Tro3 lecture 03[1]

What Is Matter?
• Matter is defined as
anything that occupies
space and has mass.
• Even though it appears to
be smooth and continuous,
matter is actually composed
of a lot of tiny little pieces
we call atoms and
molecules.

Tro's "Introductory Chemistry", 1
Chapter 3

Atoms and Molecules

• Atoms are the tiny particles
that make up all matter.
• In most substances, the
atoms are joined together in
units called molecules.
The atoms are joined in
specific geometric
arrangements.
Tro's "Introductory 2
Chemistry", Chapter 3

Classifying Matter
by Physical State
• Matter can be classified as solid, liquid, or
gas based on what properties it exhibits.
State Shape Volume Compress Flow
Solid Fixed Fixed No No
Liquid Indefinite Fixed No Yes
Gas Indefinite Indefinite Yes Yes

•Fixed = Property doesn’t change when placed in a container.
•Indefinite = Takes the property of the container.

Solids
• The particles in a solid are packed
close together and are fixed in
position.
 Although they may vibrate.
• The close packing of the particles
results in solids being
incompressible.
• The inability of the particles to
move around results in solids
retaining their shape and volume
when placed in a new container
and prevents the particles from
flowing. Tro's "Introductory Chemistry", 4
Chapter 3

Liquids
• The particles in a liquid are closely
packed, but they have some ability to move
around.
• The close packing results in liquids being
incompressible.
• The ability of the particles to move allows
liquids to take the shape of their container
and to flow. However, they don’t have
enough freedom to escape and expand to fill
the container. Tro's "Introductory 5

Gases
• In the gas state, the particles have complete
freedom from each other.
• The particles are constantly flying
around, bumping into each other and the
container.
• In the gas state, there is a lot of empty space
between the particles.
On average.

Classification of Matter
by Appearance

• Homogeneous = Matter that is uniform throughout.
 Appears to be one thing.
 Every piece of a sample has identical properties, though another sample
with the same components may have different properties.
 Solutions (homogeneous mixtures) and pure substances.
• Heterogeneous = Matter that is non-uniform throughout .
 Contains regions with different properties than other regions.


Practice—Classify the Following as
Homogeneous or Heterogeneous
• Table sugar.

• A mixture of table sugar and black pepper.

• A mixture of sugar dissolved in water.

• Oil and vinegar salad dressing.

Chapter 3

Homogeneous or Heterogeneous,
Continued
• Table sugar = homogeneous

• A mixture of table sugar and black pepper =
heterogeneous

• A mixture of sugar dissolved in water =
homogeneous

• Oil and vinegar salad dressing = heterogeneous

Classifying Matter
by Composition
• Matter that is composed of only one kind of
atom or molecule is called a pure substance.
• Matter that is composed of different kinds of
atoms or molecules is called a mixture.
• Because pure substances always have only one
kind of piece, all samples show the same
properties.
• However, because mixtures have variable
composition, different samples will show
different properties.

Classification of Matter
Matter

Pure Substance Mixture
Constant Composition Variable Composition
Homogeneous

• Pure Substance = All samples are made of the same
pieces in the same percentages.
 Salt
• Mixtures = Different samples may have the same pieces in
different percentages.
 Salt water

Pure Substances vs. Mixtures
Pure Substances Mixtures
1. All samples have the same 1. Different samples may show
physical and chemical different properties.
properties. 2. Variable composition =
2. Constant composition = All Samples made with the same
samples have the same pure substances may have
different percentages.
pieces in the same
percentages. 3. Homogeneous or
heterogeneous.
3. Homogeneous. 4. Separate into components
4. Separate into components based on physical
based on chemical properties.
properties. 5. Temperature usually
5. Temperature stays constant changes while melting or
while melting or boiling. boiling because composition
changes.

