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Chemistry 30SPhysical Properties of Matter

Unit Two

Describe the properties of gases, liquids, solids, and plasma. Use the Kinetic Molecular Theory to explain properties of gases. Explain the properties of liquids and solids using the Kinetic Molecular

Theory. Explain the process of melting, solidification, sublimation, and deposition in

terms of the Kinetic Molecular Theory. Use the Kinetic Molecular Theory to explain the processes of evaporation and

condensation. Operationally define vapour pressure in terms of observable and measurable

properties. Operationally define normal boiling point temperature in terms of vapour

pressure. Interpolate and extrapolate the vapour pressure and boiling temperature of

various substances from pressure versus temperature graphs.

Gr. 11 Chemistry Physical Properties of Matter

Personal Response SheetPhysical Properties of Matter Name: __________________

Answer the following questions below as best you can. During this topic of study you will revisit these questions and answer them again and by so doing be able to gauge your learning development.

1. Why does water evaporate on a warmer day than a colder day?First Response:

Further Responses:

2. Explain why a thermometer rises when placed in warm water and drops when placed thereafter in cold water.

First Response:

Further Responses:

3. A balloon is filled with air. It is then placed in the freezer. What will happen to it? Why will this happen?First Response:

Further Responses:

4. An unopened bag of Old Dutch chips is placed near a warm air vent. What do you think will happen to the size of the bag over the next hour?First Response:

Further Responses:


5. Two people are standing on opposite ends of a larger swimming pool. While both standing up one person bangs two rocks together above the water but the other does not hear it. When they both go under water and bang the rocks the other can now hear it. Explain why.First Response:

Further Responses:

6. Explain why water boils at lower temperatures (e.g., 90 degrees) on the top of a mountain when at sea level in boils at 100 degrees.First Response:

Further Responses:

7. A can of coke expands when frozen in the fridge. Explain why.First Response:

Further Responses:

8. A car tire becomes somewhat flatter on a cold day but once the car starts traveling down the road it goes back to its original size. Explain why.First Response:

Further Responses:

9. Explain why you can hear sounds easier on cold winter days than warm summer days.First Response:

Further Responses:


Three Basic States of Matter

There are three physical states of matter. Each has certain distinguishing characteristics.

Solidso Have a definite _______________ and ______________.o Shape doesn’t depend on the container.o Particles are tightly packed together, often in an ordered arrangement.o Will usually expand slightly when heated.o Usually __________________________.o Varying density

ex.) iron 7.87g/cm3, gold 19.3 g/cm3, calcium 1.54 g/cm3.

Liquidso Particles of a liquid are in close contact, but arrangement is not rigid or orderly.o Flow freely, liquids take the ____________ of the container (some liquids pour easier than others).o Volume remains constant, even if shape changes.o Usually ________________________.o Will expand slightly when heated.o Can diffuse easily from areas of __________ concentrations to _________ concentrations.o Varying densities

ex.) mercury 13.53 g/mL, water 1 g/mL.

Gaseso Flows freely, will take the __________ of the container.o Will expand to fill any ____________.o Particles in a gas are much farther apart than solids and liquids.o Easily ____________________ to half starting volume.o Can _______________ easily from areas of high concentrations to

low concentrations.o Varying densities depending on pressure

ex.) hydrogen 0.089 g/cm3, oxygen 1.43 g/cm3, chlorine 3.21 g/cm3.


Plasma

What is Plasma?o A gaseous mixture of _________________________ and ________________.o Formed at high temperatures greater than ___________________ Celsius when ______________ are

stripped from neutral atoms.o Very _______________.o The most common form of _______________ in the universe, comprising ____% of the visible universe,

but are the _______________ common on Earth.o DO NOT occur naturally on Earth except in the form of lightning bolts. o Examples include aurora borealis, lightening, fluorescent lights, and stars. o Neon sign - glass tubes filled with gas, electricity is turned on and charges the gas, creating plasma inside

the tube and the colour depends on type of gas.


Four States of Matter


Can you find three states of matter in this picture?

Introduction:

Most people are familiar with the three states of matter – solid, liquid and gas, but many are unaware that there is a fourth state of matter known as plasma.

Scientists have begun to study matter at the very high temperatures and pressures which typically occur on the Sun or during re-entry from space. Under these conditions, the atoms themselves begin to break down; electrons are stripped from their orbit around the nucleus leaving a positively charged ion behind. The resulting mixture of neutral atoms, free electrons, and charged ions is called plasma.

