WRITE THE FOLLOWING QUESTIONS (10*2=20)
1.Give two examples of each.
(a) Kharif crop
(b) Rabi crop
2.If wheat is sown in the Kharif season, what would happen? Discuss.
3.Can microorganisms be seen with the naked eye? If not, how can they be
seen?
4.What are the major groups of microorganisms?
5.Name the microorganisms which can fix atmospheric nitrogen in the soil.
6.Explain why some fibres are called synthetic.
7. Why are the electric wires covered with plastic ?
8.Non-metals cannot be drawn into wires. Why?
9. Complete the following equation :
Zn + 2HCl ->
10.Explain why fossil fuels are exhaustible natural resources.
11.Explain why fossil fuels are exhaustible natural resources.
12.Explain the process of formation of petroleum ? Name two places in India
where it is found.
13.Explain the difference between thermoplastic and thermosetting plastics.
14.Differentiate between biodegradable and non-biodegradable materials.
15.Write a paragraph in your own words on preparation of soil.
Please answer the 2 mark questions
Answers
1) a)rice, maize
b) Wheat, Barley
2) If wheat is sown in the Kharif season (from June to October), then the whole crop might get destroyed because of many factors such as lack of optimum temperature, adaptability, availability of pests, etc. Kharif season includes the rainy season, which is not favourable for the growth of wheat crop. Therefore, wheat crop should not be sown during this season.
3) Microbes are minute, unicellular organisms that are invisible to the naked eye.
They are also known as microorganisms or microscopic organisms as they could only be seen under a microscope or magnifying glass.
They make up almost 60% of the earth’s living matter.
4) There are five major groups of micro-organisms:
i. Bacteria – They are single celled disease-causing micro-organisms. They can be spiral or rod- shaped.
ii. Fungi – They are mostly multicellular disease-causing microbes. Bread moulds are common examples of fungi.
iii. Protozoa – They mainly include organisms such as Amoeba, Plasmodium, etc. They can be unicellular or multicellular.
iv. Virus -Viruses are disease-causing microbes that reproduce only inside the host organism.
v. Algae – They include multicellular, photosynthetic organisms such as Spirogyra, Chlamydomonas, etc.
5) The microorganism which can fix atmospheric nitrogen in the soil is bacteria. There are several species of bacteria capable of fixing nitrogen, but the most widely known species are Azotobacter and Rhizobium.
Nitrogen fixation has also observed between termites and fungi. Some of these nitrogen-fixing bacteria form symbiotic relationships with plants, more specifically, legumes.
6) Some fibres are called as synthetic fibers because these are manmade fibers prepared by using chemicals. These are made of small units that join together to form long chains.
7) Most electrical wire is covered in a rubber or plastic coating called insulation. ... The purpose of insulation covering the metal part of an electrical wire is to prevent accidental contact with other conductors of electricity, which might result in an unintentional electric current through those other conductors.
8)
9) Zinc reacts readily with hydrochloric acid to displace hydrogen to form hydrogen gas & zinc chloride.
∴Zn+2HCl⟶ZnCl
2+H2
10) The process of formation of fossil fuels requires millions of years. Dead vegetation and animals that get buried deep inside the earth require high temperature and pressure for the formation of fossil fuels, which cannot be done in the laboratory.
11) The process of formation of fossil fuels requires millions of years. Dead vegetation and animals that get buried deep inside the earth require high temperature and pressure for the formation of fossil fuels, which cannot be done in the laboratory.
12) petroleum is formed when large quantities of dead organisms, mostly zooplankton and algae, are buried underneath sedimentary rock and subjected to both intense heat and pressure. Petroleum has mostly been recovered by oil drilling (natural petroleum springs are rare).
15) Preparation of soil is the first step before growing of crop. It helps to turn the soil and loosen it to allow the roots to penetrate deep into it. The loosening of the soil helps in the growth of several soil microbes, earthworms etc., which enrich the soil with humus and other essential nutrients. The process of turning and loosening is called ploughing. This is done using a plough, hoe and cultivators.
13) Talking about the differences between thermoplastic and thermosetting plastic, well the main distinguishing factor between the two is that, thermoplastic materials typically have low melting points due to which they can further be remoulded or recycled easily.
On the other hand, thermosetting plastic is quite the opposite. They can withstand high temperatures and once hardened these cannot be reformed or recycled even with the application of heat. In any case, let’s have a look at some of the important differences between these two compounds below.