Foundation of
chemistry
Chapter 7
Chapter Introduction
Lesson 1 classifying matter
Lesson 2 physical properties
Lesson 3 physical changes
Lesson 4 chemical properties and
changes
Chapter Wrap-Up
Lesson 1
Classifying matter
Understanding matter
 Matter
is anything
that has mass and
volume or takes up
space
 Atom
is a small particle
that is a building block
of matter
 Different arrangement
of atoms make up the
many types of matter
Everything you can see is a
matter
 You
can’t see air , but air is a matter
because it has mass and takes up space
 Sound and light are not matter
 Forces and energy are not matter
 To decide whether something is matter,
ask yourself if it has mass and takes up
space
Matter: Substances and Mixtures
 Nearly
all types of matter can be sorted into just
two major categories— substances and
mixtures.
 A substance is matter that is always made up of
the same combination of atoms.
 Examples : Aluminum, oxygen, water , sugar
 A compound is matter made of atoms of two or
more elements chemically bonded together.
 An element is a substance that consists of just
one type of atoms
There are two types of substances—elements and
compounds.
Elements
 There
are 118 known elements
 There are 118 different types of atoms and
each atom contains different number of
protons in its nucleus
 Number of protons is the atomic number
of the element
 Atoms of elements exist individually or in
groups
Compounds
 It
consists of atoms of different elements
 Chemical formula :the combination of
symbols and numbers that represent a
compound, it shows the different atoms
that make up a compound
 Ex : CO2, H2O
 Compound often has different properties
from the individual elements that
compose it
Matter: Substances and Mixtures (cont.)






A mixture is two or more substances that are physically
blended but are not chemically bonded together.
The amounts of each substance in a mixture can vary.
There are two different types of mixtures—heterogeneous
and homogeneous.
A heterogeneous mixture is a mixture in which substances
are not evenly mixed.
A homogeneous mixture is a mixture in which two or more
substances are evenly mixed on the atomic level but not
bonded together.
Another name for a homogeneous mixture is solution.
How do compounds and mixtures
differ?




Because substances that make up a mixture are not
changed chemically, some of their properties are
observed in the mixture.
The properties of a compound can be different from the
properties of the elements that make it up.
Because the substances that make up a mixture are not
bonded together, they can be separated from each
other using physical methods.
The difference in physical properties, such as boiling
points, of substances can be used to separate the
substances.
• Substances have a composition that
does not change. The composition of
mixtures can vary.
• Solutions (homogeneous
mixtures) are mixed at
the atomic level.
• Mixtures contain parts that are not
bonded together. These parts can be
separated using physical means.
Compounds versus solutions
Compounds
Solution
• Its composition does not vary
• Chemical formula used can be
used to describe the atoms that
make up the compound
• Is homogeneous mixture has 2 parts
solute and solvent evenly mixed
together but are not bonded
• Composition can vary in a mixture
• Chemical formula cannot be used
to describe mixtures
Lesson 2
Physical properties
Physical properties
 Physical
properties are the properties of a
substance that can be observed or
measured without changing the identity
of the matter substance
 Density
and odor or smell can help
scientists identify gases and liquids
The Four states
of Matter
Solid
Liquid
Gas
Plasma
17
The Four States of
Matter
Basis of Classification of the Four
Types
Based
upon particle
arrangement
Based upon energy of
particles
Based upon distance between
particles
It depends on how close and
how fast
States of Matter
Size dependent properties
 State
is only one of many physical
properties that you can use to describe
matter
 Some physical properties , such as mass
and volume , depend on the size or
amount of matter
 Measurements of these properties vary
depending on how much matter is in a
sample
Size dependent properties
Mass
Volume
• Is the amount of matter in an object
• Mass doesn’t change with location
• Its value depend on the size of
sample
• Is the amount of space something
takes up
• Its value depends on the size or the
amount of a substance
Size independent
properties
 Some
physical properties of a substance
don’t depend on the amount of matter
 They are called size independent
properties
 It includes melting point , boiling point ,
density , electrical conductivity , and
solubility
Melting point
Temperature at which a
substance changes from a
solid to a liquid
Boiling point
Temperature at which a
substance changes from a
liquid to gas
Density
Is the mass per unite volume of a substance
Conductivity
Electrical conductivity is the ability
of matter to conduct electricity
Thermal conductivity is the ability of
matter to conduct thermal energy
Solubility
Is the ability of one substance to
dissolve in another
Conductivity and solubility can be
used to separate mixtures
Separating mixtures
 Substances
that make up mixtures are not
held together by bonds
 Properties
of individual substances do not
change
 Physical
properties are used to separate
mixtures not compounds
Lesson 3
Physical changes
Physical changes
 Is
a change in size , shape , form , or state
of matter in which the matter’s identity
stays the same
 During a physical change , the matter
doesn’t become something different
even thought the physical properties
change
change in size
and shape
Are physical changes so
identity of matter doesn’t
change
Changes in states


To change the state of matter , the movement of
the particles has to change
In order to change the movement of particles
thermal energy must be either added or
removed
Adding thermal energy
 thermal
energy is added to a solid, the
particles in the solid move faster and
faster, and the temperature increases.
 As
the particles move faster, they are
more likely to overcome the attractive
forces that hold them tightly together.
Adding thermal energy
When the particles are moving too fast
for attractive forces to hold them tightly
together, the solid reaches its melting
point.
 The melting point is the temperature at
which a solid changes to a liquid..

