24-25 CBSE 9 Science SA Solutions.pdf

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CLASS 9 BOOKS h i P ra c t i c e # S a a i ! Zar o o r i H National Best-selling Publisher Books: Question Banks & Sample Papers BUY Latest Syllabus & Paper Pattern at special discount NCERT Textbooks with Solutions www.educart.co  SOLUTIONS INDEX If you want to go to the answer of any Self-practice Q’s and you know it comes under Objective Q's, then just click on Objective Q's link FOR EXAMPLE within the chapter to navigate quickly. Pg. 1 : Matter in our Surroundings 1 2 : Is Matter Around Us Pure? 3 3 : Atoms and Molecules 5 4 : Structure of the Atom 7 5 : The Fundamental Unit of Life 9 6 : Tissues 11 7 : Motion 13 8 : Forces and Laws of Motion 16 9 : Gravitation 18 10 : Work and Energy 21 11 : Sound 23 12 : Improvement in Food Resources 25  SELF ASSESSMENT SOLUTION 1. (b) Liquids dissolve faster than solids in water. of other gases from their position due to weak Explanation: Due to strong forces of attraction, interparticle forces of attraction. the particles of copper sulphate crystals 5. (a) Both A and R are true and R is the correct usually do not move whereas particles of explanation of A. water are continuously moving and have some kinetic energy. As a result, the particles Explanation: Steam contains the heat energy of water move in between the spaces of of boiling water as well as the latent heat of crystals of copper sulphate and the crystals vapourisation. This heat energy and latent starts dissolving. Consequently, the particles heat causes severe burns on the skin. of water above the crystals acquire blue 6. (b) Both A and R are true and R is not the colour. As the time passes, more and more correct explanation of A. particles of water pass into particles of copper sulphate and the colour starts deepening and Explanation: The particles in gases have large spreading into more water. Ultimately, after empty spaces. Low temperature and high 60 minutes, the whole solution gets coloured. pressure are required to compress gas into a The forces of attraction between the particles liquid. of copper sulphate solution are weak and 7. (A) The phenomenon involved in drying clothes hence, they move quickly. As a result, the in evaporation. particles of copper sulphate solution rapidly get into the spaces between the particles Evaporation is a surface phenomenon of of water and therefore quickly get evenly change of a liquid into vapours at any distributed in water. Crystals of copper temperature below its boiling point. sulphate dissolve faster in water but copper (B) Mahak's clothes will dry faster than Riya's. sulphate solution being a liquid dissolves Factors affecting the evaporation: faster than the crystals. Particles of a solid (1) The rate of evaporation increases with have a strong force of attraction than liquids an increase in surface area which as the particles of liquid are not as closely Mahak did by spreading the clothes on packed as that of solid. clothline 2. (d) Sugar crystals (2) An increase in temperature – Evaporation becomes fast as the kinetic Explanation: In sugar crystals, the particles energy of the molecules increases with are closely packed so they have the strongest an increase in temperature. force of attraction between the particles. Honey and water are liquids, the particles (3) An increase in the speed of the wind are loosely packed and have less forces of – Clothes dry on a windy day faster attraction. Air is a mixture of gases in which as the wind takes away the water particles are very loosely packed, so the force molecules of the clothes and increases of attraction is very weak. the rate of evaporation. (4) A decrease in humidity – If the amount 3. (b)  Adding salt to the water increases its of water vapours is high in the air, the boiling point and cooks the egg better. clothes will dry slowly. (Any two) Explanation: Pure water has boiling point i.e., (C) Applications of Evaporation. 100°C. If we add salt to the water in which eggs are to be boiled, the boiling point increases and (1) Ice is rubbed on the burnt part of the the eggs get cooked in a better way. skin. The reason being due to burning, the temperature of the injured skin 4. (d) (II) and (IV) increases. When ice is rubbed, the Explanation: The particles of solids do not excess heat from the skin is taken by move much from their positions and hence can large latent heat of fusion of water. As only vibrate around their mean fixed positions. a result, the temperature of the injured The particles of gases can displace particles skin decreases and we feel less pain. Matter in Our Surroundings 1 Click here to buy latest Educart books on Amazon - https://amzn.to/3vfZ5nZ  (2) We sprinkle water on the roof in 11. (A) Common properties of liquids and gases: summer. The water from the roof (1) Both of them do not have a fixed shape. evaporates by absorbing heat from (2) Both can flow, i.e., show fluidity. the ground and the surrounding air. By (B) We can convert gas into a liquid: losing heat, the ground becomes cool and we feel comfortable. (1) By lowering the temperature. (3) Sweating keeps our body cool. On a (2) By increasing the pressure. hot summer day or after doing heavy (C) The heat energy which is supplied to exercise, the temperature of our body the solid once it starts melting is used to rises. Due to an increase in temperature overcome the force of attraction between our body gives out sweat. When the the particles of the solid. The temperature sweat evaporates, it absorbs heat from does not rise when the solid is melting. our body and after losing heat, our Once all the solid changes to liquid, further body feels cool. (Any two) heat supplied changes the temperature of the substance. 8. (1) Condensation is transformation of gas into liquid by cooling. 