Energy and States of Matter

1. Energy and States of Matter

2. Energy • When particles collide, energy is transferred from one particle to another. • Law of conservation of energy: energy can be neither created nor destroyed; it can only be converted from one form to the other.

3. Particle Diagram

4. Particle Diagram Solid Liquid Gas http://www.patana.ac.th/secondary/science/anrophysics/unit5/commentary.htm Motion/Kinetic Energy of Particles Force of Attraction for the Same Substance

5. PhET Simulation • PhET Simulation

6. Solids • Physical properties used to describe solids: • Hardness • Shape • Malleable • Ductile • Density • Elasticity • Characteristics of solids: • Particles are very close together • Strong attractive forces between particles • Particles vibrate but do not move out of position • Fixed shape • Fixed volume

7. Liquids • Physical properties used to describe liquids: • Viscosity (resistance to flow) • Concentration • Fluid (has the ability to flow) • Density • Characteristics of liquids: • Particles are close together • Weak attractive forces between particles • Particles slide past each other • Takes the shape of the container • Fixed volume • compressible • Cohesion (ex. water-water) • Adhesion (ex. Water-leaf surface)

8. Gases • Properties • Particles are far apart • No attractive forces between particles • Takes the shape of the container • Particles spread out to fill the container • Can be identified by “burning splint” test: • O2 gas causes the burning splint to re-light • CO2 gas causes the burning splint to go out quietly (fire extinguisher) • H2 gas causes a popping sound

9. Real-world application • Why are “air bags” safer than “liquid bags” or “solid bags”? http://www.superstock.com/stock-photos-images/1570R-134389

10. Gases as Diatomic Molecules • There are seven elements (all gasses) whose atoms are not stable as individuals. • These atoms will always bond with another atom. • If no other type of atom is available, they bond with another atom of the same type. These are called DIATOMIC MOLECULES. • They are: H2, O2, F2, Br2, I2, N2, Cl2

11. Common Gases Air is a mixture of gases: Nitrogen (N2) Oxygen (O2) Argon (Ar) Carbon dioxide (CO2) Hydrogen (H2) Ammonia (NH3) Methane (CH4) http://patti-isaacs.com/portfolio/

12. Graham’s law (of effusion) • Effusion – when a gas escapes through a tiny hole in its container • States that the rate of effusion of a gas is inversely proportional to the square root of the gas’s (molar) mass. • What you need to know: lighter gases travel faster than heavier gases. • The bottom (decimal) number on the periodic table is the mass.

13. ‘Gas has Mass’ • At your station there are two balloons filled with different gases (balloon A & balloon B). • Make observations about the following variables in both balloons: (1) Volume (is one balloon bigger, or are they about the same?) (2) Temperature (3) Pressure • Hold balloons A & B at shoulder height and release. • What happens to each balloon? • What can you conclude about the density of each balloon (remember, D=m/V) compared to the density of the gas in the room? • Find the mass of balloons B & C on the scale. • Does gas have mass? Support your response with your observations.

14. Temperature • Temperature: measure of the average kinetic energy of each particle within an object. • Gases at the same temperature have the same kinetic energy. • Kinetic energy = ½(mv2)

15. Thermal Equilibrium The arrows represent the relative movement of the particles (circles).

16. Temperature • Kelvin scale: zero is the temperature at which no more energy can be removed from matter; all motion stops. • Zero on Kelvin scale is called absolute zero; written as 0K; the temp at which all motion stops • No negative Kelvin temps • For all gas law problems, the temp must be in Kelvin

17. Temperature K = C° + 273 Convert the following temperatures into Kelvin: a. 43 oC b. –135 0C Convert the following temperatures into Celsius: a. 340 K b. 30 K

18. Kinetic Molecular Theory • Gases consist of tiny particles (atoms or molecules). • These particles are so small, compared with the distances between them that the volume (size) of the individual particles can be assumed to be negligible (zero). • The particles are in constant random motion, colliding with the walls of the container. These collisions with the walls cause the pressure exerted by the gas. • The particles are assumed to not attract nor repel each other. • The average kinetic energy of the gas particles is directly proportional to the Kelvin temperature of the gas.

