Benzene (C6H6) is a common cyclic unsaturated carbon compound.
Q2short answer1 mark
The change in magnetic field lines in a coil is the cause of induced electric current in it. Name the underlying phenomenon.
Step-by-Step AI Explanation
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The underlying phenomenon is Electromagnetic Induction.
Q3short answer1 mark
List two common signs of sexual maturation in boys and girls.
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Two common signs of sexual maturation in both boys and girls are the growth of thick hair in new areas like armpits and the genital area, and skin becoming oily resulting in pimples.
Q4short answer1 mark
What is the result of reckless female foeticide?
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Reckless female foeticide leads to a decline in the child sex ratio (number of girls per thousand boys), which disturbs the biological balance of society.
Q4short answer1 mark
Human body is made up of five important components, of which water is the main component. Food as well as potable water are essential for every human being. The food is obtained from plants through agriculture. Pesticides are being used extensively for a high yield in the fields. These pesticides are absorbed by the plants from the soil along with water and minerals and from the water bodies these pesticides are taken up by the aquatic animals and plants. As these chemicals are not biodegradable, they get accumulated progressively at each trophic level. The maximum concentration of these chemicals gets accumulated in our bodies and greatly affects the health of our mind and body.
(a) Why is the maximum concentration of pesticides found in human beings?
(b) Give one method which could be applied to reduce our intake of pesticides through food to some extent.
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(a) Maximum concentration is found in humans because they occupy the highest trophic level in the food chain, leading to the accumulation of non-biodegradable chemicals through biomagnification. (b) Washing fruits and vegetables thoroughly with water before consumption can help reduce the intake of surface pesticides.
Q4mcq1 mark
Human body is made up of five important components, of which water is the main component. [See passage above.]
(c) Various steps in a food chain represent:
a.
Food web
b.
Trophic level
Correct Answer
c.
Ecosystem
d.
Biomagnification
Step-by-Step AI Explanation
Verified Method
Each step in a food chain represents a trophic level. A 'Food web' is a network of interconnected food chains, 'Ecosystem' is the interaction of biotic and abiotic factors, and 'Biomagnification' is the process of chemical concentration increase, making (b) the correct answer.
Q4mcq1 mark
Human body is made up of five important components, of which water is the main component. [See passage above.]
(d) With regard to various food chains operating in an ecosystem, man is a:
a.
Consumer
Correct Answer
b.
Producer
c.
Producer and consumer
d.
Producer and decomposer
Step-by-Step AI Explanation
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Man is a heterotroph and cannot produce his own food, therefore he is a consumer. Producers are green plants (autotrophs) and decomposers are microorganisms. Thus, 'Consumer' is the only correct choice.
Q5short answer1 mark
Which contraceptive method changes the hormonal balance of the body?
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Oral contraceptive pills (hormonal preparations) change the hormonal balance of the body to prevent the release of an egg (ovulation).
Q5mcq1 mark
Calcium oxide reacts vigorously with water to produce slaked lime.
CaO(s) + H2O(l) → Ca(OH)2(aq)
This reaction can be classified as:
(A) Combination reaction (B) Exothermic reaction (C) Endothermic reaction (D) Oxidation reaction
Which of the following is a correct option?
a.
(A) and (C)
b.
(C) and (D)
c.
(A), (C) and (D)
d.
(A) and (B)
Correct Answer
Step-by-Step AI Explanation
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In the reaction CaO + H2O → Ca(OH)2, two substances combine to form a single product, making it a combination reaction (A). This reaction is also accompanied by a large release of heat, making it an exothermic reaction (B). Therefore, (A) and (B) are correct.
Q5mcq1 mark
When hydrogen sulphide gas is passed through a blue solution of copper sulphate, a black precipitate of copper sulphide is obtained and the sulphuric acid so formed remains in the solution. The reaction is an example of a:
a.
Combination reaction
b.
Displacement reaction
c.
Decomposition reaction
d.
Double displacement reaction
Correct Answer
Step-by-Step AI Explanation
Verified Method
The reaction is CuSO4 + H2S → CuS + H2SO4. In this reaction, there is a mutual exchange of ions between the two compounds, which is the definition of a double displacement reaction.
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In a double displacement reaction such as the reaction between sodium sulphate solution and barium chloride solution:
(A) exchange of atoms takes place
(B) exchange of ions takes place
(C) a precipitate is produced
(D) an insoluble salt is produced
The correct option is:
a.
(B) and (D)
b.
(A) and (C)
c.
only (B)
d.