12. (A) The syringe has gas particles present in it Gas æCool ææÆ Liquid which are loosely packed. So, when Tina pressed the piston, she applied pressure Freezing is the transformation of liquid into and as pressure increases, the space solid by cooling. between the particles decreases. Thus, Liquid æCool ææ Æ Solid it became difficult for Tina to press the (2) Condensation is opposite of boiling. piston deeper and deeper. Freezing is reverse of melting. (B) Syringe 1 → Syringe 3 → Syringe 2 9. (A)  All things around us occupy space and Pressing the piston will be easier in the have mass. We can sense their presence by syringe which contains the particles that our sense organs. This is common among have weak force of attraction between all the things we see around us. the particles or large space between the (B) CNG – Compressed Natural Gas particles. Thus, in the given images, difficulty level will increase from LPG – Liquified Petroleum Gas coconut oil to cotton and then to saw 10. (A)  The melting point of ice indicates the dust syringe. strength of the forces of attraction between (C) (i) Particles of both air and bromine move its particles. freely in all directions. Air particles (B) (i) He observed that the ink spreads faster which are in the upper jar move and the yellow colour of honey spreads downwards in the jar of bromine and very slowly. bromine particles which are in the (ii) We can conclude that honey is denser lower jar move upwards in the jar of than ink. The rate of diffusion of liquids air. This continues till a uniform mixture decreases with an increase in density of air is obtained. of liquids. (ii) The process involved is diffusion. 2 Science Class IX Click here to buy latest Educart books on Amazon - https://amzn.to/3vfZ5nZ  SELF ASSESSMENT SOLUTION 1. (c) (III) and (IV) 6. (a) Both A and R are true and R is the correct Explanation: A solution is a homogeneous explanation of A. mixture of two or more substances. Soda water Explanation: Sodium chloride (NaCl) is a pure and lemonade are clear solutions without any substance as it contains only a single type of visible boundaries. Whereas wood and coal are matter with its composition same throughout. solid substances. 7. (A) Smog is a mixture of smoke and fog. Smoke 2. Element Compound Mixture and fog are colloids. (B) The figure shows the Tyndall effect. Tyndall (c) Gold Water Sea water effect is observed when sunlight passes Explanation: Element is a basic form of through the canopy of a dense forest. Mist matter that cannot be broken down into present in the forest contains tiny droplets simpler substances by chemical reactions. In of water which act as particles of colloid the given table, sodium, silver, silicon, gold, dispersed in air. tin and mercury are elements. Compounds (C) (i) Liquid in gas – Fog, cloud and mist. have fixed compositions and fixed formulas. (ii) Solid in gas – Smoke and automobile Sodium chloride (NaCl) and water (H2O) are exhaust. examples of compounds in this table. Mixtures (iii) Liquid in liquid – Milk and face cream. do not have fixed composition. Elements and compounds mix together in any proportion. (iv)  Solid in liquid – Mud and milk of Sugar solution, lemonade and seawater are magnesium. mixtures in the above table. (Any one example is to be given to get full marks) 3. (a) Starch solution 8. (A) The element which is a poor conductor of Explanation: The figure shows Tyndall effect. heat and electricity is a non-metal. Scattering of a beam of light by the colloidal particles is Tyndall effect. Salt solution, copper (B) Other characteristics possessed by this sulphate solution and sugar solution are element are: homogeneous mixtures and do not scatter in (1) it is non-lustrous visible light. So, they do not show Tyndall effect. (2) it is non-sonorous (3) it is not malleable 4. (d) (I), (II), (III) and (IV) (4) it is not ductile Explanation: An element cannot be broken down into simpler substances. Soda water is Related Theory an example of solution in which carbon dioxide  Mercury is the only metal which is liquid at room gas is a solute and water is a liquids. A mixture temperature. or compound burns in air to produce carbon dioxide and water. Water on electrolysis forms 9. A salt solution does not show Tyndall effect because the particles of salt solution are two gases i.e., hydrogen and oxygen, and water extremely small in size, so such small particles freezes at 273 K (0°C) and forms steam at cannot scatter light rays falling on them. 373 K (100°C). Water is a compound. Whereas milk solution particles are bigger enough (between 1 nm to 100 nm) to scatter 5. (b) Both A and R are true and R is not the the light passing through them. correct explanation of A. Explanation: A solution is a homogeneous 10. (A) No, the two solutions are of different mixture of two or more substances. A solution concentrations. can be a solid solution (alloy) or a gaseous (B) Concentration of Ramesh's solution solution (air) or a liquid in liquid solution Mass of solute (lemonade). Mass % = Mass of solution × 100 Is Matter Around Us Pure? 3 Click here to buy latest Educart books on Amazon - https://amzn.to/3vfZ5nZ  10 g Following are the conclusions: = × 100 ( 10 + 100 g ) The observations made by Roohi suggest that on heating iron filings and sulphur powder, a 10 new substance iron sulphide (FeS) was formed. = × 100 110 The observation of Alankrita suggest that 100 mixture of iron filings and sulphur do not react = with each other and showed the properties of 11 both the components. = 9.09% = 9.1% It can also be concluded that a compound (new Concentration of Sarika's solution substance FeS) reacts with dilute hydrochloric 10 acid but a mixture does not react. Mass % = × 100 = 10% 100 12. (A)  Vivek will get a homogeneous mixture The solution prepared by Ramesh has less of lemon and water. When salt or sugar percentage by mass than that of Sarika. is added to the water, we get a salt solution or sugar solution which is also a 11. Observations made by Roohi. homogeneous mixture. Test Observations (B) No, a solution is not a liquid always. (A) Use of magnet No separation of A solution may be solid, liquid or gas. constituents was (C) No, a solution cannot be heterogeneous in seen as the magnet nature. showed no effect on (D) Volume of lemon juice (solute) = 20 mL the mixture. Volume of water (solvent) = 100 mL (B) Addition of dil. FeS + 