List of top Science Questions asked in CBSE Class X

What is the difference between the manner in which movement takes place in a sensitive plant and the movement in our legs?
Compare and contrast nervous and hormonal mechanisms for control and coordination in animals.
How are involuntary actions and reflex actions different from each other?
How does chemical coordination occur in plants?
Which signals will get disrupted in case of a spinal cord injury?
Give reasons why copper is used to make hot water tanks and not steel (an alloy of iron).
A man went door to door posing as a goldsmith. He promised to bring back the glitter of old and dull gold ornaments. An unsuspecting lady gave a set of gold bangles to him which he dipped in a particular solution. The bangles sparkled like new but their weight was reduced drastically. The lady was upset but after a futile argument the man beat a hasty retreat. Can you play the detective to find out the nature of the solution he had used?
Differentiate between metal and non-metal on the basis of their chemical properties.
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?