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.

Draw the structure for the following compounds.                

       (i)    Ethanoic acid             (ii)   Bromopentane*
       (iii)  Butanone                   (iv)   Hexanal.

*Are structural isomers possible for bromopentane?

Outline a project which aims to find the dominant coat colour in dogs.

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?

Give an example of a metal which

  (i) is a liquid at room temperature.
  (ii) can be easily cut with a knife.
  (iii) is the best conductor of heat.
  (iv) is a poor conductor of heat.

Explain the mechanism of the cleaning action of soaps.

In evolutionary terms, can we say which among bacteria, spiders, fish and chimpanzees have a ‘better’ body design? Why or why not?

List five things you have done over the last one week to —

(a) conserve our natural resources.
(b) increase the pressure on our natural resources.

Find the focal length of a lens of power – 2.0 D. What type of lens is this?

What is the function of digestive enzymes?

What are the differences between autotrophic nutrition and heterotrophic nutrition?

Write a balanced chemical equation with state symbols for the following reactions:

1. Solutions of barium chloride and sodium sulphate in water react to give insoluble barium suphate and the solution of sodium chloride.
2. Sodium hydroxide solution (in water) reacts with hydrochloric acid solution (in water) to produce sodium chloride solutions and water.

Why are traits acquired during the life-time of an individual not inherited?

What are the limitations of extracting energy from—

   (a) the wind?          (b) waves?          (c) tides?

How is the sex of the child determined in human beings?