2HCl → FeCl2 Volume of solution hydrochloric + H2S acid Hydrogen sulphide = Volume of lemon juice + Volume of water gas has a rotten egg = 20 + 100 = 120 mL smell was obtained. Volume by volume percentage of a solution Observations made by Alankrita. Volume of solute = × 100 Volume of solution Test Observations 20 (A) Use of magnet Iron filings got = × 100 = 16.67% 120 attracted to the magnet and they Caution were separated  Students must keep in mind that which quantities are from the sulphur given in which units. If mass of solute and mass of powder. solution are given in mL or kilogram, then use mass (B) Addition of dil. Fe + S + HCl → FeCl2 by mass percentage of a solution. If mass of solute hydrochloric + H2 + S in grams and volume of solution in mL is given, use acid Hydrogen gas is mass by volume percentage of a solution. If solute evolved which burns and solution both are in mL, then use volume by with a pop sound. volume percentage of solution. 4 Science Class IX Click here to buy latest Educart books on Amazon - https://amzn.to/3vfZ5nZ  SELF ASSESSMENT SOLUTION 1. (b) Potassium sulphate (1) Oxygen reacted with a large number of Explanation: In K2SO4, K+ is potassium ion. Its elements and formed compounds. Latin name is Kalium and has valency of +1. (2) This atomic mass unit gave mases of most SO4– is a polyatomic ion and has a valency of of the elements as whole numbers. 2–. Its name is sulphate ion. K SO4 7. (A) Atomic mass unit is a mass unit equals 1+ 2–  1  to exactly one-twelfth  th  the mass K2SO4  12  of one atom at carbon–12. The standard 2. (a)  Total mass of the chemicals remain the same. reference for measuring atomic masses is Explanation: Alia took BaCl2 in a test tube and taken as C–12. CuSO4 solution is a conical flak. Slowly she puts (B) The full form of IUPAC is International this set up on the electronic balance and noted Union of Pure and Applied Chemistry. the weight as 425.6 g. After a while, she tilted (C) (i) Ammonia (NH3) the solution of BaCl2 in the flask so that BaCl2 Combining elements: Nitrogen and and CuSO4 solutions react. When white residue hydrogen is formed in the solution, she again weighed the Ratio by mass: flask and found the weight as 425.6 g. It means the weight of the solutions before the reaction N : H and after the reaction remains the same. 14 : 1 × 3 It follows the law of conservation of mass. 14 : 3 3. (a) ZnS (ii) Magnesium nitrode (Mg3N2) Explanation: Chemical formula formed by two Combining elements: Magnesium and ions – Nitrogen Zn S Ratio by mass: 2+ 2– Mg : N ZnS 24 × 3 : 14 × 2 4. (a) Only (II) 72 : 28 Explanation: Ions can be monovalent, 18 : 7 bivalenter, trivalent, i.e., have single charge, (iii) Copper oxide (Cu2O) double charge or triple charge. An ion of a Combining elements: Copper and non-metal is always negatively charged ion as Oxygen the atom gains electrons to complete its octet. Ratio by mass: A + e – → A– Cu : 0 In positively charged ion formation, the atom 63.5 × 2 : 16 loses one electron or more than one electron 127 : 16 to form cations to complete its octet. A → A+ + e – 8. (A) Differences between sodium atom and sodium ion is given below. 5. (b) Both A and R are true and R is not the correct explanation of A. Sodium Atom Sodium Ion Explanation: Molecules of Helium are made up (1) It is a neutral (1) It is a positively of only one type of atoms i.e., it is monoatomic. atom. charged ion, cation – Na+. 6. (c) A is true but R is false. Explanation: Oxygen was considered relevant (2) It is very (2) It is non- due to two reasons: reactive. reactive. Atoms and Molecules 5 Click here to buy latest Educart books on Amazon - https://amzn.to/3vfZ5nZ  Sodium Atom Sodium Ion The given sample is a pure sample as all the three samples have the given (3) Number of (3) Number of composition. electrons protons are (B) The other properties which can be used are equal to more than to find out are – melting point and boiling number of the number of protons. electrons. point. We know the pure compound has fixed melting and boiling points. Melting (B) Difference between chlorine atom and and boiling points of all the three samples chloride ion is given below. can be determined. It those come out Chlorine Atom Chloride Ion same, the given simple is a pure compound. (1) It is a neutral (1) It is a negatively 11. (A) (i) A cation which does not contain a metal + atom. charged ion, atom is ammonium ion, NH4. anion Cl–. (ii) Noble gases like helium, neon and argon (2) It is very (2) It is non-reactive. occur in nature in monoatomic form. reactive. (B) (i) Trivalent ions of different elements (3) Number of (3) Number of having positive valency are Aluminum electrons electrons are (Al3+) and iron in its ferric form (Fe3+). are equal to more than (ii) Trivalent ions of two different elements number of the number of having negative valency (anions) are protons. protons. phosphate (PO43–) and nitride (N3–). (Any 2 of 3 differences will give you full 12. (A) The chemical formulae of compounds are marks.) AH2, ACl2 and AO) which indicate that the 9. Atoms of different elements join together in valency of element ‘A’ is 2. definite proportions to forms molecules of (B) Element ‘A’ is a metal because it is electro- compounds. For examples – Ammonia which positive and react with non-metals like is made up of nitrogen and hydrogen. Carbon hydrogen, chlorine and oxygen. dioxide is made of carbon and oxygen. (C) Chemical formula 10. (A) Megha can add the mass of hydrogen and A CO3 oxygen for all the three samples. If the 2 2 mass of all samples 1–3 comes the same, then the samples are pure liquids. A2(CO3)2 ACO3 Sample Mass of Mass of Mass of (D) Element ‘A’ is a metal, electropositive in hydrogen oxygen sample nature and it forms cation by losing the Sample 1 0.147 g + 0.852 g = 0.999 g electrons. Sample 2 0.292 g + 1.708 g = 2.0 g A → A2+ + 2e– (E) If the atomic number of element ‘A’ is 12 Sample 3 0.309 g + 2.240 g = 2.549 g then the element is magnesium. 