Q. During the age between 13-18 year, boys start developing beard and moustaches .Give reason? Answer: This is because of the secretion of sex hormones which bring about change in the body. Q. Why physical exercise and balanced diet are essential during adolescence. Answer: Adolescence is a stage of rapid growth and development. Hence to keep body healthy and fit, physical exercise and balanced diet are essential during adolescence. Q. Why adrenaline hormone is called emergency hormones? Answer: This is because it prepares body to fight and to run fast. It also helps the body to adjust to stress when one is very angry, embarrassed or worried. Q. What is the term used for secretions of endocrine glands responsible for changes taking place in the body? Answer: Hormones is the term used for secretions of endocrine glands responsible for changes taking place in the body. Q. Sweat gland secretes more during adolescence. Why? Answer: During adolescence, sebaceous glands enlarge and produce more sebum under the influence of hormones called androgens. Q. What will happen if a person does not take iodized salts? Answer: Deficiency of iodine in diet causes hypothyroidism due to which thyroid gland increase in size forming exopthalmic goiter. Q. Why do acne and pimple appear during adolescence? Answer: This is because of the increased activity of sebaceous glands (oil glands) in the skin. Sebaceous glands produce a substance called sebum, which is responsible for keeping the skin and hair moisturized. If sebum gets trapped in the pore, acne can develop. Q. Some gland does not have duct. How are their secretion transported in the body? Answer: Gland that does not have duct is called ductless gland like Endocrine glands. These gland release hormones directly into the blood stream. The blood transports their secretion in the body to target organ. Q. Give reasons for the following (a) Tadpoles growing in iodine deficient water have retarded growth. Answer. The process of growth and development is regulated by thyroxine hormone which is produced by thyroid gland. Iodine is required for thyroxine production. That is why retarded growth is seen in tadpoles living in iodine deficient water. (b) Voice becomes hoarse in adolescent boys. Answer. Sometimes the muscles of the growing voice box go out of control and the voice becomes hoarse. (c) Females have no role in determining gender of a child. Answer. Male has both X and Y chromosomes but a female has only two X chromosomes . When sperm containing Y chromosomes fertilize the egg leads to a boy off spring (XY) . Hence, Females have no role in determining gender of a child. Download full E-Study solution
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Q. What is reproduction? Why it is an essential life process? Or, explain the importance of reproduction in organism. Answer: Reproduction is process of producing new individual. Living organism produce young ones of their own kind by the process of reproduction. Reproduction is essential for the continuation of life from one generation to next generation. It ensures the continuation of similar kinds of individuals, generation after generation. Q. What are the different modes by which animals reproduce? Answer: there are two modes by which animals reproduce. These are: (i) Asexual reproduction and (ii) Sexual reproduction Q. Describe asexual reproduction Answer: Asexual reproduction is kind of reproduction in which single individual new individual of its own kinds. The off spring produced by asexual reproduction are similar to parents and are called clones very small animals like hydra and microscopic organisms like amoeba . Q. How new individuals developed in hydra? Answer: Hydra reproduces by budding. In each hydra, there may be one or more bulges. These bulges are called buds. These buds detached from parent body and develop into new individuals. Q. How new individuals developed in amoeba? Answer: Amoeba reproduces by binary fusion. Amoeba splits its body into two, each part receiving a nucleus and two new amoebae are produced. Q. Write some basic feature of a sexual Reproduction? Answer: Asexual Reproduction Basic features (i) Only one parent organism is involved. (ii) New organisms are genetically identical to the parent(clones) (iii)No gamete formation iv) Cell division involved – mitotic Q. Differentiate between (a) Binary fission and Multiple fission (b) fission and budding (c) fission and fragmentation Answer: Differences between binary fission and multiple fission (a) A single parent organism divides into two new organisms. e.g. Amoeba, Pramecium, Euglena (b) Only single parent organism divides into many new organisms. eg. Plasmodium. Differences between fission and budding Fission (a) A single parent organism divides into two or many new organisms. (b) Parental identity is lost (c) Amoeba, Paramecium, Plasmodium Budding (a) Parent organism forms a bud (outgrowth), it