List of top Science Questions asked in CBSE Class X

How does phototropism occur in plants?

Compounds such as alcohols and glucose also contain hydrogen but are not categorized as acids. Describe an Activity to prove it.

One-half of a convex lens is covered with a black paper. Will this lens produce a complete image of the object? Verify your answer experimentally. Explain your observations.
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.
Why is a normal eye not able to see clearly the objects placed closer than 25 cm?

What are the necessary conditions for autotrophic nutrition and what are its byproducts?

What are the differences between the transport of materials in xylem and phloem?
An electric bulb is rated 220 V and 100 W. When it is operated on 110 V, the power consumed will be –
Differentiate between metal and non-metal on the basis of their chemical properties.
Which of the following lenses would you prefer to use while reading small letters found in a dictionary?

Butanone is a four-carbon compound with the functional group

At the time of short circuit, the current in the circuit
Which of the following correctly describes the magnetic field near a long straight wire?
Draw a labelled diagram of the longitudinal section of a flower.

Describe double circulation of blood in human beings.Why is it necessary?

Write one equation each for decomposition reactions where energy is supplied in the form of heat, light or electricity.
A spherical mirror and a thin spherical lens have each a focal length of −15 cm. The mirror and the lens are likely to be
Compare the power used in the 2 Ω resistor in each of the following circuits:
  1. a 6 V battery in series with 1 Ω and 2 Ω resistors,
  2. a 4 V battery in parallel with 12 Ω and 2 Ω resistors.
Several electric bulbs designed to be used on a 220 V electric supply line, are rated 10 W. How many lamps can be connected in parallel with each other across the two wires of 220 V line if the maximum allowable current is 5 A?
An object 5.0 cm in length is placed at a distance of 20 cm in front of a convex mirror of radius of curvature 30 cm. Find the position of the image, its nature and size.
Imagine that you are sitting in a chamber with your back to one wall. An electron beam, moving horizontally from back wall towards the front wall, is deflected by a strong magnetic field to your right side. What is the direction of magnetic field?
The values of current I flowing in a given resistor for the corresponding values of potential difference V across the resistor are given below -
I (amperes) 0.51.02.03.04.0
V (volts)1.63.4  6.710.213.2
Plot a graph between V and I and calculate the resistance of that resistor.
Fe2O3 + 2Al → Al2O3 + 2Fe 
The above reaction is an example of a:

What is hydrogenation? What is its industrial application?

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.