List of top Science Questions asked in CBSE Class X

Draw a ray diagram to show the correction of eye defect of an old man who cannot see an object placed closer than 1 m from his eye clearly.
State the range of the power of accommodation of a normal human eye.
Arrange the given material mediums in increasing order of speed of light through them. Given Refractive Indices:
  • A = 1.50
  • B = 1.46
  • C = 1.31
  • D = 1.77
Define absolute refractive index of an optical medium.
Give reasons for the following: The wires carrying current in homes have a coating of PVC.
Carbon cannot reduce the oxides of Na or Mg.
Carbon cannot reduce the oxides of Na or Mg.
Solder, an alloy of lead and tin, is used for welding electrical wires.
Give reasons for the following: Ionic compounds have generally high melting points and boiling points.
Give reasons for the following: Ionic compounds have generally high melting points and boiling points.
What happens when ethanol is heated with excess concentrated sulphuric acid at 443 K? Write chemical equation involved. What is the role of concentrated sulphuric acid in this reaction?
Write the chemical equation of reaction of ethanol with ethanoic acid in the presence of concentrated H$_2$SO$_4$. Write the name of this reaction.
Write structural formula and name of 4$^{th}$ member of alcohol homologous series.
Baking soda is used as an antacid.
While diluting an acid, it is recommended that the acid should be added to water.
Name the acid present in ant’s sting.
Give any two uses of it.
Write the chemical equation of its preparation.
Give the chemical name and formula of Plaster of Paris.
What happens when Calcium carbonate is heated? Silver bromide is exposed to sunlight? Lead is added to copper chloride solution? Write balanced chemical equations of the reactions involved in support of your answer.
The volume ratio of hydrogen and oxygen gases liberated during electrolysis of water is:
Which of the following is an amphoteric oxide?
Define germination.
State the changes taking place in the following structures of flower post fertilization: Zygote Ovule Ovary Sepals
Why regeneration is not possible in all the types of animals?