Draw the electron dot diagram for the compounds given below. Represent the electrons by (.) and (x) in the diagram. [Atomic No.: Ca = 20, O = 8, Cl = 17, H = 1]

1. Calcium oxide
2. Chlorine molecule
3. Water
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1. Heat supplied to a solid change it into liquid. What is this change in phase called?                                                                
2. During the phase change does the average kinetic energy of the molecules of the substance increase?
3. What is the
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A block and tackle system of pulleys has velocity ratio 4.

1. Draw a neat, labelled diagram of the system indicating clearly the points of application and direction of load and effort.
2. What will be its
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Write the equation for the formation of aluminum at the cathode during the electrolysis of alumina.

Which of the following is a common characteristic of a covalent compound?

1. high melting point
2. consists of molecules
3. always soluble in water
4. conducts electricity when it is in the molten state

The first and last term of a Geometrical Progression (G.P.) are 3 and 96 respectively. If the common ratio is 2, find:

1. ‘n’ the number of terms of the G.P.
2. Sum of the n terms.

The following numbers, K + 3, K + 2, 3K - 7 and 2K - 3 are in proportion. Find K.

Blood flows in arteries in spurts and is under pressure.

Give scientific reason.

State two factors upon which the heat absorbed by a body depends.

"The railway is an important means of transport as compared to airways." State two reasons to support the statement.

F, Cl, Br (Increasing electronegativity)

Prove that $\sqrt {\sec^2\theta + \csc^2\theta} $ = $ {\tan\theta + \cot\theta} $

Carbon monoxide is dangerous when inhaled.

Burning of ethane in plentiful supply of air.

Write a balanced chemical equation.

How does the magnitude of this non-contact force on the two bodies depend on the distance of separation between them?

What is meant by noise pollution? Name one source of sound causing noise pollution.