Plasma is by far the most common form of matter. Plasma in the stars and in the space between them makes up over 99% of the visible universe and also most of that which is not visible. Sir William Crookes, an English physicist, identified a fourth state of matter, now called plasma, in 1879. The term plasma was coined in 1929 by Dr. Irving Langmuir.

Plasma temperatures and densities range from relatively cool and tenuous (like aurora), to very hot and dense (like the central core of a star). Ordinary solids, liquids, and gases are both electrically neutral and too cool or dense to be in a plasma state.

Did you know that fluorescent light bulbs are plasmas? They are not like regular light bulbs. Inside the long tube is a gas. Electricity flows through the tube when the light is turned on and this electricity provides energy and charges up the gas. This charging and exciting of the atoms creates glowing plasma inside the bulb.

Did you know that neon signs are also plasmas? Just like a fluorescent light, neon signs are glass tubes filled with gas. When the light is turned on, the electricity flows through the tube. The electricity charges the gas, possibly neon, and creates plasma inside of the tube. The plasma glows a special color depending on what kind of gas is inside.

Fluorescent lights are cold compared to really hot stars. They are still both forms of plasma, even with different physical characteristics.


The Four States of Matter

Properties of the Four States of Matter: Solids, Liquids, Gases and Plasmas

In a solid the molecules are closely bound to one another by intermolecular forces. A solid holds its shape and the volume of a solid is fixed by the shape of the solid.

In a liquid the intermolecular forces are weaker than in a solid. A liquid will take the shape of its container and a liquid has a fixed volume.

In a gas the intermolecular forces are very weak. A gas fills its container, taking both the shape and the volume of the container.

Liquids and gases are called fluids because they can be made to flow, or move. In any fluid, the molecules themselves are in constant, random motion, colliding with each other and with the walls of the container. Plasma is a fluid, like a liquid or gas, but because of the charged particles present in plasma, it responds to and generates electromagnetic forces.

There is also known to be a fifth state of matter, created in 1995, called the Bose-Einstein Condensate (BEC). If plasmas are super hot and super excited atoms, the atoms in a Bose-Einstein condensate (BEC) are total opposites. They are super-unexcited and super-cold atoms.

For example, a cold ice cube is still a solid. When you get to a temperature near absolute zero something special happens. Atoms begin to clump. The whole process happens at temperatures within a few billionths of a degree. The result of this clumping is the BEC. A group of atoms takes up the same place, creating a "super atom." There are no longer thousands of separate atoms. They all take on the same qualities and become one blob. This fifth state of matter will not be considered in this activity.


The Four States of Matter: Solids, Liquids, Gases and Plasma Activity:

Part One:

Below are descriptions of each of the four states of matter. Beside each description, state whether it best describes a solid, liquid, gas or plasma.

