Chem

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CHAPTER 14, 16 & 18
WHAT IS CHEMISTRY?
Quick Write

What is chemistry?

What do you expect
to do in chemistry?

What do you want to
learn from chemistry?
WHAT IS CHEMISTRY?

Chemistry is the study of matter and the
transformations it can undergo.

What is matter?
– Anything that has mass and takes up space.
IMPORTANCE OF CHEMISTRY

Chemistry is all around you.
– Air you breathe
– Food you digest
– Clothes you wear
– Textbook you read

Chemistry is often said to be the central
science.
Balloon Demonstration
(Conceptual Integrated Science Explorations: p.259)
Hypothesis – what will happen when you fill the
balloon with the fragrance?
1. Get balloon & smell it – record
2. Fill balloon with fragrance & then fill with air–
smell & record
3. Answer questions 1 & 2 under Analyze &
conclude on pg 259

Questions
Open your BOOK to page 273 and answer
questions:
 3-7

Atoms

Submicroscopic (smaller than microscope level!)
particles. Teeny-tiny basic units that make up
stuff

1 grain of sand contains around 125 MILLION
TRILLION atoms.

The # of atoms in a baseball is equivalent to the #
of ping-pong balls that could fit inside Earth

There are more than 100 different kinds & are
listed on the periodic table
Parts of an Atom

Atoms are made up of EVEN SMALLER
particles

Subatomic particles:
– Protons (positive charge)
– Neutrons (no charge)
– Electrons (negative charge)
Atomic Nucleus & Electrons

Atomic Nucleus - core of atom, makes
up most of atom’s mass, consists of
PROTONS & NEUTRONS.

ELECTRONS buzz around the empty
space surrounding the nucleus. Negative
charge
Protons & Neutrons = Nucleons

PROTON– heavy particle in the nucleus
that’s positively (electric) charged. Has
SAME quantity but OPPOSITE charge of
electron

NEUTRON – same mass as proton, but
no charge, also found in the nucleus.
The Atom
Molecules

Some atoms link together to form larger
but still incredibly small units of matter
called molecules
Syringe Activity


1.
2.
3.
4.
Materials: Syringe, rubber stopper, cup of water, mini marshmallow
Do the following & Record observations
Double the pressure
Quadruple the pressure
Reduce volume in half – let go of plunger
Start @ 0mL & try to lift plunger all the way out while tip of syringe is
blocked
Indicates atmospheric pressure
Add marshmallow. Pressurize it. Reduce pressure to less than atm remove
marshmallow
6. Completely fill syringe with water. Compress syringe
Why was it hard to quadruple pressure?
What was happening to the air particles inside as you tried to add pressure?
Why was it so hard to lift the plunger out of the syringe?
Why did the marshmallow respond as it did to the changes in pressure?
Why can’t you compress water?
5.
Phases of Matter

Liquid – matter that has a definite volume but
no definite shape, assumes shape of container

Solid – matter that has definite shape & volume

Gas – matter that has neither definite volume
nor definite shape, fills any space available
PHASES OF MATTER
Solid
Liquid
Copyright © 2005 by Pearson Education, Inc.
Publishing as Benjamin Cummings
Gas
WATER AND ITS STATES OF MATTER
Changes of Phase
 In
order to
change the phase
of a substance,
you must either
add heat or
remove heat
Change of Phase
Melting: Solid to liquid
 Boiling: Liquid to gas
(beneath the surface)
 Evaporation: Liquid to gas
(surface)
Boiling & Evaporation

Melting
– The above 3 require input of
heat energy
Condensation
Condensation: Gas to liquid
 Freezing: Liquid to solid

– The above 2 release heat
energy
Freezing
Change of Phase Diagram
PHYSICAL PROPERTIES
Any physical attribute of a substance such as
color, density, texture, hardness, & phase
 Each substance has unique physical properties
 Examples

– Sulfur appears as a yellow powder
– The boiling point of water is 100 oC
– Carbon monoxide is odorless
PHYSICAL CHANGES

Change in substance’s physical property
but doesn’t change the composition
– Examples include:
 Any change in the state of matter (e.g. freezing or
boiling water)
 Sawing wood
 Crushing a tablet
 Bending a wire
 Dissolving salt in water
CHEMICAL PROPERTIES

Describe ways pure substances behave
when interacting with other pure
substances.

Examples
– Iron reacts with oxygen to form rust.
– Platinum does not react with oxygen at room
temperature.
CHEMICAL CHANGES

Changes the identity of the substance as
the chemical composition changes.
– Also called chemical reactions

Examples:
– Tarnishing of silver
(Ag forms AgS)
– Rusting of iron
(Fe forms Fe2O3)
CHEMICAL REACTIONS

Are expressed using chemical equations.

