How are living organisms dependent on the soil? Are organisms that live in water totally independent of soil as a resource?
Almost all living organisms are directly or indirectly dependent on soil. Plants obtain water, minerals from the soil and prepare food for animals.
On the other hand, other organisms that live in water are not totally independent of soil because the microbes growing on the soil in water are the primary producers which start the food chain and even microbes that live in the soil help in the decomposition of dead plants and animals in water to return the nutrients back to the water.
List any three human activities that you think would lead to air pollution.
What causes winds?
Why is the atmosphere essential for life?
Why do organisms need water?
Why is water essential for life?
We know that many human activities lead to increasing levels of pollution of the air, water-bodies and soil. Do you think that isolating these activities to specific and limited areas would help in reducing pollution?
List any three human activities which would lead to an increase in the carbon dioxide content of air.
How does the atmosphere act as a blanket?
How is our atmosphere different from the atmospheres on Venus and Mars?
You have seen weather reports on television and in newspapers. How do you think we are able to predict the weather?
Which of the following has more inertia: (a) a rubber ball and a stone of the same size? (b) a bicycle and a train? (c) a five-rupees coin and a one-rupee coin?
State the universal law of gravitation.
Which of the following are matter?
Chair, air, love, smell, hate, almonds, thought, cold, cold-drink, smell of perfume.
A force of 7 N acts on an object. The displacement is, say 8 m, in the direction of the force (Fig. 11.3). Let us take it that the force acts on the object through the displacement. What is the work done in this case?
What is meant by a pure substance?
How does the sound produced by a vibrating object in a medium reach your ear?
In a reaction, 5.3 g of sodium carbonate reacted with 6 g of ethanoic acid. The products were 2.2 g of carbon dioxide, 0.9 g water and 8.2 g of sodium observations are in agreement with the law of conservation of mass.
sodium carbonate + ethanoic acid → sodium ethanoate + carbon dioxide + water
What are canal rays?
State any two conditions essential for good health.
Who discovered cells, and how?
Describe with the help of a diagram, how compressions and rarefactions are produced in air near a source of sound.
What are the functions of the stomata?
How will you separate a mixture containing kerosene and petrol (difference in their boiling points is more than 25oC), which are miscible with each other?
Explain with examples (i) Atomic number, (ii) Mass number, (iii) Isotopes and iv) Isobars. Give any two uses of isotopes.
What produces more severe burns, boiling water or steam?
A train is travelling at a speed of 90 km h-1. Brakes are applied so as to produce a uniform acceleration of – 0.5 m s-2. Find how far the train will go before it is brought to rest.
Diagrammatically show the difference between the three types of muscle fibres.
Draw a sketch of Bohr’s model of an atom with three shells.
Does the transfer of energy take place when you push a huge rock with all your might and fail to move it? Where is the energy you spend going?
Distinguish between loudness and intensity of sound.