P. 71 Oral Questions For Formative Assessment (Living Science)
1. acetic acid and citric acid 2. Acids are corrosive in nature. Strong acids can corrode even metals like iron and aluminium. Hence, acids are not stored in metal containers. 3. litmus paper and methyl orange; acid-base indicators 4. neutralization reaction, salt 5. Organic acids are naturally occurring acids that are present in animal and plant products. They are normally weak acids. Hydrochloric acid, sulphuric acid and nitric acid are known as mineral acids. They are normally strong acids. P. 72 Oral Questions For Formative Assessment 1. Bases which are soluble in water are called alkalis. But some bases are not soluble in water, so they are not alkalis. That is why all alkalis are bases but all bases are not alkalis. 2. I will not recommend that quicklime or slaked lime be added to the soil to neutralize the acid present in it. 3. sodium hydroxide (NaOH) 4. hydrochloric acid (HCI), magnesium hydroxide is used as an an acid to neutralize the excess add in the stomach P. 74 Oral Questions For Formative Assessment 1. If we replace hydrogen of an acid with a metal, a salt is formed. 2. a salt and water 3. a. nitric acid b. carbonic acid c. hydrochloric acid d. sulphuric acid 4. a salt; sodium bicarbonate (NaHCO3) Page 74 For Formative and Summative Assessment A. 1. d 2.a 3.c 4. d 5. c 6. a 7. d 8. d 9. b B. 1. sodium chloride 2. an acid 3. red 4. false 5. nitric acid 6. lactic 7. carbon dioxide 8. neutralization 9. sulphuric add 10. alkali 11. ammonium hydroxide 12. a base 13. pale yellow 14. caustic soda 15. magnesium hydroxide 16. true 17. blue C. 1. The substance which can be used to test if a given substance is acidic or basic in nature is known as an acid-base indicatdr, for example, methyl orange. 2. lemon, antacid, common salt 3. When dilute sulphuric acid is added to zinc, hydrogen gas is produced along with zinc sulphate. 4. Dilute acids react with carbonates such as calcium carbonate (CaCO3) to form salt and carbon dioxide gas. 5. Examples of strong acids: (I) Nitric acid (ii) Sulphuric acid Examples of weak acids: (i) Lactic acid (ii) Acetic acid 6. Ant bite injects formic acid inside the skin, and thus skin irritates for some time. To get relief, a base (baking soda) is applied to neutralize the acid. The irritation ends with forming salt and water and provides relief. 7th Acids bases and Salt Living science solution Download File For Formative and Summative Assessment
A. 1. b 2. a 3. d 4. b 5.d 6. a 7. c 8. b B. 1. Biodiversity means the variety of plants, animals and microorganisms generally found in an area. 2. `Flora' refers to plants. 3. Yes - I agree 4. False 5. Erosion 6. Overgrazing 7. True 8. renewable 9. extinct 10. forest 11.True 12. trees 13. endemic 14. endangered C.1. Biodiversity is the variety of plants, animals and microorganisms generally found in an area. 2. Flora: Species of all plants found in a particular area is known as flora of that area. Fauna: Species of all animals found in a particular area is known as fauna of that area. 3. Cutting down forests and using the land for other purposes is known as deforestation. 4. Some animals cannot adjust to the environmental changes and begin to die. These animal species become endangered as their population becomes very small. 5. A biosphere reserve is a large protected area set aside for conservation of wildlife, plant, animal and microorganism resources, and the traditional life of the tribals living in that area. 6. Endemic species are those species of plants and animals that are found exclusively in a particular area and are not naturally found anywhere else. For example, the Indian giant squirrel and flying squirrel are endemic to the Pachmarhi Biosphere Reserve area. 7. IUCN prepared Red Data Book to highlight those animals who are threatened with extinction, with the aim of promoting their conservation. Those threatened with extinction. 8th Conservation of plants_animal science solution Download File Check your result
CBSE - Class X Examination 2017 Announced on 03rd June 2017 Q. Mention one reason why tungsten is used for making filament of electric lamp. [CBSE 2014]
Ans: tungsten does not oxidize, i. e. burn easily at high temperatures as it has higher melting and boiling point than metals Q. List two characteristics of the material to be used in fuse wire. Name the material it is made of. A fuse is always connected in series in an electric circuit ? Justify this statement giving reason [CBSE 2014] Answer: two characteristics of the material to be used in fuse wire (a) Low melting and boiling point (b) high electric resistance Fuse is generally made up of an alloy of tin and lead In series connection the current for the entire house pass through the fuse. So, when fuse melts , it breaks down the entire home circuit and no current flows to the household circuitry. Thus, a fuse is always connected in series Q. A circuit has a line of 5 A. How many lamps of rating 40 W; 220 V can simultaneously run on this line safely ?[CBSE 2014] Solution : P = VI so, I = P/V = 40/220 No of lamp can simultaneously run on this line safely = 5A/(40/220 )A = 27 Q. Several electric bulbs designed to be used on a 220 V electric supply line, are rated 10 W. How many lamps can be connected in parallel with each other across the two wires of 220 V line if the maximum allowable current is 5 A? Solution : Resistance R 1 of the bulb = V^2/p1 = (220)2/10 = 4840 Ohm Let lamps can be connected in parallel with each other According to O hm’s law, V = I R Where, R is the total resistance of the circuit for x number of electric bulbs R = V/I = 220/5 = 44 Ohm Number of lamp = 4840/44 = 110 Q. Express work done in an electric field in terms of charge and potential difference. Calculate the amount of work done in carrying a charge of 5 mC against a potential difference of 100 V [CBSE 2014] Solution : Work dome = charge x potential difference the amount of work done in carrying a charge of 5 mC against a potential difference of 100 V = 5 × 10^3 × 100 = 0. 5 J Q. Distinguish between kilowatt and kilowatt hour. For a heater rated at 4.4 kW; 220 V . Calculate the - (i) current drawn by the heater (ii) resistance of the heater element (iii) energy consumed by the heater in 5 hours (iv) cost of running the heater if 1 kWh costs Rs. 6.50 [CBSE 2014] Answer: Kilowatt is the unit of Power where as KiloWatt Hour is the commercial unit of energy. Given, P = 4.4 kW = 4400 W and V = 220 volts (i) As P = V /I So, I = P/V = 4400/220 = 20 A (ii) As P = I^2R So, R = P/I^2 = 4400/(20) 2 = 11 ohms (iii) since, electric energy = electric power X time = 4.4 kW X 4 hours = 17.6 kWh (iv) Since, 1KwH costs Rs. 6.50, hence, costs of 17.6 kWh = 17.6 X 6.50 = Rs. 114.4 Q.Distinguish between resistance and resistivity of a conductor. The resistors are generally made of thin wires of Eureka or Manganin while the wires used in connections are made comparatively thicker and are of copper or aluminium. Why ? Give reason. What would happen to the resistance of a wire if it is stretched to double its length ? Justify your answer.[CBSE 2014] Solution : Resistivity 1. It is the measure of a material’s ability to oppose the flow of current. 2. It depends on the property of the material. Its value is constant for a particular range of temperature. 3. Unit of resistivity is Ohm meter Resistance 1. It is a measure of the opposition that a circuit (or an electrical element) offers to the flow of electric current. 2. Resistance of a conductor is directly proportional to its length and inversely proportional to its area of cross section. 3. Unit of resistance is Ohm The resistors are generally made of thin wires of Eureka or Manganin while the wires used in connections are made comparatively thicker and are of copper or aluminium. This is because thicker wire has less resistance than thinner wire See full Questions and answer |
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