1. We can’t feel it. _______________

2. It is an ionized gas. _______________

3. The particles move quickly. _______________

4. It has a fixed volume but it changes shape. _______________

5. The particles have some movement energy. _______________

6. It has free (not bound) electrons. _______________

7. It fills any container you put it in. _______________

8. It flows from one container to another. _______________

9. The particles are spread far apart. _______________

10. The particles are fairly close together. _______________

11. It is electrically conductive. _______________

12. The particles move slowly about. _______________

13. It does not have a fixed volume or shape. _______________

14. The particles are packed close together. _______________

15. The particles have a lot of movement energy. _______________

16. It spreads to fill the bottom of a container. _______________

17. It spreads out in all directions. _______________

18. It takes the form of natural gas-like clouds. _______________

19. The particles do not attract each other. _______________

20. The particles attract each other weakly. _______________

21. It has a fixed shape and size. _______________

22. The particles attract each other strongly. _______________

23. The particles are not in a pattern. _______________

24. It is a distinct state of matter. _______________

25. The particles have almost no movement energy. _______________

26. The particles have a weak pattern. _______________

27. The particles are in a fixed pattern. _______________


28. It is usually invisible. _______________

29. It keeps its own shape. _______________

30. Its positive and negative charges move independently. _______________

31. It stays in a lump. _______________

32. It feels hard. _______________

33. It feels wet. _______________

34. The particles are in a fixed position. _______________

35. It is the most common phase of matter in the universe. _______________

36. It flows but does not have a fixed volume. _______________

37. It can be compressed. _______________

38. It does not have a fixed shape. _______________

39. It has a fixed volume. _______________

40. All stars are made of this. _______________

41. It has a fixed volume but you cannot walk through it. _______________

42. You cannot compress it easily and you cannot pour it. _______________

43. It does not flow. _______________

44. It has a fixed volume and a fixed shape. _______________

45. It cannot be compressed easily. _______________

46. It does not spread throughout the whole room. _______________

47. It does not have a fixed shape or a fixed volume. _______________

48. You can walk through it. _______________

49. You can pour it, but it does not have a fixed volume. _______________

50. You can walk through it but it does not have a fixed volume. _______________

51. It flows but it has a fixed volume. _______________

52. It does not have a fixed shape. _______________

53. It has a fixed volume but you can walk through it. _______________

54. You can pour it and you can compress it easily. _______________

55. It can spread throughout a whole room. _______________

56. It cannot be compressed easily but you can walk through it. _______________

57. It has a fixed shape. _______________

58. It does not have a fixed volume. _______________


59. It flows. _______________

60. You cannot pour it. _______________

61. You cannot walk through it. _______________

62. It has a fixed volume. _______________

63. It does not spread throughout the room, but it does not have a fixed shape. _______________

64. It has a fixed volume but it does not have a fixed shape. _______________

65. It has a fixed shape. _______________

66. It flows but it does not have a fixed volume. _______________

Part Two:

1. Which statements describe what we find by observing solids, liquids, gases and plasma?

2. Which statements describe how the particle theory explains these observations?

Part Three:

Write a paragraph about the four states of matter. Use ideas from the activity above but also use some of your own ideas. Also draw molecular diagrams of each state of matter that illustrate your main points.


Part Four:

Take the common substances below and state whether they are solid, liquid, gas or plasma:

1. The substance in an aerosol can: _______________

2. Petrol fumes: _______________

3. Steam from a kettle: _______________

4. An ice cube: _______________

5. Wood from a tree: _______________

6. Neon Sign: _______________

7. Oxygen from a cylinder: _______________

8. Camping gas: _______________

9. Exhaust fumes from a car: _______________

10. Fluorescent light bulb: _______________

11. Water: _______________

12. Mercury: _______________

13. Syrup: _______________

14. Paint: _______________

15. Glass: _______________

16. Sugar: _______________

17. A rock: _______________

18. A gold bar: _______________

19. Lighter fluid: _______________

20. Stars: _______________

Summary:In this activity you have examined the physical properties of the four states of matter and have learned more about plasma, the less well known of the physical states of matter.Every living and nonliving thing in our universe is made up of matter. Matter can be defined as anything that takes up space.

Matter occurs in four states: solid, liquid, gas and plasma. Solids have a definite shape and take up a definite amount of space. Liquids flow so they do not have a definite shape. They take up the shape of their container. Liquids do take up a definite amount of space. Gases do not have a definite shape, nor do they take up a fixed amount of space. Gases expand to fill their container. Plasmas are a lot like gases, but the atoms are different because they are made up of free electrons and ions of the element. Plasmas are different and unique from the other states of matter.


Properties of Matter Assignment

Complete each of the following questions regarding the properties of matter. You may use a variety of sources to obtain your answers. The following web sites might help:

http://www.chem.purdue.edu/gchelp/atoms/states.html

http://www.blurtit.com/q959588.html

Questions

1. Complete the following chart with respect to the four states of matter. Begin by defining each of the terms in the first column. The first one is done for you. Be sure you understand how each property varies amongst the phases.

Define each of the terms below. Give an example, if possible

Solid Liquid Gas Plasma

Volume:The amount of space the substance occupies.

Have a definite (unchanging) volume. Particles are held tightly together.

Compressibility:

Shape:

Strength of attractive forces:

Type of motion of particles:

Density:

Diffusion:


2. Complete each of the following.

a) There are ____ states of matter.

b) Particles of the same substance get bigger / get smaller / stay the same size (circle one) when they change state.

c) Particles of the same substance move the same / differently (circle one) when they change state.

d) When particles of a substance change state, they stay the same distance apart. True or false?