gets separated &form a new organism. (b)Parental identity is maintained (c) Hydra, Yeast ( Unicellular Fungus) Differences between fission & fragmentation Fission (i) It occurs in unicellular organisms (ii)The nucleus & cytoplasm of the parent cell divides & produce two daughter cells. (iii)The daughter cells formed are equal in size. (iv)For example : Amoeba, Euglena Fragmentation (i) It occurs in multicellular organisms. (ii)The organism breaks into two or more parts &each part grows into a new organism. (iii) The new organisms formed are usually unequal in size. (iv) for example : Spirogyra Q. Describe about cloning? Answer: Cloning is the production of an exact copy of a cell, any other living part, or a complete organism. Cloning of an animal was successfully performed for the first time by Ian Wilmut and his colleagues at the Roslin Institute in Edinburgh, Scotland. They cloned successfully a sheep named Dolly . Dolly was born on 5th July 1996 and was the first mammal to be cloned. During the process of cloning Dolly, a cell was collected from the mammary gland of a female Finn Dorsett sheep Q. Describe the process of fertilization in human body? Download full E-notes
Formative Checkpoint-01 State true and false 1. Non metals are good conductor of electricity? False, except graphite. Generally metals are good conductor of electricity. 2. Whenever current passes through it causes heating of metal: True 3. The full form of LED is Light Electrical device: False 4. Pure water is bad conductor of electricity: True 5. Tap water conducts electricity through it: True Fill in the blanks: 1. The work done to carry unit charge from infinity to a point in a conductor is called ------. [Electrical potential] 2. SI unit of Electrical potential is ------. [ Volt] 3. The closed conducting path of electric current is called -------. [Electric circuit] 4. ---------- is the work done to carry charge from one end of conductor to other end. [ potential difference] 5. Potential difference is created by using ------- or ---------. [Cell or battery] 6. The rate of the flow of electric charge is called -------. [ Electric current] 7. The direction of electric current is always from ----to ---- terminal of the battery. [Positive, negative] 8. When an electric current flows through a conducting solution, there is change of colour of the solutions. This effect of current is known as --Chemical effect of current] 9. Oxygen bubbles formed on the electrode connected to the ----------- terminal of the battery called anode during electrolysis. [Positive] 10. Hydrogen bubbles formed on the other electrode connected to the ----------- terminal called cathode during electrolysis. [Negative] 11. An electrolyte when dissolve in water produce -----. [Ions] 12. Positively charged ion is called ------. [Cation] 13. Negatively charged ion is called ------. [Anion] 14. Sugar, urea, benzenes Ethyl alcohol are some examples of ------. [Non electrolyte.] 15. During electrolysis Cation gets reduced at -----. [Cathode] and anions gets oxidized at ----- [anode] Download solved paper 8th Science Chapter-14-Chemical Effects Of Current
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VIII Algebra VIII Commercial Maths VIII Geometry & Menstruation CBSE Class VIII Science Physics Chemistry Biology 8th Sample paper 8th Social Science Check Point-Formative Corner -01 1. What are natural resources? Name any three natural resources? Ans: The material that are gifted by nature for survival is called natural resources like air ,water, soil, sunlight etc. 2. Name an important fossils fuel? Answer: The remain of plants and animals that are died millions of year ago are called fossils. The fuel obtain from fossils of plants and animals are called fossils fuel like Coal, petroleum and natural gas. 3. Name one important use of fossils fuel? Answer: Fossils fuel are main source of getting energy. 4. Is coke better than coal? Ans; yes, this is because coke does not produce smoke but produce more heat than coal on burning. 5. What do you mean by destructive distillation of coal? Or, what happen when coal is heated in absence of oxygen? Answer: The process of heating coal in absence of oxygen at 1000 deg. C to 1400 deg C is called destructive distillation. We get coke, coal gas coal tar and ammoniacal liquor by destructive distillation of coal. 6. What is the composition of coal? Answer: Coal is a mixture of carbon, hydrogen, oxygen, nitrogen and sulpher. 7. Write some uses of coal? Answer: Coal is used (a) As fuel to coke food (b) To generate energy in thermal power plant (c) as a source of Download full pdf file
5. Coal Petroleum, Natural Gases see full downloadable file
Class VIII Mathematics [Click on links given below] VIII Algebra VIII Commercial Maths VIII Geometry & Menstruation CBSE Class VIII Science Physics Chemistry Biology 8th Sample paper 8th Social Science Q.1 Give one example of each: metals and nonmetals.
