48 short questions of 9th Class Chemistry Chapter 10, Environmental Chemistry, with exam-ready answers in the book's words: the textbook exercise questions plus SLO-based questions asked in board papers. Punjab Board new syllabus.
Exam-ready answers. Learn the meaning, then write them in your own words.
The short questions at the end of the chapter in your book.
The objective of environmental education is to enlighten the people, particularly students, about the importance of protection and conservation of our environment. It teaches how pollutants harm living and non-living things, and what each person can do to reduce pollution. The need for it, both formal and non-formal, is keenly felt at the national level.
Carbon monoxide (CO) is far more poisonous. It is an extremely toxic gas that stops red blood cells from carrying the oxygen the body needs, causing suffocation and death even in small amounts; it has no colour or smell. CO₂ is not poisonous at normal levels (we breathe it out); it is harmful as a greenhouse gas.
Acid rain makes the soil more acidic, dissolves and washes away the nutrients plants need, and dissolves toxic aluminium and mercury. Trees weaken, lose leaves and die. Tree roots hold the soil on hills and mountains; when trees are destroyed the soil is washed away and new plants cannot grow.
When coal and oil burn, the sulphur in them forms sulphur dioxide: S + O₂ → SO₂. SO₂ irritates the eyes and causes breathing difficulties. In the air it is oxidised to SO₃ (helped by oxides of nitrogen), which forms sulphuric acid with moisture and falls as acid rain, damaging soil, lakes, forests and buildings; it also gives haze.
Wind turns the blades of wind turbines, which drive generators and produce electricity without burning fuel, so no CO₂, SO₂, NOₓ or smoke is released. It is renewable (it will not run out) and cheap to run once installed. Pakistan has wind farms in the Jhimpir-Gharo wind corridor of Sindh. Wind is also used to pump water and to sail boats.
The book's in-text exercises first, then short questions on every topic of the chapter (SLO-based), as asked in board papers.
Late at night and early in the morning, before sunrise. The air is coolest then, so it can hold the least water vapour and its relative humidity is highest; that is when dew and fog form. Humidity is lowest in the hot afternoon.
Carbon dioxide (CO₂). It is dissolved under pressure and comes out as bubbles when the pressure is released.
Dust and soot settle on leaves, blocking sunlight and the stomata, so less CO₂ is absorbed in photosynthesis; SO₂, NOₓ and ozone damage leaves; acid rain makes soil acidic and washes out nutrients; smog inhibits plant growth.
SO₂ gives sulphurous acid H₂SO₃ (and, after oxidation to SO₃, sulphuric acid H₂SO₄). NO₂ gives nitrous acid HNO₂ and nitric acid HNO₃.
Tree roots hold the soil together on hills and mountains. If the trees are destroyed, the soil is washed away (soil erosion) and new plants cannot grow there.
All living things add CO₂ by respiration (and decay of dead matter); humans add more by burning fuels. Plants remove CO₂ by photosynthesis: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂.
Methane (CH₄). It is produced by bacteria in the waterlogged soil of rice fields, where vegetation decays without air, and escapes through the plants.
Methane (CH₄), along with carbon dioxide; landfill gas is mostly these two.
About 78 % nitrogen, 21 % oxygen, and the remainder a mixture of noble gases (mainly argon, 0.93 %) and carbon dioxide (0.04 %). Water vapour varies with humidity.
Any substance (solid, liquid or gas) in the air which has an adverse effect on human health, quality of life and the natural functioning of the ecosystem.
Parts per million: one part of pollutant per million parts of the mixture. CO₂ at 0.04 % is 400 ppm.
CO₂, CO, NOₓ, SOₓ, hydrocarbons (methane), particulates and ozone. Together they account for more than 90 % of air pollution.
| Complete | Incomplete |
|---|---|
| Enough oxygen. | Not enough oxygen. |
| Gives CO₂ and H₂O. | Gives CO, soot (particulates) and unburnt hydrocarbons. |
| Blue flame. | Yellow, smoky flame. |
| C + O₂ → CO₂ | 2C + O₂ → 2CO |
At the very high temperature inside the engine, nitrogen and oxygen of the air combine: N₂ + O₂ → 2NO; then 2NO + O₂ → 2NO₂.
