Remember

1
Remember

• Water can be a liquid or a solid or a gas.
• Solids, liquids and gases have different
  properties.
• Matter has three forms solid, liquid and gas.

2
First Activity Whats the Matter?Write Yes or
No in each box
Property Solid Liquid
Assumes the shape of its container
Can be formed into a sphere
Crumbles
Flows
3
Whats the Matter? Activity

• Cornstarch (1/4 cup)
• Water (1/8 cup)
• Craft stick
• Measuring cup
• Ziplocs
• Mix ingredients together in the ziploc bag using
  the stick.Stir quickly until the material is
  smooth.

4
Questions for Whats the Matter?

• Does the material look like a solid or liquid ?
  Why?
• Poke your finger into the material. Does it
  behave like a solid or liquid? Why?
• Take a spoonful of the material in your hand and
  roll it into a ball. How did it behave?
• Now place the ball on the desk. How did it
  behave?
• Pick it up again and hold it for a few minutes.
  Do you observe any changes that demonstrate the
  presence of a gas?
• Is this material a solid, liquid or gas?

5
Key Concepts

• Solids have a fixed shape and volume
• Liquids have a fixed volume but no fixed shape.
• Gases have neither a fixed volume or shape.

6

• In all 3 of these phases, the matter is in the
  form of atoms, molecules or ions.
• In solids, they are closely packed and at
  relatively fixed positions.
• In liquids, they are closely packed, but not in
  fixed positions.
• In gases, they are widely spaced and not in fixed
  positions.

7
Particle motion

• The states of matter (solid, liquid, gas) depend
  on molecular motion.
• In solids the atoms are closely locked in
  position and can only vibrate.
• In liquids, the atoms and molecules are more
  loosely connected and can collide with and move
  past one another.
• In gases, the atoms and molecules are free to
  move independently, colliding frequently.

8
Particle Motion

• How do we know how much the atoms or molecules
  move?
• In solids, the vibration of the particles in the
  lattice can be measured by sending in beams of
  light of specific energies
• In liquids,the movement of the particles is
  responsible for its ability to flow and to
  dissolve other substances
• In gases, the motion of the particles and their
  collisions with the walls of the container
  creates gas pressure

9
Phases of Matter (cont.)

• Are there really 3 phases of matter?
• If so, then what phase is the matter in the Sun?
  How about the stuff inside fluorescent light
  bulbs? Or fire?
• Most everything in the Universe that is luminous
  is plasma -a fourth phase of matter, in which the
  atoms are ionized, or disassociated. Plasma is a
  common subject in physics, but is not studied in
  chemistry (or in the standards.)

10
Vocabulary

• Solid phase of matter that has fixed volume and
  shape
• Liquid phase of matter with fixed volume but no
  fixed shape
• Gas phase of matter with neither fixed volume
  nor shape
• Note that all of these words have different
  meanings in colloquial English

11

• What are other meanings for the word solid?
• Note that gas is often used as slang for
  gasoline, which is a liquid, and has nothing to
  do with the usage of the word in this case.
• Why are some types of financial accounts referred
  to as liquid?

12

• Fill in the table below with common items.
• Indicate whether the item is in the form of
  solid, liquid or gas.
• Draw a picture of each item.
• Examples could include water, ice, steam.
  Others?
• Item Phase Drawing

13
Break Something to think about

• We are familiar with the effects that an increase
  in temperature has on melting solid ice to form
  liquid water, or heating water to create water
  vapor (steam)
• Are there other ways to change phases? For
  example, can you melt ice without changing the
  temperature?

14
Standard Connections

• Students know water can be a liquid or a solid
  and can be made to change back and forth from one
  form to the other (K)
• Students know the properties of substances can
  change when they are .. cooled or heated (1)
• Students know evaporation and melting are changes
  that occur when objects are heated (3)
• How do we define temperature?
• What are phase changes?

15
Defining temperature

• A thermometer consists of a chamber or bulb of
  liquid with a long narrow tube attached. When the
  liquid inside becomes hotter, it expands and
  moves up the tube. When it cools, it contracts
  and moves back down. The level of the liquid can
  therefore be used as a measure of the temperature
  of an object.

Galileos thermoscope c. 1597
16
Defining temperature

• Given beaker of water, thermometer, hot plate
• Heat a beaker of water with a thermometer in it.
• Record the temperature every 30 seconds, until it
  has been boiling at least 3 minutes.
• Graph the temperature vs. time from your data.