6 Science Class IX Click here to buy latest Educart books on Amazon - https://amzn.to/3vfZ5nZ  SELF ASSESSMENT SOLUTION 1. (b) (I) and (III) 7. (A) In the atoms Explanation: The isotopes are atoms of same Shells Atomic number element having same atomic number but 1 K different mass number. Atomic number means number of protons present in the nucleus of an 1 1 atom. 2 K L An atom is electrically neutral so it has the 2 8 10 same number of electrons. Since electrons are same, chemical properties of different isotopes 3 K L will be same but physical properties will differ 2 6 8 as the number of neutrons are different. 4 K L M N 2. (b) Protons 2 8 8 1 19 Explanation: Nucleus has two sub-atomic particles – Protons and Neutrons. Protons (i) The atom having the highest atomic are positively charged subatomic particles number is (IV). It has 4 shells and the atomic number is 19. whereas neutrons do not carry any charge. Therefore, the charge present in the nucleus is (ii) As we can see the valence shell has 1 electron in atoms (I) and (IV), so these due to the protons present in the nucleus of an two atoms have valency. atom. 3. (b) 40 40 (B) Atom Atomic Element Type 18Ar and 20Ca number Explanation: Option (a) has isotopes of carbon having same atomic number 6 and different (a) 1 Hydrogen Non-metal mass number. Option (b) shows a pair of isobars as the atomic (b) 10 Neon Noble gas number is different but mass number is same. (c) 8 Oxygen Non-metal 4. (c) Nucleus (d) 19 Potassium Metal Explanation: The size of the nucleus is very small as compared to the size of the atom. The electrons revolve around the nucleus in well (C) Chemical formula between (III) and (IV): defined orbits. Nucleus is positively charged (II) has valency –2 as it have 8 electrons. due to the presence of protons and neutrons. It needs only 2 electrons to complete its octet to be stable. (IV) has +1 valence Neutrons are neutral i.e., they do not carry any electron as it has 19 electrons can lose 1 charge. electron to complete its octet and become 5. (c) A is true but R is false. stable. D C Explanation: So long as electrons revolve in 1 2 a particular orbit, it neither emits nor absorbs D2C energy as per Neils Bohr. or after identification of elements. 6. (c) A is true but R is false. D – Potassium Explanation: The net charge on the nucleus is C – Oxygen positive which is called nuclear charge. Nucleus K O also have neutrons but neutrons are neutral 1 2 particles. K2O. Structure of the Atom 7 Click here to buy latest Educart books on Amazon - https://amzn.to/3vfZ5nZ  8. (A) Mg -→ Mg2+ +2e– Nucleus 2,8,2 2,8 n K-shell Number of electrons = 10 L-shell Number of protons = 12 Number of neutrons = 12 Nitrogen atom has atomic number 7. Its Beryllium having atomic number 4 can electronic configuration is 2, 5 and has two form Be2+ ion with number of neutrons shells, i.e., K having 2 electrons and L shell more than the electrons. Similarly, calcium with 5 electrons. Nucleus has 7 protons atom satisfies the given condition. and 7 neutrons. (C) Electrons are negatively charged and are (B) Nitrogen has 5 electrons in its valence shell not stationary. They revolve around the and it needs 3 more electrons to complete nucleus, so centrifugal force balances the its octet, so it will gain 3 electrons and form force of attraction. an anion. 11. (A) The number 13 represents atomic number N + 3e– → N3– and the number 27 represents mass 2, 5 2, 8 number of ‘X’. (B) The valency of atom ‘X’ would be 3. 9. (A) K shell can accommodate maximum 2 Its atomic number is 13. Electronic electrons, L shell’s capacity is 8 electrons configuration is 2, 8, 3. It means it has and M shell has only 2 electrons so the 3 valence electrons. Valence electrons in maximum number of electrons present in metals is the valency of that metal. the atom is 12 K L M Al → Al 3+ + 3e− 2 8 2 2, 8 , 3 The symbol of this element is Mg. (C) The element ‘X’ is Aluminium. (B) The positively charged radiations Its ion is Aluminium ion. discovered by E Goldstein in a gas Symbol of ion is Al3+ discharge tube are called canal rays. 12. (A) Rutherford selected gold foil because it is 10. (A) All atoms consist of electrons and protons. malleable and is about 1000 atoms thick. Protons and neutrons have a mass of (B) a-particles are doubly charged helium ions 1 each and electrons have almost and have a mass of 4 u and the fast moving negligible mass. The negative charge of a-particles have a considerable amount of electrons balances the positive charge on energy. If light metal is used, the nucleus protons. The atomic number of an element will be light and the a-particles may not be is the number of protons present in the deflected back. Instead, it may be pushed nucleus. Moreover, the mass and charge forward. of the nucleus of the atom of any element (C) (i) Most of the space inside the atom is are found to be whole numbers. All of this empty as most of a-particles passed shows that protons are constituents of all straight through the gold foil without elements. any deflection. (B) Most of the atoms which have two valence (ii) Some of the a-particles were deflected by the foil by small angles indicating electrons can satisfy this condition. that the positive charge of the atom Mg atom atomic number = 12 occupies very little space. Mass number = 24 (iii) A very small fraction of a-particles Electronic configuration = 2, 8, 2 appeared to rebound, indicating that Number of electrons = 12 all the positive charge and mass of the gold atom were concentrated in Number of protons = 12 a very small volume within the atom. Number of neutrons = 24 – 12 = 12 This also indicates that the size of the Mg ion which is formed by losing two nucleus is very small as compared to electrons the size of the atom. 8 Science Class IX Click here to buy latest Educart books on Amazon - https://amzn.to/3vfZ5nZ  SELF ASSESSMENT SOLUTION 1. (b) It is the cell of a plant. (ii) The unit membrane by which vacuole is Explanation: A plant cell has an outermost surround by is a tonoplast. layer as a cell wall lying outside the plasma (B) (i) Vacuole provides turgidity and rigidity membrane. It is a rigid membrane made of to the plant cells. cellulose. Vacuoles are few in number but large (ii)  In some