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Define atomic size. Give its unit of measurement. In the modem periodic table what trend is observed in the atomic radius in a group and a period and why is it so?

Atomic Size is the distance between the centre of an atom i.e from the nucleus to the outermost (valence) shell of... View Article

The position of certain elements in the Modem 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?

(i) Element E is Silicon. It will form only covalent bonds only. The outermost orbit of silicon has 4 electrons and needs 4... View Article

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.

According to the reactivity series, both sodium and magnesium as well as aluminium are more reactive than carbon as these... View Article

A V-I graph for a nichrome wire is given below. What do you infer from this graph Draw a labeled circuit diagram to obtain such a graph.

The V−I graph for a nichrome wire shows a straight line, which means the resistance of the wire remains constant when the... View Article

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.

(i) During sunrise, the light rays coming from the Sun have to travel a greater distance in the earth’s atmosphere... View Article

What happens when a narrow beam of (i) a monochromatic light and (ii) white light passes through (a) glass slab and (b) glass prism?

When a narrow beam of monochromatic light passes through: Glass Slab: It deviates from the actual path but the direction... View Article

Differentiate between a glass slab and a glass prism.

Glass Slab It is a transparent glass plate in which both reflecting surfaces are rectangular in shape, and are parallel... View Article

Why is Tyndall effect shown by colloidal particles? State four instances of observing the Tyndall effect.

The Tyndall effect is the phenomenon in which the particles in a colloid scatter the beams of light that are... View Article

What is the significance of pollination?

Pollination refers to the transfer of pollen grains from the anther of a flower to the stigma of the same... View Article

Why is chemical communication better than electrical impulses as a means of communication between cells in a multi-cellular organism?

In multi-cellular organisms, chemical communication is better than electrical impulses as a means of communication between cells because chemical communication... View Article

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?

Adrenaline is a hormone released from the adrenal glands and its major action, together with noradrenaline, is to prepare the... View Article

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 ofKMnO4 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.

(i) 5% solution of KMn04 is prepared by dissolving 5 grams of KMnO4 in 100 ml of water. (ii) Alkaline potassium permanganate is adding oxygen to alcohol... View Article

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?

Washing Soda is prepared from sodium carbonate by recrystallization. Preparation of Washing Soda Washing soda is synthesized through Solvay’s process. Solvay’s process... View Article

Give one method which could be applied to reduce our intake of pesticides through food to some extent.

Methods that can be used to reduce our intake of pesticides through food to some extent – We can avoid... View Article

Various steps in a food chain represent : (a) Food web (b) Trophic level (c) Ecosystem (d) Biomagnification

b) Tropic level Explanation The trophic level is the position an organism occupies in the food chain. The first trophic... View Article

With regard to various food chains operating in an ecosystem, man is a: (a) Consumer (b) Producer (c) Producer and consumer (d) Producer and decomposer

d) Consumer Explanation Humans are top of the food chain because they are usually omnivorous. As they eat (or consume)... View Article

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