Management of Natural Resources — Science STD 10 — Question

a. State one important function of ozone layer at the higher level in the atmosphere.
b. How is ozone formed?
c. It has been observed that ozone layer is getting depleted. Name the compound responsible for ozone depletion.

What is meant by “electric power”? Write the formula for electric power in terms of potential difference and current.

Which one has the smaller size?
K(19) or Na(1); B(5) or C(6)

Elements have been arranged in the following sequence on the basis of their increasing atomic masses.
F, Na, Mg, Al, Si, P, S, Cl, Ar, K.

1. Pick two sets of elements which have similar properties.
2. The given sequence represents which law of classification of elements?

A man went door to door posing as a goldsmith. He promised to bring back the glitter of old and dull gold ornaments. An unsuspecting lady gave a set of gold bangles to him which he dipped in a particular solution. The bangles sparkled like new but their weight was reduced drastically. The lady was upset but after a futile argument the man beat a hasty retreat. Can you play the detective to find out the nature of the solution he had used?

When a solution becomes more acidic, pH gets lower.

State the various characteristics of chemical reactions.

What is meant by the ‘concentration of ore’?

Three elements A, B and C have 3, 4 and 2 electrons respectively in their outermost shell. Give the group number to which they belong in the Modern Periodic Table. Also, give their valencies.