Smoke mixed with fog. In winter cold, still, humid air gives fog, and smoke from vehicles, industry, brick kilns and crop burning stays trapped near the ground, so Lahore and other cities are covered by smog.
When heat and sunlight cause chemical reactions between oxides of nitrogen and volatile organic compounds (hydrocarbons), mostly from car exhausts. It is a part of photochemical smog.
It has no colour, smell or taste, so it cannot be noticed; it stops red blood cells from carrying oxygen, causing headache, sleepiness, suffocation and death, often from faulty gas heaters in closed rooms.
They damage lungs, irritate the eyes and damage vegetation. They cause acid rain, which affects buildings of limestone, and photochemical smog.
It irritates the eyes, causes breathing difficulties and acid rain, and produces haze.
It irritates the eyes and causes severe breathing problems for people with asthma, increases the risk of respiratory diseases and cancer, dirties clothes and reduces visibility.
It leads to allergies, asthma and lung infections. It also inhibits the growth of plants by reducing the amount of CO₂ absorbed during photosynthesis.
Rain water with pH between 4.2 and 4.4 is known as acid rain. In 1852 Robert Angus Smith first showed its relationship with atmospheric pollution in Manchester; he is called the "Father of Acid Rain".
NO₂ oxidises SO₂ to SO₃ and becomes NO, which is oxidised back to NO₂ by air, ready to act again: NO₂ + SO₂ → NO + SO₃; 2NO + O₂ → 2NO₂. So NOₓ speeds up the formation of H₂SO₄, besides forming HNO₃ directly.
Wind can carry the acidic droplets to huge distances before they fall, even into other countries.
It falls into streams, lakes and rivers and makes the water too acidic for animals to live in. Many lakes and rivers no longer have fish.
By monitoring the soil and, when necessary, adding crushed lime to neutralise the acid.
They are made of marble (CaCO₃), which reacts with acid rain: CaCO₃ + H₂SO₄ → CaSO₄ + H₂O + CO₂. The surface dissolves and crumbles.
The progressive warming up of the Earth's surface due to the blanketing effect of man-made CO₂, methane, water vapour and other gases in the atmosphere.
Short-wave radiation from the Sun passes through them and heats the Earth. The hot surface emits long-wave radiation that is mostly absorbed by greenhouse gases, which stops it reaching space and slows the cooling of the Earth.
The thick layer of CO₂ in the lower atmosphere allows incoming solar radiation to pass but does not allow the heat to escape, just as the glass of a greenhouse lets sunlight in and keeps the warmth inside.
About half of the CO₂ released is used by plants in photosynthesis. Cutting forests diminishes the capacity of trees to remove CO₂, and burning the wood adds even more.
Higher temperature makes sea water expand, and melting ice of Antarctica and Greenland flows into the sea. Low-lying coastal areas such as the Netherlands and Bangladesh are threatened.
Long-term changes in temperature and weather patterns, mainly caused by global warming: hotter summers, shorter warmer winters, heavier rains and floods in some regions, droughts in others, and extreme events like heat waves and wildfires.
Plants absorb CO₂ and release O₂; their leaves also trap particulate matter. Planting trees is one of the best ways to clean the air.
Flue gas is the mixture of waste gases produced when fossil fuels are burnt in power plants. In desulphurisation, adsorbents like calcium oxide are added, which can remove up to 95 % of the SO₂. CaO + SO₂ → CaSO₃.
Resources that continue to exist despite being consumed over time: the Sun, wind, water, geothermal energy and biomass. Solar and wind energy make electricity without pollution.
A rating system that shows how bad the air is. A value under 50 is good; over 300 is hazardous.
Faulty fuel-burning appliances (gas heaters, geysers, stoves) can release CO, which cannot be seen or smelt. A detector sounds an alarm before the level becomes dangerous.
Cloth or dust masks may not filter out the finer particles. Well-fitted N95 masks have better filtration capabilities (they stop at least 95 % of fine particles).
