Welcome To My School Study
Practice Class 8 Science MCQs on greenhouse effect, ozone layer depletion, potable water, Ganga Action Plan, and Van Mahotsav with detailed explanations, NCERT points, memory tricks, FAQs, and revision notes.
Do You Know
Introduction
Environmental conservation is one of the most important topics in Class 8 Science. Students learn about pollution, greenhouse gases, global warming, ozone layer depletion, water conservation, and afforestation. These concepts help us understand how human activities affect the environment and what measures can be taken to protect natural resources.
Questions related to greenhouse gases, potable water, Ganga Action Plan, and Van Mahotsav are frequently asked in school examinations, Olympiads, and competitive exams. Understanding these topics not only helps in scoring better marks but also creates awareness about environmental protection.
This MCQ quiz provides detailed explanations, real-life examples, important NCERT concepts, memory tricks, and revision notes to make learning easier and more effective.
Q1. Which gas is responsible for the ‘Greenhouse Effect’?
Correct Answer: All of the above
Detailed Explanation:
The greenhouse effect is a natural process that helps maintain the Earth’s temperature and makes life possible. Certain gases present in the atmosphere trap a portion of the heat radiated by the Earth and prevent it from escaping completely into space. These gases are called greenhouse gases.
The major greenhouse gases include carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O), and water vapour. Among these, carbon dioxide is the most widely discussed because large amounts are released through burning fossil fuels such as coal, petrol, and diesel. Methane is produced from wetlands, livestock farming, rice cultivation, and decomposition of organic matter. Nitrous oxide is released from fertilizers and industrial activities.
Without the greenhouse effect, Earth’s average temperature would be much lower, making life difficult. However, excessive greenhouse gases increase heat trapping, leading to global warming and climate change. Rising global temperatures can result in melting glaciers, rising sea levels, extreme weather events, droughts, and disturbances in ecosystems.
Human activities have significantly increased greenhouse gas concentrations during the last century. Industries, vehicles, deforestation, and excessive energy consumption contribute to this increase. Therefore, reducing pollution, planting trees, and using renewable energy sources are important measures to control global warming.
The greenhouse effect is a frequently asked NCERT topic because it connects environmental science, climate change, and sustainable development.
Real-Life Examples:
- Smoke from factories increases carbon dioxide levels.
- Vehicles release greenhouse gases into the atmosphere.
- Large-scale deforestation reduces carbon dioxide absorption.
Important NCERT Points:
- Greenhouse gases trap heat in the atmosphere.
- Carbon dioxide, methane, and nitrous oxide contribute to the greenhouse effect.
- Excess greenhouse gases cause global warming.
- Trees help absorb carbon dioxide.
Why Other Options Are Wrong:
- A) Methane contributes but is not the only greenhouse gas.
- B) Carbon dioxide contributes but is not alone responsible.
- C) Nitrous oxide contributes but is not the only factor.
- D) Correct because all listed gases contribute.
Exam-Oriented Fact:
Carbon dioxide is considered the major greenhouse gas produced by human activities.
Memory Trick:
“CMN = Climate Making Network”
C = Carbon dioxide
M = Methane
N = Nitrous oxide
Quick Revision Line:
Several gases including CO₂, methane, and nitrous oxide together cause the greenhouse effect.
Related Questions:
- What is global warming?
- Name two greenhouse gases.
- How does deforestation increase global warming?
Q2. The depletion of the Ozone layer is mainly due to?
Correct Answer: CFCs (Chlorofluorocarbons)
Detailed Explanation:
The ozone layer is a protective layer located in the stratosphere of the Earth’s atmosphere. It absorbs most of the harmful ultraviolet (UV) radiation coming from the Sun and protects living organisms from its damaging effects.
Chlorofluorocarbons (CFCs) are synthetic chemicals that were widely used in refrigerators, air conditioners, aerosol sprays, and foam manufacturing. When released into the atmosphere, CFC molecules slowly rise to the stratosphere. There, ultraviolet radiation breaks them down and releases chlorine atoms.
A single chlorine atom can destroy thousands of ozone molecules through a chain reaction. As a result, the ozone layer becomes thinner, creating what is commonly called the “ozone hole.” A thinner ozone layer allows more harmful UV radiation to reach Earth’s surface.
Excessive UV exposure can cause skin cancer, cataracts, weakened immune systems, and damage to plants and marine life. Recognizing this threat, countries around the world agreed to reduce the use of CFCs through international environmental agreements.
Today, many industries use ozone-friendly alternatives instead of CFCs. This has helped slow down ozone depletion and has allowed gradual recovery of the ozone layer in several regions.
Real-Life Examples:
- Old refrigerators often contained CFCs.
- Aerosol spray cans previously used CFC propellants.
- Modern cooling systems use safer alternatives.
Important NCERT Points:
- Ozone absorbs harmful UV rays.
- CFCs damage ozone molecules.
- Ozone depletion increases UV exposure.
- International efforts reduced CFC usage.
Why Other Options Are Wrong:
- A) CO₂ mainly causes global warming.
- C) Methane contributes to greenhouse effect.
- D) Oxygen helps form ozone rather than destroy it.
Exam-Oriented Fact:
CFCs are considered the primary cause of ozone layer depletion.
Memory Trick:
“CFC = Cuts Friendly Cover”
(CFC damages Earth’s protective ozone cover.)
Quick Revision Line:
CFCs are the major chemicals responsible for ozone layer depletion.
Related Questions:
- What is the function of the ozone layer?
- What are ultraviolet rays?
- Why was CFC use reduced globally?
Q3. Water which is suitable for drinking is called?
Correct Answer: Potable Water
Detailed Explanation:
Potable water is water that is safe and suitable for human consumption. It should be free from harmful microorganisms, toxic chemicals, and excessive impurities that may cause diseases.
