1. Unit 2 B Matter, Energy, and Changes

2. Matter & Changes

3. Matter
Is anything that has mass and volume

4. States: Gas – no definite shape or volume particles randomly scattered
particles moving quickly in constant motion,
highly compressible,
low density,
rapid diffusion
high expansion on heating

5. States:Liquid no set shape definite volume
particles somewhat organized
particles free to move
slightly compressible
high density
slow diffusion
low expansion on heating

6. Properties of Liquids
Viscosity – friction or resistance to motion, increases as temperature decreases Surface tension – molecules at the surface experience imbalanced attractive forces

7. Both gasses and liqids are fluids.
This is because of weak intermolecular forces.
The molecules can slide easily over each other.

8. States:Solid has particular shape definite volume
particles very organized and close together,
particles move only very slightly
low compressibility
high density
slow diffusion
low expansion on heating

9. Solids Intermolecular forces are strong Molecules still move
Can only vibrate and revolve in place.
Particles are locked in place - don’t flow.
Melting point is the temperature where a solid turns into a liquid.
The melting point is the same as the freezing point.

10. Solids
When heated the particles vibrate more rapidly until they shake themselves free of each other.
As they are heated the temperature doesn’t change.
The energy goes into breaking bonds, not increasing motion
Move differently, not faster.

11. Basic Types of Solids
Crystalline solids – Amorphous solids -

12. Crystals
are made of atoms arranged in highly ordered, patterns called unit cells
A regular repeating three dimensional arrangement of atoms in a solid.
Most solids are crystals.
Break at certain angles
Examples Table salt, table sugar, Emerals

13. Amorphous solids
appear solid, but are more of a super-cooled liquid, have high viscosity, gradually soften as temperature increases
lack an orderly internal structure.
Think of them as super-cooled liquids.
Glasses are one type.
Rigid but lacking structure
Do not melt- just gradually get softer.
Shatter at random angles
Examples: glass, and plastics

14. Properties of Solids
Some solids are good conductors due to particles being in contact with each other and passing the energy from one to another

15. Physical State of Matter
State of matter at room temperature depends on strength of intermolecular forces ( IM)
For example, a substance with strong IM forces will be a solid while a substance with very weak IM forces will be a gas

16. Matter Intermolecular Forces
Are the forces between neighboring molecules

17. Changes of State
Energy and change of state… To change states, particles must overcome the attractive forces holding them together (the number of particles does not change)

18. Kinetic Theory and states of Matter
Kinetic theory says that molecules are in constant motion.
Perfume molecules moving across the room are evidence of this.

19. Kenetic Theory helps to explain why a gas behaves as it does.
It also helps us understand the changes in physical states of matter

21. The Kinetic Theory of Gases Makes three descriptions of gas particles

22. The Kinetic Theory of Gases Makes three descriptions of gas particles

23. The Kinetic Theory of Gases Makes three descriptions of gas particles

24. The Kinetic Theory of Gases Makes three descriptions of gas particles

25. The Kinetic Theory of Gases Makes three descriptions of gas particles

26. The Kinetic Theory of Gases Makes three descriptions of gas particles

27. The Kinetic Theory of Gases Makes three descriptions of gas particles

28. The Kinetic Theory of Gases Makes three descriptions of gas particles

29. The Kinetic Theory of Gases Makes three descriptions of gas particles

30. The Kinetic Theory of Gases Makes three descriptions of gas particles
A gas is composed of particles
molecules or atoms
Considered to be hard spheres far enough apart that we can ignore their volume.
Between the molecules is empty space.

31. The particles are in constant random motion.
Move in straight lines until they bounce off each other or the walls.
All collisions are perfectly elastic

32. The Average speed of an oxygen molecule is 1656 km/hr at 20ºC
The molecules don’t travel very far without hitting each other so they move in random directions.

33. Breaking intermolecular forces.
Vaporization - the change from a liquid to a gas below its boiling point.
Evaporation - vaporization of an uncontained liquid ( no lid on the bottle ).

34. Evaporation Molecules at the surface break away and become gas.
Only those with enough KE escape
Evaporation is a cooling process.
It requires energy.

35. Condensation Change from gas to liquid Molecules stick together
Releases energy.

36. Boiling Making bubbles of gas Forces liquid level to rise
Must push against air pressure on the liquid.

37. Boiling A liquid boils when the vapor pressure = the external pressure
Temperature is called the boiling point
Normal Boiling point is the temperature a substance boils at 1 atm pressure.
The normal boiling point of water is 100o C
The temperature of a liquid can never rise above it’s boiling point
Energy goes into breaking forces, not moving faster.

38. Changing the Boiling Point
Lower the pressure (going up into the mountains).
Lower external pressure requires lower vapor pressure.
Easier to make bubbles
Lower vapor pressure means lower boiling point.
Food cooks slower.

39. Changing the Boiling Point
Raise the external pressure (Use a pressure cooker)
Raises the vapor pressure needed.
Harder to make bubbles
Raises the boiling point.
Food cooks faster.

40. Different Boiling points
Different substances boil at different temperatures because they have different intermolecular forces
Weak forces- lower boiling point
Different vapor pressures
Low vapor pressure – high boiling point

41. Changes of State
Heat of vaporization You have 18.2 moles of water. How much energy is needed to vaporize the sample? (Molar heat of vaporization for water = 40.7 kJ/mole) kJ

42. Changes of State
Melting You have a 278 mole block of ice. How much energy is needed to melt it? (Molar heat of fusion for water = 6.00 kJ/mole) 1668 kJ

43. Phase Changes Solid Gas Liquid Melting Vaporization Freezing
Condensation

44. Solid Gas Liquid Require energy Sublimation Melting Vaporization
Condensation
Freezing
Condensation
Release energy

45. Temperature and Phase Change
The temperature doesn’t change during a phase change.
If you have a mixture of ice and water, the temperature is 0ºC
At 1 atm, boiling water is 100ºC
You can’t get the temperature higher until it boils

46. Heating Curve
A graph of Energy versus temperature.

47. Changes of State
Heating curves Describe changes of state of matter, plot of sample temperature as a function of time

48. Changes of State

49. Changes of State
Phase diagrams Relates states of matter to temperature and pressure

50. Changes of State