19. Pressure Measures the force of particles hitting the container per unit area Which has more pressure? Why? A B http://www.wisegeek.com/what-is-a-pressure-gauge.htm

20. Pressure The metric unit for measuring pressure is ATMOSPHERE (atm). Other units for measuring pressure: • mm of Hg (millimeters of mercury) 760 mm Hg = 1 atm • kPa (kilopascals) 101.3 kPa = 1 atm • psi (pounds per square inch) 14.7 psi = 1 atm

21. How to convert between pressure units Convert 795 mm Hg into atmospheres. • Identify conversion factor. 760 mm Hg = 1 atm • Set up a dimensional analysis problem • a series of fractions • First fraction is number you started with over 1 • Second fraction is the conversion factor • Units you started with should go at bottom of second fraction 795 mm Hg 1atm_____ = 1760 mm Hg • Solve the problem and cancel units (795)(1) = 795 = 1.05 atm (1)(760) 760

22. Pressure conversions – guided practice 1. The air pressure for a certain tire is 109 kPa. What is this pressure in atmospheres?

23. Pressure conversions – independent practice 1. The air pressure inside a submarine is 0.62 atm. What would be the height of a column of mercury balanced by this pressure? 2. The weather news gives the atmospheric pressure as 1.07 atm. What is this atmospheric pressure in mm Hg? 3. An experiment at Sandia National Labs in New Mexico is performed at 758.7 mm Hg. What is this pressure in atm? 4. A bag of potato chips is sealed in a factory near sea level. The atmospheric pressure at the factory is 761.3 mm Hg. The pressure inside the bag is the same. What is the pressure inside the bag of potato chips in kPa? 10 minutes

24. Atmospheric pressure • Atmospheric pressure is the result of collisions of air molecules with objects. • Atmospheric pressure decreases with an increase in altitude. The air around the earth “thins out” at higher elevations. (www.naval-technology.com) (ghccprimetimers.org) Which has more pressure exerted on it?

25. Atmospheric Pressure decreases with increasing altitude. (hendrix2.uoregon.edu) 1 atmosphere is defined as the air pressure at sea level.

26. Measuring air pressure Barometers Manometers used to measure the pressure of other gases as compared to atmospheric pressure • used to measure atmospheric pressure (weather reports)

27. STPStandard Temperature and Pressure 1 atm O°C

28. Relationships • Direct Relationship: when changing one variable causes the other variable to change in the same direction • when one goes up, the other goes up; when one goes down, the other goes down

29. Relationships • Inverse Relationship: when changing one variable causes the other variable to change in the opposite direction • when one goes up, the other goes down • Another word for inverse is indirect.

30. Boyle’s law Demo – marshmallows and vacuum pump • Independent variable:_______________________ • Dependent variable: ________________________ • Observations: ____________________________________________________________________________________ • Relationship: ______________________________

31. Boyle’s Law • Boyle’s Law states that gas pressure is inversely proportional to volume at constant temperature and number of particles of gases. • Mathematical relationship: P1V1= P2V2 This means “pressure one times volume one equals pressure two times volume two)

32. How does Boyle’s Law explain this? A was balloon inflated in San Diego, CA and then taken to Denver, CO (www.faculty.sdmiramar.edu) 

33. Explain how these represent Boyle’s law? A. B. syringe Pressure gauge ffden-2.phys.uaf.edu (www.chemwiki.ucdavis.edu)

34. Boyle’s Law Example: • A gas has a volume of 100 ml when the pressure is 1.4 atm. What is the volume, in mL, when the pressure is increased to 1.6 atm and the temperature is held constant?