Adding thermal energy
 adding
more thermal energy causes the
particles to move even faster.
 The temperature of the liquid increases.
 When the particles are moving so fast that
attractive forces cannot hold them close
together, the liquid is at its boiling point.
 The boiling point is the temperature at
which a liquid changes into a gas and the
particles spread out.
Sublimation
 Some
solids change directly to a gas
without first becoming a liquid.
 This process is called sublimation.
 An example of sublimation is shown in
Figure
Removing thermal energy
 When
thermal energy is removed from a
gas, such as water vapor, particles in the
gas move more slowly and the
temperature decreases.
 Condensation occurs when the particles
are moving slowly enough for attractive
forces to pull the particles close together.
 Recall that condensation is the process
that occurs when a gas becomes a liquid.
Removing thermal energy
 After
the gas has completely changed to
a liquid, removing more thermal energy
from the liquid causes particles to move
even more slowly
 The temperature decreases and freezing
occurs when the particles are moving so
slowly that attractive forces between the
particles hold them tightly together until it
becomes solid
Continue
 Freezing
and melting are reverse processes,
and they occur at the same temperature.
 The same is true of boiling and condensation.
Deposition
 is
the change from a gas directly to a
solid, as shown in Figure.
 It is the process that is the opposite of
sublimation.
Lesson 4
Chemical changes
Chemical properties
Recall that a physical property is a
characteristic of matter that you can
observe or measure without changing the
identity of the matter.
 However, matter has other properties
that can be observed only when the
matter changes from one substance to
another.

Examples
 what
are some chemical properties of a
piece of paper?
 Can you tell by just looking at it that it will
burn easily?
 The only way to know that paper burns is
to bring a flame near the paper and
watch it burn.
 When paper burns, it changes into
different types of matter. The ability of a
substance to burn is a chemical property.
 The ability to rust is another chemical
property
Comparing properties
All matter can be described using both
types of properties.
 Ex :The log also has mass, volume, and
density, which are physical properties that
can be measured.
 The ability of wood to burn is a chemical
property. This property is obvious only
when you burn the wood.

Comparing properties
 It
also will rot, another chemical property
you can observe
 when the log decomposes, becoming
other substances.
 When you describe matter, you need to
consider both its physical and its chemical
properties.
Chemical changes
 Chemical
change is a change in matter
in which the substances that make up the
matter change into other substances with
new physical and chemical properties.
 For example, when iron undergoes a
chemical change with oxygen, rust forms.
The substances that undergo a change
no longer have the same properties
because they no longer have the same
identity.
Chemical signs
 Signs
of chemical changes include the
formation of bubbles or a change in
energy, odor, or color.
 It is important to remember that these
signs do not always mean a chemical
change occurred.
 the only proof of chemical change is the
formation o a new substance.
Explaining chemical reactions
 Particles
in matter are in constant motion.
 As particles move, they collide with each
other.
 the bonded atoms that make up the
particles can break apart.
 These atoms then rearrange and bond
with other atoms.
Explaining chemical reactions
 When
atoms bond together in new
combinations, new substances form.
 This process is called a reaction.
 Chemical changes often are called
chemical reactions.
Using chemical formula
A
useful way to understand what
happens during a chemical reaction is to
write a chemical equation.
 A chemical equation shows the chemical
formula of each substance in the
reaction.
Using chemical formula
 The
formulas to the left of the arrow
represent the reactants.
 Reactants are the substances present
before the reaction takes place.
 The formulas to the right of the arrow
represent the products.
 Products are the new substances present
after the reaction.
 The arrow indicates that a reaction has
taken place.
Balancing chemical equations
 during
both physical and chemical
changes, mass is conserved.
 This means that the total mass before and
after a change must be equal.
 Therefore, in a chemical equation, the
number of atoms of each element before
a reaction must equal the number of
atoms of each element after the reaction.
 This is called a balanced chemical
equation
Write the equation , and check to
see if it is balanced
The rate of chemical reaction
 Particles
that make up matter are
constantly moving and colliding with one
another.
 Different factors can make these particles
move faster and collide harder and more
frequently.
 These factors increase the rate of a
chemical reaction
 A higher temperature usually increases
the rate of reaction. When the
temperature is higher, the particles move
faster. Therefore, the particles collide with
greater force and more frequently.
Temperature
A
higher temperature usually increases
the rate of reaction.
 When the temperature is higher, the
particles move faster.
 Therefore, the particles collide with
greater force and more frequently.
Concentration
 Concentration
is the amount of substance
in a certain volume.
 A reaction occurs faster if the
concentration of at least one reactant
increases.
 When concentration increases, there are
more particles available to bump into
each other and react.
Surface area
 Surface
area also affects reaction rate if
at least one reactant is a solid.
 If you drop a whole effervescent antacid
tablet into water, the tablet reacts with
the water.
 However, if you break the tablet into
several pieces and then add them to the
water, the reaction occurs more quickly.
 Smaller pieces have more total surface
area, so more space is available for
reactants to collide.