(B), (C) and (D)
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Incomplete combustion of coal and petroleum: (A) increases air pollution. (B) increases efficiency of machines. (C) reduces global warming. (D) produce poisonous gases. The correct option is:
a.
(A) and (B)
b.
(A) and (D)
c.
(B) and (C)
d.
(C) and (D)
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Assertion (A): Esterification is a process in which a sweet smelling substance is produced. Reason (R): When esters react with sodium hydroxide an alcohol and sodium salt of carboxylic acid are obtained.
a.
Both A and R are true and R is correct explanation of the Assertion.
b.
Both A and R are true but R is not the correct explanation of the Assertion.
c.
A is true but R is false.
d.
A is false but R is true.
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Assertion (A): In the process of nuclear fission, the amount of nuclear energy generated by the fission of an atom of uranium is so tremendous that it produces 10 million times the energy produced by the combustion of an atom of carbon from coal. Reason (R): The nucleus of a heavy atom such as uranium, when bombarded with low energy neutrons, splits apart into lighter nuclei. The mass difference between the original nucleus and the product nuclei gets converted to tremendous energy.
a.
Both A and R are true and R is correct explanation of the Assertion.
b.
Both A and R are true but R is not the correct explanation of the Assertion.
c.
A is true but R is false.
d.
A is false but R is true.
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1 g of copper powder was taken in a China dish and heated. What change takes place on heating? When hydrogen gas is passed over this heated substance, a visible change is seen in it. Give the chemical equations of reactions, the name and the color of the products formed in each case.
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OR
How is washing soda prepared from sodium carbonate? Give its chemical equation. State the type of this salt. Name the type of hardness of water which can be removed by it?
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3 mL of ethanol is taken in a test tube and warmed gently in a water bath. A 5% solution of alkaline potassium permanganate is added first drop by drop to this solution, then in excess.
(i) How is 5% solution of KMnO4 prepared?
(ii) State the role of alkaline potassium permanganate in this reaction. What happens on adding it in excess?
(iii) Write chemical equation of this reaction.
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A squirrel is in a scary situation. Its body has to prepare for either fighting or running away. State the immediate changes that take place in its body so that the squirrel is able to either fight or run?
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Differentiate between a glass slab and a glass prism. What happens when a narrow beam of (i) a monochromatic light, and (ii) white light passes through (a) glass slab and (b) glass prism?
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Draw a labelled diagram to show (i) reddish appearance of the sun at the sunrise or the sunset and (ii) white appearance of the sun at noon when it is overhead.
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(a) Write the mathematical expression for Joule's law of heating. (b) Compute the heat generated while transferring 96000 coulomb charge in two hours through a potential difference of 40 V.
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Carbon cannot reduce the oxides of sodium, magnesium and aluminium to their respective metals. Why? Where are these metals placed in the reactivity series? How are these metals obtained from their ores? Take an example to explain the process of extraction along with chemical equations.
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The position of certain elements in the Modern Periodic Table are shown below. Using the above table answer the following questions giving reasons in each case: (i) Which element will form only covalent compounds? (ii) Which element is a non-metal with valency 2? (iii) Which element is a metal with valency 2? (iv) Out of H, C and F which has largest atomic size? (v) To which family does H, C and F belong?
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(a) Why is there a difference in the rate of breathing between aquatic organisms and terrestrial organisms? Explain.
(b) Draw a diagram of human respiratory system and label - pharynx, trachea, lungs, diaphragm and alveolar sac on it.
OR
(a) Name the organs that form the excretory system in human beings.
(b) Describe in brief how urine is produced in human body.
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(a) What is the law of dominance of traits? Explain with an example.
(b) Why are the traits acquired during the life time of an individual not inherited? Explain.
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Draw a ray diagram in each of the following cases to show the formation of image, when the object is placed:
(i) between optical centre and principal focus of a convex lens.
(ii) anywhere in front of a concave lens.
(iii) at 2F of a convex lens.
State the signs and values of magnifications in the above mentioned cases (i) and (ii).
OR
An object 4.0 cm in size, is placed 25.0 cm in front of a concave mirror of focal length 15.0 cm.
(i) At what distance from the mirror should a screen be placed in order to obtain a sharp image?
(ii) Find the size of the image.
(iii) Draw a ray diagram to show the formation of image in this case.
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(a) What is an electromagnet? List any two uses.
(b) Draw a labelled diagram to show how an electromagnet is made.
(c) State the purpose of soft iron core used in making an electromagnet.
(d) List two ways of increasing the strength of an electromagnet if the material of the electromagnet is fixed.
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Define atomic size. Give its unit of measurement. In the modern periodic table what trend is observed in the atomic radius in a group and a period and why is it so?
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