CBSE Class 8 Science Pollution Chapter Notes

Scroll down for PDF

CBSE Class 8 Science Pollution Chapter Notes. Learning the important concepts is very important for every student to get better marks in examinations. The concepts should be clear which will help in faster learning. The attached concepts made as per NCERT and CBSE pattern will help the student to understand the chapter and score better marks in the examinations.

POLLUTION

class_8_science_concept_041

Human beings are dependent on the living and non-living components of environment for their survival. But, with the increase in population, human activities have led to deterioration of the quality of environment. For
e.g. :
• With increase in population, our living places have become congested and we face the problem of housing.
• More food is needed to feed the increasing population. So we cut forests to make space for the fields to grow crops.
• More and more industries, to manufacture useful products, are developed. These industries release harmful gases in the atmosphere and liquid wastes in water.
All these activities have led to the contamination of our physical environment, namely air, water and soil. As a result, (i) quality of air, water & soil has drastically gone down, and (ii) a large number of plant and animal species have disappeared. The contamination of our physical environment (air, water and soil) is called pollution, which is a serious problem these days.

Pollution :– Is an undesirable change in physical chemical or biological characteristic of air, water and land which is harmful to man directly or indirectly.
Pollutant :– Is a substance present in the environment in such a concentration that is harmful to the environment and living organisms.

Types of Pollutants

(i) Gaseous Pollutants : All pollutants which are in the gaseous state under normal conditions are called gaseous pollutants. e.g., Carbon monoxide, carbon dioxide, Oxides of Sulphur and Nitrogen, Chlorine gas etc.

(ii) Particulate Pollutants : Very small particles of solids and liquids suspended in the air are called particulates. Most particulates have particle size ranging from 0.1 micrometer to 10 micrometer. These particles create haziness in the atmosphere and cause air pollution. The inhalation of small particulates over longer periods may cause 'scarring' or 'fibrosis' of the lung lining leading to a disease called pneumoconiosis. Some common particulates present in the atmosphere (or air) are Dust, smoke, fumes, mist, fly ash, pesticides, insecticides, cement dust, asbestos dust, lead dust, pollen grains, bacteria, fungi, etc. Although the metallic particles are present in very low concentrations, some of them are very harmful to the living organisms.
The two metals which are extremely harmful to the human beings are lead and mercury.

(iii) Non-biodegradable Pollutants : The pollutants which are not broken down to simpler and harmless substances by the action of water, soil and/ or enzymes are called non-biodegradable pollutants. These are very serious pollutants. Substances such as metallic oxides : Particulates of mercury, lead, arsenic etc., insecticides, pesticides, DDT etc. are non-biodegradable pollutants.

(iv) Biodegradable Pollutants : These include the pollutants that can be rapidly decomposed by natural or by some artificial systems. Decomposition is naturally caused by micro-organisms. Examples of biodegradable pollutants are paper, cloth, wood, domestic sewage, faecal matter and agricultural residues.

How does a pollutant differ from a contaminant?

A contaminant is a substance which does not occur in nature, but is introduced in significant amounts into the environment by human activities. It may or may not be harmful to the living organisms and the environment. A contaminant which is harmful falls under the category of pollutant. One well-known example of a contaminant is that of Pyrosulphuric acid (H2S4O7) that had leaked from a defective tank in Delhi, leading to the death of many persons and causing skin and breathing problems to many others. As pyrosulphuric acid does not occur in the atmosphere, it is a contaminant. Further, as it
had dangerous effects, it is also a pollutant.

Threshold Limit Value (TLV) : The permissible limit of a pollutant in the atmosphere to which if a healthy worker is exposed for eight hours a day or 40 hours a week throughout his life and there is no adverse effect on him is called Threshold Limit Value (TLV). For example, TLV of carbon monoxide is 40 p.pm, while that of carbon dioxide is 5000 p.pm. On the other hand, for a poisonous gas like phosgene, TLC is 0.1 p.pm.

AIR POLLUTION
Degradation of air quality and natural atmospheric conditions constitutes air pollution. Air pollutants can be classified into two categories.

class_8_science_concept_040 

Please click the link below to download pdf file for CBSE Class 8 Science Pollution Chapter Notes.


Click on the text For more study material for Science please click here - Science

Latest NCERT & CBSE News

Read the latest news and announcements from NCERT and CBSE below. Important updates relating to your studies which will help you to keep yourself updated with latest happenings in school level education. Keep yourself updated with all latest news and also read articles from teachers which will help you to improve your studies, increase motivation level and promote faster learning

CBSE Board Secretary says Class 10 and 12 CBSE Exam Pattern to be modified

The Central Board of Secondary Education is expected to introduce a few changes to the exam pattern for class 10 and board exams by 2023. Anurag Tripathi, secretary of CBSE speaking at an Assoham School Education Summit said that although this year class 10 students...

TIPS: Study habits for success

Being a student is fairly a difficult job. Alongside maintaining your curricular as well as extra-curricular activities adds more to it. Performance in academics is one of the major concerns. Every parent now tries to get their children more indulged in studies. Need...

Extension of dates by CBSE for Single Girl Child Merit (SGC) scholarship

CBSE has announced to extend dates for SGC scholarship. Previously the dates to submit the SGC scholarship form were 18 October 2019. Now dates have shifted. For online submission, the last date is 31st October. Whereas date for submission of hard copies of renewal...

CBSE examination board hike the fee for class 10th and 12th

The CBSE (Central Board Secondary Education) increased the examination fees for classes 10 and 12 of the 2020 boards, with no profit no loss principle, from Rs. 750 to Rs 1500, for all categories of students, including SC/ST candidates for all schools throughout India...

Tips for exam preparation

Students often get nervous during their exams. The reason behind this nervousness is either a lack of confidence or a lack of preparedness. To overcome these fears students are advised to do their preparation in such a way that will retain their confidence. For this...

×
Studies Today