Microorganisms: Friend and Foe — Science STD 8 — Question

Imagine that an object is falling through a long straight glass tube held vertical; air has been removed completely from the tube. The object does not touch the walls of the tube. Will the object experience any force of friction?

Which of the two is a better conductor of electricity: drinking water (tap water) or sea water? Give reason for your answer.

Why do gases have more inter-particle space than solids?

Soil erosion and desertification are the consequences of deforestation. Justify.

If a vacuum is created between two Magdeburg hemispheres joined together, they cannot be separated easily, What presses the hemispheres together?

Where do we get coal from and how is it formed ?

The strips of an electroscope diverge when a charged body is brought in contact with the metal clip. Now the clip is touched gently by our hand. What will happen to the strips? Explain.

Why do you have to use paper or kerosene oil to start fire in wood or coal?

Name some of the preservatives which are used in the preservation of fruits as jams and jellies.

Bells used in temples are not made up of wood. Why?