English Medium कक्षा १० - CBSE Question Bank Solutions for Science

If copper is kept open in air, it slowly loses its shining brown surface and gains a green coating. It is due to the formation of

When a metal X is treated with cold water, it gives a basic salt Y with molecular formula XOH (Molecular mass = 40) and liberates a gas Z which easily catches fire. Identify X, Y and Z and also write the reaction involved.

Draw ray diagram showing hypermetropic eye.

The metal which produces hydrogen gas on reaction with dilute hydrochloric acid as well as sodium hydroxide solution is ______.

Keerti added dilute Hydrochloric acid to four metals and recorded her observations as shown in the table given below:

Select the correct observation(s) and give chemical equation(s) of the reaction involved.

Metal oxides generally react with acids, but few oxides of metal also react with bases. Such metallic oxides are:

1. MgO
2. ZnO
3. Al₂O₃ 
4. Cao

Select the appropriate state symbols of the products given as X and Y in the following chemical equation by choosing the correct option from table given below: 

\[\ce{Zn_{(s)} + H_2SO_{4(l)} ->ZnSO_{4(X)} + H_{2(Y)}}\]

List two difference in the characteristic properties of the virtual images formed by the two types of spherical lenses (concave and convex). How are these characteristics of the two lenses use in the correction of the two common defects of vision namely myopia and hypermetropia?

Write a chemical equation showing the ionic products formed on dissolving potassium hydroxide in water.

On adding dilute sulphuric acid to a test tube containing a metal ‘X’, a colourless gas is produced when a burning match stick is brought near it. Which of the following correctly represents the metal ‘X’?

Why is the amount of gas collected in one of the test tubes in the following Activity double of the amount collected in the other? Name this gas.

• Take a plastic mug. Drill two holes at its base and fit rubber stoppers in these holes. Insert carbon electrodes in these rubber stoppers as shown in the following Fig.
• Connect these electrodes to a 6 volt battery.
• Fill the mug with water such that the electrodes are immersed. Add a few drops of dilute sulphuric acid to the water.
• Take two test tubes filled with water and invert them over the two carbon electrodes.
• Switch on the current and leave the apparatus undisturbed for some time.
• You will observe the formation of bubbles at both the electrodes. These bubbles displace water in the test tubes.
• Is the volume of the gas collected the same in both the test tubes?
  • Once the test tubes are filled with the respective gases, remove them carefully.
• Test these gases one by one by bringing a burning candle close to the mouth of the test tubes.

Caution: This step must be performed carefully by the teacher.

• What happens in each case?
• Which gas is present in each test tube?

Write the balanced chemical equation for the following and identify the type of reaction.

\[\ce{Zinc carbonate(s) -> Zinc oxide(s) + Carbon dioxide(g)}\]

What does one mean by exothermic reaction? Give example.

Why are decomposition reactions called the opposite of combination reactions? Write equations for these reactions.

Write one equation for decomposition reactions where energy is supplied in the form of heat.

Which part of the brain maintains posture and equilibrium of the body?

How do we detect the smell of an agarbatti (incense stick)?

What is the role of the brain in reflex action?

How are involuntary actions and reflex actions different from each other?

A person needs a lens of power -5.5 dioptres for correcting his distant vision. For correcting his near vision he needs a lens of power +1.5 dioptre. What is the focal length of the lens required for correcting (i) distant vision and (ii) near vision?