2<\/sub>\u00a0gas produce during the reaction makes the cake or bread spongy and fluffy.<\/p>\nOR<\/p>\n
i) Write the name given to bases that are highly soluble in water. Give an example.
\nii) How is tooth decay related to pH.
\niii) Why does bee – sting cause pain and irratiation?
\nRubbing of baking soda on the sting area gives relief. How?
\nAnswer:
\ni) Alkali, NaOH
\nii) Tooth decay starts when the pH of the mouth is lower than 5.5. It can be prevented by using toothpaste which are generally basic.
\niii) Bee sting has acid that cause pain and irritation.
\nBaking soda being alkaline, Neutralises acid and given relief.<\/p>\n
Question 29.
\nHow does a solenoid behave like a magnet? Can you determine the north and south poles of a current carrying solenoid with the help of a bar magnet?
\nAnswer:
\nWhen electric current flows through a solenoid, magnetic field is set up around the solenoid. The pattern of the magnetic field is same as that of the magnetic field of a bar magnet. One end of the solenoid behaves as north pole and the other end of the solenoid behaves as south pole.<\/p>\n
To determine the north and south poles of a current carrying solenoid with the help of a bar magnet, suspend it with a strong thread. Now bring the north pole of a bar magnet towards one end of the solenoid. If the solenoid attracts towards the magnet then the face of the solenoid is south pole. If the bar magnet moves away from the solenoid, then the face of the solenoid is the north pole.<\/p>\n
<\/p>\n
Question 30.
\na) What is meant by least distance of distinct vision?
\nAnswer:
\nIt is the minimum distance up to which eye can see clearly and is called the least distance of distinct vision.<\/p>\n
b) What happens to the image distance in the eye when we increase the distance of an object from the eye.
\nAnswer:
\nThe size of the eye can change, so the image distance is fixed when we increase the distance if the eye does not change, due to power of accommodation of the eye, focal length of the eye lens is changed, which compensates the increase in object distance. Hence image distance remains fixed and image is formed on the retina of the eye.<\/p>\n
OR<\/p>\n
a) Why are we not able to see the things clearly when we come out of a dark room?
\nAnswer:
\nWhen we are in dark, pupil size is bigger, as we come out of dark room, its size needs to become smaller. For that time interval person is unable to see.<\/p>\n
b) Why does the sun appear reddish early in the morning.
\nAnswer:
\nDuring sunrise, the light rays coming from the sun have to travel a greater distance in the earth\u2019s atmosphere before reaching our eyes.<\/p>\n
In this journey, the shorter wave length of lights are scattered out and only longer wavelength are able to reach our eyes. Since blue colour had a shorter wavelength and red colour has longer wave length, the red colour is able to reach our eyes after the atmospheric scattering of light. Therefore the sun appear reddish early in the morning.<\/p>\n
Question 31.
\na) Define speciation?
\nAnswer:
\nSpeciation is arising of a new species from a sub-population of a species which is geographically or reproductively isolated over a long period of time from the other population of the same species.<\/p>\n
b) Mention the sex chromosomes present in human male and human female with the help of a flow chart determine genetically in human beings the sex of the offspring if the sperm carrying x chromosomes fertilizers the egg.
\nAnswer:
\n<\/p>\n
Question 32.
\na) Define 1 dioptre of power of a lens.
\nAnswer:
\nThe SI unit of power of lens is dioptre which is denoted by the letter D. 1 Dioptre is defined as the power of a lens of focal length 1 meter.<\/p>\n
b) The refractive index of diamond is 2.42. What is the meaning of this statement.
\nAnswer:
\nThe refractive index of diamond is 2.42 this means that the speed of light in diamond will reduce by a factor of 2.42 as compared to its speed in air. In other words the speed of light in diamond is 2.42 times less than the normal speed of light in vacuum.<\/p>\n
c) In which type of lens linear magnification is always less than one?
\nAnswer:
\nConcave lens always has linear magnification less than one, because it always gives diminished images.<\/p>\n
<\/p>\n
Question 33.
\na) What will be the formula and electron dot structure of cyclopentane.
\nAnswer:
\nThe formula for cyclopentane is C5<\/sub>H10<\/sub>. Its electron dot structure is given below.
\n<\/p>\nb) How would you distinguish experimentally between an alcohol and carboxylic acid.
\nAnswer:
\nWe can distinguish between an alcohol and a carboxylic acid on the basis of their reaction with carbonate and hydrogen carbonates. Acids reacts with carbonate and hydrogen carbonate to evolve CO2<\/sub>\u00a0gas that turns lime water milky.
\nMetal carbonate \/ metal hydrogen carbonate + carboxylic acid.
\n\u2193
\nSalt + water + Carbondioxide.
\nAlcohols on the other hand, do not react with carbonates and hydrogen carbonates.<\/p>\nOR<\/p>\n
What are addition reaction? What are catalysts? Illustrate with an example.
\nAnswer:
\nReactions which involve addition of two reactants to form a single product are called addition reactions. Catalysts are the substances which can change, usually increase the speed of a chemical reaction without being used up in that reaction.<\/p>\n
For example, vegetable oils having long unsaturated carbon chains are converted into vegetable ghee by heating them in presence of Nickel, platinum or palladium metals used as catalysts.
