Which of the following are environment-friendly practices?
(a) Carrying cloth-bags to put purchases in while shopping
(b) Switching off unnecessary lights and fans
(c) Walking to school instead of getting your mother to drop you on her scooter
(d) All of the above
All of the above.
If we carry cloth- bags to put purchases while shopping, we can deny the use of polythene bags that is provided by the shopkeepers because polythene is a non- biodegradable substance. We should switch off the unnecessary lights or fans for the conservation of energy, light and the bill. And, at last if we prefer walking instead of getting our mother to drop on scooter, we can minimise the use of petrol or diesel or can contribute in reducing the air pollution that is released by the vehicles, gases release like CO2. So, all of the above options contribute in environment- friendly practices.
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?
Translate the following statements into chemical equations and then balance them.
(a) Hydrogen gas combines with nitrogen to form ammonia.
(b) Hydrogen sulphide gas burns in air to give water and sulpur dioxide.
(c) Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate.
(d) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.
What is the difference between displacement and double displacement reactions? Write equations for these reactions.
Write the balanced equation for the following chemical reactions.
1. Hydrogen + Chlorine → Hydrogen chloride
2. Barium chloride + Aluminium sulphate → Barium sulphate + Aluminium chloride
3. Sodium + Water → Sodium hydroxide + Hydrogen
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 an aqueous solution of an acid conduct electricity?
How do Mendel’s experiments show that traits may be dominant or recessive?
What type of oxides are formed when non-metals combine with oxygen?
What are amphoteric oxides? Give two examples of amphoteric oxides.
State Fleming’s left-hand rule.
Why are human beings who look so different from each other in terms of size, colour and looks said to belong to the same species?