3. Create a drawing of the three most common states of matter in each of the following categories. Be sure to draw the individual molecules clearly.

a) The Spacing of Particles

solid liquid gas

b) The Movement of Particles

solid liquid gas

4. a) Separate the following list of densities into solids, liquids, and gases. Air-0.001293 g/cm3; aluminum-2.7 g/cm3; antifreeze- 1.10 g/cm3; carbon dioxide-0.001977 g/cm3; copper-8.9 g/cm3; diamond-3.3 g/cm3

; gasoline-0.70 g/cm3; gold-19.3 g/cm3; helium-0.000178 g/cm3; hydrogen-0.00009 g/cm3; magnesium-1.7 g/cm3; milk-1.03 g/cm3; nitrogen-0.001251 g/cm3; olive oil-0.8 g/cm3; platinum-21.4 g/cm3; rubbing alcohol--0.785 g/cm3; silver-10.3 g/cm3; vinegar-1.05 g/cm3; water-0.998 g/cm3

Solids Liquids Gases

b) How do the densities of solids, liquids, and gases compare?


Kinetic Energy and Temperature

Kinetic Energy: energy due to motion of an object

Potential Energy: stored portion of energy

Average kinetic energy: used when talking about the kinetic energy of a substance.

Temperature: a measure of the average kinetic energy of the particles of a substance.

Kinetic Energy Distribution Curve

If kinetic energy and temperature are related, there is a temperature at which all particles of a substance will stop moving, called ____________________________ (-273°C or 0 Kelvin)

Kelvin Temperature: directly proportional to the average kinetic energy of the particles in a substance. K = °C + 273.15


The Nature of Solids

There are two categories of solid:o Amorphous

o Crystalline

Amorphous Solidso Particles are arranged randomlyo created by rapid coolingo no fracture planes (break points)o poor conductors o Examples include rubber, plastic, and asphalt

Crystalline Solids o Particles are arranged into an orderly, repeating 3 dimensional pattern: a ________________.o Created by slow cooling o Lots of fracture planes (diamond armour is terrible)o Ordered structure makes them great conductors of heat and electricityo Examples include: salt, sugar, quartz, iron, and many more


The Nature of Solids

Allotropeso 2 or more molecular forms of the same elemento Allotropes of an element have _____________ properties because of their arrangement of the atoms.o Only a few elements have allotropes: carbon, phosphorous, sulfur, oxygen, boron, and antimony.o Example: carbon

Diamond: Each atom bonded to 4 others making a tetrahedral shape that is extremely rigid with highest hardness of any substance.

Graphite: Each atom is bonded to 3 others creating hexagon sheet. These sheets are stacked but weakly letting a layer slide off when you press.

Graphene: A single sheet of graphite is called graphene. It’s strong and a great conductor.

Carbon Nanotube: Basically graphene rolled in a tube. Very strong for their weight and great conductors.


The Nature of Solids Review

Use this completion exercise to check your understanding of the concepts and terms that have been introduced to you.

Part A: Fill in the BlankUse the vocabulary list below to complete the following paragraph.

melting point crystalline unit cell allotropes

compress fixed lattice melts

freezing point amorphous covalent

low high ionic

Solids tend to be dense and difficult to ______________. They do not flow or take the shape of their

containers, like liquids do, because the particles in solids vibrate around ______________ points. When a solid

is heated until its particles vibrate so rapidly that they are no longer held in fixed positions, the solid

_____________. The __________________ is the temperature at which a solid changes to a liquid. The

melting and ______________________ of a substance are at the same temperature. In general, ionic solids

tend to have relatively ___________ melting points, while molecular solids ten to have relatively __________

melting points. Most solids are _____________. The particles are arranged in a pattern known as a crystal

_____________. The smallest subunit of a crystal lattice is the _______________. Some solids lack an ordered

internal structure and are called ________________ solids.

Part B: Explanation

Explain what happens at the particle level when a solid melts.


Part C: True or FalseClassify each of these statements as always true, AT; sometimes true, ST; or never true, NT.

_____ 1. Solid substances can exist in more than one form.

_____ 2. Allotropes are two or more different elements that exist in the same state with the same crystal system.

_____ 3. When the atoms in a solid have a random arrangement, the solid is a glass.

_____ 4. The type of bonding that exists between the atoms in a crystal tends to determine the melting point of the solid.

Part D: MatchingMatch each description in Column B to the correct term in Column A.

