Chapter 8 Fire: Friend and Foe
Textbook Questions and Answers
Working with the Text
Answer the following questions :
निम्न प्रश्नों के उत्तर दीजिए :
Question 1.
What do you understand by the ‘flash point’ of a fuel?
आप ईंधन के ‘दहन बिंदु’ से क्या समझते हैं?
Answer:
Every fuel has a particular temperature at which it burns. It burns only when it reaches to that particular temperature. This temperature is called the “flash paint” of a fuel.
प्रत्येक ईंधन एक विशेष तापमान पर जलता है। यह केवल तभी जलता है जब वह विशेष तापमान पर पहुंच जाए। यह तापमान ही ‘दहन बिन्दु’ कहलाता है।
Question 2.
(i) What are some common uses of fire?
आग के कुछ सामान्य उपयोग क्या है?
Answer:
Fire is commonly used for cooking, keeping our homes warm during winters and it is also used for producing electricity
आग का उपयोग आमतौर पर खाना पकाने, सर्दियों में घरों को गर्म रखने और बिजली के उत्पादन हेतु भी किया जाता है।
(ii) In what sense is it a “bad master”?
किस अर्थ में इसे ‘बुरा मालिक’ कहा जाता है?
Answer:
Fire is a bad master when it goes out of control. An uncontrolled fire can be the cause of great damage to our lives and property.
आग जब नियंत्रण से बाहर हो जाती है तो यह बुरा मालिक बन जाती है। एक अनियंत्रित आग हमारे जीवन और सम्पत्ति को बड़ा नुकसान कर सकती है।
Question 3.
Match items in Column A with those in Column B.
निम्न कॉलम A को कॉलम B से मिलाइये।
Answer:
(i) Fuel — Coal, wood, cooking gas.
(ii) Oxygen — Air
(iii) Heat — Lighted matchstick,smouldering paper,burning coal.
Question 4.
What are the three main ways in which a fire can be controlled or put out?
तीन मुख्य तरीके कौनसे हैं जिनसे आग को नियंत्रित किया या बुझाया जा सकता है?
Answer:
The three main ways in which a fire can be controlled or put out are as following
(i) Taking away or removing the fuel.
(ii) Stopping the supply or flow of oxygen.
(iii) Bringing down the temperature around the fuel below its flash point.
तीन मुख्य तरीके, जिनमें आग को नियंत्रित किया या बुझाया जा सकता है, निम्न हैं-
(1) ईंधन को दूर ले जाना या हटा देना।
(2) ऑक्सीजन का वितरण या बहाव रोक देना
(3) ईंधन के तापमान को दहन बिन्दु से नीचे लाना।
Question 5.
Match the items in Box A with those in Box B:
Answer:
A — B
(i) To burn paper or a piece of wood — we heat it before it catches fire.
(ii) Small fires can be put out — with a damp blanket.
(iii) When water is spread on fire — it absorbs heat from burning material and lowers its temperature.
(iv) A carbon dioxide extinguisher is the best thing — to put out an electric fire.
(v) Space left between buildings — reduces the risk of fire.
Question 6.
Why does a burning candle go out when you blow on it?
जब आप फूंक मारते हैं तो एक जलती हुई मोमबत्ती क्यों बुझ जाती है?
Answer:
When we blow on a burning candle, the carbon dioxide present in our breath reduces the oxygen around the candle and the candle goes out.
जब हम जलती हुई मोमबत्ती के फूंक मारते हैं तो हमारी श्वास में मौजूद कार्बन डाई ऑक्साइड मोमबत्ती के चारों ओर की ऑक्सीजन को कम कर देती है और मोमबत्ती बुझ जाती
Question 7.
Spraying water is not a good way of putting out an oil fire or an electrical fire. Why not?
तेल से या बिजली से लगी आग को पानी डाल कर बुझाना अच्छा तरीका नहीं है। क्यों नहीं?
Answer:
Spraying water is not a good way of putting out an oil fire because when we do that, oil, being lighter than water, comes on the top and keeps burning. Apart from this, water flows and spreads faster making the fire to spread to a wider area. We should also not use water to extinguish an electrical fire because water being a good conductor of electricity can give an electric shock to the person spraying it.
तेल से लगी आग पर पानी डालकर बुझाना अच्छा नहीं है क्योंकि जब हम ऐसा करते हैं तो तेल पानी से हल्का होता है और ऊपर आकर जलने लगता है । इसके अलावा पानी बहकर तेजी से फैलता है और बड़े क्षेत्र में आग लगती है। बिजली से लगी आग पर पानी नहीं डालें क्योंकि पानी बिजली का सुचालक है और पानी छिड़कने वाले व्यक्ति को झटका लग सकता है।
Question 8.
What are some of the things you should do to prevent a fire at home and in the school?
स्कूल या घर पर आग को रोकने के लिए आपको क्या कार्य करने चाहिए?
Answer:
When we make a building, we should leave some space to reduce fire risk. School must observe the fire safety norms strictly.
