List of top Science Questions asked in CBSE Class X

Write one function each of the parts - (i) petals (ii) anther (iii) style and (iv) ovary of a bisexual flower.

Name the type of lenses required by the persons for the correction of their defect of vision called presbyopia. Write the structure of the lenses commonly used for the correction of this defect giving reason for such designs.

What happens when butane is burnt in air? Write the chemical equation for the reaction. Differentiate between the flames obtained when butane and butyne both are burnt in air in similar conditions.

Explain the mechanism of inheritance used by sexually reproducing organisms to ensure the stability of DNA of the species.

Draw the pattern of the magnetic field lines for the two parallel straight conductors carrying current of same magnitude 'I' in opposite directions as shown. Show the direction of magnetic field at a point O which is equidistant from the two conductors. (Consider that the conductors are inserted normal to the plane of a rectangular cardboard.)

What is stainless steel? How is it prepared? Write one important property which makes it more useful in making cooking utensils as compared to its primary metal.

The minimum number of identical bulbs of rating 4V, 6W, that can work safely with desired brightness, when connected in series with a 240V mains supply is:

"In human beings the genes inherited from the parents decide whether the newborn individual is male or female." Explain this statement with the help of a flow diagram.

To get an image of magnification -1 on a screen using a lens of focal length 20 cm, the object distance must be:

Write chemical equations to show what happens when an acid reacts with a:
Write chemical equations to show what happens when an acid reacts with a:
(i) Metal
(ii) Base
(iii) Carbonate
Write the name of the main product formed in each case

State the chemical property in each case on which the following uses of baking soda are based upon:
(i) As an antacid
(ii) As a constituent in making baking powder
(iii) In soda-acid fire extinguishers

Name a metal found in the earth's crust:
(i) in free state and
(ii) in the form of its compound.
State where each of these metals are placed in the reactivity series of metals

Name the method by which Amoeba and Leishmania reproduce. Write a major difference in the way they divide to produce new individuals.

The sky appears dark to passengers flying at very high altitude

While burning a magnesium ribbon in air, list two safety measures which should be followed. Also state two observations of this activity.

Show the formation of magnesium chloride by electron transfer. Write the name of the cation and anion present in the compound formed. (Atomic Number of Mg = 12, Cl = 17)

What changes are observed in the uterus:
(i) Subsequent to the implantation of the zygote and
(ii) If an egg does not get fertilized?

Select from the following a statement which is not true about the burning of magnesium ribbon in air: