Class 7 Social Science Chapter 2: Understanding the Weather NCERT Solutions

Concept used. Each element of weather (temperature, precipitation, atmospheric pressure, wind, humidity) needs its own instrument because each one measures a different physical quantity. The chapter names the instrument for every element: thermometer, rain gauge, barometer, anemometer (with the wind vane for direction) and hygrometer. To match correctly, we recall what quantity each instrument is built to sense.

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1. Hygrometer. The chapter states that humidity, "the amount of water vapour present in the air," is measured with a hygrometer. So Hygrometer matches (d) Humidity.
2. Anemometer. An anemometer has three or four metal cups that spin faster as the wind blows harder; a meter attached at the base counts the spins and works out both how fast the wind is moving and, together with a wind vane, which way it blows (shown in Fig. 2.10). So Anemometer matches (c) Wind direction and speed.
3. Barometer. Atmospheric pressure, "the weight of the air above us," is read off a barometer in millibars (mb); the normal sea-level value is about 1013 mb. So Barometer matches (b) Atmospheric pressure.
4. Thermometer. Temperature, how hot or cold the atmosphere is, is read on a Celsius or Fahrenheit scale using a thermometer. So Thermometer matches (e) Temperature.
5. Rain gauge. Precipitation, water that falls as rain, snow, sleet or hail, collects in the funnel and measuring tube of a rain gauge (Fig. 2.6), where a scale reads the depth in millimetres. So Rain gauge matches (a) Precipitation.

(1)\(\to\)(d), (2)\(\to\)(c), (3)\(\to\)(b), (4)\(\to\)(e), (5)\(\to\)(a).

Concept used. The chapter explains two elements of weather together here: temperature (29 C, which is warm) and relative humidity (84%, which the text calls "humid weather," since it falls well above the 60–80% humid range). When air is already carrying a lot of water vapour, the sweat on our skin evaporates slowly, so a warm day feels even hotter and stickier than the number 29 C alone suggests.

1. Read the temperature. 29 C is a warm day, not extreme, but warm enough to make Jyotsna sweat while walking or sightseeing.
2. Read the humidity. 84% relative humidity is very high (close to the saturated end of the 0–100% scale), so the air is already holding most of the water vapour it can. Jyotsna's sweat will evaporate slowly, and the day will feel hotter and more uncomfortable than 29 C on its own would suggest.
3. Turn these two readings into packing advice. Loose, light-coloured, breathable cotton clothes let air move around the body and help whatever sweat does evaporate. Heavy, dark or synthetic fabrics trap heat and moisture against the skin and should be avoided.
4. Remember that June is also when the south-west monsoon usually reaches Mumbai, so hot, humid days are often followed by sudden rain. Jyotsna should also pack a light raincoat or umbrella and water-resistant footwear, along with a water bottle to replace the fluids she will lose to sweating.

Pack light, loose cotton clothes for the heat and humidity, plus a raincoat/umbrella and water bottle, since Mumbai in June is both hot, humid and at the start of the monsoon.

Concept used. A rain gauge (Fig. 2.6) works by letting rain fall freely into an open funnel, which drains into a graduated measuring tube. For its reading to be accurate, the chapter's own instructions matter: "Place the rain gauge in an open area, away from objects that might obstruct rain," and ensure "the rain gauge is on a flat surface and will not tilt or topple with the wind." Any site that blocks the sky above the funnel, tilts the gauge, or is unsafe to visit daily will give wrong or unusable readings.

1. Vegetable garden. Rejected. The soil is uneven and gets watered separately, plants nearby can block or funnel extra drips into the gauge, and gardening activity could easily knock the gauge over.
2. Terrace of the school building. Rejected. The terrace does have open sky above it, but it is usually more exposed to strong wind, which can blow rain sideways past the funnel (causing an undercount), and climbing to the terrace every day is not safe or convenient for young students.
3. Open ground with elevated platform. Selected. This site has a completely open sky above the funnel with nothing to obstruct falling rain, the elevated platform keeps the gauge above splash-back from wet ground, and a flat platform keeps it from tilting or toppling in the wind. It is also at ground level, so students can reach it safely every day to take readings.
4. Compound wall of school. Rejected. A wall top is narrow and unsafe to stand on for a daily reading, and its flat surface is too small to keep the gauge stable in strong wind.
5. Verandah of the school laboratory. Rejected. A verandah has a roof overhead, which blocks rain from reaching the funnel at all. This site fails the most basic requirement of a rain gauge and cannot be used.

Open ground with an elevated platform is the best site: open sky above the funnel, no splash-back, a flat and stable base, and safe daily access for readings.

Concept used. A weather report script must translate a data table into plain, spoken sentences that cover, station by station, the same elements this chapter introduced: temperature (with its range, the maximum minus the minimum), precipitation (rain and snow), and humidity. Departure from normal (actual reading minus the normal reading for that date) tells us whether a place was colder or warmer than usual.

1. Work out the temperature range for each station (maximum actual minus minimum actual): Srinagar \(6.5 - 0.2 = 6.3\degsym\)C; Qazigund \(3.2 - (-0.4) = 3.6\degsym\)C; Pahalgam \(1.1 - (-4.1) = 5.2\degsym\)C; Kupwara \(5.1 - (-0.7) = 5.8\degsym\)C; Kukernag \(2.6 - (-1.4) = 4.0\degsym\)C; Gulmarg \(-2.6 - (-7.6) = 5.0\degsym\)C.
2. Identify the coldest and warmest spots. Gulmarg, a hill station, recorded the lowest minimum of all, \(-7.6\degsym\)C, matching its own normal exactly (departure 0.0 C). Among the main stations, Srinagar had the highest maximum, 6.5 C, though it was still 2.4 C below its own normal for the date.
3. Read the departures. Every station in the table (except Gulmarg's minimum) was colder than normal: Qazigund's maximum was the furthest below normal, at \(-5.3\degsym\)C, showing a noticeably cold day there.
4. Cover precipitation. Kukernag and Gulmarg received the heaviest snow in the preceding 24 hours, 30.0 cm and 35.0 cm respectively, alongside rainfall of 35.2 mm each; Kupwara had the lightest precipitation, 21.9 mm of rain with 10.0 cm of snow.
5. Cover humidity. Most stations stayed above 90% relative humidity through the day, showing very moist, likely overcast conditions; Gulmarg was the exception, drier in the morning at 76% but fully saturated by evening at 100%, consistent with fresh snowfall.

Script: ``Good evening. On 1 February 2024, Jammu and Kashmir recorded a cold, snowy day. Gulmarg was the coldest spot at \(-7.6\degsym\)C, while Srinagar was the warmest at 6.5 C, still below its seasonal normal. Temperature ranges stayed narrow, between 3.6 C in Qazigund and 6.3 C in Srinagar, typical of an overcast winter day. Kukernag and Gulmarg saw the heaviest snow, 30 and 35 centimetres respectively, and humidity stayed above 90% almost everywhere, confirming continued wet, cloudy weather.''