1. The air in the atmosphere is made up of a number of gases.
Lesson PLan
What is “Air-pressure”?
The air in the atmosphere is made up of a number of gases.
STD 8, SUB science, CH-1, Air-pressure, DAY-1
Gajwani Schools and Colleges

2. Although we are usually unaware of this pressure.
Lesson PLan
OV:
These gases press down on the Earth’s surface, exerting a force that we call atmospheric pressure or air pressure.
Although we are usually unaware of this pressure.
STD 8, SUB science, CH-1, Air-pressure, DAY-1
Gajwani Schools and Colleges

3. S8S1SCCH1-Air-pressure-Day1
Lesson PLan
S8S1SCCH1-Air-pressure-Day1
“Variations”
OV:
Air pressure varies over time and from place to place. If we travel up a mountain or go up in a hot air balloon.
STD 8, SUB science, CH-1, Air-pressure, DAY-1
Gajwani Schools and Colleges

4. for example, the air pressure gets less the higher we go
for example, the air pressure gets less the higher we go. We can explain this difference by comparing air pressure to a pile of blankets on your bed.
STD 8, SUB science, CH-1, Air-pressure, DAY-1

5. Lesson PLan
“HEIGHTS”
Air pressure at sea level is the equivalent of having many blankets, which would feel very heavy. If you have only one blanket though, it would feel very light, and this is like the air pressure at the top of a mountain.
STD 8, SUB science, CH-1, Air-pressure, DAY-1
Gajwani Schools and Colleges

6. STD 8, SUB science, CH-1, Air-pressure, DAY-1
Each layer of air presses down on the layers below, and so the greatest pressure is at ground level where we have the maximum amount of air above.
STD 8, SUB science, CH-1, Air-pressure, DAY-1

7. STD 8, SUB science, CH-1, Air-pressure, DAY-1
Lesson PLan
Air pressure also varies over time, and these temporal differences are usually caused by the temperature of the air.
STD 8, SUB science, CH-1, Air-pressure, DAY-1
Gajwani Schools and Colleges

8. STD 8, SUB science, CH-1, Air-pressure, DAY-1
Lesson PLan
Cool air is denser (heavier) than warm air. Warm air is less dense (lighter) than cool air and will therefore rise above
STD 8, SUB science, CH-1, Air-pressure, DAY-1
Gajwani Schools and Colleges

9. STD 8, SUB science, CH-1, Air-pressure, DAY-1
Lesson PLan
Changes in air pressure bring changes in the weather and make winds blow. Air usually moves from areas of high pressure to areas of low pressure, and this produces winds.
STD 8, SUB science, CH-1, Air-pressure, DAY-1
Gajwani Schools and Colleges

10. STD 8, SUB science, CH-1, Air-pressure, DAY-1
Lesson PLan
Air-pressure :
Air-pressure is the weight of the column of air above a horizontal surface of unit area.
As we go up and reach and reach a higher altitude, the pressure is lower because the column of air is reduced
STD 8, SUB science, CH-1, Air-pressure, DAY-1
Gajwani Schools and Colleges

11. How to measure Air-pressure?
Lesson PLan
How to measure Air-pressure? a
Mercury barometer and aneroid barometer and digital barometer are commonly used to measure Air-pressure.
STD 8, SUB science, CH-1, Air-pressure, DAY-1
Gajwani Schools and Colleges

12. STD 8, SUB science, CH-1, Air-pressure, DAY-1

13. How to measure Air-pressure?
The principle of mercury barometer is illustrated in following figure.
STD 8, SUB science, CH-1, Air-pressure, DAY-1

14. STD 8, SUB science, CH-1, Air-pressure, DAY-1
Lesson PLan
The height of the mercury column AB will vary according to the Air-pressure.
The higher the Air-pressure the greater will be the height of mercury column.
STD 8, SUB science, CH-1, Air-pressure, DAY-1
Gajwani Schools and Colleges

15. STD 8, SUB science, CH-1, Air-pressure, DAY-1
Lesson PLan
Aneroid Barometer
STD 8, SUB science, CH-1, Air-pressure, DAY-1
Gajwani Schools and Colleges

16. STD 8, SUB science, CH-1, Air-pressure, DAY-1
Lesson PLan
DIGITAL BAROMETER
STD 8, SUB science, CH-1, Air-pressure, DAY-1
Gajwani Schools and Colleges

17. STD 8, SUB science, CH-1, Air-pressure, DAY-1
Lesson PLan
DIGITAL BAROMETER
Now a days Digital Barometer is used.
Because it is portable and accurate.
An electrical capacitor in it is used to measure the change in air-pressure.
STD 8, SUB science, CH-1, Air-pressure, DAY-1
Gajwani Schools and Colleges

18. STD 8, SUB science, CH-1, Air-pressure, DAY-1
Lesson PLan
UNIT OF PRESSURE
Pascal(Pa) is the international standard unit of pressure.
The meteorological community uses hecto-pascal (hPa) as the unit of pressure.
It is the same as 1millibar,a unit of pressure no longer used nowdays.
STD 8, SUB science, CH-1, Air-pressure, DAY-1
Gajwani Schools and Colleges

19. Immerse M/Involve oneself deeply in a particular activity.
Lesson PLan
Immerse W1
M/Involve oneself deeply in a particular activity.
A/In cellular networks, adjacent cell cannot use the same radio frequency.
STD 8, SUB science, CH-1, Air-pressure, DAY-1
Gajwani Schools and Colleges

20. SUCKING M/Draw fluid from(something) into the mouth by suction.
Lesson PLan
SUCKING
Suck-ing
M/Draw fluid from(something) into the mouth by suction.
A/It seems to me mosquito release a liquid to facilitate sucking the blood.
STD 8, SUB science, CH-1, Air-pressure, DAY-1
Gajwani Schools and Colleges

21. Why does the bicycle tube burst,if excess of air is filled in it?
Lesson PLan
QUESTION 1
Why does the bicycle tube burst,if excess of air is filled in it?
STD 8, SUB science, CH-1, Air-pressure, DAY-1
Gajwani Schools and Colleges

22. STD 8, SUB science, CH-1, Air-pressure, DAY-1
Lesson PLan
QUESTION 2
Where do you use air pressure in your day-to-day life?Give four exanple?
STD 8, SUB science, CH-1, Air-pressure, DAY-1
Gajwani Schools and Colleges

23. STD 8, SUB science, CH-1, Air-pressure, DAY-1
Lesson PLan
QUESTION 3
Give four names of devices working on air-pressure?explain any one of them?
STD 8, SUB science, CH-1, Air-pressure, DAY-1
Gajwani Schools and Colleges

24. TOMORROW END OF TODAY’S WORK Read the next few pages of in the chapter
Lesson PLan
TOMORROW N:
Read the next few pages of in the chapter
Be ready to discuss the
FORMATION OF BUBBLE
END OF TODAY’S WORK
STD 8, SUB science, CH-1, Air-pressure, DAY-1
Gajwani Schools and Colleges