KERALA PUBLIC SCHOOLS ACADEMIC YEAR 2021-22 CLASS : VIII HOME ASSIGNMENT DATE : 30.06.2021 to 15.07.2021 SUBJECT ASSIGNMENT MATHS Ch 10. Profit & loss Exercise – 10 A (Q 1 to 34) Exercise – 10 B (Q 1 to 14) Exercise – 10 C ( Q 1 to 11) CH (6)- Combustion and Flame. 1. Read the chapter carefully and write important words in the notebook. 2. Key terms /definitions should be written in notebook. 3. Write exercise questions and answers in notebook. 4. Fill in the blanks and MCQs should be answered in textbook only. ANSWERS :- A. VERY SHORT ANSWER TYPE QUESTIONS Q. 1. Why is a matchstick rubbed against a rough surface to light it ? Ans. A matchstick is rubbed against a rough surface to reach its ignition temperature. Q. 2. Name the various zones of the candle flame. Ans. Various zones of a candle flame are ● Outermost nonluminous (blue) zone of complete combustions. ● Central (or middle) luminous zone of incomplete combustion. ● Inner zone of no combustion. ● Lowest blue zone. SCIENCE Q. 3. What is a supporter of combustion ? Ans. The substance that helps burning is called the supporter of burning. Q. 4. What constitues a fire triangle ? Ans. A fire triangle comprises fuel, air (oxygen) and heat (to reach ignition temperature). Q. 5. Name a and a gaseous fuel. solid, a liquid Ans. Solid fuel : Wood Liquid fuel : Petrol Gaseous fuel : Liquified petroleum gas (LPG) A. SHORT ANSWER TYPE QUESTIONS Q. 1. What is the difference between a combustible and a non-combustible substance ? Ans. A combustible substance is one that burns readily. While, a non-combustible substance does not burn. Examples of combustible substance : Paper, wood etc. Examples of non-combustible substance : Water, glass etc. Q. 2. Why does a phuljhari (sparking light) require some heating before it sparks ? Ans. A phuljhari requires some heating to reach its ignition temperature. Q. 3. What is explosion ? Ans. When combustion is accompanied by sudden production of heat, sound and large amount of gas, it is called explosion. Q. 4. What harmful products are formed by the burning of fuels ? Ans. Burning of fuels produces gases like carbon monoxide, carbon dioxide, oxides of nitrogen and oxides of sulphur. In addition to the gases, burning solid fuels produces smoke also. These products cause air pollution. Q. 5. What is acid rain ? Does it harm the environment ? Ans. The rainwater containing dissolved oxides of nitrogen and sulphur is called acid rain. Acid rain is highly acidic and corrosive. Due to its corrosive nature it harms metallic structures historical monuments, plants and aquatic life. B. LONG ANSWER TYPE QUESTIONS Q. 1. Mention any four characteristics that you would consider for selecting the most ideal fuel. Ans. Characteristics of Ideal Fuel ● It should be fairly cheap and easily available. ● It should burn at a moderate rate. ● It should not produce any poisonous and irritating fume during burning and should not leave any residue (ash) after burning. ● It should produce large amount of heat per unit mass, i.e., it should have high calorific value. Q. 2. What is meant by luminous and nonluminous flames ? Ans. A blue-coloured flame which produces very little light is called non-luminous flame. It is obtained when the fuel is burnt completely. A yellow