Class 7 Science Chapter – Winds, Storms and Cyclones Notes

Introduction: The chapter “Winds, Storms and Cyclones” is a very important part of Class 7 Science. It teaches us about air, wind, pressure, storms, cyclones, and their impact on human life and the environment. Understanding these natural processes is not only useful for exams but also for our daily life because weather conditions affect travel, farming, construction, and safety.

Air Exerts Pressure

Air is present all around us, and it has weight. The pressure exerted by air is called atmospheric pressure. We do not feel this pressure because it is balanced by the air inside our body. For example, when you invert a glass full of water with a cardboard, the water does not fall. This happens because the air around us pushes the cardboard upward, proving that air exerts pressure.

High Speed Winds and Air Pressure

Wind is the movement of air. Air moves from a high-pressure area to a low-pressure area. The faster the wind blows, the lower the pressure it creates. For example, when you blow over the top of a strip of paper, the strip rises. This happens because high-speed wind reduces the pressure above the paper, and the higher pressure below pushes it up.

Air Expands on Heating

When air is heated, it expands and becomes lighter. Warm air rises upward, while cold air comes in to take its place. This movement of air due to heating is the basic cause of winds. For example, land heats up faster than water during the day. So, air above land rises and cool air from the sea moves in. This movement of air is called sea breeze. The reverse happens at night, called land breeze.

Formation of Winds

The uneven heating of the earth’s surface creates winds. On the seashore, the difference in heating between land and water causes regular breezes. On a larger scale, the uneven heating between the equator and the poles causes global winds. These winds are responsible for carrying heat and moisture around the earth, balancing the climate.

Thunderstorms

Thunderstorms are formed when warm, moist air rises rapidly. The moisture in the rising air cools down and condenses into water droplets, forming clouds. When condensation releases heat, the air rises further, causing strong upward winds. These winds carry water droplets upward, where they freeze and fall back, leading to lightning and thunder. Thunderstorms usually occur in hot and humid areas.

Cyclones

Cyclones are very large low-pressure systems with very strong winds circulating around the center, called the eye of the cyclone. They are caused by the difference in air pressure and the continuous supply of warm, moist air from the sea. Cyclones can bring heavy rainfall, strong winds, and cause floods. They are extremely powerful and can affect large coastal areas.

Tornadoes

Tornadoes are smaller but extremely violent air columns that extend from the base of a thunderstorm cloud to the ground. They have a funnel shape and very high wind speeds. Although smaller than cyclones, tornadoes can be highly destructive.

Precautions During Cyclones

Governments and people should take certain safety measures during cyclones:

  • Move to safe shelters.
  • Avoid staying near windows.
  • Keep an emergency kit ready with food, water, torch, and medicines.
  • Stay away from electric poles and trees.
  • Listen to weather updates and warnings.

Role of Technology

Satellites and weather forecasting help in predicting cyclones and storms. Governments use early warning systems to save lives. Modern communication systems inform people in advance, reducing damage and casualties.

Summary: Winds, storms, and cyclones are natural processes caused by air pressure and uneven heating. Understanding them helps us to stay safe and prepare in advance.

Class 7 Science – Winds, Storms and Cyclones Questions & Answers

Multiple Choice Questions (MCQs)

  1. Air exerts pressure because:
    a) It is weightless
    b) It has weight ✔
    c) It is made of oxygen only
    d) It moves upward
  2. Warm air always:
    a) Moves downward
    b) Expands and rises ✔
    c) Contracts
    d) Becomes heavy
  3. The low-pressure center of a cyclone is called:
    a) Head
    b) Base
    c) Eye ✔
    d) Core
  4. Which of the following is NOT a precaution during a cyclone?
    a) Going to a safe shelter
    b) Listening to weather news
    c) Staying near trees ✔
    d) Keeping an emergency kit ready
  5. Tornadoes have:
    a) Funnel-shaped clouds ✔
    b) Circular eye
    c) Large rainfall
    d) Calm winds
  6. Sea breeze occurs during:
    a) Day ✔
    b) Night
    c) Morning only
    d) Winter
  7. Cyclones are caused due to:
    a) Heavy mountains
    b) Uneven heating of air and supply of moisture ✔
    c) Ice melting
    d) Earthquakes

Very Short Answer Questions

  1. What is atmospheric pressure?
    The pressure exerted by air around us.
  2. Why does the strip of paper rise when we blow over it?
    Because high-speed air reduces pressure above the strip.
  3. What is the name of the wind that blows from sea to land during day?
    Sea breeze.
  4. Define cyclone in one sentence.
    A large low-pressure system with strong winds circulating around the center.
  5. What is the shape of a tornado?
    Funnel-shaped.
  6. Name one safety item to keep ready during a cyclone.
    Emergency kit with torch, food, water.
  7. Which technology helps predict cyclones?
    Satellites and weather forecasting.

Short Answer Questions

  1. Why does warm air rise upward?
    Warm air expands and becomes lighter, so it rises. Cold air is heavier and moves to replace it, creating wind.
  2. Explain how sea breeze forms.
    During the day, land heats faster than sea. Air above land rises, and cool air from sea moves in to replace it. This movement is sea breeze.
  3. Explain the role of air pressure in cyclone formation.
    Low-pressure area develops over warm sea water. High-speed winds rush towards it, carrying moist air. This cycle continues, forming a cyclone.
  4. Why is it safer to stay away from trees during a cyclone?
    Strong winds can uproot trees, which may cause accidents. Hence, staying away is safer.
  5. What is thunderstorm?
    A storm caused by strong rising air currents, leading to heavy clouds, lightning, and thunder.
  6. What are the main causes of global winds?
    Uneven heating of the earth between equator and poles.
  7. Why is early warning important during cyclones?
    It helps people to move to safe shelters and reduce loss of life and property.

Long Answer Questions

  1. Describe the process of cyclone formation in detail.
    Cyclones form when warm, moist air rises over the sea, creating low pressure. Surrounding air rushes in, carrying more moisture. The cycle continues, and the system grows with strong winds circulating around the eye. The rotation of earth also influences cyclone movement.
  2. Explain the difference between thunderstorms, cyclones, and tornadoes.
    Thunderstorms are local storms with lightning and thunder. Cyclones are large-scale low-pressure systems with strong winds and rain, covering large coastal areas. Tornadoes are smaller, funnel-shaped, but extremely violent air columns with very high speed winds.
  3. List five safety measures during a cyclone.
    (1) Move to safe shelter. (2) Stay away from windows and trees. (3) Keep an emergency kit ready. (4) Listen to official weather news. (5) Avoid touching electrical wires and poles.
  4. How does uneven heating of land and water create winds?
    Land heats and cools faster than water. During the day, air above land rises, and sea breeze flows in. At night, land cools faster, so air above sea is warmer, and land breeze flows. This uneven heating creates regular winds.
  5. What is the importance of satellite technology in predicting cyclones?
    Satellites provide real-time weather data. Meteorologists track low-pressure areas, wind speed, and cloud patterns. This helps to predict cyclones in advance and issue warnings to save lives.
  6. Write a detailed note on air pressure with daily life examples.
    Air pressure is the force exerted by air per unit area. Examples: inverted glass of water experiment, rising strip of paper when blown, use of suction pumps. These examples show that air has weight and exerts pressure in all directions.
  7. How do cyclones affect human life and economy?
    Cyclones cause heavy rainfall, floods, and damage houses, crops, and power supply. Transport and communication are disrupted. Fishing and farming communities suffer major losses. However, with preparedness and early warning, these impacts can be reduced.