P-1 Heat — Science STD 10 — Question

Explain why, the first period of the modern periodic table has only two elements whereas second period has eight elements.

A student sitting in the last row of the class-room is not able to read clearly the writing on the
blackboard.

1. Name the type of defect he is suffering from.
2. How can this defect by corrected?

Write the characteristics with reference to their classification:
Bathsponge:

Explain why does the lime water turns milky in the reaction of acetic acid with sodium carbonate.

Water of mass 200 g and temperature 30 °C is taken in a copper calorimeter of mass 50 g and temperature 30 °C. A copper sphere of mass 100 g and temperature 100 °C is released into it. What will be the maximum temperature of the mixture? [c (water) = 1 cal/g·°C, c (copper) =0.1 cal/g·°C]

Explain how, harmful ultraviolet radiations of sunlight are prevented from reaching the earth’s surface.

Name some of the solar energy devices.

If T.V. of rating 100 W is operated for 6 hr per day. Find the number of units consumed in a leap year

Define :Satellite Launch vehicle

How were the positions of cobalt and nickel resolved in the modern periodic table?