Transcript Chapter 3 Matter Properties and Changes

Chapter 3 Matter Properties
and Changes
DENSITY
Density is a ratio that compares an
objects mass to its volume. The unit
for density is g/ L or g/ cm3.
A large piece of Styrofoam has the
same mass as a quarter, but the
quarter has a smaller volume. The
quarter has a greater density,
because there is a greater amount of
mass contained in a smaller space.
1) A 5-mL sample of water has a mass
of 5 g. What is the density of water?
2) An object with a mass of 7.5 g
raises the level of water in a
graduated cylinder from 25.1 mL to
30.1 mL. What is the density of the
object?
3) The density of aluminum is 2.7
g/mL. What is the volume of 8.1 g?
Section 3.1
Matter is anything that has mass and
takes up space.
Matter that has a uniform and
unchanging composition is called a
substance.
Common examples of substances
include salt and water.
Matter has specific properties.
Properties of matter can be physical
or chemical.
Physical properties are properties
that can be observed or measured
without changing the composition of
the substance.
Physical properties include density,
color, odor, hardness, melting/ freezing/
boiling points.
Physical properties can be described
as extensive or intensive.
Extensive properties depend on the
amount of the substance present.
Length, for example is an observable,
extensive physical property.
Intensive properties do not depend on
the amount of substance. Density, for
example is an intensive physical
property, because the density of a
substance does not change, no matter
how much of the substance is present.
Chemical properties of matter allow a
substance to change composition as
a result of contact with another
substance or because of the
application of thermal or electrical
energy. If a substance is not reactive
with another substance, HCl and
Copper, that is a chemical property,
also.
Examples of chemical properties include
the ability to rust, burn, release gas,
absorb or give off energy.
All matter exists as either a solid,
liquid, or a gas. Plasma is also a
form of matter, but is only present on
earth in lightning bolts. These are
called STATES OF MATTER. States
of matter are physical properties.
Vapor is NOT the same as a gas!! A
vapor is a word used to describe
when a substance that is a solid or
liquid at room temperature is heated
enough to take a gaseous form.
Solid
Liquid
Gas
Definite shape Takes shape of
Definite
volume
Takes shape
container, but
of containers
does not have to
and fills it
fill it
completely
Definite volume
Particles held
Particles held
tightly
close, but not
together
tight
No definite
volume
Particles are
far apart, so it
Particles
Particles expand
can be
expand when when heated
compressed
heated
Section 3.2
Physical changes are changes which
alter a substance without changing its
composition.
Examples are breaking glass, tearing
paper, melting ice.
Changes of state are physical changes.
When energy is added to solid water, it
changes to liquid water, when more
energy is added, it is changed to
gaseous water. All the time it is still
water. Only a physical change has
taken place.
Melting and boiling points are
intensive physical properties. They
do not change when the amount of
substance changes. These intensive
physical properties can be used to
identify unknown substances.
Chemical change is defined as one or
more substances combining to
become one or more new
substances. AKA chemical reaction
Examples of common chemical
reactions include burning wood,
rusting iron, fermenting of barley and
hops to make beer, and explosions.
Signs that a chemical reaction have
taken place include:
Thermal energy is given off or absorbed
Light is produced
Precipitate is formed
Color has changed permanently
Gas is formed
The Law of Conservation of Mass states
that mass is neither created nor destroyed
in any process, it is conserved.
Mass of reactants = Mass of products
A student carefully placed 15.6 g of sodium in
a reactor supplied with an excess quantity
of chlorine gas. When the reaction was
complete, the student obtained 39,7 g of
sodium chloride. How many grams of
chlorine gas reacted? How many grams of
sodium reacted?
24.1 g of chlorine gas is used in the
reaction. Because the sodium reacts
with excess chlorine, all of the sodium
(15.6 g) is used in the reaction.
Law of Conservation of Energy
In any chemical reaction or physical
process, energy can be converted
from one form to another, but it is
neither created nor destroyed.
Classify each of the following as
examples of physical or chemical
changes
1. Crushing an aluminum can
2. Recycling used aluminum cans to
make new cans
3. Aluminum combining with oxygen to
form aluminum oxide
Section 3.3
A mixture is a combination of two or
more pure substances in which each
pure substance retains its individual
chemical properties. The composition
of a mixture is variable. Mixtures can
be heterogeneous or homogeneous.
A heterogeneous mixture is one in
which the substances still remain
distinct.
Examples include sand/ water, Skittles,
fruit salad, vegetable soup.
The existence of two or more distinct
areas indicate a heterogeneous mixture.
A homogeneous mixture has a
consistent composition throughout. It
exists in one phase.
Examples include salt and water, KoolAid, gold jewelry.
Homogeneous mixtures are often
referred to as solutions.
System
Example
Gas-gas
Air is primarily a mixture of nitrogen,
oxygen, and argon gasses
Gas-liquid
Carbonated beverages contain
carbon dioxide gas in solution
Liquid-gas
Moist air contains water droplets in
air
Liquid-liquid
Vinegar contains acetic acid in
water
Solid-liquid
Sweetened powder drink contains
sugar and other solid ingredients in
water
Solid-solid
Steel is an allow of iron containing
carbon
A mixture is a combination of
substances physically combined.
Physical separation methods take
advantage of known physical
properties of individual components of
a mixture.
Filtration uses a solid barrier to
separate heterogeneous mixtures of a
a solid and a liquid (sand & water).
Distillation uses differences in boiling
points to separate a homogeneous
mixture.
Crystallization separates a mixture
and forms a solid that is pure. Like
making rock candy.
Chromatography separates
components of a mixture on the basis
of the tendency of each to travel or be
drawn across the surface of another
material.
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Section 3.4
Elements are substances that cannot
be broken down any further by either
chemical or physical methods.
Elements are pure substances.
Elements have a unique name and
chemical symbol. The symbol
consists of one, two or three letters.
The first letter is always capitalized
and any following letters are
lowercase.
The elements are grouped by
patterns in their physical and
chemical properties.
In 1869, Dmitri Mendeleev organized
the elements in rows and columns
based on their masses. That was the
first version of the periodic table. One
of the greatest aspects of
Mendeleev’s table was that it left
spaces for elements not yet
discovered.
The horizontal rows in the periodic
table are called periods and the
vertical columns are called groups or
families. The table is called a
“periodic” table, because the
elements have patterns of similar
properties as you move from period to
period.
Compounds are two or more
elements chemically combined. The
names of compounds are written by
using the element’s symbols. Salt is
written NaCl, water is written H2O,
hydrochloric acid is written HCl.
Compounds can be broken down into
simpler substances, unlike elements.
In order to do that, electrical or heat
energy must be added.
Compounds do not resemble the
elements from which they are made.
For example, salt, NaCl, is made from
sodium (a silvery metal that burns
when exposed to water), and chlorine
(a greenish, poisonous gas).
However, when these two combine,
they form simple table salt that flavors
food.
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Law of Definite Proportions
Regardless of the amount, a
compound is always composed of the
same elements in the same
proportions by mass.
The ratio of the mass of each element to
the total mass of the compound as a
percentage is called the percent by
mass.
Percent by mass
% mass = mass of element x 100
mass of compound