Download Unit 1 – Matter and Change

Scientific Method
Unit 1 – Matter and Change
•What is matter and how is it classified?
•How can matter be changed?
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I’M TAD
Identify a Problem
Make a Hypothesis
Test the Hypothesis (Perform an Experiment)
Analyze the Data
Draw Conclusions
Sometimes a 6th step is included in which you
share your conclusions with others
Scientific Method
• Hypothesis
– An educated guess
• Scientific Theory
– A hypothesis supported by many experiments
– Best explanation with data gathered
– Explains a phenomenon
• Scientific (Natural) Law
– Facts of nature accepted as truth
– Describes a phenomenon
Scientific Method
• Controlled Experiment
– Tests hypothesis 1 variable at a time
– Not necessarily safe
– Contains a Control Group
• Doesn’t receive the experimental treatment
• Used as standard for comparison
– Why is it important to test 1 variable at a time?
• Prove which variable affects results
Scientific Method
Chemistry
• Independent Variable
– Variable in the experiment you change
– Test only 1 at a time
• Dependent Variable
– Variable in the experiment that only changes
because you changed the independent variable
– The effect you are looking for
• Chemistry
– The study of matter and the changes it undergoes
• Chemistry deals with the Submicroscopic world
– Things that we cannot see with the naked eye or
even a microscope
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Chemistry
Chemistry
• Matter
– Anything with mass and volume
• Mass
– The amount of matter in an object
• Weight
– The effect of gravity on an object
• Volume
– Amount of space taken up by matter
Chemistry
• Branches of Chemistry
1. Organic Chemistry
–Study of carboncontaining
compounds
2. Inorganic Chemistry
–Study of matter that
does not contain
carbon
Mars Curiosity – Organic Chemist
Pure Substances
• Pure Substances
• Branches of Chemistry
3. Biochemistry
–Processes of living things
4. Analytical Chemistry
–Components and composition of substances
–Ex: Quality Control
5. Physical Chemistry
–Laws of physics with substances
Pure Substances
• Elements
– Made up of ONE type of Atom
• Smallest unit of an element that maintains the
chemical identity of that element
• Smallest unit of matter with unique properties
• Can be found on the Periodic Table
• Ex: Carbon (C), Nitrogen (N), Calcium (Ca),
<100 others
– Cannot be separated by physical means
– Every sample has the same characteristics
• Characteristics can identify substance
Pure Substances
• Compounds
– Made up of two or more types of atoms
– Chemically bonded
– Can be broken down into simple, stable
substances
• Must be chemical separation, not physical
separation
– Ex: water (H2O), sugar (C12H22O11), salt (NaCl), etc.
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Mixtures
• Mixture
Mixtures
• Homogeneous Mixtures
– Blend of two or more
kinds of matter
(elements and/or
compounds)
– Each substance retains
its own identity and
properties
– Also known as Solutions
– Have uniform
composition
• Same all the way
through
– Particles are too small to
be seen
– Examples: saltwater, tea
Mixtures
Mixtures
• Alloys
– Solid solutions that contain at least 1 metal
– Blended together so they have more desirable
properties
• Common Alloys:
– Stainless Steel: iron, chromium, and zinc
– Bronze: tin and copper
• Heterogeneous Mixtures
– Do not have uniform composition
– You can see the particles in them
– Examples:
• Italian Dressing (oil, water, vinegar, veggies)
• Soil (dirt, rocks, worms, etc.)
Mixtures
Mixtures
• Suspensions
– Heterogeneous mixture
– Solid particles eventually settle out of
solution
– Examples:
• Muddy water
• Mixtures of two solids
• Italian Dressing
• Colloid
– Heterogeneous mixture
– Won’t separate upon
standing
– Can’t be separated by
filtration
– Shows Tyndall Effect
• Scattering of light
– Sometimes mistaken for
solutions
– Ex: paint, dairy, Jello
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Properties of Matter
Physical Properties
• Physical Property
• All pure substances
have characteristic
properties
• Properties are used to
distinguish between
substances
• Properties are also used
to separate substances
– Characteristic
observed/measured
without changing
substance’s
composition
– Describe the
substance itself
Physical Properties
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State of matter
Color
Mass, shape, length, volume
Density
Malleability – ability to bend/hammer into thin
sheet
• Ductility – ability to make wire
• Magnetism
• Melting/boiling point, etc.
States of Matter
• Solids
– Particles packed tightly together and held in fixed
positions
– Definite shape and definite volume
– Lowest energy, highest structure
– Particles vibrate about fixed points
States of Matter
• Liquids
– Definite volume
– Takes the shape of its container
• Ex: Milk in a glass vs. a gallon jug
– Particles can move past each other (Fluid)
• Fluid – Anything that can be poured
– Particles move more rapidly than in a solid
States of Matter
• Gases
– No definite shape
• Takes the shape of its container
– No definite volume
• Can be compressed
– Fluid
– Particles are spread far apart and move past each
other rapidly
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States of Matter
Chemical Properties
• Plasma
– 4th state of matter
– Similar to charged
gas
– Found in stars,
lightning, neon signs,
and television
– Rarely occurs
naturally on Earth
Chemical Properties
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Reactivity w/ a substance
Combustibility – burn in air
Flammability – burn
Toxicity
Oxidation
Decomposition
• Chemical Property
– Indicates how a substance
will react with another
• Can be a failure to react
– Determined by changing
substance’s identity
• Ex:
– Iron Rusting
– Silver Tarnishing
Intensive/Extensive Properties
• Extensive properties
– Depend on the amount of matter that is present
– Examples: energy in a substance, volume, mass
• Intensive properties
– Do not depend on the amount of matter present
– Examples: density, melting point, color
Qualitative/Quantitative Data
• Qualitative Data
– Data we observe without
measuring
– Ex: Physical State, Color, Shape,
Sound, Smell, texture
• Quantitative Data
– Data that is measured with
numbers
– Ex: length, mass, volume, density
Physical Changes
• Physical Change
– Change in a substance that does not
alter the substance’s identity
• Examples:
• Grinding
• Cutting
• Mixing/Dissolving
• Changes of State
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Changes of State
• Melting
Changes of State
• Condensation
– Solid becomes a liquid
• Freezing
– Gas becomes a liquid
• Boiling
– Liquid becomes a solid
• Melting and Freezing
Points are the SAME
TEMPERATURE
Changes of State
– Liquid becomes a gas
• Condensation and Boiling
Points are the SAME
TEMPERATURE
Chemical Changes
• Chemical Change
• Sublimation
– Solid becomes a gas
– Ex: dry ice, air
fresheners, freeze
drying
• Deposition
– Gas becomes a solid
– Iodine, frost
Signs of a Chemical Change
– One or more
substances are
converted into
different substances
– Always results in new
substances with
different properties
– