Coal and Petroleum — Science STD 8 — Question

State some of the characteristics of chemical changes brought about by the chemical effect of electric current.

Prepare a list of objects around you that are electroplated.

What would you observe when a strip of zinc is placed in copper sulphate solution? Write a word equation of the reaction which takes place.

Your family is planning to travel to another city where malaria is prevalent.
1. What precautions should you take before, during, and after the trip?
2. How can you explain the importance of mosquito nets or repellents to your sibling?
3. What could happen if travellers ignore health advisories in such areas?

State five uses of artificial satellites.

A group of students is experimenting. They have two beakers, A and B, each containing 100 mL of water. In beaker A, they add 5 grams of salt and stir. In beaker B, they add 20 grams of salt and stir. They observe that all the salt in beaker A dissolves, but in beaker B, some salt remains at the bottom, even after stirring vigorously.
Q.1. Why did all the salt dissolve in beaker A, but not in beaker B?
Q.2. What kind of solution is formed in beaker A?
Q.3. What about beaker B (considering the undissolved salt)?

Describe one method of putting out a fire caused by burning wood or paper.

What is meant by deforestation? what are the causes of deforestation?

What does a Fire Brigade do when it arrives at a place where a building is on fire?