Sound — Science STD 8 — Question

The biodiversity of Earth including plant and animal species are mandatory to maintain the balance and functioning of all ecosystems on Earth. Still people are destroying their habitats to fetch benefits out of it. What fundamental principles one should follow for the preservation of biodiversity.

How do astronauts talk to one another on the surface of moon and why?

Give reasons for the following.
(i) Fresh milk is boiled before consumption while processed milk is stored in packets and can be consumed without boiling.
(ii) Raw vegetables and fruits are kept in refrigerators, whereas jams and pickles can be kept outside.
(iii) Farmers prefer to grow beans and peas in nitrogen deficient soils.
(iv) Mosquitoes can be controlled by preventing stagnation of water though they do not live in water. Why ?

State two physical properties on the basis of which metals can be distinguished from non-metals.

Discuss the effects of deforestation on the following. Earth.

Can you hold a hot metallic pan which is without a plastic or a wooden handle? Give reason for your answer.

A science team is planning to create a small habitat on Mars to grow plants for future settlers. They know Mars has a thin atmosphere, extreme cold, and no liquid water, but they can bring Earth soil and water.
Q.1. Why does Mars’ thin atmosphere make plant growth difficult?
Q.2. What conditions must the team provide to grow plants in the Martian habitat?
Q.3. Suggest one challenge the team might face in maintaining the habitat.

What precautions would you take to protect yourself during an earthquake if you are inside the house?

Identify the lightning conductor and the copper plate in Fig.

Give two examples each for a solid, liquid and gaseous fuel along with some important uses.