\n<\/p>\n
V. Answer the following questions. ( 4 \u00d7 4 = 16 )<\/span><\/p>\nQuestion 34.
\na) Define Mendeleev\u2019s periodic law.
\nAnswer:
\nMendeleev\u2019s periodic law states that the properties of elements are a periodic function of their atomic masses, b) The elements of the third period of the periodic table are given below :
\n
\na) Which atom is bigger, Na or Mg? Why?
\nAnswer:
\nSodium is bigger than magnesium at it has lesser nuclear charge so there is less force of attraction between nucleus and valence electrons and less effective nuclear charge. It is, therefore bigger in size.<\/p>\n
b) Identify the most i) Metallic and ii) Non-metallic element in period 3.
\nAnswer:
\ni) Sodium is the most metallic as it can lose electrons easily due to its larger atomic size.
\nii) Chlorine is the most non – metallic element because it can gain electrons easily due to its smallest atomic size.<\/p>\n
OR<\/p>\n
a) What are groups and period in the periodic table?
\nb) Two element M and N belong to group I and II respectively and are in the same period of the periodic table. How do the following properties of M and N vary?
\n1) Size of their atoms
\n2) This metallic characters
\n3) Their valencies informing oxides.
\n4) Molecular, formulae of their chlorides.
\nAnswer:
\na) The vertical columns in the periodic table are called group. The horizontal rows in the periodic table are called periods.
\nb) 1. M and N belong to the same period but group I and li. Therefore N will be smaller than M as a atomic size is decreases from left to right.
\n2. M is more metallic than N. Metalic character goes on decreasing from left to right as tendency to lose electrons.
\n3. Their valencies are 1 and 2 respectively in forming oxides. Valency goes on increasing first and then decreases.
\n4. MCl, NCl2<\/sub>\u00a0are molecules formulae of their chlorides.<\/p>\n<\/p>\n
Question 35.
\nDraw the diagram showing the structure of human alimentary canal and label the following parts.
\na) The part which stores bile juice
\nb) The longest part of the alimentary
\nAnswer:
\n<\/p>\n
Question 36.
\na) Oil and fat containing food items are flushed with nitrogen. Why?
\nAnswer:
\nTo prevent the oxidation of oil and fat present in food items, nitrogen gas is flushed in food packets products formed due to oxidation of oil and fat have unpleasant smell and taste due to rancidity. Flushing food items containing fat and oil with nitrogen prevents rancidity.<\/p>\n
b) Write the balanced chemical equations for the following reactions.
\nAnswer:
\ni) Calcium hydroxide + Carboridioxide \u2192 Calcium carbonate + water
\nAnswer:
\nCa(OH)2(aq)<\/sub>\u00a0+ CO2(g)<\/sub>\u00a0\u2192 CaCO3(s)<\/sub>\u00a0+ H2<\/sub>O(l)<\/sub><\/p>\nii) Zinc + Silver nitrate \u2192 Zinc nitrate + silver
\nAnswer:
\nZn(s)<\/sub>\u00a0+ 2AgNO3<\/sub>\u00a0\u2192 Zn(NO3<\/sub>)2(aq)<\/sub>\u00a0+ 2Ag(s)<\/sub><\/p>\niii) Aluminium + Copper chloride \u2192 Aluminium chloride + Copper
\nAnswer:
\n2Al(s)<\/sub>\u00a0+ 3CuCl2(aq)<\/sub>\u00a0\u2192 2AlCl3(aq)<\/sub>\u00a0+ 3Cu<\/p>\nQuestion 37.
\na) List the physical properties of metals.
\nAnswer:
\nPhysical properties of metals are :<\/p>\n
\n- Metals are usually hard.<\/li>\n
- They are Sonorous.<\/li>\n
- They are lustrus<\/li>\n
- Metals exhibit malleability and ductility<\/li>\n
- They exhibit high tensil strength and have high densities.<\/li>\n<\/ul>\n
b) Differentiate between roasting and calcination. Explain the two with the help of suitable chemical equations.
\nAnswer:
\nRoasting : It is a process in which sulphide ore is heated in the presence of oxygen to convert into oxide.
\n2Zns + 3O2<\/sub>\u00a0\u2192 2ZnO + 2SO2<\/sub><\/p>\nCalcination : It is a process in which carbonate ore is heated in the absence of air to form oxides.
\n
\nBy reduction process Zn can be extracted from its ore.
\nReduction : 2ZnO + C \u2192 ZnO + CO2<\/sub><\/p>\n<\/p>\n
VI. Answer the following question. ( 1 \u00d7 5 = 5 )<\/span><\/p>\nQuestion 38.
\na) What is fertilisation? Distinguish between external fertilisation and internal fertilisation. What is the site of fertilisation in human beings.
\nAnswer:
\nFertilisation is defined as the fusion of a male gamete (sperm) with a female gamete (an ovum or egg) to form a zygote during sexual reproduction external fertilisation.<\/p>\n