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.

First Activity: What’s 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

What’s 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.

                                 

                   

Questions for What’s 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?

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.

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.

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.

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

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.)

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

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?

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

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?

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?

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. Galileo’s

thermoscope c. 1597

– 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.

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.

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.

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.

Phase Changes

Phase Changes

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

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

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?

Standard Connections Students know metals have properties in

common, such as high…thermal 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?

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?

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?

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.

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?

Fourth activity: Math connections

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?

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

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.

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.

Evaporation vs. Boiling

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?

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 In many places, it takes weeks or months for snow weeks or months for snow that accumulated during the that accumulated during the winter to melt. Why doesn’t winter to melt. Why doesn’t all of the snow melt as soon all of the snow melt as soon as the temperature climbs as the temperature climbs above 0above 0ooC?C?

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.

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 person’s temperature to rise (if they could not cool off)? Assume the person is

made entirely of water.

Vocabulary

Boiling – process where heat is added to Boiling – process where heat is added to turn a liquid into a gasturn a liquid into a gas

Freezing – process where heat is Freezing – process where heat is removed to turn a liquid into a solidremoved to turn a liquid into a solid

Melting – process where heat is added Melting – process where heat is added to turn a solid into a liquidto turn a solid into a liquid

Condensation – process where heat is Condensation – process where heat is removed to turn a gas into a liquidremoved to turn a gas into a liquid

Vocabulary

Evaporation – surface process where Evaporation – surface process where a liquid turns into a gas, removing heat a liquid turns into a gas, removing heat from the liquidfrom the liquid

Conduction – direct transfer of heat Conduction – direct transfer of heat from one object to another from one object to another

Convection – transfer of heat by the Convection – transfer of heat by the formation of gas bubbles within a liquid formation of gas bubbles within a liquid that is unevenly heatedthat is unevenly heated

Academic Language

Why do we say someone that is very angry Why do we say someone that is very angry is is boiling madboiling mad??

Why do we say someone who is motionless Why do we say someone who is motionless is is frozen in placefrozen in place??

Think of other common uses of the Think of other common uses of the vocabulary words that describe human vocabulary words that describe human behavior, rather than physical phenomenabehavior, rather than physical phenomena

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.

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.

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

Phase Diagram for CO2

solid

gas

liquid

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?

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?