Ch. 7
Kinetic Molecular Theory Explains
the Characteristics of Solids, Liquids
and Gases
States of Matter
7.1
Matter – anything that has mass and volume
Mass – quantity of matter that a substance or
object contains. More matter, more mass.
Volume – amount of space taken up by a
substance or object.
States of Matter
7.1
Solid – definite shape and volume
Liquid – definite volume but not shape
Gas – no definite shape or volume
Watch Brainpop:
“States of Matter”
http://www.brainpop.com/science/matterandch
emistry/statesofmatter/
Kinetic Molecular Theory
1.
All matter is made up of very small particles (atoms and
molecules)
2.
There is empty space between particles
3.
Particles are constantly moving
4.
1.
Solid – particles are tightly packed together and cannot move freely
– only vibrate
2.
Liquid – Particles are farther apart and they can move by sliding past
each other
3.
Gas – particles are very far apart and move freely.
Energy makes particles move. The more energy the particles
have, the faster they can move and the farther apart they can get
Thermal Expansion
Thermal Expansion – as the temperature of a
solid liquid or a gas increases, the particles move
farther apart and they take up more room or
volume.
Thermal Contraction
• Thermal contraction – as the temperature of a
solid, liquid, or a gas decreases, the particles
move closer and they take up less room or
volume
Thermal Expansion and Contraction
Different materials expand or
contract with changing
temperatures at different rates.
An aluminum rod will expand 3
times faster than glass for the
same temperature change.
What about Water to Ice?
• Question
I am learning that the particles in matter
expand when heated and contract when
cooled. But how come when you put water in
the freezer to make ice cubes, the ice
expands? Shouldn't the water have contracted
because its being cooled?
What about Water to Ice?
•
•
•
•
•
•
For most substances; the solid form of the substance is more dense than the liquid
phase (a block of pure solid substance will sink in a tub of pure liquid substance).
However, a block of ice will float in a tub of water because solid water is less dense
than liquid water.
At 4 °C, just above freezing, water reaches its maximum density.
As water cools further toward its freezing point, the liquid water, expands to
become less dense.
The physical reason for this is related to the crystal structure of ordinary ice,
known as hexagonal ice. Each oxygen atom has it's own 2 electrons, and grabs
hold of 2 more electrons from the water molecule next to it. They crystallize into a
big hexagon shape, which takes up more space than the same molecules do when
the water is in liquid form. An ice crystal's form is called a 'network structure.'
Same molecules, but they take up more space.
Water, gallium, bismuth, acetic acid, antimony and silicon are some of the few
materials which expand when they freeze.
Heat and Temperature
Heat – energy transferred from one material to
another. When you touch a hot cup of hot chocolate,
you feel the heat transfer from the cup to your hands.
Temperature is the average kinetic energy of a
substances’ particles.
Temperature is not energy, but a measure of it.
Heat is energy
Great video to explain
http://www.youtube.com/watch?v=rU-sPzshVnM
Changes of State:
Chemical
• In a chemical change where there is a
chemical reaction, a new substance is formed.
• Examples: piece of paper is burned, it is a
different substance that in no longer paper,
when metal rusts.
• Chemical changes cannot be reversed.
• Example: cooking an egg
Changes of State:
Physical
• A physical change in a substance doesn't
change what the substance is.
• Examples: a piece of paper is cut up into small
pieces it still is paper, a crushed can of pop
• Physical changes can be reversed
• Example: a cup of water can be frozen and
then can be returned to a liquid form when
heated.
Watch Brainpop:
“Property Changes”
http://www.brainpop.com/science/matterandch
emistry/propertychanges/
Changes of State:
Physical
• Matter (elements and compounds) can
change from one state to another.
• Change of state/phase happen when certain
points (temperature or pressure) are reached.
• With temperature, the state of matter can
change when the temperature increases or
decreases.
Changes of State:
Physical
Solid
• Melting: from a solid form to a liquid form
• ice (solid) -> water (liquid)
• Sublimation: from a solid form to a gas form
(skips liquid).
