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.
Why is variation beneficial to the species but not necessarily for the individual?
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 does menstruation occur?
Compare and contrast nervous and hormonal mechanisms for control and coordination in animals.
Name two metals which will displace hydrogen from dilute acids, and two metals which will not.
What do you mean by a precipitation reaction? Explain by giving examples.
An electric lamp of 100 Ω, a toaster of resistance 50 Ω, and a water filter of resistance 500 Ω are connected in parallel to a 220 V source. What is the resistance of an electric iron connected to the same source that takes as much current as all three appliances, and what is the current through it?
The essential difference between an AC generator and a DC generator is that
(a) AC generator has an electromagnet while a DC generator has permanent magnet.
(b) DC generator will generate a higher voltage.
(c) AC generator will generate a higher voltage.
(d) AC generator has slip rings while the DC generator has a commutator.
Define the following terms.
(i) Mineral (ii) Ore (iii) Gangue
Which of the following is not an example of a bio-mass energy source?
(a) wood (b) gobar-gas
(c) nuclear energy (d) coal
Why does micelle formation take place when soap is added to water? Will a micelle be formed in other solvents such as ethanol also?
Why is the amount of gas collected in one of the test tubes in Activity 1.7 double of the amount collected in the other? Name this gas.