17
Questions for the Temperature activity

• Where on your graph does the water start to boil?
• Does the temperature of the water change in the
  same way before it has begun to boil and after?
• Explain how you can tell from your graph.
• How do we calibrate a thermometer?
• Write an operational definition for temperature.

18
Key concepts

• On the Celsius scale, the boiling point of water
  is defined as 100o C, while the freezing point is
  defined as 0o C.
• You can use these two fixed points to define a
  temperature scale, and to calibrate a
  thermometer.
• Water changes phase from liquid to gas form when
  it boils.

19
Phase Changes

• There is a complicated relationship between
  temperature and pressure that describes the
  phases of matter for a substance.
• This relationship is summarised in a phase
  diagram.
• For example, the boiling point of water is 100o C
  at one atmosphere pressure, but increases as the
  pressure increases.

20
Phase Changes
21
Phase Changes
22
Phase Changes

• Boiling can occur at much lower temperatures than
  100o C if the pressure is also much lower than
  1 atm.
• Boiling therefore does not necessarily mean hot
  instead, it refers to the process of changing
  liquid to gas
• Along the boiling point line, water vapor and
  liquid water can both exist
• Heat is needed in order for the phase to change
  from liquid to gas

23
Phase Changes

• The heat required to boil (1 g of) water (without
  changing its temperature) is called its heat of
  vaporization
• Along the melting point line, ice and liquid
  water can both exist
• Heat is required in order to melt ice to liquid
  water
• The heat required to melt (1 g of) water (without
  changing its temperature) is called its latent
  heat of fusion
• At the triple point, all 3 phases of water can
  coexist

24
Lunch puzzler

• Consider a figure skater.
• How does the phase diagram for water help you to
  understand what happens when the skater presses
  her blades on the ice?
• In other words, how does ice skating work?

25
Standard Connections

• Students know metals have properties in common,
  such as highthermal conductivity (5)
• Students know heat flows in solids by conduction
  (6)
• How can we measure thermal conductivity?
• What is the difference between temperature and
  conductivity?

26
Third activity Thermal Conductivity

• Given blocks of plastic, wood and aluminum that
  have been sitting out in the classroom for a
  while
• Measure the temperature of each with a
  thermometer. Do not hold them while making the
  measurements leave them on the table
• Place the inside of your wrist against each
  object. How do they feel?

27
Third activity Thermal Conductivity

• According to your operational definition, do the
  two blocks have the same temperature?
• Is it possible for two objects to feel different
  to the touch and yet have the same temperature?
• Does the feeling of hotness or coldness give a
  reliable indication of the temperature of an
  object?
• What is happening to make the objects feel
  different?

28
Fourth activity Math connections

• It takes one calorie of heat to raise the
  temperature of 1 g of water by 1o C. This is
  known as the specific heat of water
• The heat of vaporization (of 1 g) of water (at
  100o C) is 540 calories. (This is how much it
  energy it takes to turn 1 g of water into 1 g of
  steam, without changing its temperature.) Before
  and after vaporization, the water and steam
  remain at 100o C.

29
Fourth activity Math connections

• The heat of fusion (of 1 g) of water (at 0o C) is
  80 calories. (This is how much it energy it takes
  to melt 1 g of ice into 1 g of water, without
  changing temperature.) Before and after melting,
  the water and ice remain at 0o C.
• How much heat does it take to melt 10 g of ice,
  heat the resulting water up to 100o C, and then
  boil the water until 1 g has turned into steam?

30
Fourth activity Math connections
31
Standard Connections

• Students know water left in an open container
  evaporates, but water in a closed container does
  not (K)
• Students know evaporation and melting are changes
  that occur when objects are heated (3)
• Students know physical processes include freezing
  and boiling in which a material changes form with
  no chemical reaction (8)
• What is happening when water evaporates?
• What is the difference between evaporation and
  boiling?

32
Key concepts Evaporation

• Evaporation occurs when some of the molecules at
  the surface of the liquid have enough energy to
  escape as gas
• In a closed container, these molecules stay
  trapped as vapor

33
Key concepts Evaporation

• One way to estimate how much energy is required
  to vaporize water at (for example) 20oC room
  temperature is
• Vaporize 1 g of water at 100oC 540 cal
• Cool 1 g of steam from 100oC to 20oC 40 cal (as
  you get 0.5 cal when you cool 1 g of steam by 1
  degree.)
• So the total heat needed to evaporate 1 g of
  water at 20oC is about 580 cal. In other words,
  580 cal is removed from the mass of liquid for
  every gram of water that evaporates. This is why
  evaporation is a cooling process.

