English Medium Class 9 - CBSE Question Bank Solutions for Science

What are ultrasonic waves ? Name two animals which can produce ultrasonic waves.

The audible range of frequencies of an average human ear is from 20 Hz to 20 kHz. Calculate the corresponding wavelengths. (Speed of sound in air is 344 ms^–1)

Three different vibrating objects produce three-types of sounds X, Y and Z. Sounds X and Y cannot be heard by a man having normal range of hearing but sound Z can be heard easily. The sound X is used in hospitals to break kidney stones of a patient into fine grains which then get flushed out with urine. The sound Y is similar to that which is produced during an earthquake before the main shock wave is generated.

(a) What type of sounds are (i) X (ii) Y, and (iii) Z ?
(b) Name one device which can produce sound like X.
(c) Name one device in a science laboratory which can produce sound like Y.
(d) Name one device in our homes which can produce sound like Z.
(e) What is the frequency range of sounds like Z ?

If 1.4 g of calcium oxide is formed by the complete decomposition of calcium carbonate, then the amount of calcium carbonate taken and the amount of carbon dioxide formed will be respectively :

One of the following can hear infrasound. This one is :

What is the physical state of water at 100°C.

During summer, water kept in an earthen pot becomes cool because of the phenomenon of

Choose the correct statement of the following

The boiling points of diethyl ether, acetone and n-butyl alcohol are 35°C, 56°C and 118°C respectively. Which one of the following correctly represents their boiling points in kelvin scale?

Which condition out of the following will increase the evaporation of water?

A sample of water under study was found to boil at 102°C at normal temperature and pressure. Is the water pure? Will this water freeze at 0°C? Comment.

Evaporation of a liquid at room temperature leads to a ____________ effect.

____________ is the change of solid state directly to vapour state without going through the ____________ state.

The phenomenon of change of a liquid into the gaseous state at any temperature below its boiling point is called ____________.

‘Osmosis is a special kind of diffusion’. Comment.

Alka was making tea in a kettle. Suddenly she felt intense heat from the puff of steam gushing out of the spout of the kettle. She wondered whether the temperature of the steam was higher than that of the water boiling in the kettle. Comment.

Conversion of solid to vapour is called sublimation. Name the term used to denote the conversion of vapour to solid.

Why does the temperature of a substance remain constant during its melting point or boiling point?

An atom with 3 protons and 4 neutrons will have a valency of

Which of the following in Fig. 4.2 do not represent Bohr’s model of an atom correctly?