Classification of Pure Substances
• Substances that cannot be broken down into simpler
substances by chemical reactions are called elements.
 Basic building blocks of matter.
 Composed of single type of atom.
 Although those atoms may or may not be combined into molecules.
• Substances that can be decomposed are called compounds.
 Chemical combinations of elements.
 Although properties of the compound are unrelated to the properties of the
elements in it!
 Composed of molecules that contain two or more different kinds
of atoms.
 All molecules of a compound are identical, so all samples of a
compound behave the same way.
• Most natural pure substances are compounds.
Chapter 3

Atoms and Molecules
• Atoms
 Are submicroscopic particles that are the
unit pieces of elements.
 Are the fundamental building blocks of all
matter.
• Molecules
 Are submicroscopic particles that are the
unit pieces of compounds.
 Two or more atoms attached together.
 Attachments are called bonds.
 Attachments come in different strengths.
 Molecules come in different shapes and
patterns.

Classification of Pure Substances
Elements Compounds
1. Made of one
type of atom. 1. Made of one
(Some elements type of
are found as molecule, or
multi-atom array of ions.
molecules in 2. Molecules
nature.) contain 2 or
2. Combine more different
together to make kinds of atoms.
compounds.


Elements or Compounds
• Chlorine, Cl2
• Table sugar, C12H22O11
• A red solid that turns blue when heated and
releases water that is always 30% of the solid’s
mass.
• A brown-red liquid that, when energy is applied to
it in any form, causes only physical changes in the
material, not chemical.

Chapter 3

Elements or Compounds, Continued
• Chlorine, Cl2 = element.
• Table sugar, C12H22O11 = compound.
• A red solid that turns blue when heated and
releases water that is always 30% of the solid’s
mass = compound.
• A brown-red liquid that, when energy is applied to
it in any form, causes only physical changes in the
material, not chemical = element.


Classification of Mixtures
• Mixtures are generally classified based on
their uniformity.
• Mixtures that are uniform throughout are
called homogeneous.
Also known as solutions.
Mixing is on the molecular level.
• Mixtures that have regions with different
characteristics are called heterogeneous.

Classification of Mixtures, Continued
Heterogeneous Homogeneous
1. Made of 1. Made of
multiple multiple
substances, substances, but
whose appears to be
presence can one substance.
be seen. 2. All portions of
2. Portions of a a sample have
sample have the same
different composition
composition and properties.
and properties.


Classifying Matter

20

Properties Distinguish Matter
• Each sample of matter is distinguished by
its characteristics.
• The characteristics of a substance are called
its properties.
• Some properties of matter can be observed
directly.
• Other properties of matter are observed
when it changes its composition.

Properties of Matter
• Physical Properties are the characteristics of matter
that can be changed without changing its
composition.
 Characteristics that are directly observable.

• Chemical Properties are the characteristics that
determine how the composition of matter changes as
a result of contact with other matter or the influence
of energy.
 Characteristics that describe the behavior of matter.


Changes in Matter
• Changes that alter the state or appearance of the
matter without altering the composition are
called physical changes.
• Changes that alter the composition of the matter
are called chemical changes.
During the chemical change, the atoms that are
present rearrange into new molecules, but all of the
original atoms are still present.

Chapter 3

Changes in Matter, Continued
• Physical Changes—Changes in
the properties of matter that do
not effect its composition.
Heating water.
Raises its temperature, but it is still
water.
Evaporating butane from a lighter.
Dissolving sugar in water.
Even though the sugar seems to
disappear, it can easily be separated
back into sugar and water by
evaporation.
Chapter 3

Changes in Matter, Continued
• Chemical Changes involve a change
in the properties of matter that change
its composition.
 A chemical reaction.
 Rusting is iron combining with oxygen to
make iron(III) oxide.
 Burning results in butane from a lighter to
be changed into carbon dioxide and water.
 Silver combines with sulfur in the air to
make tarnish.


Is it a Physical or Chemical Change?
• A physical change results in a different form of
the same substance.
 The kinds of molecules don’t change.
• A chemical change results in one or more
completely new substances.
 Also called chemical reactions.
 The new substances have different molecules than the
original substances.
 You will observe different physical properties because
the new substances have their own physical properties.

