List of top Science Questions

You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice. Explain why these sour substances are effective in cleaning the vessels.
Give reasons:
  1. Platinum, gold and silver are used to make jewellery.
  2. Sodium, potassium and lithium are stored under oil.
  3. Aluminium is a highly reactive metal, yet it is used to makeutensils for cooking.
  4. Carbonate and sulphide ores are usually converted into oxides during the process of extraction.
What type of oxides are formed when non-metals combine with oxygen?
How does phototropism occur in plants?
Draw the structure of a neuron and explain its function.
What is the function of receptors in our body? Think of situations where receptors do not work properly. What problems are likely to arise?
The brain is responsible for
The gap between two neurons is called a
Explain the following terms with one example each. 
(a) Corrosion 
(b) Rancidity
Oil and fat containing food items are flushed with nitrogen. Why?
Which of the following is a plant hormone?
Why do we apply paint on iron articles?
A shiny brown coloured element ‘X’ on heating in air becomes black in colour. Name the element ‘X’ and the black coloured compound formed.
Explain the following in terms of gain or loss of oxygen with two examples each. 
(a) Oxidation
(b) Reduction
What do you mean by a precipitation reaction? Explain by giving examples.
State two ways to prevent the rusting of iron.
In the electrolytic refining of a metal M, what would you take as the anode, the cathode and the electrolyte?
Name two metals which will displace hydrogen from dilute acids, and two metals which will not.
What are amphoteric oxides? Give two examples of amphoteric oxides.
In the refining of silver, the recovery of silver from silver nitrate solution involved displacement by copper metal. Write down the reaction involved.
You are given a hammer, a battery, a bulb, wires and a switch.
  1. How could you use them to distinguish between samples of metals and non-metals?
  2. Assess the usefulness of these tests in distinguishing between metals and non-metals.
Food cans are coated with tin and not with zinc because
What is the difference between displacement and double displacement reactions? Write equations for these reactions.
Write one equation each for decomposition reactions where energy is supplied in the form of heat, light or electricity.
An element reacts with oxygen to give a compound with a high melting point. This compound is also soluble in water. The element is likely to be