Unit Test (Solution): Understanding the Weather | Social Science Class 7 - New NCERT PDF Download

M.M: 30
Attempt all questions.

• Question numbers 1 to 5 carry 1 mark each.
• Question numbers 6 to 8 carry 2 marks each.
• Question numbers 9 to 11 carry 3 marks each.
• Question numbers 12 & 13 carry 5 marks each.

Q1. What is the layer of gases surrounding the Earth called? (1 Mark)
Ans: Atmosphere.

Q2: Which of the following is NOT an element of weather? (1 Mark)
(i) Temperature
(ii) Precipitation
(iii) Soil type
(iv) Humidity
Ans: (iii) Soil type.

Q3: Fill in the blank: 
The instrument used to measure atmospheric pressure is called a ________. (1 Mark)
Ans: Barometer.

Q4: Which instrument is used to measure the speed and direction of wind? (1 Mark)
(i) Hygrometer
(ii) Anemometer
(iii) Rain gauge
(iv) Thermometer
Ans: (ii) Anemometer.

Q5: What is the unit of measurement for rainfall? (1 Mark)
Ans: Millimetres (mm).

Q6: Define weather and explain where most weather phenomena occur. (2 Marks)
Ans: Weather is the state of the Earth's atmosphere at a particular time and place, described by elements like temperature, precipitation, humidity, wind, and atmospheric pressure. Most weather phenomena occur in the troposphere, the layer of the atmosphere closest to the Earth's surface, extending 6 to 18 kilometres from the ground.

Q7: What is relative humidity, and what is its range in humid weather? (2 Marks)
Ans: Relative humidity is the measure of the amount of water vapour present in the air compared to the maximum it can hold, expressed as a percentage. In humid weather, relative humidity typically ranges between 60% and 80%.

Q8: Explain the purpose of a rain gauge and how it works. (2 Marks)
Ans: A rain gauge measures the amount of rainfall in a specific area. It consists of a funnel that collects rainwater, which flows into a cylinder with a scale to measure the depth of the water in millimetres. For example, 5 mm of water collected indicates 5 mm of rainfall.

Q9: Describe the role of a weather station in monitoring weather conditions. (3 Marks)
Ans: A weather station is a system that combines instruments like thermometers, rain gauges, barometers, anemometers, and hygrometers to measure weather elements such as temperature, precipitation, atmospheric pressure, wind, and humidity. It takes regular readings to track weather changes, and automated weather stations (AWS) use sensors to record data without human intervention. This data helps in mapping, monitoring, and forecasting weather, supporting fields like agriculture, aviation, and disaster management.

Q10: Why is it important to measure atmospheric pressure, and what instrument is used for this purpose? (3 Marks)
Ans: Measuring atmospheric pressure is crucial because it indicates weather changes, such as the formation of low-pressure systems that can lead to storms or cyclones. It also affects human activities, like aviation and mountaineering, as pressure decreases with altitude, impacting oxygen availability. The instrument used to measure atmospheric pressure is a barometer, which typically displays pressure in millibars (mb), with normal sea-level pressure around 1013 mb.

Q11: How do traditional methods of weather prediction differ from modern methods? (3 Marks)
Ans: Traditional methods of weather prediction rely on observing natural signs, such as birds flying low, ants moving eggs, frogs croaking, or pine cones opening and closing, to forecast events like rain or storms. These methods, passed down through generations, are based on experience and local knowledge. Modern methods, however, use scientific instruments like thermometers, barometers, and automated weather stations to collect precise data on weather elements. Meteorologists analyze this data to make accurate predictions, especially for extreme weather events like cyclones or droughts, using advanced technology and statistical models.

Q12: Explain the five elements of weather and their significance in understanding weather patterns. (5 Marks)
Ans: The five elements of weather are:

• Temperature: Measures how hot or cold the atmosphere is, affecting human comfort, agriculture, and energy use. It is measured using a thermometer in degrees Celsius or Fahrenheit.
• Precipitation: Includes rain, snow, sleet, or hail, indicating the amount of water falling from the sky. It impacts water supply and farming, measured by a rain gauge in millimetres.
• Atmospheric Pressure: The weight of air above the Earth's surface, measured by a barometer in millibars. It helps predict storms or cyclones, as low pressure often signals bad weather.
• Wind: The movement of air, characterized by speed and direction, measured by an anemometer and wind vane. It influences weather patterns, aviation, and farming.
• Humidity: The amount of water vapour in the air, measured by a hygrometer as relative humidity. It affects comfort, evaporation rates, and industrial processes like food processing.
  These elements collectively define weather conditions at a place and time, and their data helps meteorologists forecast weather and prepare for extreme events.

Q13: Discuss the importance of weather forecasting and how it benefits society. (5 Marks)
Ans: Weather forecasting involves predicting future weather conditions using data collected from instruments like thermometers, barometers, and automated weather stations. Its importance lies in its ability to prepare society for various weather events, enhancing safety and efficiency. Key benefits include:

• Disaster Preparedness: Accurate forecasts warn of extreme weather like cyclones, floods, or heat waves, allowing governments to evacuate areas, mobilize resources, and reduce loss of life and property.
• Agriculture: Farmers rely on forecasts to plan sowing, irrigation, and harvesting, improving crop yields and food security.
• Aviation and Navigation: Pilots and sailors use wind and pressure data to ensure safe travel, avoiding turbulent weather.
• Daily Planning: Individuals use forecasts to choose appropriate clothing, plan outdoor activities, or prepare for temperature changes.
• Environmental Monitoring: Forecasting supports conservation efforts by predicting conditions that affect ecosystems, such as droughts or heavy rainfall.

By providing timely and accurate information, weather forecasting helps society adapt to changing conditions, making it an essential tool for modern life.