Phase Changes Are
Physical Changes
• Boiling = liquid to gas.
• Melting = solid to liquid.
• Subliming = solid to gas.
• Freezing = liquid to solid.
• Condensing = gas to liquid.
• Deposition = gas to solid.
• State changes require heating or cooling the substance.
 Evaporation is not a simple phase change, it is a solution
process.
Chapter 3

Practice—Classify Each Change as Physical
or Chemical

• Evaporation of rubbing alcohol.
• Sugar turning black when heated.
• An egg splitting open and spilling out.
• Sugar fermenting.
• Bubbles escaping from soda.
• Bubbles that form when hydrogen peroxide is
mixed with blood.
Chapter 3

Practice—Classify Each Change as Physical
or Chemical, Continued
• Evaporation of rubbing alcohol = physical.
• Sugar turning black when heated = chemical.
• An egg splitting open and spilling out =
physical.
• Sugar fermenting = chemical.
• Bubbles escaping from soda = physical.
• Bubbles that form when hydrogen peroxide is
mixed with blood = chemical.

Separation of Mixtures
• Separate mixtures based on different
physical properties of the components.
Physical change.
Different Physical Property Technique

Boiling point Distillation

State of matter (solid/liquid/gas) Filtration
Adherence to a surface Chromatography
Volatility Evaporation
Density Centrifugation and
decanting

Distillation


Filtration


Law of Conservation of Mass
• Antoine Lavoisier
• “Matter is neither created nor destroyed in a
chemical reaction.”
• The total amount of matter present before a
chemical reaction is always the same as the
total amount after.
• The total mass of all the reactants is equal to
the total mass of all the products.
Chapter 3

Conservation of Mass
• Total amount of matter remains constant in a
chemical reaction.
• 58 grams of butane burns in 208 grams of oxygen to
form 176 grams of carbon dioxide and 90 grams of
water.
butane + oxygen carbon dioxide + water
58 grams + 208 grams 176 grams + 90 grams
266 grams = 266 grams


Energy
• There are things that do not have mass and
volume.
• These things fall into a category we call energy.
• Energy is anything that has the capacity to do
work.
• Although chemistry is the study of matter, matter
is effected by energy.
It can cause physical and/or chemical changes in
matter.

Law of Conservation of Energy
• “Energy can neither be created nor destroyed.”
• The total amount of energy in the universe is
constant. There is no process that can increase
or decrease that amount.
• However, we can transfer energy from one
place in the universe to another, and we can
change its form.


Matter Possesses Energy
• When a piece of matter
possesses energy, it can
give some or all of it to
another object.
It can do work on the other
object.
• All chemical and physical
changes result in the matter
changing energy.
Chapter 3

Kinds of Energy
Kinetic and Potential
• Potential energy is energy that is
stored.
 Water flows because gravity pulls it
downstream.
 However, the dam won’t allow it to
move, so it has to store that energy.
• Kinetic energy is energy of
motion, or energy that is being
transferred from one object to
another.
 When the water flows over the
dam, some of its potential energy is
converted to kinetic energy of motion.


Some Forms of Energy
• Electrical
 Kinetic energy associated with the flow of electrical
charge.
• Heat or Thermal Energy
 Kinetic energy associated with molecular motion.
• Light or Radiant Energy
 Kinetic energy associated with energy transitions in an
atom.
• Nuclear
 Potential energy in the nucleus of atoms.
• Chemical
 Potential energy in the attachment of atoms or because of
their position. Tro's "Introductory
39

Converting Forms of Energy
• When water flows over the dam, some of its
potential energy is converted to kinetic energy.
 Some of the energy is stored in the water because it is
at a higher elevation than the surroundings.
• The movement of the water is kinetic energy.
• Along the way, some of that energy can be used to
push a turbine to generate electricity.
 Electricity is one form of kinetic energy.
• The electricity can then be used in your home.
For example, you can use it to heat cake batter you
mixed, causing it to change chemically and storing
some of the energy in the new molecules that are
made.

Units of Energy
• Calorie (cal) is the amount of energy needed to
raise one gram of water by 1 °C.
kcal = energy needed to raise 1000 g of water 1 °C.
food calories = kcals.

