Revision Notes: Class 8 Science Chapter 6 Pressure Winds Storms and Cyclones

Class 8 Science Chapter 6: Pressure, Winds, Storms and Cyclones — Quick Revision Notes

• Pressure: Force ÷ Area; SI unit pascal (Pa) = N/m². The same force spread over a larger area produces lower pressure, and vice versa.
• Liquid pressure: liquids exert pressure in all directions — on the base and the walls of a container, not just downward.
• Liquid pressure and height: increases with the height/depth of the liquid column, independent of the container’s shape or width — why overhead tanks are built tall and placed high.
• Wind: the movement of air from a region of higher pressure to a region of lower pressure.
• Sea breeze (daytime): land heats faster than the sea, air over land rises creating low pressure, and cooler high-pressure sea air flows in to replace it.
• Land breeze (night): the reverse process — land cools faster than the sea after sunset.
• Thunderstorm formation: warm moist air rises and cools → water vapour condenses into droplets/ice → charge separates (positive ice near the cloud top, negative water droplets lower down) → sudden discharge produces lightning, and the rapid heating/expansion of air produces thunder.
• Cyclone: intensifies over warm ocean water as rising moist air creates a very low-pressure centre; surrounding air rushes in and, due to Earth’s rotation, begins to spin.
• Eye of a cyclone: the calm, low-pressure centre, surrounded by a ring of the storm’s highest wind speeds.
• Safety: during thunderstorms, avoid isolated tall trees and open fields, and a car’s metal body offers protection; during cyclones, stay indoors and away from windows.
• Why banners/hoardings have holes: holes let wind pass through, reducing the pressure difference (and hence the net force) between the two faces that would otherwise tear the structure loose.

Frequently Asked Questions

What causes wind to blow from one place to another?
Wind is caused by differences in air pressure between two regions; air naturally moves from a region of higher pressure to a region of lower pressure, and the greater the pressure difference, the stronger the wind.

Last Updated: September 23, 2026

How does uneven heating of the Earth surface lead to the formation of storms and cyclones?
Uneven heating causes warm air to rise rapidly in some regions, creating a zone of low pressure that draws in surrounding air at high speed, and over warm oceans this can intensify into a large rotating storm system or cyclone.

Written by Satish

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