Transcript Unit 1 Lecture PPT

Introduction to Chemistry
Chapter 1
What is Chemistry ?

Chemistry is
– the study of the composition of matter
– the study of all substances and the changes that
they can undergo

Chemistry is everywhere!!!!
Chemistry Applications

Daily Uses
 Medicine
 Biotechnology
 Agriculture
 Environment
 Space Exploration
 Textiles
What is the scientific method?

The scientific method is
– A systematic approach to solve a problem
– An organized process used by scientists to do
research
– A method by which scientists can verify the
work of others
Scientific Method - 5 Steps
1) Observation
2) Question- Propose a problem
3) Hypothesis- Tentative answer to question
4) Experiment- set up variables,collect data
5) Conclusion- Analyze data results
Parts of an Experiment

Experiment: a set of controlled observations
that test a hypothesis
 Consists of:
– Independent variable - the variable you plan to
change
– Dependent variable - the variable that changes
in response to a change in the independent
variable
Parts of an Experiment cont’d
– Control - a standard for comparison
– Data – information/ observation recorded

can be either:
1) Qualitative: uses descriptive words
Example- colors
2) Quantitative: uses numbers
Class Practice
 Identify
each piece of data as
either qualitative or quantitative
 1. Smells like apples
6. red
 2. 100 lbs
7. 40 mph
 3. 105 degrees C
8. round
 4. Tall
9. cold
 5. Pink with purple dots
Scientific Method
Theory & Law

Theory
– a broad and extensively tested explanation of
“WHY” experiments give results.
– Supported by many experiments
– Considered successful if it can be used to make
predictions that are true

Law
– a concise statement that summarizes the results
of many observations and experiments
Observation vs. Inference

Observation
– is an experience perceived through one or more
of the senses
– What you feel, smell, see, hear, or taste

Example of observation
– The temperature of a flask goes up as a
reaction proceeds
Observation vs Inference
cont’d
 Inference
is
– an interpretation of an observation
– goes one step beyond an observation.
– What “story” you create about
what you see, feel, hear, smell or
taste
– based upon a direct observation
Observation vs Inference
cont’d
Example
– Observation: feel flask getting
hot and see the temperature
rising on the thermometer
– Inference: an exothermic
reaction (heat given off) is
taking place
Observation vs Inference
Examples

Observation
– A purple solution over time separates
– Results in a blue and red color

Inference
– Blue and red make up purple
The End!!

Lab – Alka Seltzer

HW – Experimental Design Worksheet
Matter
Properties and Changes
Chapter 2
Four Phases of Matter
Solids
1. Solids
– have a definite shape and volume
– have strong intermolecular forces between
particles


Therefore, the particles are very close to each
other
What are intermolecular forces?
– Attractive forces BETWEEN molecules
– usually the most dense phase
– In most cases incompressible
Four Phases of Matter
Liquids
2. Liquids
– have a definite volume
– takes the shape of the container they are in
– “flow” and are incompressible
 What does that mean?
– the intermolecular forces are intermediate
 Weaker than solids, but stronger than gases
 therefore the densities are average
Four Phases of Matter
Gases
3. Gases
– have no definite shape or volume (dependent
upon the container they fill),
– very weak intermolecular forces so they have
very low densities
– they are compressible and gases “diffuse”
Four Phases of Matter
Plasma
4. Plasma
– Energy is very high due to extremely high
temperatures
– atoms are stripped of their electrons
– they are “ionized”

What does that mean?
– moves quickly and unevenly
– Examples
 the sun and lightning
Classification of Matter

Matter
– anything that has mass and occupies space

Pure substance
– has a constant, invariable composition
– It’s identified by a formula or symbol
– Examples
 water- H2O – always has 2 hydrogens and 1
oxygen
 Helium - He
Classification of Matter

Compound– Composed of two or more elements that
cannot be decomposed by physical means
– chemically combined
– Examples


Sodium chloride- NaCl
Carbon dioxide- CO2
Classification of Matter

Element
– simple substance that cannot be decomposed
into simpler substances by any chemical
change
Classification of Matter

Mixtures
– Composed of 2 or more components that can
be separated by physical means
– There are no chemical bonds between the
separate parts
– The components or parts can vary in
composition
– 2 types of mixtures
2 Types of Mixtures

Homogeneous mixture
– Sometimes called solutions
– are evenly mixed
– Appears as one component even though
there are 2 or more parts.
– Example



plain jello
Air
salt water
2 Types of Mixtures cont’d

Heterogeneous mixture
– are unevenly mixed
– Can see separate components
– Examples
 dirt
 concrete
 muddy water
Heterogeneous Mixtures
Colloid vs. Suspensions
1) Colloids
2) Suspensions
- particles are very small - particles are large
- do not settle out of
- settle out of solution
solution
- Example:
-Examples:
Muddy water
Fog
smoke
whipped cream
Take a Break – Identification
and Classification Activity
Physical Separation of
Mixtures Techniques
1. Filtration- to separate by size
– use filter paper and funnel
– used for heterogeneous mixtures
– Ex: muddy water
 What can be separated?
Physical Separation of
Mixtures Techniques
2. Evaporation- boiling off liquid
– Used for homogeneous solutions
– Example: Salt water
3. Decant- to pour off liquid
– Used for heterogeneous mixture
Physical Separation of
Mixtures Techniques
4. Distillation- separate a mixture of liquids
by boiling points
– How is that possible?
5. Chromatography- to separate pigments
from a homogeneous solution
– pigments separate because of differences in
1) mass
2) adsorption rates
Physical Separation of
Mixtures Techniques
6. Crystallization
– formation of pure solid particles of a substance
from a solution containing the dissolved substance
– What does that mean?
– Example



Dissolve sugar into water
Place a string into solution
What forms around the string?
Conservation Laws
Law of Conservation of Matter (Mass)
– matter is neither created or destroyed
– In reactions:
Amount of reactants used = amount of products made
Law of Conservation of Energy
– Energy is neither created or destroyed BUT rather it is
transferred from one form to another
The End!!