Q.2 Name the metal, which is the best onductor of heat and electricity. Q.3 Name the property by which metals can be drawn into thin wires. Q.4 Name the gas produced, when metals react with acids. Q.5 What is the color of the copper sulphate solution ? Q.6 State the nature of oxides of non-metals. Q.7 Which metal is stored in kerosene ? Q.8 Name the property of the metal by which it can be drawn into thin sheets. Q.9 What happens when sulphur reacts with oxygen ? Q.10 Which non-metal catches fire, if exposed to air ? Q.11 Name the gas that burns with a POP sound. Q.12 What are Displacement reactions ? Q.13 Give one use of non-metal in our daily life. Q.14 What are metalloids ? Q.15 Which metal is use to wrap food items ? Sol.1 Metals : Copper Non-Metals : Sulphur Sol.2 Silver Sol.3 Ductility Sol.4 Hydrogen gas Sol.5 Blue Sol.6 The oxides of non-metals are acid in nature. Sol.7 Sodium Sol.8 Malleability Sol.9 Sulphur di oxide is formed. S + O2 = SO2 Sol.10 Phosphorus Sol.11 Hydrogen gas Sol.12 The reactions in which more reactive metals displace less reactive metals from their compounds in aqueous solution are called displacement reaction. Sol.13 Chlorine is used in purification of water Sol.14 Metalloids are those which posses the character of both metals and non-metals. Sol.15 Aluminium Q.1 What happens when sulphur di-oxide reacts with water ? Give the chemical reaction involved. Q.2 Why lemon pickle cannot be stored in an aluminium foil ? Q.3 Write two important properties of metals. Q.4 Why copper cannot displace zinc from zinc sulphate solution ? Q.5 Why immersion rods for heating are made up of metallic substances ? Q.6 What happens when iron nails are dipped in water in a test tube for a week ? Q.7 What happens when iron reacts with oxygen and water ? Give the chemical reaction involved. Q.8 What happens when copper vessel is exposed to moist air for a long time ? Give the chemical reaction that takes place. Q.9 Why gold is preferred in making jewellery? Q.10 What happens when dilute sulphuric acid is poured on a zinc plate ? Write the chemical reaction takes Q.11 What happens when magnesium ribbon is burnt in air ? Q.12 Why metals are used in making aeroplanes, bridges, satellites etc. Q.13 Complete the following chemical reactions. Zn + H2SO4 → 2Cu + H2O + CO2 → 2Fe + O2 + H2O → SO2 + H2O → Cu + HCl → LONG ANSWER TYPE QUESTIONS Q.14 What will happen when ash of magnesium is dissolved in water ? Is the solution acidic or basic ? What effect does litmus show in case of oxides of metals ? Q.15 Explain the following terms : (i) Malleability (ii) Ductility (iii) Sonorous (iv)Lustrous (v) Metalloids. Solution: Sol.1 Sulphrous acid is formed. SO2 + H2O = H2SO3 Sol.2 Aluminium reacts with the citric acid present in the lemon. Sol.3 (a) Good conductors of heat and electricity. (b) Lustrous, i.e., they can shine. Sol.4 Because copper is less reactive than zinc. Sol.5 Because metals are good conductors of heat. Sol.6 A brown layer gets deposited on the iron nails, which is called as the rust. Sol.7 Iron oxide is formed and hydrogen gas is produced. The chemical reaction that takes place is : 2Fe + O2 + H2O → Fe2O3 + H2 Sol.8 When copper vessel is exposed to moist air for a long time, it acquires a dull green coating. The green material is a mixture of copper hydroxide and copper carbonate. The following chemical reaction takes place: 2Cu + H2O + CO2 + O2 → Cu(OH)2 + CuCO3 Sol.9 Gold is preferred in making jewellery because gold is a lustrous metal and also possess the property of malleability. Sol.10 As we know that zinc is more reactive than hydrogen, so it displaces hydrogen from sulphuric acid and forms zinc sulphate. The chemical reaction that takes place during the process is given by Zn + H2SO4 → ZnSO4 + H2 Sol.11 As magnesium is a metal and we know that when metals react with oxygen the oxide formation takes place. 2Mg + O2 → 2MgO Sol.12 Due to their hardness, metals are preferred in making such things. Sol.13. Zn + H2SO4 → Zn SO4 + H2 2Cu + H2O + CO2 →CuCO3+H2O 2Fe + O2 + H2O → Fe2O3 + H2SO2 + H2O Cu + HCl →CuCl2 + H2 Sol.14 When ash of magnesium is dissolved in water then magnesium oxide is formed. 2Mg + O2 → 2MgO The oxides of metals are basic in nature. In case of metals the red litmus will turn to blue color. Sol.15 (i) Malleability : The property of the metals by which they can be drawn into sheets. (ii) Ductility : The property of the metals by which they can drawn into thin wires. (iii) Sonorous : The property of the metals by which they produce ringing sound when struck hard. (iv) Lustrous : The property of the metals by which they appear to be shiny. (v) Metalloids : Those materials that posses the property of both metals and non-metals. |
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