unicellular organisms, in size. Centrioles are not present in the plant specialised vacuoles maintain water cell. Nucleus is displaced to one side due to the balance. large size of the vacuole. (C) (i)  Vacuoles are called storage sacs of 2. (d) only (D) the cell. The stored material may be Explanation: Nerve cell is the largest cell in the solid or liquid food or toxic metabolic human body. It is a branched cell. byproducts or end products of the cell. (ii) A vacuole can store amino acids, 3. (c) Golgi apparatus sugars, proteins, water and another Explanation: The material synthesised near metabolic wastes. the ER is packaged and dispatched to various targets inside and outside the cell through the 8. (A) X – Normal or turgid plant cell. Golgi apparatus. Y – Plasmolysed cell. (B) If Y – cells are kept in a hypotonic solution, Related Theory the cells will become deplasmolysed and  Its functions also include the storage and appear as X – cells, i.e., normal plant cells. modification of products in vesicles. It is also involved in the formation of lysosomes. In some cases, The process involved is plasmolysis. complex sugars may be made from simple sugar in The phenomenon of shrinkage of the Golgi apparatus. protoplast from the cell wall due to 4. (b) Safranin exosmosis in a plant cell when placed in a hypertonic solution is called plasmolysis. Explanation: Iodine is used to test the presence of starch in the leaves of the plants. Methylene 9. (A) (i)  Unicellular organism which has an blue stain is used to prepare human cheek cells. irregular shape – Amoeba Glycerine is used to mount the sample as well (ii) A cell which has an irregular shape – as to avoid drying of the sample. white blood cells. 5. (b) A is false but R is true. (B) (i) Amoeba is a freshwater organism Explanation: Central vacuoles occupy 50- which continuously gains water in its 70% of the plant cell volume. That is why the body due to osmosis. nucleus is displaced to one side of the cell. (ii) Amoeba has contractile vacuole by which it throws out excess water from 6. (b) Both A and R are true and R is not the its body. correct explanation of A. Explanation: Eukaryotic cells are generally 10. (A) The diagram is of prokaryotic cell. larger than prokaryotic cells, up to ten A – cell wall times larger on an average. In addition, their (B) The term used for genetic material which cells contain significantly more DNA than lies in the cytoplasm and not covered by prokaryotic cells. Mitochondria, endoplasmic any envelope is nucleoid. reticulum, Golgi apparatus, lysosomes, (C) The only cell organelle present in a microtubules, microfilaments, and centrioles prokaryotic cells which is not membrane are all absent in prokaryotic cells. bound is ribosome. 7. (A) (i) The fluid present in the vacuole is cell There is only one chromosome present in sap. this cell. The Fundamental Unit of Life 9 Click here to buy latest Educart books on Amazon - https://amzn.to/3vfZ5nZ  11. Similarities between plant cells and animal (iv) Organelle which takes part in storage, cells. modification and packaging – Golgi (1) Cells are the building blocks of plant and Apparatus animal cells. (B) ‘X’ is the plasma membrane or cell (2) Both have membrane-bound cell membrane. It is called a selectively organelles to perform different functions. permeable membrane because it allows (3) Both have a nucleus as the control centre. or permits the entry and exit of some Dissimilarities between plant cells and animal materials in and out of the cell. It also cells. prevents the movement of some other (1) Cell wall is present in plant cells but animal materials. cells do not have cell wall. (C) The structure marked as ‘Y’ is centriole. (2) Plants have plastids but absent in animal (D) Organelle ‘Z’ is mitochondria. It is called a cells. strange organelle because it has its own (3) Plant cells have large vacuole but animal DNA and ribosomes. So, it is able to make cells either have small vacuoles or are absent. some of its own proteins. Function of mitochondria – Mitochondria 12. (A) (i) The diagram is of animal cell. The brain is called the powerhouse of the cell. The of the cell – Nucleus. energy required for various chemical (ii) The jelly – like substance present in the processes released by mitochondria in the brain of the cell – Nucleoplasm. form of ATP. Inner foldings of mitochondria (iii) Organelle which contains powerful called cristae increase the surface area for digestive enzyme – Lysosomes. ATP generates chemical reactions. 10 Science Class IX Click here to buy latest Educart books on Amazon - https://amzn.to/3vfZ5nZ  SELF ASSESSMENT SOLUTION 1. (a) Secretion of substances 7. (A) Blood is a fluid connective tissue. Explanation: In some instances, cells of (B) The components present in the blood are: columnar and cuboidal epithelium fold inward Plasma, Red Blood Cells (RBC), White Blood and forms a multicellular gland whose main Cells (WBC) and Platelets. function is the secretion of useful substances like enzymes, hormones etc. (C) Blood platelets are minute, anucleated and fragile segments of bone marrow. They 2. (b) only (II) help in the clotting of blood the site of Explanation: The cells of connective tissue injury. are loosely spaced and embedded in an (1) Blood is red in colour due to intercellular matrix. These matrices may be haemoglobin present in RBC whereas jelly-like, fluid, dense or rigid. All the tissues are lymph is a colourless fluid that is filtered not flexible, like bone is strong and inflexible out of the blood capillaries. and all the bone cells are embedded in the (2) Lymph has more WBCs than blood. hard matrix. Only bone forms a framework that provides support to the organs. None of 8. (A) Xylem and phloem are complex vascular the other connective tissue like blood, tendon, tissues. They are conducting tissues of the ligament, cartilage, areolar and adipose tissues plants. They are called complex tissues forms a framework. because each of them is made of more 3. (d) Both muscles show involuntary movements than one type of cells that coordinates their Explanation: Movement of muscles of activities to perform a common function. the heart for pumping blood as well as (B) Water hyacinth has spongy petioles which movement of food inside the intestine are enclose a lot of air in tissue aerenchyma. Air not controlled by our will. It happens on its makes the plant lighter than water so that own and are called involuntary muscles. it is able to float on the surface of water. 