Column A Column B_____ 1. crystal A. describe a solid in which the particles are randomly

arranged

_____ 2. unit cell B. transparent fusion products of inorganic substances that have cooled to a rigid state without crystallizing

_____ 3. orthorhombic C. the smallest group of particles within a crystal that retains the geometric shape of the crystal

_____ 4. amorphous D. the temperature at which a solid changes to a liquid

_____ 5. glasses E. has a regular three-dimensional arrangement of particles

_____ 6. solid F. one of the seven crystal systems

_____ 7. melting point G. dense state of matter that has a fixed shape and is not easily compressed


Electronegativity

Previously we said that element families like halogen etc. ‘wanted electrons’ but just because you’re hunger doesn’t mean you get to eat. An atom’s ability to pull on electrons is called ______________________.

The higher the electronegativity of an atom the more it attracts electrons.

When an atom wants electrons and pulls strongly they have a ______ electronegativity. When an atom doesn’t want electrons and pulls weakly they have a ______ electronegativity.

The table below is referred to as a Table of Electronegativity Values. These values are useful in calculating whether a bond is called a polar covalent bond or a nonpolar covalent bond or an ionic bond.

Electronegativity follows a trend if we look at the periodic table. As you move from left to right electronegativity ________________________. As you move from the bottom to the top of the table electronegativity _____________________.

Electronegativity is made of two competing aspects for each atom. How much the ______ pulls on an electron. How much the ______ push away a new electron.

Bigger atoms have more shells so the push or ___________ is stronger.


Bond Polarity

If the difference in electronegativity between two atoms is: Very large you get _____________Moderate/Small you get ____________

Previously we treated these types of bonding as two separate things but they are actually a continuum or range of values. Like a rainbow. We are going to talk about some of the options or ‘colours’ in that rainbow.

As you know when a bond is formed the electrons will move. Ionic bonds the electron is fully ____________ making one positive and one negative ion. Covalent bonds the electron is ____________, but they are _______ always shared equally.

The electronegativity of an atom tells us how hard it pulls on the shared electron. It’s like a tug of war. The bigger pull gets the electron. Or like that one friend who ‘shares’ your pizza and somehow eats most of it.

We call an electron shared equally ________. We call an electron not shared equally ________.

Symmetry and Polarity

Equal sharing can be accomplished by two methods. 1) ____________________: where the electronegativities are exactly the same.

2) ____________________: where the shape of the molecule balances the pulls.


In both cases the electrons are pulled evenly in all directions so they are neither on one side or the other. No one wins the tug of war.


Polar vs. Non-Polar

1. Explain what is meant by electronegativity?

2. On the following periodic table:a. Circle the element with the highest electronegativity.b. Put a square around the element with the lowest electronegativity.c. Draw one arrow to show the trend in increasing electronegativity.

3. For the following compounds, circle the element with the higher electronegativity. What charge does it become? ____________

a. SiO4 b. BaBr2 c. PH3 d. Al2O3 e. CCl4


4. Indicate if the following compounds are polar or non-polar.

a. SnCl2 b. NH3 c. BCl3

d. CCl4 e. CH2O f. HCN

g. CO2 h. C3H8 i. C6H6

j. N2O k. Caffeine


Bonding between Molecules

During our discussion on the states of matter and the K.M.T. we mentioned that there are forces between particles but we didn’t talk about specifics. Now we are going to look into the interactions between particles in detail.

Chemists group these unnamed forces between into two broad categories:

_____________ forces occur _________________________________________. The intramolecular forces of an ionic or covalent bond. ex: the bond between H – O in water.

__________________ forces occur_________________________________________. The intermolecular forces between two water molecule.

Intermolecular forces (IMF) are weaker than intramolecular forces (either ionic or covalent bonds). The intermolecular forces determine if a compound is a gas, liquid or solid at room temperature. These forces are responsible for holding water molecules together to form drops, or holding cellulose particles together in paper, or graphite together in pencils.

Since we’ve already talked about Intramolecular forces in detail let’s focus on intermolecular bonds but to do that we must discuss electronegativity.

Intramolecular Forces

We already covered these during grade 10 chemistry: Ionic and Covalent Bonds. But we now know that there are more options on the covalent side.


Intermolecular Forces

Intermolecular Forces – Ionic/Ionic

Ionic molecules, for example NaCl, are held together by the attraction between opposite charges. An ionic bond forms when a positive cation and a negative anion are attracted to one another. These are very strong.

Intermolecular Forces – Dipole/Dipole

o Occur when ______________ molecules are attracted to one another.

o The electrical attraction involved occurs between the oppositely charged regions of polar molecules.

o Similar to, but much weaker than ionic bonds.

o A ________ is another name for an uneven sharing of electrons. o Polar molecule have a dipole.o We use the lowercase greek letter delta _____ to mark the ends of a dipole.

