Our Environment — Science STD 10 — Question

Which of the following represent tall plants and which represent short plants (or dwarf plants)? Which of the following represent tall plants and which represent short plants (or dwarf plants)?

1. Tt
2. tt
3. TT

Give reason for your choice (The symbols have their usual meaning).

1. How do you calculate the possible valency of an element from the electronic configuration of its atoms?
2. Calculate the valency of an element X whose atomic number is 9.

Write names and formulae of hydrocarbons containing a single and a double bond (one example for each). Give one characteristic chemical property of each.

What will you do if you see a person coming in contact with a live wire?

An element A has 4 valence electrons in its atom whereas element B has only one valence electron in its atom. The compound formed by A and B does not conduct electricity. What is the nature of chemical bond in the compound formed? Give its electron-dot structure.

Write any two advantages of using biogas.

Explain why, the galvanised iron article is protected against rusting even if the zinc layer is broken.

What would happen if the ozone layer in the atmosphere completely disappears?

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.

Describe briefly the ‘khadin’ system of rainwater harvesting practised in Rajasthan.