List of top Science Questions

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.
How does the change in curvature of the eye lens help us in the process of seeing the nearby objects clearly?
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.
Rays from the sun converge at a point 25 cm behind a convex lens. The distance at which an object be placed in front of the lens to get a virtual image, is:
To restore clear vision in persons whose size of the eyeball has reduced, he/she is suggested to use suitable
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.
Assertion : Reaction of quick lime with water is an exothermic reaction. Reason (R): A large amount of heat is evolved on the reaction of quick lime and water.
On reaction with dilute HCl, which of the following pair of metals will evolve hydrogen gas?