Intermolecular Forces – Hydrogen Bonding

o A version of a Dipole/Dipole that involves Hydrogen.o The __________________ type of IMFo Extremely strong dipole-dipole force between the H

(_____) of one molecule and the F, O, N atom (_______) of another molecule.

o It is not a bond, just a strong IMF.


o The strength of the hydrogen bond depends on the __________ of the molecule.

Hydrogen bonding is why water is a liquid at room temperature. The mass of

Intermolecular Forces - London Dispersion Forces (LDF)

o Force of attraction between induced __________________ (dipole is a molecule where the centers of the positive and negative charges are not the same).

o Exist in all molecules.o Generally important in diatomic molecules because they are ___________________.o Increased force with _________.o If strong – ________ melting point/boiling point.o Caused by movement of __________________.o Looking at the halogens: fluorine and chlorine are ___________, bromine is a ___________ and iodine is a

___________ (as mass ______________, the LDF ______________, pulling the molecules in _____________.

Dispersion Forces occur when clouds of electrons of two molecules within close proximity of each other are distorted because of the repulsion between the electrons.


The atomic charge distribution is disrupted for a split second, this results in a brief dipole (induced dipole). One side of the molecule becomes slightly more negative and the other becomes slightly more positive. This dipole can induce similar dipoles in nearby molecules.

This can continue to occur. This is called a London Dispersion Force.

Summary of Molecular Forces:

The ___________________ the intermolecular forces the more _______________________ it becomes to break apart a molecule into its simpler components, therefore the _______________ the melting and boiling points. More ________________(heat) is required to get the bonds to break.

The ___________________ the intermolecular forces the ________________________ it becomes to break apart a molecule into its simpler components, therefore the _______________ the melting and boiling points. __________________ energy is required to break the bonds.


Strength of Bond Type of Molecular Force Melting and Boiling Points

Strongest Bond

________________________

Highest MP and BP

________________________

________________________

Weakest Bond

________________________

Lowest MP and BP


Intermolecular Forces

1. Why are dipole-dipole forces stronger than London dispersion forces for particles of comparable mass?

2. Draw the structure of the dipole-dipole interaction in a sample of carbon monoxide.

3. State the type of intermolecular forces found in each of the following. Give reasons for your answers.

HF Cl2 NO

CO NaF

4. Draw the hydrogen bonding between one ammonia molecule and one water molecule.


Phase Changes

When a sample is heated, the temperature usually ________________. As heat energy enters a body, the kinetic energy of its particles ___________________. However, sometimes a substance can gain or lose heat energy without changing _____________________. This is when a phase change occurs. A _____________ refers to the mixture of states of matter that coexist as physically distinct parts of mixture. Changes of state require that energy be added or removed. Heat energy is used to break and reform the IMF that holds molecules together.

Endothermic: energy is added to the system, allowing IMF to be broken down so molecules can move further apart from each other.

Exothermic: energy is released into the surroundings from bonds forming.

Freezing (Solidification) and Melting (Fusion)o When a substance melts, it passes from the solid phase to the liquid phase. Energy (in the form of heat) is

gained during this change.o Freezing is when the reverse happens and energy is __________.o When a solid is heated, the kinetic energy of the atom/molecule ____________, the molecule vibrates

_______________ and eventually will break away from the more ordered arrangement of a solid.o Added energy remains stored in the particles that are now further apart.o When cooled, particles slow down and the force of attraction tend to hold molecules together.o As the particles slow down and move closer together, potential energy is _____________________.

Freezing Point: the temperature at which the solid and liquid forms of the substance exist in equilibrium. Normal freezing point is measured at 1 atm.

Ex.) water 0°C, NaCl 801°C, Diamond 3700°C

Melting Point: same as freezing point but changes in opposite direction.

Note: For most substances, the freezing point and the melting point are the same.


Phase Changes

Sublimationo Occurs when a solid changes directly to a gas, without passing through the liquid state.o Lots of energy required in a short period of time.

Depositiono Occurs when a gas changes directly to a solid, without passing through the liquid state.o Loss of energy at a rapid rate in a short period of time.

