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Practice Class 9 Science Chapter 1 Matter in Our Surroundings MCQ Questions with Answers based on the latest NCERT syllabus. Solve important MCQs on cooling effect of evaporation, Kelvin scale, humidity, liquefaction of gases, and dry ice with detailed solutions for CBSE, State Board, Olympiad, and scholarship exams.
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Chapter Information
Subject: Science
Class: 9
Chapter: Matter in Our Surroundings
Question Type: Multiple Choice Questions (MCQs)
Difficulty Level: Easy to Moderate
Based On: NCERT Latest Syllabus (2026)
Introduction
Matter changes its state when temperature or pressure changes. Concepts such as evaporation, humidity, Kelvin temperature scale, and liquefaction of gases help us understand many natural and industrial processes that occur around us every day.
What You Will Learn
✔ Cooling effect of evaporation
✔ Kelvin temperature scale
✔ Humidity and evaporation
✔ Liquefaction of gases
✔ Dry ice
✔ Change of state of matter
✔ NCERT-based concepts
Why This Topic Is Important?
Questions based on evaporation, humidity, and temperature scales are frequently asked in school examinations and competitive tests. Understanding these concepts also helps students relate science to everyday life.
1. MCQ Questions with Detailed Solutions
Q1. Why do we feel cool when sweat evaporates from our skin?
A) Sweat increases body temperature
B) Evaporation absorbs heat from the body
C) Sweat produces cold air
D) Water releases heat during evaporation
Answer
B) Evaporation absorbs heat from the body
Concept Behind This Question
Evaporation requires energy, which is taken from the surroundings.
Step-by-Step Solution
- Sweat absorbs heat from the skin.
- It uses this heat to evaporate.
- As heat is removed from the body, we feel cool.
Therefore, the correct answer is:
Evaporation absorbs heat from the body
Exam Tip
Cooling effect is one of the most important applications of evaporation.
Q2. What is the Kelvin temperature corresponding to 25°C?
A) 248 K
B) 273 K
C) 298 K
D) 325 K
Answer
C) 298 K
Concept Behind This Question
Kelvin temperature is obtained by adding 273 to Celsius temperature.
Step-by-Step Solution
Formula:
K = °C + 273
25 + 273 = 298
Therefore, the correct answer is:
298 K
Exam Tip
Remember the simple conversion: K = °C + 273.
Q3. On a humid day, clothes dry slowly because:
A) Temperature is very high
B) Air already contains a large amount of water vapour
C) Wind speed is high
D) Evaporation stops completely
Answer
B) Air already contains a large amount of water vapour
Concept Behind This Question
Humidity reduces the rate of evaporation.
Step-by-Step Solution
- Humid air already contains water vapour.
- Less water can evaporate into the air.
- Therefore, drying becomes slower.
Exam Tip
Higher humidity means slower evaporation.
Q4. Which process is used to convert gases into liquids?
A) Sublimation
B) Condensation only
C) Applying high pressure and lowering temperature
D) Melting
Answer
C) Applying high pressure and lowering temperature
Concept Behind This Question
Gases can be liquefied by changing temperature and pressure.
Step-by-Step Solution
- Gas particles are far apart.
- High pressure brings particles closer.
- Low temperature reduces kinetic energy.
- Together they convert gas into liquid.
Exam Tip
LPG and liquid oxygen are stored using this principle.
Q5. What is the common name of solid carbon dioxide?
A) Ice
B) Snow
C) Dry Ice
D) Frost
Answer
C) Dry Ice
Concept Behind This Question
Carbon dioxide can exist as a solid at low temperatures.
Step-by-Step Solution
- Solid CO₂ is called dry ice.
- It changes directly into gas without becoming liquid.
- This process is sublimation.
Therefore, the correct answer is:
Dry Ice
Exam Tip
Dry ice is commonly used for cooling and preservation.
Important Formulas & Concepts
1. Kelvin Scale
K = °C + 273
2. Cooling Effect of Evaporation
Evaporation absorbs heat from surroundings and produces cooling.
3. Humidity
The amount of water vapour present in air.
4. Liquefaction of Gases
Conversion of gases into liquids by increasing pressure and decreasing temperature.
5. Dry Ice
Solid carbon dioxide (CO₂).
Related Practice Questions
- Why does sweating cool our body?
- Convert 30°C into Kelvin.
- What is humidity?
- How are gases liquefied?
- What is dry ice?
Mini Quiz Challenge
Fill in the blanks
- Kelvin = Celsius + __________.
- Humidity decreases the rate of __________.
- Solid carbon dioxide is called __________.
Answers
- 273
- Evaporation
- Dry Ice
Exam Tips
✔ Learn Celsius to Kelvin conversion.
✔ Understand factors affecting evaporation.
✔ Revise humidity and its effects.
✔ Remember applications of liquefaction of gases.
✔ Learn examples of sublimation and dry ice.
Quick Revision Notes
✔ Evaporation causes cooling.
✔ Sweat cools the body through evaporation.
✔ K = °C + 273.
✔ Humidity slows down evaporation.
✔ Gases can be liquefied by pressure and cooling.
✔ Dry ice is solid carbon dioxide.
✔ Dry ice undergoes sublimation.
Common Mistakes Students Make
❌ Forgetting to add 273 while converting Celsius to Kelvin.
❌ Confusing humidity with temperature.
❌ Assuming evaporation releases heat.
❌ Mixing dry ice with ordinary ice.
❌ Forgetting the conditions required for liquefaction of gases.
Key Takeaways
✔ Evaporation absorbs heat and causes cooling.
✔ Kelvin scale is widely used in science.
✔ Humidity reduces evaporation rate.
✔ Gases can be converted into liquids by cooling and compression.
✔ Dry ice is solid carbon dioxide.
✔ These concepts explain many everyday observations.
FAQs
1. Why does evaporation cause cooling?
Because it absorbs heat from the surroundings.
2. How do you convert Celsius into Kelvin?
Add 273 to the Celsius temperature.
3. What is humidity?
The amount of water vapour present in air.
4. What is dry ice?
Solid carbon dioxide.
5. How are gases liquefied?
By increasing pressure and lowering temperature.
Conclusion
The study of evaporation, humidity, temperature scales, and liquefaction of gases helps us understand important scientific and real-life phenomena. These concepts form an essential part of the foundation of chemistry and are frequently tested in examinations.
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