List of top Science Questions asked in CBSE Class X

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

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:

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

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

"Aluminium oxide is an amphoteric oxide." Justify this statement giving chemical equation for the reactions involved.

What is asexual reproduction? Explain the process of budding in Hydra.

State two limitations of electrical impulses in multicellular organisms. Why is chemical communication better than electrical impulses as a means of communication between cells in multicellular organisms?

Why do we balance a chemical equation? Name and state the law that suggests the balancing of a chemical equation. Balance the following chemical equation: \[ {Zn} + {H}_3 {PO}_4 \rightarrow {Zn}_3 {(PO}_4{)}_2 + {H}_2 \]

You have three aqueous solutions A, B and C as given below:
A - Potassium nitrate
B - Ammonium chloride
C - Sodium carbonate
The ascending order of the pH of these solutions is:

What is a rainbow? 'We see a rainbow in the sky only after the rainfall.' Why?

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

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.

How is the brain protected in our body?

Name the part performing the following functions in the human female reproductive system:
(i) Production of eggs
(ii) Site of fertilization
(iii) Site of implantation
(iv) Entry of the sperms

Out of the two media - Medium 1 and Medium 2, in which is the speed of light more?

path of a ray of light going from Medium 1 to Medium 2

Identify from the following the ray diagram which shows the correct path of the reflected ray for the ray incident on a concave mirror as shown:

Assertion (A): Concentrated nitric acid is diluted by adding water slowly to acid with constant stirring.
Reason (R): Concentrated nitric acid is easily soluble in water.
In the light of the above statements, choose the most appropriate answer from the options given below:

In our houses we receive A.C. electric power of 220 V. In electric iron or electric heater cables having three wires with insulation of three different colours – red, black and green are used to draw current from the mains. What are these three different wires called? Name them colourwise. What is the potential difference between the red wire and the black wire? What is the role of the wire with green insulation in case of accidental leakage of electric current to the metallic body of an electrical appliance?

A tall pea plant with round seeds (TTRR) is crossed with a short pea plant with wrinkled seeds (ttrr). The F₁ generation will be:

Give one example each of a unisexual flower and a bisexual flower. Mention the changes which a flower undergoes after fertilization.

Give two methods used to grow rose and jasmine plants by vegetative propagation.

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

"Proteins control the expression of various characters." Explain this statement by taking an example of "tallness" as a characteristic in plants.

A person uses lenses of power -0.5 D in his spectacles for the correction of his vision. (a) Name the defect of vision the person is suffering from.

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