Chapter 16: Macroscopic Description of Matter

1. Chapter 16: Macroscopic Description of Matter • Stop to think 16.2 page 485 • Stop to think 16.3 page 487 • Stop to think 16.5 page 494 • Stop to think 16.6 page 498 • Stop to think 16.7 page 498 • Example 16.2 page 485 • Example 16.3 page 492 • Example 16.6 page 495 • Example 16.10 page 498

2. Chapter 16: Macroscopic Description of Matter Temperature: T is related to a system’s thermal energy. Temperature scale: 1) CelsiusC: The world most common temperature scale As the old centigradescale, has 100 degree between melting point and boiling point of water, taken to occur 0 and 100 degrees, respectively. 2) Kelvin K : Temperature is measured as thermal energy of system. Takes its zero to be absolute zero. 3) Fahrenheit F: used primarily in US

3. Solids, Liquids and Gases • Solid: a rigid macroscopic system with a definite shape and volume. An atom is not free to move around inside the solid: Solids are nearly incompressible. • Liquid: Liquid flows and deform to fit the shape of its container. It is nearly incompressible • Gas: a system in which each molecule moves through space as a free noninteracting particle until it collides with another molecule or with the wall of the container. A gas is also highly compressible.

4. Density • Mass density

5. Pressure • Pressure P, as defined • Units of P, 1pascal = 1 Pa = 1 N/m2 • Atmospheric Pressure: • 1 standard atmosphere = 1 atm = 101,300 Pa =101.3kpa

6. Atoms and Moles • Atomic massunit: m(12C) = 12u • Molecular mass m(O2) = 32u • Mole, the amount of any substance containing 6.02×1023 particle is defined as one mole. • Avogadro’s number NA= 6.02×1023 • Number of mole

7. Ideal gases • The ideal-gas law • R = 8.31 J/mol•K Universal gas constant • P– pressure, units is Pa • V—volume, units is m3 • PV– units is Pam3= Nm= joules. • n– the number of moles • T—temperature in Kelvin scale.

8. Application of ideal gas law (16.20) • A 20 cm-diameter cylinder that is 40 cm long contains 50 g of oxygen gas at 20 C? • How many moles of oxygen are in the cylinder? • Notice the molar mass of oxygen is 32 g, therefore the number of mole for 50 g oxygen is 50g/32 g = 1.56 mole • How many oxygen molecules are in cylinder N = 1.56/mol x NA= 9.4×1023 • What is the number density of oxygen: • What is the reading of pressure gauge attached to the tank • Using the ideal gas law to get pressure inside the tank, P = nRT/V • Notice the reading of pressure gauge is the difference of pressure inside of tank from the pressure of outside.

9. Ideal-gas processes • The PV Diagram: Pressure –vs – volume • Each point on the graph represents a single unique state of the gas • Assuming that n is known, from ideal-gas law PV=nRT, we can get T for each point.

10. Constant Volume Process • Constant-volume process---isochoric process, volume does not change during the process.

11. Constant-Pressure Process • Constant-pressure Process—isobaric process • The pressure does not change during the process

12. Constant-temperature process • Constant-temperature process – isothermal process.

13. Problem 16.31 • 0.0040mol of gas undergoes the process as Fig. • What type of process is this? • The Fig. shows that the pressure is inversely proportional to the volume. So the process is isothermal. PV = nRT • The initial and final temperatures should be same T = PV/nR Notice 1atm = 1.013×105 Pa, 1cm3=10-6 m3

14. Masteringphysics Up Up and away • For the balloon float, at least the buoyant force should equal the total weight (basket, fabric, hot air inside etc), that is: • With • We get