Rusting of iron:
4 Fe + 3 O2  2 Fe2O3 (rust)
reactants
products
Meaning:
Four atoms of iron react with three
molecules of oxygen to form two
molecules of rust
CHEMICAL REACTIONS (Cont)
Zn + 2 HCl
Zinc
hydrochloric acid

ZnCl2 + H2
zinc chloride
hydrogen gas
Meaning:
One atom of zinc reacts with two
molecules of hydrochloric acid to produce
one molecule of zinc chloride and one
molecule of hydrogen gas.
Review Quiz – DON’T PANIC
1.
2.
3.
4.
5.
6.
Chemistry is the study of _______ and the __________it
can undergo
_____ are submicroscopic (smaller than microscope level!)
particles. Teeny-tiny basic units that make up stuff
Subatomic particles: ______(positive charge), _______(no
charge), ______(negative charge)
______ is matter that has a definite volume but no definite
shape, _______ is matter that has definite shape & volume,
______ is matter that has neither definite volume nor
definite shape
Any physical attribute of a substance such as color, density,
texture, hardness, & phase are _________ _________
Changes the identity of the substance as the chemical
composition changes. Also called _________ __________
Practice Balancing Equations
1
__Fe + __Cl2  __FeCl3
2
__Al + __O2  __Al2O3
3
CO__ + 4H__  CH4 + 2H2O
4
__ Fe + 3 O2  2 Fe2O__
Practice Balancing Equations:
ANSWERS

_2_Fe + _3_Cl2  _2_FeCl3

_4_Al + _3_O2  _2_Al2O3

CO_2_ + 4H_2_  CH4 + 2H2O

4 Fe + 3O2  2 Fe2O3
CLASSIFICATION OF MATTER
ELEMENTS




Any material made of only one type of
atom
Elements are the building blocks of
matter
There are 115 known elements today, 90
which occur naturally
The periodic table displays the elements
ELEMENTS (Cont)

Each element has a unique symbol
– The first letter is always capitalized, the
second letter is always lower case
 Fluorine is F, not f
 Cobalt is Co, not CO (which is carbon monoxide)
 Oxygen is O

The smallest unit of an element is the
atom
COMPOUNDS

Atoms of different elements bond to one another
to make a compound
– NaCl (table salt)
 Contains sodium (Na) and chlorine (Cl)
 NaCl is the chemical formula
– H2O (water)
 Contains 2 atoms of hydrogen (H) and 1 atom of oxygen (O)
 H2O is the chemical formula

Elements in compounds are combined in a
definite ratio
– H2O is water but H2O2 is hydrogen peroxide
COMPOUNDS (cont)

Are H2 and O3 considered elements or
compounds? Why?
Heterogeneous Mixture
The different
components can be
seen as individual
substances
 Different parts are
visible
 Ex: Pulp in orange
juice, sand in water, oil
& water, pizza

Homogeneous Mixture
Have same
composition
throughout
 Can’t see separate
parts
 Ex: Air, blood, fog,
salt water

CLASSIFICATION OF MATTER
Classify the following as an element,
compound, homogeneous mixture, or
heterogeneous mixture.
a.
b.
c.
d.
e.
Fog
Gasoline
Helium
Sulfuric acid (H2SO4)
Orange juice from squeezed oranges
PRACTICE PROBLEM
Identify the following properties and
changes as physical or chemical.
a. The copper sheets that form the “skin” of
the Statue of Liberty have acquired a
greenish coating over the years.
b. Carbon appears as black powder.
c. Adding food coloring to water.
d. Wood burns in air.
Periodic Table of Elements
Atomic Symbol
YOU ALREADY HAVE THESE NOTES
 Please go back and label it – ATOMIC
SYMBOL
 Each element has a unique symbol

– The first letter is always capitalized, the
second letter is always lower case
 Fluorine is F, not f
 Cobalt is Co, not CO (which is carbon monoxide)
 Oxygen is O
Groups
Vertical column of
table
 Also called a family
 All elements in the
same Group have
similar properties
Ex: Noble Gases He, Ne, & Ar are all
gases

Groups cont’d
Group Names
Group 1: Alkali Metals
 Group 2: Alkaline-earth Metals
 Group 3 – 12: Transition Metals
 Group 13 – 15: No Common Name
 Group 16: Chalcogens
 Group 17: Halogens
 Group 18: Noble Gases

Periods


Horizontal row
Across any period
(horizontal row) the
properties of
elements gradually
change – called a
periodic trend

Trends repeat from
one row to the next
Periods

Ex: Atom Size - atoms get smaller as you
move from left to right
BIGGER to smaller
Atomic Number
= to the number of
PROTONS in atomic nucleus
 Order of elements
 Ex:

– Hydrogen (H) has 1 proton
per atom, the atomic number
– Helium (He) has 2 protons in
nucleus & atomic number is 2

Which element does the
diagram represent?
Nitrogen!
Atomic Mass & Mass Number

Atomic Mass: The sum of the masses of
all the atom’s electrons, protons and
neutrons

Mass Number: the total number of
protons and neutrons
Valence Electrons
Electron in outermost
shell of an atom
 Atoms combine to
form molecules by
valence electrons
 “combining power” of
an atom

Electron Shells
Within the atom, electrons
behave as though they are
arranged in shells.
 Each shell can hold a certain
number of electrons

– Innermost shell: 2
– Shells 2-3: 8 each
– Shells 4-5: 18 each
– Shells 6-7: 32 each
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