flame which produces heat and appreciable amount of light is called a luminous flame. A luminous flame is obtained when the fuel undergoes incomplete combustion. Q. 3. What is spontaneous combustion ? What is the common cause of fire in coal mines ? Ans. When a substance suddenly starts burning into a flame, without the supply of any external cause (such as heating), the combustion is called spontaneous combustion. In coal mines, the spontaneous combustion of coal dust causes fire. Q. 4. Give reasons : (a) Kerosene burns with a blue flame in a stove but produces a yellow flame when burnt in a lamp. (b) It is not advisable to sleep in a closed room with a coal-fired fire place. Ans. (a) In a wick stove a perforated cylinder is placed around the burning wicks. Air is supplied continuously through these holes so the kerosene vaporises completely and a blue flame is produced. In a lamp, kerosene burns partially due to lack of air. Thus a yellow flame is obtained. (b) Burning of coal produces carbon monoxide which is very poisonous. When inhaled, carbon monoxide combines with haemoglobin in the blood. Thus blood cannot carry oxygen and lack of oxygen causes suffocation and even death. That’s why it is not advisable to sleep in a closed room with a coal fired fire place. C. CHOOSE THE CORRECT ANSWER 1. Combustion is a / an (a) endothermic process (b) exothermic process (c) decomposition process (d) reversible process 2. The gas that supports combustion is (a) nitrogen (b) carbon monoxide (c) carbon dioxide (d) oxygen 3. The lowest temperature, at which a substance catches fire, is called (a) critical temperature (b) alsolute temperature (c) ignition temperature (d) normal temperature 4. The condition not necessary for combustion to take place is (a) availability of fuel (b) supply of oxygen (c) proper ignition temperature (d) supply of water 5. The fire caused by electric defects or oil can be extinguished by using (a) water (b) blanket (c) carbon dioxide (d) sand Ans. 1. (b) 2. (d) 3. (c) 4. (d) 5. (c) D. FILL IN THE BLANKS 1.Generally, fire in a coal mine is a kind of spontaneous combustion. 2. A good fuel has a high calorific value. 3. Acid rain is caused due to dissolved oxides of sulphur and nitrogen. 4. Burning of fuels leads to environmental pollution. 5. Water, glass, steel are non-combustible substances. E. STATE TRUE OR FALSE 1. The calorific value of a fuel determines its efficiency. 2. All combustible substances give flame while burning. 3. Water is one of the best fire extinguisher used to extinguish all kinds of fire. 4. CNG is a clean fuel. 5. Incomplete combustion of a fuel gives poisonous carbon monoxide gas. Ans. 1. True 2. False, only those substances that vaporise on burning produce flame. 3. False, water cannot be used to extinguish all kinds of fire. 4. True 5. True F. HIGHER ORDER THINKING SKILLS [HOTS] Q. 1. Can we think of hydrogen as a future fuel ? Justify your answer. Ans. It can be the best alternative fuel. It is a clean fuel with high calorific value. It gives out water on burning. So it doesn’t pollute the environment. Q. 2. In an overheated oil kitchen fire, Rohit’s mother put a lot of dry white powder ‘X’ on the pan. The fire got extinguished. (a) What could be the dry powder X ? (b) How does ‘X’ extiguish the fire ? (c) Name an another substance like ‘X’ used to extinguish fire. Ans. (a) ‘X’ may be sodium bicarbonate or baking soda. (b) When powder of sodium bicarbonate (baking powder) is spread over or near the fire, it releases carbon dioxide gas. It covers the burning material and cuts off the air supply. This puts off the fire. (c) Potassium bicarbonate. दी साह त्य कक्षा-8ﴂ ह पाठ 2 अन्याय के हि셁द्ध (तोन चेखोि ह न्दी अनुिादक श्री प्रभाकर हििेदीﴂ셂सी कथाकार: अ) पाठ को ध्यानपूिवक पढ़ें। म़ें हिख़ें। ﴂदर अक्षरोﴂसु ﴂहदए गए सभी कायव को अपनी उत्तर पुस्तिका म़ें साफ एि हदमागी माप अपनी उत्तर पुस्तिका म़ें बनाएँ। अत्यजिक जवनम्रता दब्बू पन अपने मन माना िाता है की आवाि को उठाना HINDI अन्याय का अन्याय को सशक्त ना सहना जवरोि करना कहठन शब्द:- तनख्वाह लापरवाही मास्टरनी बािजूद अस्तित्व 셂बि क्रुद्ध ख्याि हृदय हीन दब्बू शब्दार्थ:- तनख्वा िेतन 셂बि 셂स की मुद्रा अनथव जिसका अर्थ ना हो हिनीत नरम और जशष्ट अचरज हैरानी दय ीन जिसके ह्रदय ना हो अस्तित्व जकसी विु या व्यस्तक्त के होने का भाव भी셁 डरपोक कायर क्रूर कठोर, जनदथय बोदा कमिोर प्र�ोⴂ के उत्तर सⴂक्षेप मᴂ दᴂ 1. य क ानी मूि 셂प से हकस भाषा म़ें हिखी गई ै? • यह कहानी मूल 셂प से 셂सी भाषा मᴂ जलखी गई है। 2. इस क ानी के मूि िेखक का नाम क्या ै? • इस कहानी के मूल लेखक अⴂतोन चेखोव हℂ। ?को पढाने का काम कौन करती थी ﴂबच्ो .3 • ब楍ोⴂ को पढाने का काम करती र्ी िूजलया। 4. 셂बि हकस देश की कऱेंसी का नाम ै? • 셂बल 셂स देश की करᴂसी का नाम है। प्र�ोⴂ के उत्तर जलस्तखए 1) िेखक के हकतने बच्े थे? उनके नाम क्या-क्या थे? • लेखक के दो ब楍े र्े। उनके नाम र्े कोल्या और वान्या। ? ﴂिेखक ने जूहिया की तनख्वा से बार 셂बि काटने के कौन-कौन से कारण बताए (2 • नौ इतवार और तीन छुजियोⴂ या बारह जदन के बारह 셂बल काट जलए। बारह जदन काम नहीⴂ हुआ। ?गीﴂिेखक ने जूहिया से हकस बात के हिए माफी मा (3 • लेखक ने िूजलया को नसीहत देने के जलए एक छोटा सा क्रूर मिाक करने के जलए माफी माⴂगी। ?त म़ें जूहिया को कट कटाकर हकतने 셂बि हमिे इस पर जूहिया की की क्या प्रहतहक्रया थीﴂअ (4 • अⴂत मᴂ कट-कटाकर िूजलया को केवल ग्यारह 셂बल जमले। इस पर भी िूजलया ने लेखक को िन्यवाद जदया। 5) िेखक जूहिया को क्या सीख देना चा र ा था? • लेखक िूजलया को यह सीख देना चाह रहा र्ा जक इस कठोर,जनमथम और ह्रदयहीन दुजनया मᴂ रहने के जलए अपनी पूरी ताकत के सार् उन से लड़ना होगा। बोदा, भी셂, दब्बू लोगोⴂ को इस सⴂसार मᴂ कोई िगह नहीⴂ। हििोम शब्द झठू सच अच्छा बुरा कठोर कोमल ऊँचा नीचा ह न्दी भाषा पाठ: 14 िाच्य वाच्य का अर्थ है– बोिने का हिषय। जक्रया के जिस 셂प से इस बात का बोि हो जक वह वाक्य मᴂ कताथ, कमथ अर्वा भाव जकस के अनुसार प्रयुक्त हुई है, िाच्य कहलाता है। 1) कततथवाच्य- कततथवाच्य मᴂ जक्रया का सीिा सⴂबⴂि कताथ के सार् होता है जक्रया का जलⴂग और वचन भी कताथ के अनुसार होता है। खाना बना र ी ै। ﴂउदा रण- मा 2) कमविाच्य- िब जक्रया का सीिा सⴂबⴂि कमथ से हो तो जक्रया कमथवाच्य मᴂ होगी अर्ाथत् जक्रया का जलⴂग तर्ा वचन कमथ के अनुसार ही होगा। िारा गाने गाए जाते ℂ। ﴂउदा रण- बच्ो 3) भाििाच्य- जिस वाक्य मᴂ ना तो कताथ प्रिान हो और ना ही कमथ बस्ति जक्रया मᴂ भाव की प्रिानता हो, वहााँ भाववाच्य होता है। जाता। ﴂउदा रण- उससे दौडा न ी अभ्यास कायथ पाठ्य पुिक म़ें कऱें 115 ﴂख्या 114 एिﴂपृष्ठ स हनदेशानुसार िाक्य पररितवन कऱें (उत्तर पुस्तिका कायव) 1) रीना ने आम खाया। ( कमविाच्य म़ें बदहिए) 2) हलवाई के द्वारा जमठाई बनाई िाती है। (कतृविाच्य म़ें बदहिए) 3) हार्ी ने गन्ना खाया। (कमविाच्य म़ें बदहिए) 4) रमा कार चला रही है। (भाििाच्य म़ें बदहिए) Chapter -CLAUSES Clause A clause is a group of words that includes a subject and a verb.