In this post, you will learn about NCERT
class 10 science activity solutions chapter 15. You will find all the activities
of the chapter Our Environment.
Explain NCERT Class 10 Science Activity Solutions Chapter 15
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Activity 15.1 Class 10 Science Explanation
Activity –
According to this activity you should collect waste material from your house.
This could include all the waste generated during a day, like kitchen waste
(spoilt food, vegetable, peels, used tea leaves, milk packets, and empty
cartons), waste paper, empty medicine bottles/strips/bubbles packs, old and
torn clothes and broken footwear.
Procedure/method-
You will have to bury this material in a
pit in the school garden or if there is no space available, you can collect the
materials in an old bucket/flower pot and cover them with at least 15 cm of soil. Keep this material moist and observe at 15 days intervals.
Discussion
– The household waste material consists of some amount of biodegradable and non-biodegradable
waste. So you should observe after 15 days intervals.
Observation
– After 15 days intervals, you will find that some materials like spoilt food,
leaves, vegetable peels, etc have been decomposed by microbes and fungi.
There are good conditions for the growth of
microbes, fungi, and anaerobic bacteria due to moisture and warmth. So after 15
days, all the organic matter gets decomposed.
On the other hand, clothes cardboards, etc
get decomposed after three months but plastic bags, bottles remain unchanged.
Conclusion
- The activity shows that organic matter is biodegradable
and gets decomposed but the inorganic matter remains unchanged.
Now you can answer the following questions
-
Q1. What are the materials that remain
unchanged over long periods of time?
Ans. Plastic packs, glass, bottles, medicine
strips, cans, etc. are non-biodegradable so they remain unchanged over long
periods of time.
Q2. What are the materials which change
their form and structure over time?
Ans. – Vegetable peels, spoilt food, waste
paper, tea leaves, cardboards are biodegradable and get changed over time.
Q3.Of these materials that are changed,
which ones change that fastest?
Ans. Spoilt food, vegetable peels, change
quickly because they are easily decomposed by microbes.
Activity 15.2 Class 10 Science Explanation
Activity -
Use the library or internet to find out more about biodegradable and non-biodegradable
substances.
How long are various non-biodegradable
substances expected to lose in our environment?
These days, new types of plastics that are
said to be biodegradable are available. Find out more about such materials and
whether they do or do not harm the environment.
Procedure/method
– To perform this activity, you will have to the library or use the internet.
Discussion
Biodegradable waste can be used to produce
biogas and manures. The biogas can be used to generate electricity. Electricity
can also be generated from landfill sites. In the future, waste-to-energy incineration
plants are likely to become the main method of waste disposal.
Some non-biodegradable waste and the time
in their removal from the environment are given here:
Article Time taken in decay
Steel can 100 years
Aluminium Cans 350 year
Plastic
bags 400 years
Plastic rings 450 years
Car tyre Never
Glass bottle Never
Banana peels 2 months
Paper 3 months
Cardboard 5 months
Conclusion
– From the above table we can say the different materials – biodegradable and
non – biodegradable get decomposed in different time intervals.
Among biodegradable substances, a banana
peel may take 2 months, notebook paper 3 months, cardboard container of milk 5
months for their complete decomposition.
Biodegradable Plastic:
Biodegradable plastics are those plastics that can be decomposed by microbes.
Two types of bioplastics are made. One
from renewable substances and the other from petrochemicals with biodegradable
activity.
Activity 15.3 Class 10 Science Explanation
Activity
- You might have seen an aquarium. Let us try to design one.
What are the things that we need to keep
in mind when we create an aquarium? The fishes would need free space for
swimming (it could be a large jar), water, oxygen, and food.
Procedure/method
–
An aquarium is a small man-made aquatic
ecosystem. We need the following materials are required for making an aquarium –
i.
a rectangular glass box
(jar) with lid
ii.
pebbles to form the bottom of the aquarium
iii.
clean water
iv.
provision for aeration (an oxygen/air pump)
v.
fishes, fish food,
aquatic plants
Discussion –
·
We should keep one thing
in mind the aquarium should be large enough so that fish move freely in the water.
·
Clean water should be
taken for aquarium.
·
To continuously aerate
the water a good quality air pump should be used, as fish use oxygen dissolved
in water.
·
Only herbivorous fish
should be kept in an aquarium (a fish which feeds on readymade fish feed).
Predator fish should not be taken in an aquarium.
·
The temperature of the
water should be normal, neither cold nor too hot.
·
Regular food supply
should be ensured.
In the aquarium, we should keep a few aquatic
plants that can be used. These green plants will make their food as well as oxygen
in the process of photosynthesis.
In this way, an aerator would not be
required or its work can be minimized. The carbon dioxide produced by fish will
be used by the green plants in the process of photosynthesis. The fish must be
able to eat the plant material if aquatic plants are used in an aquarium.
