List of top Science Questions asked in CBSE Class X

Write the formula and the molecular mass of the third homologue of alcohols. State how the boiling point of an alcohol changes as one moves from lower to higher homologues.
Copper powder is taken in a china dish and heated over a burner.Name the product formed and state its colour. Write the chemical equation for the reaction involved.
The filament of an electric lamp draws a current of 0.5 A, which lights for 2 hours. Calculate the charge that flows through the circuit.
Write chemical equation for the chemical reaction which occurs when the aqueous solutions of barium chloride and sodium sulphate react together. Write the symbols of the ions present in the compound precipitated in the reaction.
Is the reaction exothermic or endothermic?
Identify the organ in the human female reproductive system where the sperm encounters the egg cell. What will happen if it is blocked? Name the technique by which it can be blocked.
Assertion (A): Sex of the children will be determined by what they inherit from their mother. Reason (R): Women have XX sex chromosomes.
Sometimes while running, athletes suffer from muscle cramps. Why? How is the respiration in this case different from aerobic respiration?
Assertion (A): Some vegetable oils are healthy. Reason (R): Vegetable oils generally have long unsaturated carbon chains.
Write the other name given to lymph. State its two functions.
Assertion (A): Electrons move from lower potential to higher potential in a conductor. Reason (R): A dry cell maintains electric potential difference across the ends of a conductor.
The phenomena of light involved in the formation of a rainbow are:
Which one of the following is not a natural ecosystem?
The current carrying device which produces a magnetic field similar to that of a bar magnet is:
uniform magnetic field
A uniform magnetic field exists in the plane of paper as shown in the diagram. In this field, an electron (e−) and a positron (p+) enter as shown. The electron and positron experience forces :
The colour of light for which the refractive index of glass is minimum is:
How will the image formed by a convex lens be affected, if the upper half of the lens is wrapped with a black paper?
Which of the following is a redox reaction, but not a combination reaction?
An aqueous solution of sodium chloride is prepared in distilled water. The pH of this solution is:
The correct sequence of events when someone’s hand touches a hot object (reflex action):
The process in which transport of soluble products of photosynthesis takes place in plants is known as:
To balance the chemical equation, the values of the coefficients x, y, z, and t must be: Zn(NO₃)₂ → ZnO + NO₂ + O₂
A metal ‘X’ is used in the thermite process. When ‘X’ is heated with oxygen, it gives an oxide ‘Y’, which is amphoteric in nature. ‘X’ and ‘Y’ respectively are:
Sense organ in which olfactory receptors are present is:
Select from the following the conditions responsible for the rapid spread of black mould on a slice of bread: (i) Formation of large number of spores (ii) Presence of moisture and nutrients in bread (iii) Low temperature (iv) Presence of hyphae