1. Chapter 13 States of Matter By: Zak and Megan

2. 13.1 The Fluid States Fluids include both liquids and gases –Fluids are materials that flow and have no definite shape –Liquids have definite upper surface area –Gases do not have any definite surface area Properties of Fluids

3. Applying force to a surface is pressure –Pressure is the force on a surface divided by the area of the surface. –P = The force (F) is perpendicular the surface area (A). –The unit for pressure is the pascal (Pa). More commonly used is the kilopascal (kPa) –Pressure is exerted up from a solid surface equal to the weight of the object resting on it. F A

4. Gas Particles and Pressure The kinetic molecular theory of gases states that gases are made up of very small particles that are widely separated in constant, random motion at high speed, and making elastic collisions with each other. –Gas particles “bounce” off a surface without losing kinetic energy and these collisions result in gas pressure on the surface. Atmospheric Pressure exerts approx 10N of force on every cm 2 of Earth’s surface. –P atm = 10 N/cm 2 or 100 kPa

5. A woman weighs 495 N and wears shoes that touch the ground over an area of 412 cm 2. a. What is the average pressure in kPa that her shoes exert on the ground? b. How does the pressure change when she stands on only one foot? c. What is the pressure if she puts all her weight on the heel of one shoe with the area of the high heel of 2.0 cm 2. Known: F = 495 N A a = 412 cm 2 A b = 206 cm 2 A c = 2.0 cm 2 Example Problem

6. Ex. Problem Cont. Calculations: a. A a 412 cm 2 (1 m/100 cm) 2 = 0.0412 m 2 P a = 495 N/ 0.0412 m 2 = 1.20 x 10 4 N/m 2 (1 kPa/1000 N/m 2 ) = 12.0 kPa b. A b = 0.0206 m 2 P b = 495/(.0206 x 1000) = 24.0 kPa c. A c =.00020 m 2 P c = 495/(.00020 x 1000) = 2500 kPa

7. Fluids at Rest Pascal's Principal states that any change of pressure applied at any point on a confined fluid is transmitted undiminished throughout the fluid.

8. Swimming Under Pressure The downward pressure of the water is equal to the weight (F g ) of the column of water above its surface area. –F g =  Ahg  = density –P =  gh

9. SUP Cont. The upward force on an object in water is called the buoyant force. –F buoyant = F bottom – F top –F buoyant =  Vg Archimedes' principle states that an object immersed in a fluid has an upward force on it equal to the weight of the fluid displaced by the object. The net downward force of an object is its apparent weight. F apparent = F g – F buoyant

10. Fluids In Motion The relationship between the velocity and pressure exerted by a moving fluid is described by Bernoulli's Principle. –As the velocity of a fluid increases, the pressure exerted by that fluid decreases. As a fluid moves through a narrower area the velocity of the fluid increases.

11. Forces Within Liquids In real liquids particles exert electromagnetic forces of attraction on each other called cohesive forces. –Surface tension is a result of cohesive forces between the particles of a liquid. Adhesion is the attractive force that acts between particles of different substances. –Capillary action is when a liquid moves up a tube because its adhesive forces are stronger than the cohesive forces.

12. Forces Within Liquids The escape of particles from a liquid is called evaporation. –Evaporation has a cooling effect. –A liquid that evaporates quickly is called a volatile liquid. The returning of evaporated particles to a liquid is called condensation.

13. 13.2 The Solid State Solid Bodies When the temperature of a liquid is lowered to the point where the particles can no longer move past each other, the particles lock into a pattern called a crystal lattice and form a crystalline solid. –The solids still vibrate. Some solids do not form a fixed crystal lattice and are called amorphous solids. –Known as being viscous, or slowly flowing, liquids.

14. Effects Of Freezing Solids are usually more dense than liquids (except water). An increase in pressure on the surface of a liquid usually increases its freezing point (except water).

15. Elasticity The ability of an object to return to its original form when bent or twisted is called the elasticity of the solid. –The elasticity limit is the point a solid is deformed to the point that it will not return.

16. Thermal Expansion Temperature changes in both solid and liquid matter causes it to expand when heated and to contract when cooled (thermal expansion). When heated matter becomes less dense and fills more space. The change in length of a solid is propotional to the change in temperature. Liquids expand considerably more than solids.

17. Plasma If the temperature of a gas is increased enough, the particles of the substance start to tear apart into negative electrons and the positive ions. The resulting state is called plasma. Most of the matter in the universe is plasma. –Stars consist mostly of plasma. –Much of space consists of hydrogen w/o electrons. The main difference between a gas and plasma is that a plasma can conduct electricity. –Lightning bolts are in the plasma state.

18. Practice Pg. 303 # 1-4, Pg. 309 # 6