4. (c) (II) and (IV) 9. (A) (i) Striated muscles are also called Explanation: Root hairs help in the skeletal muscles or voluntary muscles. absorption of water and minerals from After vigorous exercise, the striated the soil. Blood transports oxygen, carbon muscles contact rapidly and remain dioxide, nutrients, enzymes, hormones, etc. like that for a longer duration, they get fatigued due to the accumulation of 5. (a) Both A and R are true and R is the correct explanation of A. lactic acid in them. Explanation: Phloem is a complex vascular (ii) When a ligament gets overstretched tissue that helps in the translocation of food a person gets sprain. Ligament tissue manufactured in leaves to the different is very elastic and contains very little parts of the plant. The four elements of matrix. Two bones can be connected to phloem are, sieve tubes, companion cells, each other by a ligament. phloem parenchyma and phloem fibres. (B) Adipose connective tissue is present in Related Theory the blubber of a whale and the hump of a  Xylem is also a conducting tissue but it transports camel. water and minerals from roots to the apical parts of 10. (A) The elongated pair of cells are known as the plant only. guard cells. They are kidney-shaped cells. 6. (b) Both A and R are true and R is not the Stomata are necessary for the exchange of correct explanation of A gases and transpiration. Explanation: Nervous system comprises of (B) Desert plants grow where there is a scarcity brain, spinal cord, and nerves that functions of water. To help desert plants to minimise to receive and transmit impulse. A neuron loss of water, the plants have smaller and is the basic structural and functional unit of fewer stomata as compared to rainforest the nervous system. plants. Rainforest plants have plenty Tissues 11 Click here to buy latest Educart books on Amazon - https://amzn.to/3vfZ5nZ  of water so they have larger and more stomata. Moreover, desert plants have thicker epidermis since protection against Striations water is critical. In desert plants, epidermis has a thick waxy coating on its outer surface. Thick waxy coating is a chemical substance with waterproof qualities. 11. (A) Neha was trying to find out about the Nuclei function of the shoot tip and whether plant 2 will grow or not. Shoot tip has apical meristematic tissue, she had cut the apical tissue so plant 2 did not show any growth after a week. (B) Both the plants chosen by Neha were of the same height and same species so they also need the same conditions. Both plants need water, sunlight and manure to grow. Conditions (i) and (ii) would make the (c) experiment invalid only option (ii) is no, rest Types of muscles fibres: (a) striated muscle, (i) and (iii) are yes. (b) smooth muscle, (d) cardiac muscle (C) Meristematic tissue take up a specific role (B) (i) The muscle fibres which show rhythmic and lose the ability to divide. As a result, contraction and relaxation throughout they form a permanent tissue. This process life are cardiac muscles. of taking up a permanent shape, size and function is called differentiation. Cells of (ii) Smooth muscles help in the movement meristematic tissue differentiate to form of food in the alimentary canal. different types of meristematic tissue. (iii) Smooth muscles are found in the iris of the eye, in the ureters and in the 12. (A) bronchi of the lungs. Nucleus (C) Skeletal connective tissue includes bones Striations and cartilage. Functions of skeletal connective tissue. (1) It forms the endoskeleton of the body (a) of vertebrates. (2) It gives support to the body. (3) It gives a definite shape to the body. (4) It protects the vital organs of the body such as brain, lungs, ears, etc. (5) It anchors the muscles and provides (b) movement to the animal body. 12 Science Class IX Click here to buy latest Educart books on Amazon - https://amzn.to/3vfZ5nZ  SELF ASSESSMENT SOLUTION 1. (c) 60 50 Distance (m) Velocity 40 0 (km/hr) 30 20 Time (s) 10 0 5 10 15 20 Velocity-time graph is used to represent Time (minutes) acceleration. Explanation: Graph (a) shows non-uniform Velocity (m/s) retardation, graph (d) shows uniform retaration and graph (b) shows that the body is moving with constant velocity. 2. (b) 3 m Time (s) Explanation: Rate of growth of hair on 5. (b) Both A and R are true and R is not the the human head in one day = 0.44 mm or correct explanation of A. 0.44 × 103 m or 44 × 105 m. Explanation: Acceleration of a body is a In one month = 44 × 105 × 30 m measure of change in the velocity of the In one years = 44 × 105 × 30 × 12 m body per unit time. In twenty years = 44 × 105 × 30 × 12 × 20 Related Theory = 3.168 m  Acceleration is a vector quantity: So, the normal adult male cut hair on (i) When v > u; a = 0 the human head is 3 m approximately in (ii) When v > u; a = positive. The acceleration is in the direction of velocity. 20 years. (iii) v > u; a = negative. The negative acceleration is 3. (c) called retardation. 6. (d) A is false but R is true. Explanation: Units of speed and velocity are same. They are expressed in m/s or Speed cm/s or km/h. Speed is distance travelled per unit time. Dis tan ce travelled ( s ) Speed (v) = 0 Time 10s Time taken ( t ) Velocity is distance travelled in a given Explanation: In graph (c), a ball moves direction per unit time. vertically up and then comes down, and caught again after 10 seconds by the Displacement Velocity = person. This is because in this case, the Time speed first decreases and when the ball 7. (A) The diameter of circular track = 200 m. strats coming down the speed increases. Graph (b) shows that the body is moving with constant velocity. 