Hydrogen has been used as a rocket fuel. Would you consider it a cleaner fuel than CNG? Why or why not?

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?

The device used for producing electric current is called a

(a) generator.
(b) galvanometer.
(c) ammeter.
(d) motor.

Which metals do not corrode easily?

Fresh milk has a pH of 6. How do you think the pH will change as it turns into curd? Explain your answer.

Give the names of two energy sources that you would consider to be exhaustible. Give reasons for your choices.

A shiny brown coloured element ‘X’ on heating in air becomes black in colour. Name the element ‘X’ and the black coloured compound formed.

How does chemical coordination take place in animals?

How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light?

Explain the underlying principle and working of an electric generator by drawing a labelled diagram. What is the function of brushes?

Define 1 dioptre of power of a lens.

Why are decomposition reactions called the opposite of combination reactions? Write equations for these reactions.