Energy Conversion Factors
1 calorie (cal) = 4.184 joules (J)
1 Calorie (Cal) = 1000 calories (cal)
1 kilowatt-hour (kWh) = 3.60 x 106 joules (J)

Chapter 3

Exothermic Processes
• When a change results in the release of energy it is
called an exothermic process.
• An exothermic chemical reaction occurs when the
reactants have more chemical potential energy
than the products.
• The excess energy is released into the surrounding
materials, adding energy to them.
 Often the surrounding materials get hotter from the
energy released by the reaction.
Chapter 3

Endothermic Processes
• When a change requires the absorption of energy
it is called an endothermic process.
• An endothermic chemical reaction occurs when
the products have more chemical potential energy
than the reactants.
• The required energy is absorbed from the
surrounding materials, taking energy from them.
 Often the surrounding materials get colder due to the
energy being removed by the reaction.

Temperature Scales
• Fahrenheit scale, °F.
Used in the U.S.
• Celsius scale, °C.
Used in all other countries.
A Celsius degree is 1.8
times larger than a
Fahrenheit degree.
• Kelvin scale, K.
Absolute scale.

Fahrenheit vs. Celsius
• A Celsius degree is 1.8 times larger than a
Fahrenheit degree.
• The standard used for 0° on the Fahrenheit
scale is a lower temperature than the
standard used for 0° on the Celsius scale.
F - 32
C
1.8
Chapter 3

The Kelvin Temperature Scale
• Both the Celsius and Fahrenheit scales have
negative numbers.
 Yet, real physical things are always positive amounts!
• The Kelvin scale is an absolute scale, meaning it
measures the actual temperature of an object.
• 0 K is called absolute zero. It is too cold for
matter to exist because all molecular motion
would stop.
 0 K = -273 °C = -459 °F.
 Absolute zero is a theoretical value obtained by
following patterns mathematically.
Chapter 3

Kelvin vs. Celsius
• The size of a “degree” on the Kelvin scale is the
same as on the Celsius scale.
 Although technically, we don’t call the divisions on the
Kelvin scale degrees; we call them kelvins!
 That makes 1 K 1.8 times larger than 1 °F.
• The 0 standard on the Kelvin scale is a much lower
temperature than on the Celsius scale.
• When converting between kelvins and °C, remember
that the kelvin temperature is always the larger
number and always positive!

K C 273

Specific Heat Capacity
• Specific heat is the amount of energy required to raise
the temperature of one gram of a substance by 1 °C.
• The larger a material’s specific heat is, the more
energy it takes to raise its temperature a given amount.
• Like density, specific heat is a property of the type of
matter.
 It doesn’t matter how much material you have.
 It can be used to identify the type of matter.
• Water’s high specific heat is the reason it is such a
good cooling agent.
 It absorbs a lot of heat for a relatively small mass.


Heat Gain or Loss by an Object
• The amount of heat energy gained or lost by an
object depends on 3 factors: how much material
there is, what the material is, and how much the
temperature changed.

Amount of Heat = Mass x Heat Capacity x Temperature Change
q=mxCx T

Chapter 3

Practice—Calculate the Amount of Heat Released
When 7.40 g of Water Cools from 49° to 29 °C

Chapter 3

Practice—Calculate the Amount of Heat Released
When 7.40 g of Water Cools from 49° to 29
°C, Continued
• Sort Given: T1 = 49 °C, T2 = 29 °C, m = 7.40 g
Information
Find: q, J
• Strategize Solution Map: Cs m, T q
q m Cs ΔT

Relationships: q = m ∙ Cs ∙ T
Cs = 4.18 J/g C (Table 3.4)
• Follow the Solution: q m Cs ΔT
concept T T2 T1 J
plan to T 29 C - 49 C 7.40 g 4.18 g C
- 20 C
solve the
- 20 C 618.64 J 6.2 102 J
problem.
• Check. Check:
The unit and sign are correct.

Tro3 lecture 03[1]

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