English Medium कक्षा १० - CBSE Question Bank Solutions for Science

The diagram shown below depicts pollination. Choose the options that will show a maximum variation in the offspring.

How are variations useful for species if there is drastic alteration in the niches?

A metal 'M' on reacting with dilute acid liberates a gas 'G'. The same metal also liberates gas 'G' when reacts with a base.

1. Write the name of gas 'G'.
2. How will you test the presence of this gas?
3. Write chemical equations for the reactions of the metal with (1) an acid and (2) a base.

Give reason for the following:

During reproduction inheritance of different proteins will lead to altered body designs.

To balance the following chemical equation the value of x and y should respectively be:

\[\ce{2NaOH + xAl_2O_3->yNaAlO_2 + H_2O}\]

When aqueous solutions of potassium iodide and lead nitrate are mixed an insoluble substance separates out. The chemical equation for the reaction involved is: 

A student took a small amount of copper oxide in a conical flask and added dilute hydrochloric acid to it with constant stirring. He observed a change in colour of the solution. 

1. Write the name of the compound formed and its colour.
2. Write a balanced chemical equation for the reaction involved.

• Assertion: The probability of survival of an organism produced through sexual reproduction is more than that of an organism produced through asexual mode.
• Reason: Variations provide advantages to individuals for survival.

Dil. HCl is added to Zn granules. How will you prove that chemical change has taken place here? Support your response with two arguments.

Exlain the following:

\[\ce{H3PO3}\] is not tribasic acid.

A plant growth inhibitor hormone which causes wilting of leaves is ______.

Why should a magnesium ribbon be cleaned before burning in air?

What does an electric circuit mean?

Define the unit of current.

Calculate the number of electrons constituting one coulomb of charge.

Why are metals good conductors of electricity whereas glass is a bad conductor of electricity? Give reason?

The work done in moving a unit charge across two points in an electric circuit is a measure of ______.

Which of the following units could be used to measure electric charge?

(a) ampere
(b) joule
(c) volt
(d) coulomb

One coulomb charge is equivalent to the charge contained in:

(a) 2.6 × 10¹⁹ electrons
(b) 6.2 × 10¹⁹ electrons
(c) 2.65 × 10¹⁸ electrons
(d) 6.25 × 10¹⁸ electrons

Three 2 V cells are connected in series and used as a battery in a circuit.

1. What is the p.d. at the terminals of the battery?
2. How many joules of electrical energy does 1 C gain on passing through
   1. one cell
   2. all three cells?