Natural Resources — Science STD 9 — Question

What was the basic classification of element in ancient time? Name them.

Calculate the number of moles present in a drop of chloroform (CHCl₃) weighing 0.0239g.
(Atomic masses: C = 12u; H = 1u; Cl = 35.5u)

Mass of a planet is twice that of the earth and its radius is four times of the earth. Find the value of 'g'on its surface.

Describe an activity to demonstrate that sound follows the same laws of reflection as light.

Calculate the force of gravitation between the earth and the Sun, given that the mass of the earth = 6 × 10²⁴kg and of the Sun = 2 × 10³⁰kg. The average distance between the two is 1.5 × 10¹¹m.

Which method is better for recovering sugar from sugar solution: evaporation or crystallization? Give reason for your answer.

Complete the following table.

Elements	Atomic number	Mass number	Protons	Electrons	neutrons	Electronic configuration	Valency
Chlorine	17	___	___	___	18	___	___
Silicon	___	28	___	14	___	___	___
Fluorine	___	___	9	___	10	___	___

List out some useful traits in improved crop?

Explain any one method of crop production which ensures high yield.