2. Chapter 13 States of Matter
Glencoe Physics
Chapter 13
States of Matter

3. Objectives:13.1
Describe how fluids create pressure and relate how Pascal’s Principle to some everyday occurences.
Apply Archimedes’ and Bernoulli’s Principles
Explain how forces within liquids cause surface tension and capillary action, and relate the kinetic model to evaporation and condensation

4. Objectives:13.2
Compare solids, liquids, gases, and plasmas at a microscopic level, and relate their properties to their structures.
Explain why solids contract and expand when the temperature changes
Calculate the expansion of solids and discuss the problems caused by expansion

5. Fluids A fluid is anything that flows (easily moves, changes shape).
Liquids (system is a hydraulic system)
Gases (system is a pneumatic system)
To move fluids, a pressure difference is needed

7. Pressure
Motion of fluids can be understood by understanding the concept of pressure.
Pressure is created by fluids when particles of fluid (atoms or molecules) impact a surface.
Pressure is defined as the ratio of a force and the area over which that force is applied
Where P = Pressure
F = force applied
A = area over which force
is applied
**Pressure is directly related to the number and strength of the collisions of the particles with container.

8. Pressure Units of pressure…. pounds/inch2 (PSI)
Evangelista
Torricelli
1000 Pa = 1 kPa = 1000 N/m2
First man
To create a sustained vacuum, and discovered principle of the barometer
Units of pressure….
pounds/inch2 (PSI)
newtons/meter2 (Pascal) (SI unit)
kilopascals
mmHg
InHg
Torr
atmospheres
bar
millibar
Standard Sea Level barometric Pressure
14.69 psi
101,325 Pa
kPa
760 mmHg
29.92 inHg
760 torr
1 atm
1.013 barr
1013 mb

9. Measurement of pressure
Barometers
Aneroid

10. Why is “Fair Weather” or “Dry Weather” associated with higher atmospheric pressure?

11. Measurement of Pressure
Barometers
Mercury

13. Measurement of Pressure
Pressure gauge
Tire gauge
Altimeter
Digital instrument

14. Magdeburg Hemispheres
The Magdeburg hemispheres were a pair of large copper hemispheres precisely cast so that their rims fit tightly together.
The Magdeburg hemispheres were designed by German scientist Otto von Guericke in 1650 to disprove Aristotle's famous supposition that 'Nature abhors a vacuum'. To get the air out of the sphere, von Guericke also designed the world's first vacuum pump, which consisted of a piston and cylinder with one-way flap valves.

15. Problem…..
The atmospheric pressure at sea level is 101,325 Pa. What is the force, at sea level, that air exerts on the top of a typical desk, 152 cm long X 76 cm wide? Report in SI unit.
P=F/A
PA = F
F = PA
F = 101, 325 n/m2 X (1.52 m X .76m)
F = 1.2 X 105 N

16. Problem…
A car has a mass of 900. kg. If each tire on the car has a contact area of 80. cm2, what internal air pressure (in Pa) will each tire have? In atm? In PSI?
Area of Contact
P = F/A
P = (mg/4)/A
P= ((900.kg X 9.8m/s)/4) / m2
P = Pa
P = 2.8 X 105 Pa
2.8 ATM
41 psi

17. Fluid Pressure Fluid pressure can be “created” in at least two ways
For an enclosed fluid, the container may provide the force (physical confinement) or there may be an external force applied
For an open fluid, the “weight” of the fluid creates the pressure

18. Pascal’s Principle
Blaise Pascal ( ), a French physician, noted that the shape of the container did not affect the pressure of the fluid that it contained, at any particular depth.
Pascal’s Vases

19. Pressure in Closed System

20. Pascal’s Principle
“Any change to the pressure of a confined fluid is transmitted undiminished throughout the fluid”

21. Fluid is at same pressure, everywhere……

22. F1/A1 = F2/A2
F1A2/A1 = F2

25. Basic hydraulic cylinder

26. Problem…
Dentist’s chairs are examples of hydraulic lift systems. If a chair weighs 1600 N and rests on a piston with a cross-sectional area of 1440 cm2, what force must be applied to the smaller piston with a cross-sectional area of 72 cm2 to lift the chair?