Cleaning the aquarium on a periodical basis
is essential. The scales of fish, their excreta, dead remains of plants all get
accumulated in the water. This would change the concentration of the water of the aquarium, which may be injurious to the fish. Therefore, periodical cleaning of
aquariums is essential. This organic matter may serve as a potential source of
infection for fishes.
In natural ponds and lakes, this cleaning
is not required because there are a large number of decomposers (bacteria and
fungi). They decompose and mineralize the organic material accumulated in pond
water. Rainwater also dilutes the pond water periodically. There is a recycling
of material.
Activity 15.4 Class 10 Science Explanation
Activity
- While creating an aquarium did you take care not to put an aquatic animal that
would eat others?
What would have happened otherwise?
Make groups and discuss how each of the
above groups of organisms is dependent on each other.
Write the aquatic organism in order of who
eats whom and form a chain of at least three steps.
Would you consider any one group of
organisms to be of primary importance? Why or why not?
Discussion
Yes, When we create an aquarium, it must be kept in mind and no predator fish or any other
animal should be taken in the aquarium which
could eat others. If such predator animals are used they will have eaten up all small fish in the aquarium.
This mistake would have spoiled the very
aim of making an aquarium.
In an aquarium, the green plants act as
producers. They capture light energy and convert it into the chemical energy of
food. Herbivores feed on plants. So the energy made by plants is transferred to
herbivores. A linear relationship between eating and being eaten is found in a pond
ecosystem.
.webp "Activity 15.4 Class 10 Science Explanation")
In such a relationship, the green plants or
producers are of primary importance, because only the green plants have the
ability to capture the energy of the sun and transform it into chemical energy. All
organisms (herbivores, carnivores, and decomposers depend on plants directly or
indirectly for their food).
Activity 15.5 Class 10
Science Explanation
Activity - Newspaper reports about pesticides levels in readymade food items are often seen these days and some states have banned these products. Debate in groups the need for such bans.
What do you think would be the source of
pesticides in these food items? Could pesticides get into our bodies from this
source or through other food products also?
Discuss what methods could be applied to
reduce our intake of pesticides?
Discussion-
Yes, we often read many reports, based on experimental evidence about the presence of pesticides in many food
items. These pesticides reach the human body through the growth and
development process of human being adverse.
In many birds including vultures, kites' egg production is affected. The eggs become
very much fragile and break easily. Due to this population is at risk of
extinction. These chemicals cause many diseases in human beings also. Therefore,
food items having pesticide residue must be banned immediately.
These pesticides might have reached the
food item through the raw material used for making this item. In raw food
material, these chemicals enter by the process of biological magnification.
They might have entered in food items at a later stage also during spraying of
pesticides.
Pesticides may enter our body through other sources also. For
example, by eating unwashed fruits and vegetables, consuming packed food only, consuming food items grown by using synthetic chemicals, by inhalation of
polluted air, etc.
We can reduce the intake of pesticides by following steps -
i. by consuming organic food only.
ii. Food prepared from items grown by using organic manures and biopesticides).
iii. Don’t use packed food items and eat fresh fruits and vegetables.
iv. Wash the fruit and vegetable thoroughly in water before eating them raw.
v. By reducing the production of chemical pesticides and switching over to organic farming.
Activity 15.6 Class 10 Science Explanation
Activity
-Find out from the library, internet or newspaper reports, which chemicals are
responsible for the depletion of the ozone layers.
Find out if the regulations put in place
to control the emission of these chemicals have succeeded in reducing the
damage to the ozone layer. Has the size of the hole in the ozone layer changed in recent years?
Procedure/ method – We should read newspaper
reports or find from the library or internet
Discussion -
After reading newspapers reports, libraries, or the internet, we find that CFCs are the most serious ozone-depleting substance.
The best-known CFC is freon. These chemicals release chlorine into the atmosphere.
In the stratosphere chlorine atoms (Cl)
combine with ozone and form chlorine monoxide (ClO). This ClO also breaks down
ozone before releasing the same chlorine atom once again. One atom of chlorine can destroy up to 1,00,000 molecules of ozone before setting to the Earth’s surface as chloride
years later.
Methyl chloroform which is used as a cleaning solvent is also a source of harmful chlorine atoms. Therefore,
chlorine pollution is mainly responsible for ozone depletion.
Most of the countries of the world have
stopped using CFCs. UNEP finalized an agreement to reduce CFC in 1987. That was the Montreal Protocol in 1987(Effective in 1989) the U.S. did not agree and agreed to
reduce the emission of CFCs since 1995 only.
Since then many more efforts have been
made like Kyoto Protocol.