200 m X Y 4. (b) Speed and acceleration respectively O Explanation: Distance-time graph is used to determine the speed of the body. Motion 13 Click here to buy latest Educart books on Amazon - https://amzn.to/3vfZ5nZ  Since athletes ‘A’ fell down half way, he 9. (A) Y B 1 1 covered only round of the track, i.e., 2 2 the circumference of the circular track. A Distant Circumference of cirle = 2pr = pD = 3.14 × 200 = 628 m. \ The distance covered by athlete ‘A’ when X 0 Time 628 (B) h = 18 km/h he way half way will be = 314 m. 2 5 1 km/h = m/s Athletes ‘A’ started from x. On completion of 18 half round he was at ‘y’. This displacement  5 xy = 2000 m = 18 × = 5 m/s. 18 (B) Time taken to complete one round by v =0 athlete ‘B’ = 40 sec. t = 5 sec. Total time = 3 minutes 20 sec. v = u + at (3 × 60 + 207) = 200 sec. 0 =5+a×5 200 −5 Number of rounds completed = a= = 5 rounds 40 5 Displacement of athlete ‘B’ is zero as he = –1 m/s2 reached at ‘X’ the initial point. Distance Negative sign indicates retardation. covered by him in 3 minutes 20 seconds is 10. (A) The net displacement of the car is 30 km, 5 rounds or i.e., from house to school is the shortest Distance covered = 2pr distance travelled by the car 200 House 30 km  → School ←  → Library. 20 km 2 × 3.14 × × 5 = 3140 m. 2 The displacement will be zero. (B) The total distance travelled by a car is 70 km. (C) Time taken by athlete ‘C’ to complete the 20 km race – House 30 km  → School ←  → Library. 20 km Time taken to complete one round = 50 sec. (C) The car did not move with uniform motion Time taken to complete five rounds = from house to school as different distances 5 × 50 = 250 sec. = 4 min. 10 sec. are travelled at different speeds. Time taken by athlete ‘D’ to complete the House to school – 30 km, school to library race – 20 km library to school 20 km Time taken by athlete D = 25 sec. \ The total distance travelled is 30 + 20 + Time taken to complete the race = 20 = 70 km. 5 × 25 = 125 sec. 2 min. 5 secs. 11. (A) Total distance by students covering four Athletes move at different speeds and rounds of track = 4 x 150 m = 600 m. speed may be different at different points (B) As the initial and final positions of students of time. So, the motion of the athletes is are the same, the displacement of students non-uniform. is zero. (C) Motion of students is non-uniform, as they 8. (A) B is 100 km ahead of A. cover unequal distances in equal intervals of time. QR 150 − 100 (B) Speed of B = = = 25 km/h PR 2−0 12. (A) u = 15 ms–1 (C) A will catch B at point Q after 2 hrs and at v =0 a distance of 150 km. v = 20 m Difference = 50 km/h v2 – u2 = 2as (D) Uniform motion. Both are straight line v 2 − u2 a= graphs. 2s 14 Science Class IX Click here to buy latest Educart books on Amazon - https://amzn.to/3vfZ5nZ  N (0) − (15) 1 2 a= 2 × 40 (D) 10 km C B −225 a= = – 11.25 ms–2 40 She must have deceleration 11.25 ms–2. (B) (i)Distance-time graph gives speed. W E OI 5 km A Distance (km) S OA = 5 km, AB = 5 km, BC = 10 km Time (min) The distance travelled by Reema from O to C = OA + AB + BC (ii) Speed (or velocity)-time graph gives the distance travelled. = 5 + 5 + 10 = 20 km. (C) The displacement of the object in going  from O to C = OC Velocity (m/s) By applying Pythagoras theorem. OC2 = 52 + 52 OC = 52 + 52 0 2 4 6 8 10 12 14 16 18 20 Time (s) OC = 5 2 km. Motion 15 Click here to buy latest Educart books on Amazon - https://amzn.to/3vfZ5nZ  SELF ASSESSMENT SOLUTION 1. (a) Trolley 1 action, there is always an equal and Explanation: We know that, opposite reaction, i.e. the forces of action the more the mass, the more is and reaction are always equal and the inertia. Trolley 1 has mass opposite. 2.5 kg whereas trolley 2 has mass 0.8 kg. 6. (C) A is true but R is false. Hence, trolley 1 will have more inertia. Explanation: Inertia of direction means 2. (d) Newton that a body moving along a direction cannot change the direction of motion Explanation: by itself. In this case, the person tries to maintain his original direction of motion SI unit Term due to inertia of direction. Pascal Pressure Caution Watt Power  Many of the students get confused between Inertia of rest, Inertia of motion and Inertia of direction. Try Joule Work done to learn the difference between three types of Inertia Newton Force by writing them in tabulated form. 3. (a) 8 N upwards 7. (A) The force acting on each box is unbalanced because acceleration is produced for each Explanation: 5N force is the force to the box which indicates that a force is produced left and 5N is to the right, so the resultant which helps each box to move. Also, the force is zero as these forces balance each force acting on each box was unbalanced other. The force 10N is upwards and 2N as the boxes moved forward. downwards and the resultant force is (B) Box 1– Mass of box (m) = 10 kg 10N – 2N = 8N upwards. Acceleration (a) = 200 m/s2 1 F =m×a 4. (b) times 4 = 10 × 200 Explanation: Mass of the loaded truck = 2000 N becomes 2 times Box 2– m = 20 kg m = 2 times a = 100 m/s2 F F =m×a Driving force is halved 2 = 20 × 100 = 2000 N As we know, Box 3– m = 40 kg F = ma a = 50 m/s2 F F =m×a a= = 40 × 50 = 2000 N m Box 4– m = 80 kg F F = a = 25 m/s2 2×2 4 F =m×a 1 So, the acceleration would change th = 80 × 25 = 2000 N times. 4 The amount of force is 2000 N exerted by the man on each box. 5. (a) Both A and R are true and R is the correct (C) When we talk of force acting on a body, we explanation of A. mean an unbalanced force. Explanation: The rotation of the sprinkler If the resultant of all the forces acting on is explained on the basis of third law a body is not zero, the forces are called Newton's third law states that to every unbalanced forces. 