CBSE Class 7 Social Science Weather, Climate and Weather Instruments Worksheet Set 20

Answer: (b) 32°F. Water freezes at 0°C, which equals 32°F.

Teacher's Note:
1. Water boils at 100°C or 212°F.
2. Fahrenheit is used in a few countries such as the USA.

Answer: (a) Aneroid barometer. An aneroid barometer has no liquid and measures pressure through a metal chamber.

Teacher's Note:
1. A mercury barometer is the other common type.
2. Pressure is read in millibars.

Answer: (c) rainfall. A rain gauge collects rain in a cylinder with a scale.

Teacher's Note:
1. Rainfall is recorded in millimetres or centimetres.
2. It must be placed in an open area.

Answer: (b) Anemometer. An anemometer has rotating cups that turn faster in stronger wind.

Teacher's Note:
1. A wind vane shows only the direction.
2. Wind speed is given in kilometres per hour.

Answer: (a) wind vane. The arrow of a wind vane points towards the direction from which the wind blows.

Teacher's Note:
1. Wind is named after the direction it comes from.
2. A west wind blows from the west.

Answer: (a) hygrometer. A hygrometer measures the water vapour in the air.

Teacher's Note:
1. A wet and dry bulb thermometer can be used as a hygrometer.
2. Humidity is given as a percentage.

Answer: (c) both highest and lowest temperatures of a day. It has two indices that stay at the extreme temperatures reached.

Teacher's Note:
1. It is reset with a magnet.
2. The readings are used to find the mean daily temperature.

Answer: (b) the time period considered. Weather is for a short time, while climate is the average over many years.

Teacher's Note:
1. Weather can change within hours.
2. Climate changes very slowly.

Answer: False. Weather is the condition of the atmosphere at a place over a short time; the long-term pattern is climate.

Teacher's Note:
1. Weather includes temperature, rain, wind and humidity on a given day.
2. Climate is based on records of 25 to 30 years or more.

Answer: False. A hygrometer measures humidity; temperature is measured with a thermometer.

Teacher's Note:
1. Match each instrument with the weather element it measures.
2. A thermometer works on the expansion of liquid on heating.

Answer: True. A barograph draws a continuous line showing pressure variations over time.

Teacher's Note:
1. The paper is wrapped on a rotating drum.
2. A pluviograph does a similar job for rainfall.

Answer: Absolute humidity. It is usually given in grams per cubic metre of air.

Teacher's Note:
1. Relative humidity is a percentage of the maximum possible.
2. Both are measured with hygrometers.

Answer: Pluviograph. It is a self-recording rain gauge.

Teacher's Note:
1. An ordinary rain gauge gives only the total amount.
2. Records help in flood and crop planning.

Answer: Climate is the average weather condition of a place over a long period, usually 25 to 30 years or more. It is described using temperature, rainfall, wind and humidity.

Teacher's Note:
1. It changes from region to region.
2. Delhi and Chennai have different climates.

Answer: The main elements are temperature, atmospheric pressure, wind, humidity and precipitation. Cloud cover and visibility are also noted.

Teacher's Note:
1. Each element has its own instrument.
2. Together they describe the weather of a day.

Answer: Steady high pressure usually indicates clear, dry and fair weather. A fall in pressure often warns of clouds, rain or storms.

Teacher's Note:
1. Pressure charts help weather forecasters.
2. Sinking air in high pressure areas prevents cloud formation.

Answer: Warm air can hold more water vapour than cold air. When it cools below its dew point, the extra vapour condenses.

Teacher's Note:
1. This is why clouds form when air rises and cools.
2. Hot, humid air feels sticky.

Answer: An anemometer measures the speed of the wind. Its cups rotate faster when the wind is stronger, and the speed is shown on a dial.

Teacher's Note:
1. Wind speed is given in kilometres per hour.
2. Direction is shown by a wind vane.

Answer: Mean daily temperature = (maximum + minimum) ÷ 2. Here it is (34 + 22) ÷ 2 = 56 ÷ 2 = 28°C.

Teacher's Note:
1. The maximum and minimum are read from Six's thermometer.
2. Mean monthly temperature is the average of all daily means in the month.

Answer: Find the mean temperature for each day of the month and add them all. Divide the total by the number of days in that month.

Teacher's Note:
1. Mean annual temperature is found the same way for the year.
2. Annual range is the difference between the hottest and coldest monthly means.

Answer: Annual range = highest monthly mean − lowest monthly mean = 30 − 14 = 16°C.

Teacher's Note:
1. A large range shows a continental climate.
2. Coastal places have a smaller range.

Answer: F = 20 × 9/5 + 32 = 36 + 32 = 68°F.

Teacher's Note:
1. Multiply first, then add 32.
2. Check: 0°C gives 32°F.

Answer: 1. Time: weather is the state of the atmosphere on a particular day; climate is the average over 25 to 30 years or more.
2. Change: weather changes within hours or days; climate changes very slowly.
3. Area: weather is described for a place; climate generally for a large region.
4. Example: a rainy afternoon in Mumbai is weather; hot and humid with heavy summer rain is its climate.

Teacher's Note:
1. Think of weather as today's mood and climate as the personality.
2. Climate is found by averaging many years of weather records.

Answer: Observers read the maximum and minimum thermometers for temperature and a barometer for pressure. They use a rain gauge for rainfall, a hygrometer for humidity, a wind vane for direction and an anemometer for speed. The readings are noted at fixed times and sent to a central office for forecasting.

Teacher's Note:
1. Instruments are kept in a ventilated shelter called a Stevenson screen.
2. Satellites and radars also help in weather observation.

Answer: A rain gauge has a funnel that leads rain into a measuring cylinder. The funnel diameter is fixed so that the scale directly gives the depth of rain. It is placed in an open space away from trees and buildings, and the water is measured once a day.

Teacher's Note:
1. Rainfall is measured in millimetres.
2. One millimetre of rain means one litre of water on each square metre.

Answer: The two readings give the mean daily temperature. From daily means we find the monthly and annual means, and these averages over many years describe the temperature climate of the place.

Teacher's Note:
1. Averages smooth out unusual hot or cold days.
2. The same method is used for rainfall.

Answer: Temperature falls by about 6.5°C for every 1000 m of height, so hill stations are cooler than plains. Places near the sea have mild climates with small temperature ranges because water heats and cools slowly. Places far from the sea have extreme summers and winters.

Teacher's Note:
1. Shimla is cooler than Delhi because of its height.
2. Mumbai is milder than Nagpur because it is on the coast.

Answer: Mountains block moist winds, giving heavy rain on the windward side and a dry rain shadow on the leeward side. High land is cooler than low land at the same latitude. Valleys may trap cold air, while open plains allow winds to move freely.

Teacher's Note:
1. Topography means the physical features of the land.
2. The Himalayas also stop cold winds from entering India.