• dry ice (solid) -> fog (gas)
Changes of State:
Physical
Liquid
• Solidification: from liquid to solid
• water (liquid) -> ice (solid)
• Evaporation: from liquid to gas
• water (liquid) -> steam (gas)
Changes of State:
Physical
Gas
• Condensation: from gas to liquid
• steam (gas) -> water (liquid)
• Deposition: from gas to solid
• air (gas) -> frost (solid)
Changes of State:
Physical
Wild, Weird, Wonderful: What Is Plasma?
• Solids, liquids, and gases are not the most common forms of matter in the
universe. The most common form of matter is called “plasma.” Most of
the universe, including our solar system, is made up of plasma.
• Plasma is a very hot gas in an ionized state. It has a mixture of positively
and negatively charged particles. When matter is heated to extremely high
temperatures, the particles begin to collide violently and to break apart
into smaller particles that can conduct electricity.
• The particles in plasma vibrate at certain frequencies, which allows
scientists to measure the electric fields in plasma. They can use this
information to determine the electron density of plasma.
• Glowing plasmas occur naturally in stars such as the Sun and in lightning.
Much cooler plasmas are formed in fluorescent tubes and neon signs.
Further applications of plasma technology are being studied because
plasma technology seems to be efficient in many ways. For example, gas
plasma technology seems to be cleaner and to require less energy than
conventional methods.
Watch Brainpop:
Matter Changing States
http://www.brainpop.com/science/matterandch
emistry/matterchangingstates/
Text Work
• Check Your Understanding
• P. 259
• # 1, 2, 3, 4, 5, 6, 7, 8, 10
Watch
Bill Nye the Science Guy:
“Phases of Matter”
7.2 Fluids and Density
Fluid:
• Any form of matter that can flow
• liquids and gases are fluids
• No fixed shape
Watch
Bill Nye the Science Guy:
“Fluids”
7.2 Fluids and Density
Mass – quantity of matter that a substance or
object contains. More matter, more mass.
Volume – amount of space taken up by a
substance or object.
Density – mass of a given volume
(or how close together the particles are)
7.2 Fluids and Density
• The key to density = spacing of particles:
tightly packed vs. free to move
• When a substance changes states; density
changes as well
• As you increase the temperature of a
substance, particles move further apart and
density decreases
• The solid & liquid state are denser than the
gas state
• Less dense objects float on top of more dense
objects
• In general, the solid state of a substance is
denser than the liquid state
• An exception is water. Water is denser than
ice. That is why ice floats on water
• http://www.bing.com/videos/search?q=densit
y+fluid&view=detail&mid=95B2ECC172F5390
31E6395B2ECC172F539031E63&first=0&adlt=
strict
7.2 Fluids and Density
Reading Check: p. 263
1. Gases and liquids can flow, but solids cannot.
2. Density decreases when matter is heated due to particles
moving farther apart.
3. Water is unique in the sense that the particles actually
move slightly farther apart when it freezes. Ice has a lower
density than liquid water.
4. Water has a lower density than corn syrup.
7.2 Fluids and Density
Reading Check: p. 263
5. When air is heated near the ground on a hot summer day, the particles gain
energy and move farther apart. The warm air has a lower density than the air
around it, and as a result, it begins to rise. As the warm air rises, cooler air
rushes in beneath it, and a breeze is created.
6. The higher you go in the atmosphere, the farther apart the air particles are
spread out. The lower you go in the atmosphere, the closer together the air
particles are, so more air particles enter the lungs with every breath.
7.2 Fluids and Density
Think About It: p. 262
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1. Gold
2. Hydrogen
3. Mercury
4. Styrofoam, cork, and oak
5a. All substances with a density of less than 1.00
g/mL
• 5b. All substances with a density greater than 1.00
g/mL
• 6. Aluminum, iron, nickel, copper, lead
7.2 Fluids and Density:
Measuring Matter
• Layering is a technique used for comparison of
densities.
• However it does not provide a specific
measurement.
• To measure you need: 1) mass, 2) volume of
the substance
• Volume is measured in cm³
7.2 Fluids and Density:
Measuring Matter
• Displacement is used to find the volume of an
irregular shaped substance
• Use this formula to calculate the density of an
object:
Density = mass / volume
or
D=m/v
• Density of fluids is g/ml
• Density of solids is g/cm³
Watch Brainpop:
“Measuring Matter”
http://www.brainpop.com/science/matterandch
emistry/measuringmatter/preview.weml#
7.2 Fluids and Density
Reading Check: p. 264
1. Use the equation: volume = length × width ×
height.
