Write equations for the reactions of

   (i) iron with steam
   (ii) calcium and potassium with water.

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?

What is the role of saliva in the digestion of food?

Can the wing of a butterfly and the wing of a bat be considered homologous organs? Why or why not?

Why do stars twinkle?

What is the principle of an electric motor?

Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?

Do basic solutions also have H⁺(aq) ions? If yes, then why are these basic?

Explain the mechanism of the cleaning action of soaps.

How are water and minerals transported in plants?

An electric motor takes 5 A from a 220 V line. Determine the power of the motor and the energy consumed in 2 h.

Why is respiration considered an exothermic reaction? Explain.