English Medium कक्षा १० - CBSE Important Questions for Science

State the reason to explain why covalent compounds "are bad conductors of electricity".

Complete the following chemical equation:

\[\ce{CH3COOC2H5 + NaOH ->}\]

Complete the following chemical equations : C₂H₅OH + Na →

The following vegetables are kept in a basket :

Potato, Tomato, Radish, Brinjal, Carrot, Bottle-gourd

Which two of these vegetables correctly represent the homologous structures?

(A) Carrot and Tomato

(B) Potato and Brinjal

(C) Radish and Carrot

(D) Radish and Bottle-gourd

What happens when a small piece of sodium is dropped in ethanol? Write the equation for this reaction.

How does fertilisation occur in flowers? Name the parts of the flower that develop into (i) seed, and (ii) fruit after fertilisation.

Draw a ray diagram to show the dispersion of white light.

State the cause of dispersion of white light

Three incandescent bulbs of 100 W each are connected in series in an electric circuit. In another circuit another set of three bulbs of the same wattage are connected in parallel to the same source.

1. Will the bulb in the two circuits glow with the same brightness? Justify your answer.
2. Now let one bulb in both the circuits get fused. Will the rest of the bulbs continue to glow in each circuit? Give reason.

A student was asked to perform an experiment to study the force on a current carrying conductor in a magnetic field. He took a small aluminium rod AB, a strong horse shoe magnet, some connecting wires, a battery and a switch and connected them as shown. He observed that on passing current, the rod gets displaced. On reversing the direction of current, the direction of displacement also gets reversed. On the basis of your understanding of this phenomenon, answer the following questions: 

1. Why does the rod get displaced on passing current through it?
2. State the rule that determines the direction of the force on the conductor AB.
3. 1. If the U-shaped magnet is held vertically and the aluminium rod is suspended horizontally with its end B towards due north, then on passing current through the rod from B to A as shown, in which direction will the rod be displaced?
   2. Name any two devices that use current carrying conductors and magnetic fields.

OR

Draw the pattern of magnetic field lines produced around a current carrying straight conductor held vertically on a horizontal cardboard. Indicate the direction of the field lines as well as the direction of current flowing through the conductor.

"Energy flow in a food chain is unidirectional" Justify this statement.

Give reason to justify the following: The existence of decomposers is essential in a biosphere.

List two main components of ecosystem?

We do not clean natural ponds or lakes but an aquarium needs to be cleaned regularly. Why is it so ? Explain.

What is a trophic level?

With the help of an appropriate example, justify that some of the chemical reactions are determined by Evolution of a gas.

Give chemical equation for the reaction involved in the above case.

With the help of an appropriate example, justify that some of the chemical reactions are determined by Change in colour 

Give chemical equation for the reaction involved in the above case. 

With the help of an appropriate example, justify that some of the chemical reactions are determined by Change in temperature.

Give chemical equation for the reaction involved in the above case.

State the change in colour observed in following case mentioning the reason:

Silver chloride is exposed to sunlight.