Why are some substances biodegradable and some non-biodegradable?
Some substances are biodegradable and some are non- biodegradable because some microbial actions, radiations and some pollutants may get biologically magnified as they passed through the food chain and some bacteria and the decomposers have a specific role to play.
Like, biodegradable substances (like paper, wood) are those which are degraded naturally. These can disposed by the action of microbes and the radiations. And, non- biodegradable substances are those which cannot be degraded or if degradation occurs, it will be very slow in the process. Non- biodegradable substances are man- made products like D.D.T (Dichloro- diphenyl- trichloroethane), glass, heavy metals, tins, radioactive materials and plastics.
When a 12 V battery is connected across an unknown resistor, there is a current of 2.5 mA in the circuit. Find the value of the resistance of the resistor.
Outline a project which aims to find the dominant coat colour in dogs.
Draw the structure for the following compounds.
(i) Ethanoic acid (ii) Bromopentane*
(iii) Butanone (iv) Hexanal.
*Are structural isomers possible for bromopentane?
A hot plate of an electric oven connected to a 220 V line has two resistance coils A and B, each of 24 Ω resistance, which may be used separately, in series, or in parallel. What are the currents in the three cases?
How is the sex of the child determined in human beings?
(a) What property do all elements in the same column of the Periodic Table as boron have in common?
(b) What property do all elements in the same column of the Periodic Table as fluorine have in common?
Calculate the number of electrons constituting one coulomb of charge.
What is an homologous series? Explain with an example.
A man with blood group A marries a woman with blood group O and their daughter has blood group O. Is this information enough to tell you which of the traits – blood group A or O – is dominant? Why or why not?
Why is variation beneficial to the species but not necessarily for the individual?
Will the impact of removing all the organisms in a trophic level be different for different trophic levels? Can the organisms of any trophic level be removed without causing any damage to the ecosystem?
How do we detect the smell of an agarbatti (incense stick)?
Compute the heat generated while transferring 96000 coulomb of charge in one hour through a potential difference of 50 V.
On what factors does the resistance of a conductor depend?
What is the function of an earth wire? Why is it necessary to earth metallic appliances?
Write the balanced chemical equations for the following reactions.
(a) Calcium hydroxide + Carbon dioxide → Calcium carbonate + Water
(b) Zinc + Silver nitrate → Zinc nitrate + Silver
(c) Aluminium + Copper chloride → Aluminium chloride + Copper
(d) Barium chloride + Potassium sulphate → Barium sulphate + Potassium chloride
Choose the correct option.
A rectangular coil of copper wires is rotated in a magnetic field. The direction of the induced current changes once in each
(a) two revolutions (b) one revolution
(c) half revolution (d) one-fourth revolution
Why are coils of electric toasters and electric irons made of an alloy rather than a pure metal?
What will happen if we kill all the organisms in one trophic level?
Did Döbereiner’s triads also exist in the columns of Newlands’ Octaves? Compare and find out.