Condensation (Liquefaction)o The formation of a liquid from a gas. o This occurs when the attraction between molecules is ________________. o Lowering the temperature causes the particles to move ______________. They are less able to overcome

the ___________________________________. o By __________________ the pressure, the distance between particles is ________________, therefore

________________ attraction.

Evaporation o When a substance evaporates, it passes from the liquid phase to the gas phase. o Process that occurs specifically on the __________________ of a liquid.o Molecules have enough kinetic energy to escape from the surface of the liquid at a temperature that is

____________ than the boiling point.o Substances that evaporate quickly are said to be _________________, and have __________ IMF’s.

Vaporizationo Process in which a liquid changes to a gas.o Energy needs to be added to the system for the phase change to occur.o Also known as __________________.


SOLIDGAS

LIQUID

Phase Changes


Heating and Cooling Curves

Phase changes are physical changes; they do not involve a change in the composition of a substance. Instead, they involve a change in the forces of attraction among the particles of a substance. The role of energy during phase changes is very specific.

Heating Curve

A. Temperature __________ as heat is absorbed by the solid. An increase in temperature = ______________ in kinetic energy.

B. Solid is being converted to liquid at its melting point. As the solid melts, it absorbs energy from its surroundings. All the energy absorbed by the solid is used to overcome the _________ that hold the solid together. The absorbed energy is converted to ________________ energy. The temperature stays the same while melting because the kinetic energy is not changing during the melting process.

C. Added heat now increases the temperature. An increase in temperature = increase in kinetic energy.

D. Liquid is being converted to a gas at its boiling point.

E. Temperature of the gas rises increasing the kinetic energy of the gas.


A B

C

D

E

Heating and Cooling Curves

Temperature changes involve a change in the ______________ energy of the particles in a substance. These changes do not involve changes in the forces of attraction between particles. It is the ________________ of the particles that changes when temperature changes. As molecules absorb heat they move _________ and their temperature (the indicator of their average kinetic energy) ___________.

At any point on a heating curve, just one of the two types of energy change is occurring. Either kinetic energy is increasing or potential energy is increasing, but never both at the same time.

Cooling CurveThe regions of a cooling curve can be interpreted in the same way as those of a heating curve. The essential difference is that energy is constantly being ________ to the surroundings by the system. The result is either a _____________ in kinetic energy or a _______________ in potential energy.


Gas Pressure (Textbook pg. 386-387)

While reading the following text pages, answer the following questions.

1. What is gas pressure?________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

2. What is a vacuum?________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

3. Define atmospheric pressure.________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

4. What does a barometer measure? How does it work?________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

5. List some units that are used to signify pressure.________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________


Vapour Pressure

Vapour: gaseous state of a substance, which is liquid or solid at room temperature.

Vapour Equilibrium: the state in which vaporization and condensation are taking place at the same rate.

Vapour Pressure: the pressure (force per unit area) generated by a vapour in equilibrium with its liquid. Vapour pressure is a characteristic physical property, and is also a measure of the size or strength of the intermolecular forces (IMF) of a liquid.

Vapour Pressure and Intermolecular ForcesThe strength of _________ between the particles of a sample determines the rate of vaporization. If __________ strength is weaker, the amount of vapour that is produced ________________. It is therefore easier for the particles of liquid to escape the forces of attraction in the liquid and become gaseous.

Vapour Pressure and Boiling Point________________ occurs when vaporization takes place throughout the _____________ and the temperature of the liquid remains constant. Bubbles of vapour collect below the surface of the liquid and then __________ to the surface.

Boiling point: the temperature at which the vapour pressure of a substance is equal to the external or atmospheric pressure.


Vapour Pressure

Atmospheric Pressure and Boiling PointSince boiling occurs when the atmospheric pressure and the vapour pressure of a liquid are ______________, any change in atmospheric pressure will produce a change in the boiling point.

As atmospheric pressure _______________, so will the _____________ point. Since ___________ vapour pressure is required to match a lower atmospheric pressure, _________ heat is needed by the system to reach the boiling point.

Everyday Applications

Cooking on a Mountain At sea level (1 atm) water will boil at 100°C. To hard boil an egg it takes ~10 min. Pike’s Peak in Colorado is 14000 ft above sea level. The atmospheric pressure is 0.6 atm and water boils at 86°C. To hard boil an egg at this elevation take ~20-30 min.

Pressure CookerPressure cookers are often used to speed up cooking. It operates by increasing the pressure inside the pot. As pressure increases, the boiling point of the water also increases because more energy is need to create more vapour so that the vapour pressure can become equal to the atmospheric press. The higher the temperature at which water boils, the shorter the cooking time, because a greater amount of heat will have already been delivered to the food by the time boiling occurs.

