Transcript Chem unit 1.1x - ChemistryProvidence

Chemistry
The Science of Matter
Do Now
• List at least 5 chemicals that you are familiar
with from past experience.
Learning Objective
• Understand composition and their impact on
the properties of matter
• Be able to classify chemical vs. physical
changes
Chemistry
• The science that investigates the structure and
properties of matter
– Matter: anything that takes up space and has
mass
• Mass: the measure of the amount of matter that an
object contains
• NOT Matter– Heat
– Light
– Radio waves etc.
Matter continued
• Structure: refers to what it is made of and of
how it is organized
• Properties: Describe the characteristics and
behavior of matter including the changes it
undergoes
Behavior of Matter
• Determined by BOTH
–The elements it contains
–Arrangement of those elements
Example
Salt
vs.
Water
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Sodium and Chloride
Hydrogen and Oxygen
Contain different elements --- Have different
properties!
• Aspirin
Example
Vs
Table Sugar
• Both contain only Carbon, Hydrogen and Oxygen
molecules --- same composition
• Different Structures Cause Different Behaviors!
Example
Two Different Artificial Sweeteners
Aspartame
Saccharine
Different Compositions
Both have: C, H, O and N and are sweet
Only Saccharine has Na+ and S
Their arrangement must be a factor!
Properties
• Many are easy to observe by simple tests
• Use heat, magnets, electricity etc
– Color
– State: solid, liquid or gas at room temp and
pressure
– Soft or hard
– Does it burn?
– Does it dissolve in water?
• These are from a macroscopic perspective
– Things you can touch, taste, feel, smell and see
What is it made of?
• This question is harder to answer
– Must take measurements
– Must observe chemical changes
• Macroscopic Observations
• Submicroscopic perspective
– To understand hidden structure influences
behavior
Physical change vs. Chemical change
Physical Change
Chemical Change
Doesn't change what the
substance is.
A new substance is formed
and energy is either given off
or absorbed.
Can be reversed
Cannot be reversed with the
substance changed back
without extraordinary means,
if at all.
Examples
Physical Change
Chemical Change
Paper cut into pieces, small
pieces are still paper
Paper burned is no longer
paper
Dissolve sugar in water
Make a cake with flour, water,
sugar and other ingredients
and bake them, it would take
extraordinary means to
separate the various
ingredients out to their original
form.
Physical Vs. Chemical Change
Worksheet (15 minutes)
• In pairs complete the given handout
• You may use your notes
• Students should each complete an answer
sheet as a study guide
• Be sure that you are prepared to share your
answers with the class
Share Answers
Chemical properties vs. Physical properties
• Chemical Property
• Flammability: The ability to burn
• Ability to rust: Reacts with oxygen to produce rust
• Reactivity with vinegar: Reacts with vinegar to produce new
substances
• Physical Property
• Transparency: The property of letting light pass through
something
• Boiling point: Temperature at which a substance goes from liquid
to gas
• Melting point: Temperature at which a substance goes from solid
to a liquid
• Brittleness: Tendency to crack or break
• Ductility: Ability to bend without breaking
• Elasticity: Ability to be stretched or compressed then return to original size
• Density: Mass per unit volume
Submicroscopic Level of Matter
• Matter is made of Atoms
• Atoms
– So small they can not be seen with the most powerful light
microscope
– So small that if a period at the end of a sentence were
made of Carbon atoms it would be made of 100 quintillion
carbon atoms
• (100, 000,000,000,000,000,000)
• Counting them at 3 per second would take you a trillion years!
– Scanning Tunneling Microscope (STM)
• creates computer images which are a visible perspective showing
atomic location
Scanning Tunneling Microscope (STM)
• individual iron atoms on a silver substrate
Using Chemical Models
• Show types and numbers of atoms
• Show arrangement of the atoms and space
filled
Why Models?
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Submicroscopic structural representation
Explains observed behavior
Used to predict behavior not yet observed
Built on investigation and experimentation
Show Connections Between Atoms
Mixtures
• A material that is made of 2 or more things
which are not combined chemically
• Each of the parts still keep their own identities
• Made by blending, but NOT forming chemical
bonds or chemical change!
• Most everyday matter occurs as mixtures
Heterogeneous and Homogeneous
Mixtures
• A classification of matter based on composition
• Homogeneous mixture: no clumping or grouping
but rather a uniform dispersal of the material it is
made of.