2. Measure the amount of fluid displaced by the
object.
3. Mass, volume
4. 100 cm³
7.2 Fluids and Density
Practice Problems: p. 265
P. 265
Mark it Yourself (to the right)
P. 269
1. 1780g / 200 cm³ = 8.9 g/cm³ (nickel)
2. 972g / 360 cm³ = 2.7 g/cm³ (aluminum)
3. 132.97g / 9.8 mL = 13.55g/mL (mercury)
4. 1404 g/650 cm³ = 2.16 g/cm³ (salt)
5. 1422 g/1800 mL = 0.79 g/mL (ethyl alcohol)
7.2 Fluids and Density
Check Your Understanding
• p. 271 #1-5
7.2 Fluids and Density
Check Your Understanding: p. 271 #1-5
1. Styrofoam, oil, plastic, water, grape, corn syrup
2. The density of the helium has decreased. In the warm room, the helium
particles gained energy and moved farther apart, increasing the volume of the
balloon. With the same mass but greater volume, the density is lower.
3. The diet soft drink has a lower density than that of water, and water has a
lower density than that of the regular soft drink.
4. 1080 g ÷ 500 cm3 = 2.16 g/cm³. This is the density of salt.
5. The copper is solid, therefore the particles are very close together. Even though
the mercury has a greater density, the particles of mercury cannot move in
between the copper particles.
Chapter 7:
Chapter Review
• p. 272-273 #1-7, 9b-15, 17
Chapter 7:
Chapter Review: p. 272-273 #1-7, 9b-15, 17
1. The particles in a gas are much farther apart than the particles in a solid. Gas
particles move freely, therefore gases spread out or diffuse in their container.
Solids have particles that are very close together and held in position. Solids
have a defined shape and volume that is independent of any container.
2. (a) Kinetic energy is the energy of motion.
2. (b) Particles move slower when their kinetic energy is decreased.
3. Thermal energy is the total amount of kinetic energy in all the particles of a
substance. Heat is the energy transferred from one material or object to another.
4. (a) When a state change occurs from solid to liquid, particles gain energy and go
from being in a fixed position to being able to change position and slide past one
another.
Chapter 7:
Chapter Review: p. 272-273 #1-7, 9b-15, 17
4. (b) When a change of state occurs from gas to liquid, particles lose energy. In the
gas state, particles are free moving with lots of space between them. When the
state change to liquid occurs, the particles move much closer together, until they
are in contact with each other, but can still move past one another.
5. Condensation is a change of state from gas to liquid. Evaporation is a change of state from
liquid to gas.
6. Solids are denser than gases because they have more particles in a given area of volume. This
means the mass of a solid will be greater than the mass of a gas for an equal volume.
7. Density = mass/volume, therefore mass = density × volume. For example, if a substance has a
density of 2 g/mL, and there is 10 mL of the substance, then 2 g/mL × 10 mL = 20 g.
Chapter 7:
Chapter Review: p. 272-273 #1-7, 9b-15, 17
9. (b) When the ball is heated, its particles gain energy and as a result, the particles move farther
apart. This results in an increase in volume of the ball. When the volume of the ball increases
enough, it will no longer fit through the ring.
10. When the heat was added to the cold glass, the particles of the glass increased in kinetic
energy very rapidly. As a result, the motion of the particles increased rapidly. This rapid
increase in motion caused the particles to move farther apart. This rapid thermal expansion
caused the glass to crack.
11. Saturated fats have a higher melting point because they are solid at room temperature, while
unsaturated fats have already melted at room temperature.
12. Hot water has a lower density than cold water, therefore it will layer on top of cold water. The
particles of hot water have more energy and are farther apart, and so have a lower density.
Chapter 7:
Chapter Review: p. 272-273 #1-7, 9b-15, 17
13. (a) D = m/V = 192 g ÷ 800 cm3 = 0.24 g/cm3
13. (b) The mass will float on water because it has a lower density than water.
14. (a) Fluid A: 1.03 g/mL, Fluid B: 0.791 g/mL, Fluid C: 0.9 g/mL
14. (b) The drawing should show Fluid A on the bottom, Fluid C in the middle, and Fluid B
on top.
15. (a) 0.917 g/cm3
15. (b) Yes