Note: heating a boiling liquid more strongly (higher number on the stove) does not raise the temperature of the liquid, but does cause the liquid to vaporize quicker.

Normal Boiling Point (n.b.p.): the temperature at which the vapour pressure of the liquid is equal to 101.3 kPa. Ex: Water n.b.p. = 100˚C if the vapour pressure is 101.3

kPa and the atmospheric pressure is also 101.3 kPa.


Vapour Pressure

Comparing Vapour Pressures

Low Vapour Pressure:

High Vapour Pressure:


Vapour Pressure Graphs

We can plot the vapour pressure of different substances as a function of temperature and get a graph like the one below.

You will notice that regardless the substance there is a similar trend in the vapour pressure as temperature increases. We can use this graph to determine the normal boiling point of each substance and the temperature each will boil, at various pressures.

1. What is the normal boiling point of ethanol?

2. If the pressure in a city is 90 kPa, at what temperature will water boil?

3. Which substance has the largest forces of attraction at 60°C?


Evaporation vs Boiling

Ordinary evaporation is a surface phenomenon – since the vapour pressure is low and since the pressure inside the liquid is equal to atmospheric pressure plus the liquid pressure, bubbles of water vapor cannot form. But at the boiling point, the saturated vapour pressure is equal to atmospheric pressure, bubbles form, and the vaporization becomes a volume phenomenon.

Phase Changes and Vapour Pressure

1. List the similarities present in all three states of matter (not including plasma).

2. During a phase change:a. What happens to the energy being added to a liquid as the liquid is being warmed?

b. What happens to the energy being added as a liquid changes to a gas?

3. If the atmospheric pressure over ethanol is increased, what happens to the boiling point of ethanol?


4. Acetone has a greater vapour pressure than ethanol at 25°C. What does this difference indicate about the strength of the attractive forces between acetone molecules and ethanol molecules?

5. A liquid will boil when its vapour pressure equals atmospheric pressure. Answer the questions following the graph.

a. At what temperature would Liquid A boil at an atmospheric pressure of 400 torr? ________

b. Liquid B? ________

c. Liquid C? ________

d. How low must the atmospheric pressure be for Liquid A to boil at 35° C? _____

e. Liquid B? ________

f. Liquid C? ________

g. What is the normal boiling point of Liquid A? ________

h. Liquid B? ________

i. Liquid C? ________

j. Which liquid has the strongest intermolecular forces? ________


6. Using the graph below, answer the following questions.a. Give the normal boiling points of the three liquids.

b. Arrange the liquids in order of decreasing intermolecular attractive forces.

c. Which is the most volatile liquid?

d. Which is the least volatile?

e. If the liquids were taken to a planet where the atmospheric pressure was 50 kPa, at what temperature would each liquid boil?


7. Using the data in the table below, make a graph of vapour pressure vs. temperature on graph paper. Put temperature on the x-axis and vapour pressure on the y-axis. Connect the data for each substance with a smooth curve. Graph all three substances on the same graph. Include a legend to identify the three curves.

10mmHg 40mmHg 100mmHg 400mmHg 760mmHg

Ethanol -2.3 19.0 34.9 63.5 78.4

Acetone -31.1 -9.4 7.7 39.5 56.5

Cyclohexane -15.9 6.7 25.5 60.8 80.7

Using your graph, determine the following:a. The vapour pressure of ethanol at 50°C.

b. The vapour pressure of acetone at 50°C.

c. The temperature at which the vapour pressure of cyclohexane is 200mmHg.

d. The temperature at which the vapour pressure of acetone is 200mmHg.

e. Which of the substances has the highest vapour pressure?

f. Which of the substances has the lowest vapour pressure?

g. Which of the substances would evaporate fastest at room temperature?

h. Which of the substances would evaporate the slowest at room temperature?

i. Which of the substances has the greatest forces of attraction between molecules? Which has the

smallest? Explain how you know.

j. Which of the substances would require the most energy to evaporate one mole of the liquid? Which

would require the least? Explain how you know.

k. Using your graph, predict the temperature at which the vapour pressure of each substance would be

at 800mmHg.

l. Using your graph, determine the normal boiling temperature of each substance.

m. Using your graph, determine the boiling temperature of each substance at 300mmHg.


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