lesson 5 gas pressure kelvins
TRANSCRIPT
8/3/2019 Lesson 5 Gas Pressure Kelvins
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Do now!
• . Can you readthrough thework we did
last lesson?
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Last lesson
• Understand that a substance can change statefrom solid to liquid by the process of melting
• Understand that a substance can change state
from liquid to gas by the process of evaporationor boiling
• Recall that particles in a liquid have a randommotion within a close-packed structure
• Recall that particles in a solid vibrate about fixedpositions within a close-packed regular structure
• Understand the significance of Brownian motion
8/3/2019 Lesson 5 Gas Pressure Kelvins
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Draw these sentences!
1. The particles in a solid are close packed.
2. The particles in a solid are in regular positions
vibrating around a fixed point.
3. The particles in a liquid are also close packed.
4. The particles in a liquid also vibrate and move
around randomly.
5. The particles in a gas are far apart.
6. The particles in a gas are moving very quickly.
7. For the same substance (e.g. water), the particles are the same size
in the solid, liquid or gaseous forms.
8. Mr Porter is the world’s best science teacher.
8/3/2019 Lesson 5 Gas Pressure Kelvins
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Solids
• Fixed shape
• Cannot flow
• Difficult to compress• Generally dense
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Liquids
• Shape can change
• Can flow
• Not easy to compress• Generally dense
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Gases
• Shape can change
• Can flow
• Easy to compress• Low density
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Changes of state
• .
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Brownian motion – Fat droplets in milk
• .
Einstein's Explanation of BrownianMotion http://www.practicalphysics.o
rg/fileLibrary/wmv/brownian_
Brownian
Motion
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.
• Brownian motion is the seeminglyrandom movement of particles suspendedin a fluid (i.e. a liquid or gas). It is due to
the instantaneous imbalance in thecombined forces exerted by collisions ofthe particle with the much smaller liquid
molecules surrounding it.
8/3/2019 Lesson 5 Gas Pressure Kelvins
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Today’s lesson
• Recall that molecules in a gas have arandom motion and that they exert a forceand hence a pressure on the walls of the
container• Understand that there is an absolute zero
of temperature which is – 273 oC
• Describe the kelvin scale of temperatureand be able to convert between the kelvinand Celsius scales
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Pressure in a gas
What is origin of the pressure of a gas?
Volunteers please!
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Pressure versus temperature (atconstant volume)
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P/T = constant
• P1 /T1 = P2 /T2
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At -273°C, P = 0!!
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Kelvins
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Absolute/Kelvin temperature andCelsius
T (in Kelvin) = T (in degrees Celcius) + 273
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Kelvin Temperature
The kelvin Temperature is proportional tothe average kinetic energy of the particlesin a substance.
Note that they arenot all travelling at
the same speed.
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Temperature
The hotter the temperature, the faster theaverage speed of the particles
Note that they arenot all travelling at
the same speed.
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Pressure and Volume atconstant temp?
• . Volunteers again?