D) Answer the following questions Briefly-

1) Distribution of air pressure shown in weather map is called Isobars. Isohytes is the method to show the distribution of rainfall on weather map. Isotherms are used to show distribution of temperature.

2) A thermograph can register different temperatures on the surface of the body and shows visual representation. Where as thermometer can show the temperature of only taken from inside the body.

3) Rain gauge has a funnel and cylinder. Cylinder is marked in millimeters which records the rainfall. Funnels is used to collect the rainfall.

4) Weather forecasting helps in taking safety measures in case of possible bad weather or any natural calamity.

5) Anemometer has cups, which rotates when wind blows. The anemometer counts the number of rotation which is used to calculate wind speed.

F) Answer the following questions:-

1)  Six maximum and minimum thermometer is a U shaped parallel tube made of glass. The bend at the bottom of the thermometer contains mercury which moves up or down based on the contraction of alcohol. When temperature rises the alcohol expands and pushes the mercury up the maximum column. This also pushes the mercury down in the minimum column.

2) We can measure humidity in air by Hygrometer with the help of Dry and wet bulb thermometers. The difference of temperatures between dry and wet bulb thermometers whether small or large will show the status of the atmosphere with respect to humidity.

3) The aneroid Barometer does not have mercury despite it has a metal box sealed with corrugated lid. There is a system of levers and springs for the movement of the indicators.

4) The precautions are:-

a) There should be no obstruction for incoming rainwater.

b) No seepage or Evaporation should occur for correct readings.

5) Wind vane is a Revolving plate which is balanced to a rod, so that it can rotate smoothly. The pointed end is called the arrow, while broad end is called the tail. A cross is below which shows Directions.


CLASS-7   CH-4


1) Land breeze occurs during night time when the land gets cool at night but the sea remains warm, thus the cool air starts blowing from land to sea called Land breeze. Sea breeze occurs at day time when the Land gets warmer, than from sea the cool air blows towards land.

2)  Insolation affects the temperature. The more the insolation, the higher the temperature.

3)  The significance of atmospheric pressure are:-

i) Diversity in atmospheric pressure responsible for changes in weather.

ii) Low atmospheric pressure associated with cloudy skies and wet weather.

4) Relative humidity is the amount of water vapour present in the air expressed  as a percentage of the maximum amount that the air could hold at the given temperature. The benefit of relative humidity is that it is better way of expressing the level of humidity in the air.

5) The small droplets of water in the cloud come together thus forming large droplets of water. The strong current carries these droplets to higher levels, where it freezes and forms into ice pellets. These ice pellets when become heavier  then fall as hailstones.

6) Weather represents the atmospheric events over short period of time such as in hour or a day. Climate represents aggregate weather condition over a long period of time.

F) Answer the following:-

1) The pressure belts are divided into four belts:-

i) The Equatorial pressure belt- extends  from about 10’N to around 10’S latitudes. Due to intense heating  air expands and becomes light and rises up causing low pressure belt.

ii) The subtropical high pressure belt- lies near 30’ N and south of Equator. Where the rising equatorial air currents move downward ,developing a high pressure. This is called Horse latitudes

iii) The sub-polar low pressure belt- located between 60’N and 70’ in both hemisphere. The winds coming from sub tropics and polar regions converge in this belt and rises upward. The region is marked with winter storms.

iv) The polar high pressure belt- Located around North  and south pole. The temperature is low in these belts. The  cold air blowing here develops high pressure in polar regions.

2) There are three types of rainfall-

I) Convectional rainfall- The heated air with moisture rises in the form of convectional current, leading to development of clouds. Due to humid air it causes condensation results in heavy rainfall.

ii) Orographic rainfall- It occurs due to cooling of warm moist air which ascends in mountain barrier lying in direction of prevailing winds. And due to cool air results in condensation and rainfall occurs.

iii) Cyclonic rainfall-  When warm and cold air masses confront each other, the warmer air generally climbs above the cooler air. The rising air is cools and causes heavy rainfall.