– Ex. Air; made of N2, O2, CO2 and other gases
– A liquid in which there is a solvent and a solute is
called a solution
• Heterogeneous mixture: it is easy to identify all if
the different components
Heterogeneous mixture
Heterogeneous mixture
Colloids (look homogeneous but
microscopically heterogenous)
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Hair spray
Smoke
Cloud
Whipped cream
Shaving cream
Blood
Styrofoam
Gello
Dispersion (Heterogeneous)
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Dust
Milk
Hand cream
Gravel
Granite
Sponge
Homogeneous Mixtures
Solutions (homogeneous)
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Air (gas)
Martini (liquid)
Salt water (liquid)
Plastic (solid)
Substances
• Homogeneous materials that contain only 1
kind of matter
• Have definite composition and properties
• Substances which can not be broken down
into a simpler substance is an ELEMENT.
• Substances which can be broken down into a
simpler substance is a COMPOUND.
– They are made of 2 or more elements
Elements
• Made of only one kind of atom
• Can not be made simplified by physical or
chemical means
• Can exist as atoms (carbon) or molecules (N2)
Compounds
• Consist of 2 or more DIFFERENT atoms bound
together (H2O)
• Can be broken down into smaller types of
matter by chemical means only.
• Have properties which are different than the
elements they are made of
• Always contain the same ratio of its
components atoms ( ex 2 hydrogen's to 1
oxygen, in water)
Answers to pg 7 questions
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Ocean water- solution
Calcium- element
Vitamin C- Compound ( L-asorbic acid)
Dry ice – compound (CO2)
Copper- element
Grain alcohol- compound (C2H5OH)
after shave lotion- heterogenous mixture
Hamburger- hetero
Al foil – element
Milk- solution
Salt- cmpd
Iron nail- element
Learning Objectives
• Investigate various ways to separate
mixtures
• Identify the properties of the matter
that allow for a particular method of
separation
REMEMBER Mixtures
• A re made of 2 or more things which are not
combined chemically
• Each of the parts still keep their own identities
• Made by blending, but NOT forming chemical
bonds or chemical change!
• Most everyday matter occurs as mixtures
REMEMBER
Chemical properties vs. Physical properties
• Chemical Property
• Flammability: The ability to burn
• Ability to rust: Reacts with oxygen to produce rust
• Reactivity with vinegar: Reacts with vinegar to produce new
substances
• Physical Property
• Transparency: The property of letting light pass through
something
• Boiling point: Temperature at which a substance goes from liquid
to gas
• Melting point: Temperature at which a substance goes from solid
to a liquid
• Brittleness: Tendency to crack or break
• Ductility: Ability to bend without breaking
• Elasticity: Ability to be stretched or compressed then return to original size
• Density: Mass per unit volume
Separating Mixtures
• Mixtures can be separated through a
physical process, the identity of the
substance remains unchanged.
–Using their Physical properties
–Bringing about physical changes to
separate the mixture into its
components (different substances it is
made of)
Making a Mixture
AND
SAND
SUGAR
The Mixture
How can we separate it?
• What do you think?
– Work with your lab partner to come up with a
suggested method. (10 minutes)
– You may use your class notes, but your brain is
your best asset.
– Write your thoughts in your notebooks.
– Do not be afraid to try!
Report out on ideas
• So, what did you come up with?
• Share your thoughts! (10 minutes)
What can we do?
Method #1
•Use a pair of
tweezers and a
microscope to
physically separate
the particles
•Requires a lot of
time and
patience
Step #1
•Recall the
properties
of water
and of sand
•Sugar
dissolves
in water
•Sand
does NOT
•Use the
difference!
Method #2
Step #2
•Recall the
properties again
•sand will not
pass through
a filter
•Sugar and
water
solution will
•Use the
difference!
Step #3
•Recall the
properties of
sugar and water
•sugar will not
evaporate
(change state)
at 100 degrees
Celsius
•water will !
•Use the
difference!
You have the two pure
substances again!
• Sand in the filter!
• Sugar in the bottom of the
beaker!
Lab Thursday!
• Paper Chromatography!
Learning objective
• Understand the relationship
between chemical change and
energy change
Mixtures vs. Pure substances
• Mixtures can be separated based physical
properties and through physical change
• Pure substances can only be separated
through chemical changes
– Separated from compounds into elements
• H2O- H and O2
– Made into compounds from elements
• H + O  H2O
Chemical Change and Energy
• All chemical changes involve some sort of
energy change!
• Many chemical changes (reactions) release
energy
– Exothermic reactions: release energy as
heat
• Some reactions absorb energy
– Endothermic reactions: absorb heat energy
Demo
Epsom salt and laundry detergent
More methods of separating mixtures
• Paper chromatography
–Separating the dyes in ink
• Dyes are usually made of several
basic colors called pigments
• Using the property of these dyes
–Soluble in water we will separate
the pigments
Develop a question!
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Make a claim (hypothesis)
Follow the Procedure
Answer the lab analysis questions
Draw a conclusion
Ask a new question
Create a poster presentation of your results
Unit Test on Monday!
Be sure to study your notes
and your review sheets!