Although water appears clear, it may contain bacteria, viruses, parasites, or harmful dissolved substances. Therefore, water intended for drinking must undergo purification processes such as filtration, sedimentation, chlorination, and boiling.
Access to potable water is essential for maintaining good health. Drinking contaminated water can lead to diseases such as cholera, typhoid, dysentery, and diarrhea. Public health systems focus on ensuring a regular supply of safe drinking water to communities.
Many rural and urban water treatment plants remove contaminants before supplying water to households. People can further improve water safety by boiling water or using domestic purification systems.
Clean drinking water is one of the most valuable natural resources and plays a major role in public health and development.
Real-Life Examples:
- Filtered tap water.
- Water purified through RO systems.
- Boiled drinking water.
Important NCERT Points:
- Potable water is safe for drinking.
- It should be free from harmful germs.
- Water treatment improves water quality.
- Safe drinking water prevents diseases.
Why Other Options Are Wrong:
- A) Distilled water is highly purified but not the general term.
- C) Pure water may not always indicate drinking suitability.
- D) Sparkling water contains dissolved gases.
Exam-Oriented Fact:
Potable water means water that is safe for drinking purposes.
Memory Trick:
“Potable = Possible To Drink”
Quick Revision Line:
Potable water is clean and safe drinking water.
Related Questions:
- Why should drinking water be purified?
- What causes waterborne diseases?
- How is water treated before supply?
Q4. Ganga Action Plan was launched in?
Correct Answer: 1985
Detailed Explanation:
The Ganga Action Plan (GAP) was launched by the Government of India in 1985 to reduce pollution in the River Ganga and improve water quality. The river is one of India’s most important rivers and supports millions of people for drinking, irrigation, agriculture, transportation, and religious activities.
The main objective of the plan was to control the discharge of untreated sewage, industrial waste, and pollutants into the river. Various sewage treatment plants, drainage improvement projects, and public awareness programs were introduced under the scheme.
The program highlighted the importance of river conservation and inspired several future environmental protection projects in India.
Real-Life Examples:
- Installation of sewage treatment plants.
- River cleaning campaigns.
- Public awareness drives for pollution control.
Important NCERT Points:
- Started in 1985.
- Focused on reducing Ganga pollution.
- Encouraged water conservation.
- Improved environmental awareness.
Why Other Options Are Wrong:
- 1980, 1990, and 2000 are not the launch years.
Exam-Oriented Fact:
The Ganga Action Plan was India’s first major river-cleaning program.
Memory Trick:
“GAP = Ganga Action Plan = 85”
Quick Revision Line:
Ganga Action Plan was launched in 1985 to clean the River Ganga.
Related Questions:
- Why is the Ganga important?
- What are sources of river pollution?
Q5. Van Mahotsav is celebrated in which month?
Correct Answer: July
Detailed Explanation:
Van Mahotsav is a tree-planting festival celebrated every year in July across India. The festival was started to encourage people to plant trees and increase awareness about environmental conservation.
Trees provide oxygen, absorb carbon dioxide, prevent soil erosion, support biodiversity, and help regulate climate. Rapid urbanization and deforestation have reduced forest cover in many regions, making tree plantation programs increasingly important.
During Van Mahotsav, schools, colleges, government organizations, and local communities organize plantation drives. Students actively participate in planting saplings and learning about environmental protection.
The festival promotes sustainable development and encourages citizens to take responsibility for preserving natural resources.
Real-Life Examples:
- School plantation drives.
- Community tree-planting campaigns.
- Forest conservation awareness programs.
Important NCERT Points:
- Celebrated every year in July.
- Promotes tree plantation.
- Helps environmental conservation.
- Encourages public participation.
Why Other Options Are Wrong:
- January, October, and December are not the months of celebration.
Exam-Oriented Fact:
Van Mahotsav is known as India’s annual tree-planting festival.
Memory Trick:
“Van Mahotsav = Monsoon + July = Tree Plantation Time”
Quick Revision Line:
Van Mahotsav is celebrated in July to promote tree plantation and environmental awareness.
Final Revision Notes
- Greenhouse effect is caused by gases like CO₂, methane, and nitrous oxide.
- CFCs are the main cause of ozone layer depletion.
- Potable water is safe drinking water.
- Ganga Action Plan was launched in 1985.
- Van Mahotsav is celebrated every July.
FAQ Section
Q1. What is the greenhouse effect?
It is the trapping of heat by greenhouse gases in Earth’s atmosphere.
Q2. Which chemical mainly damages the ozone layer?
Chlorofluorocarbons (CFCs).
Q3. What is potable water?
Water that is safe and suitable for drinking.
Q4. Why was the Ganga Action Plan started?
To reduce pollution and improve the water quality of the River Ganga.
Q5. Why is Van Mahotsav celebrated?
To encourage tree plantation and environmental conservation.
Related links
- Class 8 Science: Stars, Planets and Solar System
- Class 8 Science MCQ Quiz: Light, Human Eye & Multiple Reflections
- Class 8 Science MCQ Quiz: Some Natural Phenomena
- Class 8 Science MCQ Quiz: Reproduction & Hormones
- Class 8 MCQ Questions Answers – History, Civics, Geography
- Class 8 MCQ Questions with Answers– History, Civics, Geography
Latest Posts
- NCERT Class 7 Maths Chapter 1 Integers,addition, subtraction
- Class 10 Maths Chapter-1 Real Numbers-Rational numbers-MCQ
- Class9 Maths- Number Systems, decimal expansion, exponents
- Class 8 Maths Chapter 1 Rational Numbers, multiplicative
- Class 10 Maths Chapter 1 Real Numbers MCQ Questions with Solutions
Join Our Other Communities
Instagram , Youtube , Facebook