जब हम किसी भवन को बनाएं, हम आग के खतरे को कम करने के लिए इनके बीच में कुछ जगह छोड़ दें। विद्यालय को आग से सुरक्षा के नियमों को सख्ती से लागू करना चाहिए।
Comprehension Check Page118.
Question 1.
Mark the correct answer in each of the following:
निम्न में से प्रत्येक के सही उत्तर पर निशान लगाइए :
(i) Early man was frightened of :
(a) Lightning and volcanoes
(b) The damage caused by them
(c) Fire
Answer:
(c) Fire
(ii) (a) Fire is energy
(b) Fire is heat and light
(c) Fire is the result of a chemical reaction
Answer:
(c) Fire is the result of a chemical reaction
Question 2.
From the boxes given below choose the one with the correct order of the following sentences.
नीचे दिये गये बॉक्स में से निम्न वाक्यों के सही क्रम वाला एक उत्तर चुनिये
(i) That is fire.
(ii) A chemical reaction takes place.
(iii) Energy in the form of heat and light is released.
(iv) Oxygen combines with carbon and hydrogen.
(a) (i), (ii), (iii), (iv)
(b) (ii), (iii), (i), (iv)
(c) (iv), (iii), (ii), (i)
(d) (iv), (ii), (iii), (i)
Answer:
(d) (iv), (ii), (iii), (i)
Seen Passages
Read the following passages carefully and answer the questions given below it.
Passage -1.
Fire may have puzzled early man but we now know that fire is the result of a chemical reaction. When the oxygen in the air combines with carbon and hydrogen in a fuel, a chemical reaction takes place. Energy in the form of heat and light is released in this process.
This is what we call fire. Three things are needed to make fire- fuel, oxygen and heat. Wood, coal, cooking gas and petrol are some examples of fuel. Oxygen comes from the air. That is why, when you blow on smouldering paper, it often bursts into flame. The third thing needed to make fire is heat.
Questions :
1. What is fire caused by?
2. What may have puzzled early man?
3. What are needed to make fire?
4. From where does oxygen come?
5. What happens when one blow on smouldering paper?
6. Write the Hindi meaning of the word, “reaction”.
7. गद्यांश में से वह वाक्य लिखिए जिसका अर्थ है, “आग उत्पन्न करने के लिए जिस तीसरी चीज की आवश्यकता होती है वह ऊष्मा है।
Answers :
1. Fire is caused by a chemical reaction.
2. Fire may have puzzled early man.
3. Fuel, oxygen and heat are needed to make fire.
4. Oxygen comes from air.
5. When we blow on smouldering paper it often bursts into flame.
6. प्रतिक्रिया
7. The third thing needed to make fire is heat.
Passage – 2.
We generally do it with a lighted match. Every fuel has a particular temperature at which it begins to burn. This temperature is called the ‘flash point’ or ‘kindling temperature of the fuel. It is sometimes said that fire is a good servant but a bad master.
It only means that fire is very useful as long as it is kept under control. For instance, we use it to cook our food, warm our homes in winter and to generate electricity. But, on the other hand, if fire gets out of control it can be very dangerous. Each year thousands of homes and shops are damaged by fire.
Questions:
1. When does a fuel burn?
2. What is said about fire?
3. When is fire very useful?
4. What are the uses of fire?
5. When is fire very dangerous?
6. Write the Hindi meaning of the word, “generate”.
7. Write the opposites of the following from the passage
(i) ends
(ii) good.
Answers :
1. A fuel burns at a particular point.
2. It is said about fire that fire is a good servant but a bad master.
3. Fire is very useful when it is under control.
4. Fire is used to cook food, warm our homes in winter and to generate electricity.
5. Fire is very dangerous when it gets out of control.
6. उत्पन्ना करना
7. (i) begins
(ii) bad.
Passage – 3.
If the fire has no fuel to feed on, no burning can take place. We often let a fire die out simply by not adding more fuel to it. The second way of putting out a fire is to prevent oxygen from reaching it. No supply of oxygen means no fire. Small fires can be put out or ‘smothered’ with a damp blanket or a sack. This stops oxygen reaching the burning material. Sometimes, carbon dioxide is used to extinguish fire. It does not allow oxygen to reach the burning material.
Questions :
1. What will happen if the fire has no fuel to feed on?
2. What will happen if oxygen is prevented from reaching fire?
3. How can we put out small fires?
4. What is the use of carbon dioxide?
5. What does a damp blanket do?
6. Write the Hindi meaning of ‘extinguish’.
7. गद्यांश में से वह वाक्य लिखिए जिसका अर्थ है, “ऑक्सीजन का वितरण नहीं होने का अर्थ है आग का नहीं होना।”
Answers :
1. If the fire has no fuel to feed on, it will not burn.
2. If oxygen is prevented from reaching fire, it will put out.
3. Small fires can be put out with a damp blanket or a sack.
4. Sometimes, carbon dioxide is used to extinguish fire.
5. A damp blanket stops oxygen reaching the burning material.
6. बुझाना
7. No supply of oxygen means no fire.