Read the following passage and answer the questions that follow :
Ozone is a peculiar gas: close to the ground it is a harmful substance, but at a height of 20-50 km above the earth's surface it forms a protective layer. For almost two decades, we have known that this invisible shield is crumbling. At first, a large hole formed above Antarctica. Researchers noted that the ozone content in this region had fallen to more than 70% below normal. This set alarm bells ringing, for the ozone layer acts as a protective radiation filter, without which living beings on earth would be exposed to the sun's energy-rich ultraviolet radiation. At present, the ozone supply seems to be diminishing by 3-4% each decade near the equator, and by more than double that amount at higher latitudes.
There are a lot of questions surrounding the ozone issue. Most people are unsure what the ozone layer is, how it is formed and where it is located. Ozone, which comes from the Greek word Ozein, meaning 'to smell', is the name for the form of oxygen with three atoms (03; oxygen is O2) compounded in a single molecule. The gas has a characteristic odour; it is poisonous and aggressive, and causes damage to plants and buildings even in small amount. Air that becomes contaminated by ozone can cause eye irritation and lung complaints. For this reason, some countries monitor ozone levels during the summer months; if it rises above a safe level, environmental authorities issue, an ozone warning. Usually, however, the ozone content in the lower layers of the atmosphere remains relatively low. A rise in ozone concentration occurs under certain weather conditions, such as in summer when automobile exhaust gases (which consist of a mixture of nitrogen and hydrocarbons) react with sunlight to produce more ozone than normal. Questions :
(i) Why is ozone said to be a peculiar gas ?
(ii) Where was a large hole noticed in the ozone layer ? What had caused this hole ?
(iii) What is the meaning of the statement "This set alarm bells ringing" ?
(iv) What is the difference in composition between ozone and oxygen ?
(v) What are the drawbacks of O3 ?
Vocabulary Skill
A. Find the appropriate word as the antonyms of the following expressions.
(i) What can be seen through eyes.
(ii) increasing
(iii) dangerous
B. Use the following in sentences of your own
(i) aggressive
(ii) irritation
Answers
Answer:
1.Ozone is a peculiar gas: close to the ground it is a harmful substance, but at a height of 20-50 km above the earth's surface it forms a protective layer.
2.At first, a large hole formed above Antarctica. Researchers noted that the ozone content in this region had fallen to more than 70% below normal.
3.This set alarm bells ringing, for the ozone layer acts as a protective radiation filter, without which living beings on earth would be exposed to the sun's energy-rich ultraviolet radiation.
4.Ozone, which comes from the Greek word Ozein, meaning 'to smell', is the name for the form of oxygen with three atoms (03; oxygen is O2) compounded in a single molecule.
5.some countries monitor ozone levels during the summer months; if it rises above