HW: Classification of matter worksheet

Finish Activity Worksheet on Identification
and Classification

Experimental Design Quiz TOMORROW!!!
Physical and Chemical
Properties
Physical Properties
properties that don’t involve a change in
the chemical identity of the substance
 can measure these
properties/characteristics without
changing the identity
 Examples

– melting point
– boiling point
– density
- electrical conductivity
- solubility
Physical Properties cont’d
1)
Extensive properties
Intensive properties
- dependent upon the amount of substance present
-
Examples:
Mass, length, volume
independent of the
amount of substance
present
-
Examples
Density, boiling point
Chemical Properties

Chemical property
– refers to the way a substance undergoes a
chemical reaction to form new products
– When you measure this property
(characteristic) at least one new product is
formed

Examples: the ability to rot, rust, burn,
ferment, grow, decay, sprout, combust
Physical and Chemical
Change
Physical Change

Physical change
– a process that will alter a substance’s appearance without
changing its composition or identity

Any change that describes a
1) Phase change
- melting, freezing, evaporating, condensing
2) Size change
- tearing, breaking, expanding, dissolving
3) Shape change
- Hammering, stretching
Chemical Change

Chemical Change– a process that occurs that will change the
identity and composition of the reactants

Examples: Burning, rusting, exploding
Difference between Properties
and Changes
(physical & chemical)
Properties
Changes
 Measure a
 Measure a process
CHARACTERISTIC
or trait
Observations that Determine a
Chemical Change in Lab
1. Gas is released
•
bubbles in liquid, smoke, odor
2. Heat is absorbed or released
3. Precipitate (solid) is formed in a homogeneous
solution
–
Start as liquid, then you see “things” floating or
settled on the bottom
Observations that Determine a
Chemical Change in Lab
4. Definite color change occurs
– Color is a _______ property
– but the process of changing colors is a chemical
change
5. Change in mass
6. Flash of light is released
Energy

Energy is the capacity to do work

The Law of Conservation of Energy
– states that energy cannot be created or destroyed BUT
rather transferred from one form to another

Forms of energy
– Electrical, Heat (Thermal), Kinetic, Potential,
Chemical, Nuclear (Atomic), Wind, Hydraulic,
Mechanical, Solar
The End!!

HW: Properties Worksheet
Law of Definite Proportions

Compounds are made up of elements

A compound is ALWAYS composed of the
SAME elements in the SAME proportion
by mass

What makes up water? How many of these
atoms are present? Is this ALWAYS true?
Law of Definite Proportions

The percent by mass shows the ratio of the
mass of each element to the total mass of
the compound
mass of element
x100
mass of compound

Percent by mass (%) =

If you take table sugar (sucrose) from sugar
cane or bag of sugar, how should the
compositions compare to each other?
Law of Definite Proportions
Sucrose Analysis from Bag of
Sugar
Element
Analysis by Mass
(g)
Percent by mass
(%)
Carbon
8.44 g C
42.20 % C
Hydrogen
1.30 g H
6.50 % H
Oxygen
10.26 g O
51.30 % O
Total
20 g Sucrose
100 %
Law of Definite Proportions
Sucrose Analysis from Sugar
Cane
Element
Analysis by Mass
(g)
Percent by mass
(%)
Carbon
211.0 g C
42.20 % C
Hydrogen
32.5 g H
6.50 % H
Oxygen
256.5 g O
51.30 % O
Total
500 g Sucrose
100 %
The End is really here!!
January 15

Study for test tomorrow!
 Review packets due!

Do you know the 1st 7 elements?
 Don’t forget your calculators!!
Sharing NOT allowed!!
Physical & Chemical Change
Lab
Part One:

Touch and describe the copper before &
after heating
 Don’t forget to record the masses BEFORE
& AFTER of the crucible and copper (Cu)
together!!
– Individual mass is NOT important!!

While waiting for the crucible to cool for 10
minutes, do NOT turn off the burner, go on
to part 3 & 4
Part Three:

dissolve salt with a glass stirring rod
– be careful NOT to break the test tube
– after using, make sure to rinse off!!
Part 4

Use only ONE wooden splint that is in your
tray!!
 Hold test tube at the top end!!
 Dirty but clean???
Part Two:
– Get 3 toothpicks to mix the solutions; you can
use both ends
– after you mix, wait at least 3 minutes to see if
precipitates form (lift well plate)

Assignment Sheets
The # in ( ) are total possible points for that grade
 Homework:
 Parent/ Student Contract (10)

Quiz:
 Binder Week #1
 Unit 1 Quiz
(10)
(18)

Lab:
 Safety Test
(50)