NASA reports of 2013 say that hole over Antarctica has reduced in size.
Activity 15.7 Class 10 Science Explanation
Activity
- Find out what happens to the waste generated at home? Is there a system in
place to collect this waste?
Find out how the local body (Panchayat,
municipal corporation, resident welfare association) deals with the waste. Are
there mechanisms in place to treat biodegradable and non-biodegradable
waste separately?
Discussion-
A lot of waste material is generated at home
and it is collected in a dustbin. This is collected every day by employees of the municipal corporations.
There are other collection centers as well
where household waste can be dumped. The municipal employee also dump the
collected waste here.
From there the trawlers of municipal
corporations collect the waste and dump it in the outskirt of the city. Rag pickers
separate the materials which can be recycled, like paper, plastic, metal, etc.,
at every stage.
From there the waste is treated in various
ways. Some of the waste is recycled, while the other is dumped in a trench
after compaction and covered with mud every day. These are called sanitary
landfills. This is also not a solution to the huge problem of garbage
treatment.
Categorization of waste into biodegradable
recyclable and non-biodegradable at its generation point only because it can be
done there easily. This is not being done at most places. The liquid
waste (sewage) is treated in sewage treatment plants.
Activity 15.8 Class 10 Science Explanation
Activity-
Calculate how much waste is generated at home in a day.
How much of this waste is biodegradable?
Calculate how much waste is generated in
the classroom in a day.
Suggest ways of dealing with this waste.
.webp "Activity 15.8 Class 10 Science Explanation")
Discussion-
1. We
generate a lot of waste at home. After observing, we find that on average
about 1 kg to 1.5 Kg solid waste is generated at home in a day. It includes
kitchen waste, (like vegetable and fruit peel, used tea leaves, empty milk
packets), waste paper, cardboard, polythene, packets, and wrappers of different
items. dust etc.
2. Approximately
half(about 500- 700g) of it is
biodegradable.
3. In the classroom about 100 gm of waste is generated in the form of waste paper, pencil
sharpening, refill of pen, chalk dust etc. Almost all of it is biodegradable
except refill which is made of plastic.
4. At home as well as in schools there should be 3
types of dustbins:
(a) Dustbin for biodegradable waste.
(b) Dustbin for recyclable waste.
(c) Dustbin for non-biodegradable waste.
Wastes from different homes should be piled at a place and from there it should be
sent to a place for its proper disposal/recycling etc.
Activity 15.9 Class 10 Science Explanation
Activity-
Find out how the sewage in your locality is treated. Are these mechanisms in
place to ensure that local water bodies are not polluted by untreated sewage?
Find out how the local industries in your
locality treat their waste. Are these mechanisms in place to ensure that soil
and water are not polluted by this waste?
Discussion
–
In our locality, sewage is collected by underground pipelines.
These pipelines make it to the sewage treatment plants. In a sewage treatment plant
the sewage is treated in the following
steps:
Physical treatment: Sewage is filtered by wire mats so that larger and solid hard impurities are
separated. Floating wastes are separated by allowing the water to stand still
for some time.
Biological treatment:
There are two parts of it-
(i)Aerobic treatment: At first, the sewage
is aerated in large open tanks where aerobic bacteria use its organic material
to make if free from organic impurities.
(ii)Anaerobic treatment: Now remaining
organic matter is removed by the treatment with anaerobic bacteria. Anaerobic
digestion is done in a large digester. The sludge (solid) left after anaerobic
degradation by bacteria may be used as manure. This treatment produces biogas as
well.
Many untreated sewage pipelines are directly
released in river water also.
Chemical treatment: water becomes pure enough after the two
above stages but to make it cleaner,
it is sometimes treated with chemicals, like chlorine.
Industries in our area dump their waste in
nearby areas, Soil and water both are polluted by them This waste should not be
dumped into soil and water before its proper treatment.
Activity 15.10 Class 10 Science Explanation
Activity
- Search the internet or library to find out what hazardous materials have to
be dealt with while disposing of electronic items. How would these materials
affect the environment?
Find out how plastics are recycled? Does
the recycling process have any impact on the environment?
Discussion-
Disposal of computers and other electronic
goods are known as electronics wastes or e-wastes. In developed countries, they
are either incinerated or buried in landfills. Over half of the e-waste generated
in developed countries is exported to countries, like copper, iron, silicon,
gold, nickel, etc. These are recovered during the recycling process. Heavy metals
need serious attention.
In Bangalore, to deal with the ever-increasing
amount of plastic waste Polyblend (a fine powder of recycled modified plastic)
has been developed. This mixture is mixed with the bitumen that is used to lay
roads.
Plastic can be recycled and inferior
quality of plastic can be made from it.
Recycle processes also have a bad impact on the environment. This process causes air, water pollution
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