3) Monsoon winds blow from the sea towards the land during summer season and from land towards the sea during winter season. The monsoon has been derived from the Arabic word Mausim meaning season. During the summer season the remains hot and cool air blows from sea causes heavy rainfall in June – September. This is reverse during winter season, high pressure develops in landmass, thus wind from land blows towards sea and bring dry weather in November to Febuary.

4) The temperature is not uniform because temperature depends upon various factors i) Insolation ii) latitude of the place iii) height of place above sea level  iv) distance from sea iv) direction of prevailing winds vi) natural vegetation vii) deferential heating and cooling of the land and water. Temperature varies at different altitudes of the atmosphere at different places over the surface of the earth and even at different times during a day or during a month or year.

5) The factors of winds depends on following factors-

i) The difference in the atmospheric pressure between two places gives gradient.

ii) The rotation of the earth produces Coriolis force, which deflects the wind. The minimum deflection at the equator the maximum at poles.

iii) The roughness of earth’s surface reduces the speed of wind and changes the direction of wind.


Class- 7 Chapter-3

D) Answer the following questions briefly:-

1) When the sunlight enters the glass chamber it warms up the soil and this warm soil emits long wave radiation which does not come out of glass and hence it keeps greenhouse warmer.

2) The greenhouse effect is a process that occurs when gases in Earth’s atmosphere trap the sun’s heat. This process make the Earth much warmer than it would be without atmosphere.

3)  The main cause of global warming is increase of carbon dioxide in atmosphere.

4) The significance of ozone layer is that it protect us from harmful ultraviolet rays of sun.

5) we can reduce the emission of carbon dioxide by reducing the use of fossil fuels and planting more floras.

F) Answer the following Questions:-

1) The main reason for depletion of ozone layer is the increase of chlorofluorocarbon. The impact is that it can covert the ozone into oxygen, which cannot absorb ultraviolet rays.

2) Due to global warming the level of sea and ocean are increasing rapidly and this is happening due to melting of glaciers, thermal expansion of sea water, melting of ice sheet in Greenland and Antarctica.

3) Increase in temperature due to global warming may lead to emergence of many diseases because bacteria may survive in warmer conditions. It can cause hurricanes and cause depletion of many flora and fauna.

4) The five ways are:-

i) reduce the emission of carbon dioxide

ii) Minimize the use of nitrogenous fertilizers for agriculture.

iii) Plant more and more tress around your places.

iv) Find alternatives to Chlorofluorocarbon.

v) organize international awareness and campaign.

5) The modest global warming is beneficial to natural world and human civilizations. Some of the benefits are:-

i) The heating cost will be less for those living in colder areas.

ii) Warmer winters mean longer growing season.

iii) Warmer world will prove to be a wetter world which will be good for plants and animal life.


Chapter-2 Cl- 7

D) ANSWER the following questions briefly:

1) On the basis of temperature and atmospheric pressure the atmosphere is divided into five layers.

2) The composition of atmosphere is of tiny dust particles, smoke and water vapour.

3) Ionosphere contains ions particles which reflect radio waves to enable wireless communication.

4) Water vapour is added to the atmosphere by evaporation from seas, lakes, ponds etc.

5) Dust particles, Salt particles, Pollens from plants, Smoke from fires etc. scatter the sun radiation during sunrise and sunset.

6) Carbon dioxide is used by plants for survival of plants.

E) Answer the following questions:

1) The features of the troposphere are:-

i) It is lowest and densest layer.

ii) About 75% mass of atmosphere is found in this layer.

2) The composition of air mixture of gases like nitrogen, oxygen, carbon dioxide, helium, argon, ozone and hydrozen, tiny dust particles, smoke and water vapour.

3) The significance of atmosphere for human is that it protect us from harmful ultraviolet rays and supports life with gases like oxygen and carbon dioxide.

4) Mesosphere extends upto height of about 90 km above sea level and the temperature here falls to-110 c.

Whereas Exosphere is uppermost layer lies between 400 km to1500 km above earth’s surface and the temperature here rises to 5000 c.

5) The dust particles and smoke act as nuclei for water vapour to form rain drops around them and scatter the sun radiation during sunrise and sunset.

6) The importance of Nitrogen in air is that plant needs it for survival and it also dilutes with oxygen to slow down the process of oxidation.