35. If a gas has a volume of 100 ml when the pressure is 1.4 atm, what is the volume, in mL, when the pressure is increased to 1.6 atm and the temperature is held constant? List variables: • V1 = 100 mL • P1 = 1.4 atm • V2 = ? mL • P2 = 1.6 atm Write formula: • P1V1 = P2V2 Substitute in known values: • (100mL)(1.4atm) = (V2)(1.6atm) Rewrite without units. • (100)(1.4) = (V2)(1.6) • If desired, switch the sides… (V2)(1.6) = (100)(1.4) • If desired, switch the unknown and number… (1.6)(V2) = (100)(1.4) Solve for unknown: • Combine terms (1.6)(V2) = 140 • Isolate the variable • (1.6)(V2) = 140 1.6 1.6 • V2 = 87.5 mL Very Important: Check to see if your answer makes sense… pressure increased by a little (1.4 to 1.6) so volume should decrease by a little (100 to 87.5).

36. Boyle’s Law Guided Practice: • The pressure of a balloon is 101 kPa. What is the new pressure of a balloon after its volume is changed from 502 mL to 301 mL?

37. Boyle’s Law Independent Practice: A gas tank holds 2785 L of propane (C3H8) at 830. mm Hg. What is the volume of the propane at standard pressure? 2. A sample of neon (Ne) occupies a volume of 85.0 mL at STP. What will be the volume of the neon when the pressure is reduced to 65.5 kPa? 3. 352 mL of chlorine (Cl2) under a pressure of 680. mm Hg are transferred in a 450. ml container. The temperature remains constant at 296 K. What is the pressure of the gas in the new container? 10 minutes

38. Charles’ law • Demo – balloons • Independent variable:_______________________ • Dependent variable: ________________________ • Observations: ______________________________________________________________________________________________________________________Relationship: ______________________________

39. Charles’ Law • The volume of a given amount of gas varies directly to its kelvin temperature when pressure is constant. • Mathematical relationship: V1 = V2 T1 T2 This means “volume one divided by temperature one equals volume two divided by temperature two)

40. Charles’ Law

41. Charles’ Law cfbt-us.com

42. Charles’ Law example • A balloon inflated in an air conditioned room at 27◦C has a volume of 4.00 L. If it is heated to 57◦C and the pressure remains constant, what is the new volume?

43. A balloon inflated in an air conditioned room at 27◦C has a volume of 4.00 L. If it is heated to 57◦C and the pressure remains constant, what is the new volume? List variables and Convert temp to Kelvin: • T1= 27°C + 273 = 300 K • V1 = 4.00 L • T2 = 57°C + 273 = 330 K • V2 = ? L Write formula: • V1 = V2 T1 T2 Substitute in known values: (4.00L) = (V2)_ (300K) (330K) Rewrite without units • (4.00) = (V2)_ (300) (330) Cross multiply… (4.00)(330) = (300)(V2) Combine terms… 1320 = (300)(V2) If desired, switch sides… (300)(V2) = 1320 Isolate variable… (300)(V2) = 1320 300 300 Solve for unknown : V2 = 4.4 L Check to see if your answer makes sense… • temp went up by 10%, • volume went up by 10%.

44. Charles’ law guided practice: • A container holds 50.0 mL of nitrogen at 25° C and a pressure of 736 mm Hg. What will be its volume if the temperature increases by 35° C?

45. Gay-Lussac’s law • Demo – crush the can • Independent variable:_______________________ • Dependent variable: ________________________ • Observations: ______________________________________________________________________________________________________________________ • Relationship: ______________________________

46. Gay Lussacs Law • The pressure of a gas varies directly to the Kelvin temperature of the sample, if the volume remains constant. • Mathematical relationship P1 = P2 T1 T2 This means “pressure one divided by temperature one equals pressure two divided by temperature two)

47. Gay-Lussac’s law

48. Gay Lussac’s Law cfbt-us.com

49. Graph of Gay-Lussac’s Law(direct relationship)

50. Gay-Lussac’s Law example • A gas in an aerosol can is at a pressure of 1.00 atm and 27.0 oC. If the can is thrown into a fire, what is the internal pressure of the gas when the temperature reaches 927 oC?