Class 4 Science - Our Environment - CBSE Worksheets Solutions - 1

Q1: Cross Puzzle

Use the clues to solve the crossword puzzle.
ACROSS
1. Fruit peels are Biodegradable waste.
2. Solid waste is called garbage.
3. Compost is a manure made from biodegradable waste.

DOWN
4. Biodegradable substances Rot and mix with the soil.
5. To Recycle means to make something useful from waste.

Q2: Name the following.

(i) A gas that absorbs harmful rays from the sun.
Ans: Ozone
The ozone layer is a thin part of the Earth's atmosphere that absorbs almost all of the sun's harmful ultraviolet light. "Ozone holes" are popular names for areas of damage to the ozone layer.

(ii) Things that rot and mix with the soil.
Ans: Biodegradable Waste
Wastes that rot by the action of decomposers are called biodegradable wastes. These wastes mix with the soil and produce manure. Some examples are dead plants and animals and their products.

(iii) Warming up of the atmosphere because of increasing carbon dioxide.
Ans: Global Warming
Global warming, the gradual heating of Earth's surface, oceans and atmosphere, is caused by human activity, primarily the burning of fossil fuels that pump carbon dioxide (CO₂), methane and other greenhouse gases into the atmosphere. 

Q3: True or False.

(i) If you use a plastic bag again and again you help reduce garbage.
Ans: True
Reduce your use of disposable shopping bags by using a reusable bag or container when shopping.

(ii) A safe way to dispose of garbage is to burn it.
Ans: False
In many cases, the garbage can or recycling bin is the best option.

(iii) Non-biodegradable waste does not rot.
Ans: True
Plastic is a non-biodegradable waste, as it does not rot by the action of decomposers

(iv) Water pollution leads to melting of ice at the poles and flooding of coastal areas.
Ans: True

Q4: Fill in the blanks.

(i) Drinking polluted water can cause diseases such as _____ and _____.
Ans: cholera, diarrhoea
Contaminated water and poor sanitation are linked to transmission of diseases such as cholera, diarrhoea, dysentery, hepatitis A, typhoid, and polio.

(ii) Harmful substances in the air, water and soil are called _____.
Ans: pollutants
These harmful materials are called pollutants. Pollutants can be natural, such as volcanic ash. They can also be created by human activity, such as trash or runoff produced by factories. Pollutants damage the quality of air, water, and land.

(iii) Getting regular vehicle pollution reduces _____ pollution.
Ans: air

(iv) Trees and plants help to clean the _____ by producing oxygen.
Ans: air
Trees and plants play a crucial role in cleaning the air by taking in carbon dioxide and releasing oxygen through the process of photosynthesis.

(v) Recycling materials like paper, plastic, and glass helps to reduce _____ waste.
Ans: landfill
Recycling materials helps reduce the amount of waste that ends up in landfills, conserving natural resources and reducing pollution.

Q5: Answer the following questions in brief.

(i) What is recycling? Name three materials that can be recycled.
Ans: Recycling is defined as a process of converting waste and non-useful products into new and useful products for human use. Recycling is an excellent and cost-efficient system of conserving the environment and saving energy. Recyclable materials include many kinds of glass, paper, cardboard, metal, plastic, tires, textiles, batteries, and electronics.

(ii) What harm do plastic bags cause if thrown in a drain?
Ans: When plastic enters the drainage and sewerage system, they block the pipes and the drains causing waterlogging. The improperly disposed of food bags, when eaten by animals, cause stomach and intestine related disease which even lead to suffocation and death.

(iii) List the causes of land pollution.
Ans: Causes of land pollution are: 

• Deforestation and Soil Erosion. Deforestation carried out to create drylands is one of the major concerns.
• Agricultural Activities. 
• Mining Activities. 
• Overcrowded Landfills.

(iv) Explain how global warming occurs.
Ans: Global warming refers to the general increase in the earth's average temperature, which causes changes in climate patterns across the globe. Greenhouse gases are in the atmosphere, absorbing and holding heat, which causes earth's temperature to rise.

Q6:Multiple Choice Questions (MCQs).

(i) Acid rain is caused by
(a) air pollution
(b) water pollution
(c) soil pollution
(d) neither of these
Ans: (a)
Acid rain is caused by a chemical reaction that begins when compounds like sulfur dioxide and nitrogen oxides are released into the air. These substances can rise very high into the atmosphere, where they mix and react with water, oxygen, and other chemicals to form more acidic pollutants, known as acid rain.

(ii) Our environment consists of
(a) living things only
(b) non-living things only
(c) both living and non-living things
(d) neither living nor non-living things
Ans: (c)
An environment includes living things such as plants, animals, people, and even the tiniest of microbes. The living portions of the environment are called the biotic parts. The nonliving portions, such as rocks, sunlight, and air, are called the abiotic parts.

(iii) Which of these causes soil pollution?
(a) Garbage
(b) Smoke
(c) Cutting trees
(d) All of these
Ans: (d)
Illegal dumping of the solid wastes, polluted water absorbed by the soil, use of chemical fertilizers and pesticides, dumping of minerals, oils, and radioactive wastes are the major causes of soil pollution.

(iv) This is a gas which protects us from the ultra violet rays of the sun.
(a) Oxygen
(b) Ozone
(c) Methane
(d) Carbon dioxide
Ans: (b)
Ozone in the stratosphere protects life on Earth from harmful ultraviolet (UV) radiation and is therefore often called 'good' ozone. This in contrast to ozone in the troposphere, the lowest layer of the atmosphere, where it is an air pollutant and can be harmful to humans, animals and vegetation.