34
Evaporation vs. Boiling

• Since the vapour particles are a gas, they can
  exert pressure on the liquid or on the walls and
  top of the container. This pressure is called the
  vapour pressure.
• When a liquid boils, the vapor pressure is so
  large that bubbles form throughout the liquid,
  and carry the gas particles to the surface, where
  they boil off.
• During evaporation, the vapour pressure is less
  than the air pressure, so no bubbles are formed.
  Vapour particles only leave from the surface.

35
Evaporation vs. Boiling
36
Standard Connections

• Students know heat flows in fluids by conduction
  and convection (6)
• Consider a pot water on an electric hot plate,
  which has been boiling steadily for some time
• Describe all of the heat transfers taking place
  at the interfaces between the different elements
  air, water, pot, hot plate
• What type of heat transfer is taking place at
  each interface?

37
Heating and Cooling

• It is possible to keep foods quite cold without a
  refrigerator by wrapping them in a towel soaked
  in cold water. Why does this procedure work?

• In many places, it takes weeks or months for snow
  that accumulated during the winter to melt. Why
  doesnt all of the snow melt as soon as the
  temperature climbs above 0oC?

38
Evaporation Melting

• Students know evaporation and melting are changes
  that occur when objects are heated (3)
• Is this third grade standard strictly true?
• It requires energy to melt an object (heat of
  fusion) BUT
• Evaporation can occur without heating an object.
  In fact, it cools an object as it removes the
  heat of vaporization.
• Heating enhances the rate of evaporation, but it
  is not necessary.

39
Calories and Calories

• We have defined a unit of heat (energy) known as
  a calorie. For example, it takes 1 calorie to
  heat 1 g of water by 1 degree C.
• The calories that are used in discussing the
  energy content of food are usually written as
  Calories (capital C). These Calories are equal
  to1000 times the heat calorie (lower case c), so
  they are also called kilocalories (kcal).
• How much would a 200 Cal candy bar cause a 50 kg
  persons temperature to rise (if they could not
  cool off)? Assume the person is made entirely of
  water.

40
Vocabulary

• Boiling process where heat is added to turn a
  liquid into a gas
• Freezing process where heat is removed to turn
  a liquid into a solid
• Melting process where heat is added to turn a
  solid into a liquid
• Condensation process where heat is removed to
  turn a gas into a liquid

41
Vocabulary

• Evaporation surface process where a liquid
  turns into a gas, removing heat from the liquid
• Conduction direct transfer of heat from one
  object to another
• Convection transfer of heat by the formation of
  gas bubbles within a liquid that is unevenly
  heated

42
Academic Language

• Why do we say someone that is very angry is
  boiling mad?
• Why do we say someone who is motionless is frozen
  in place?
• Think of other common uses of the vocabulary
  words that describe human behavior, rather than
  physical phenomena

43
Analogies and Student Involvement

• Ask the students to record their Caloric intake
  for a day and make a list of what they did during
  that day (school work, activities, sports, etc.)
  
• With the help of a reference book (Health book
  for example), have them compare their food
  calorie (C) intake, converted into energy (c),
  with how much energy they needed to do all the
  activities they were involved in during that day.

44
Vaporization Challenge

• Which will burn more? A gram of boiling water at
  100o C that hits your skin (at a temperature of
  around 40o C) or a gram of steam at 100o C?
• Why?
• Explain your reasoning.

45
Sublimation

• Materials like CO2 have phase diagrams that show
  a different relationship between pressure and
  temperature compared to water
• At atmospheric pressure, CO2 is a solid, which
  changes directly into a gas
• This process is called sublimation

46
Phase Diagram for CO2
liquid
solid
gas
47
Questions about CO2

• Compared to 1 atm and room temperature, what type
  of conditions are necessary for CO2 to appear in
  liquid form?
• If the temperature is held constant, what must
  happen in order for CO2 to boil ?
• What must happen in order for CO2 to freeze?

48
Standard Connections

• Students know properties of solid, liquid and
  gaseous substances, such as water (H2O) .. and
  carbon dioxide (CO2). (5)
• What differences did you observe between water
  and carbon dioxide at room temperature?
• What phases will these substances be in at a
  temperature of 100o C?