16 Science Class IX Click here to buy latest Educart books on Amazon - https://amzn.to/3vfZ5nZ  8. (A) Acceleration of trolley 1: 11. (A) No, the tennis and the football will not hit Mass (m) = 2.5 kg the floor with the same momentum as F = 12 N their masses are different. We know F = m × a (B) An equal and opposite force exerted by the floor on the balls caused them to bounce F back. a= m (C) The balls will reach a height of less than 5 m as some energy or velocity or 12 = 4.8 m/s2 momentum of balls will be lost after the 2.5 balls hit the floor. (B) Mass of trolley 2: Related Theory a = 2 m/s2  When a person hits the ball on the ground, then F =8N there is an equal and opposite force acting on the As we know, ball in the upward direction, making it bounce. This supports the Newton’s third law of motion. F =m×a F 12. (A)  If the acceleration (a) is the common m= acceleration for all the three blocks X, Y and a Z, then 8 =4N F =m×a 2 F = 3m × a 9. (A)  The reading on the force-meter is a F constant 100N because balanced forces a= 3m are acting on each other. These forces are equal in size and opposite in direction. (B) Net force on block ‘X’ = (B) If the algerbraic sum of two ore more F =m×a forces acting on a body is zero, they are F F said to have balanced forces i.e., = m × =. 3m 3 F1 + (–F2) = 0. (C) Force applied by ‘X’ on ‘Y’ 10. (A) Sheela used balance or weighing scale to F = (m + m) × a measure the mass of the brick. F 2F (B) Measure length (l) and height (h) = 2m × = 3. 3m Volume = l × b × h (D) Force applied by ‘Y’ on ‘Z’ Related Theory F =m×a  The formula for volume is v = length × breadth × height. F F = m × =. 3m 3 mass ( m ) (C) Density (d) = Volume (v ) (E) Action reaction force pairs on the contact surfaces of the blocks. 500 = = 25 g/cm3 20 F X Y Z She can also use calibrated water container. For example, measuring cylinder. Note the initial volume of water. 2F/3 2F/3 F/3 F/3 Force and Laws of Motion 17 Click here to buy latest Educart books on Amazon - https://amzn.to/3vfZ5nZ  SELF ASSESSMENT SOLUTION solid cube is placed in vegetable oil having 1. (c) density almost same as the wax itself, the 1m 5 kg 4 kg cube will stay in the liquid at any pant it is placed without sinking or floating. Explanation: In case (a), m1 = 5 kg m2 = 4 kg d =2m 3. (d) Substance 4 G = 6.7 × 10–11 Nm2-kg–2 Explanation: Density of substance 1 G m1 × m2 m Fa = d= d 2 v 6 6.7 × 10−11 × 5 × 4 = = 2 g/cm3 = 3 2×2 Density of substance 2 In case (b), m1 = 2 kg m m2 = 2kg d= v d =2m 8 = = 2 g/cm3 6.7 × 10−11 × 2 × 2 4 Fb = 2×2 Density of substance 3 In case (c), m1 = 5 kg m d= m2 = 4 kg v r =1m 10 = = 5 g/cm3 6.7 × 10−11 × 5 × 4 2 Fc = Density of substance 4 1 ×1 In case (d), m1 = 2 kg m d= m2 = 2 kg v 2 d =3m = 0.5 g/cm3. 4 6.7 × 10−11 × 2 × 2 A body having density greater than that Fd = 3×3 of a liquid sinks into it while a body having In all four cases (a), (b), (c) and (d), the value density smaller than that of the liquid of G is common. floats on it. Substance 1, 2 and 3 have So Fa = 5 N densities more than that of water (Density of water is 1 g/cm3). So, all of them will sink Fb = 1 N whereas density of substance 4 is less than Fc = 20 N that of water, so it will floats in water. Fd = 0.44 N 4. (a) Liquid 1 Therefore, pair (c) having masses of objects Explanation: The more the density of a as 5 kg and 4 kg which are separated by 1 liquid, the more will be the force exerted by m will have the strongest force of gravity the liquid. The marble takes longer time to between them. reach the bottom in liquid 1, so it is denser 2. (d) The solid will stay in the liquid at any point than other. Since liquid 1 has more density, it is placed without sinking or floating. so, it will exert most upward buoyant force on the marble. Explanation: Density of solid cube made of wax is more (0.9 g/cc) than that of alcohol 5. (c) A is true but R is false. (0.8 g/cc) in which it is dipped, so it sinks. Explanation: We do not feel the buoyant The density of solid cube is less than that force. This is due to the reason because the of water when placed in it, so it floats. If a density of air is very small. 18 Science Class IX Click here to buy latest Educart books on Amazon - https://amzn.to/3vfZ5nZ  6. (a) Both A and R are true and R is the correct As the density of solid is less than water, explanation of A. the solid will float on water. Explanation: The identical packets 9. (A) Locations 2 and 4 will experience the low dropped from two airplanes from height tide as these are North and South Poles. h, the packet at poles will take less time Radius of Earth (R) is not constant as than the packet at the equator to reach Earth is not a perfect square. Therefore, the Earth’s surface. value of g changes from place to place 7. (A) Box 4 will be the most difficult of lift. In on the surface of earth. Acceleration due box 4, handle is very thin and it exerts to gravity at locations 1 and 3 (these are the greatest pressure on the hands. As equatorial locations) is minimum as radius pressure is inversely proportional to the is maximum at equator. As these locations 1 are for from sea, and ge is minimum. The area. P ∝. Whereas box 1 is the easiest low tides are not experienced at equator A on locations 2 and 4 which are poles, to lift due to more area of the handle. the distance Rp is minimum and gravity (B) All four boxes have the same weight as at poles is maximum, so these locations their mass is the same as well as the experience low tides. gravity. We know, (B) Gravitational pull of the earth keeps the W =m×g moon in its orbit. For example, gravitational Since the boxes, mass and acceleration due force or pull of the Earth makes the moon to gravity of all are same, the weight of all move in a fixed orbit. the boxes is same. 10. (A) Two bodies A and B of masses M and m (C) (i) On the surface of Earth, W = 10 kg are lying at a distance of d. Mass of body m = 10 kg Mm At the centre of Earth mass = 10 kg as F=G it does not change, it remains constant. d2 At the centre of Earth, g = 0 F is due to attraction between masses. Weight = m × g The force between two bodies having mass M and m is directly proportional to the = 10 × 0 = 0 product of their masses. (ii) Mass of object, m = 10 kg F a m1 × m2 This is the same on Earth and Moon. The force between two bodies is inversely Weight of the object on Earth proportional to the square of distance We = mge = 10 × 9.8 = 98 N 1 between two objects F ∝ Weight of the object on the Moon d2 1 G is the Universal Gravitational constant. Wm = mgm = 10 × 9.8 × 6 = 16.3 N Related Theory  The value of G does not depend on the medium 8. (A) B