
Answer: The change of a solid directly into a gas without becoming a liquid, for example camphor or dry ice.
Q5.EvaporationMedium · 3m
Why does evaporation cause cooling?
Answer: During evaporation the fastest particles escape from the surface, taking energy with them. The remaining liquid loses energy, so its temperature falls and we feel cooling.
More for this chapter
NCERT Solutions
Step-by-step chapter solutions
Revision Notes
Quick notes & key points
Formula Sheets
All formulas in one place
Search this topic
All content related to “Matter in Our Surroundings”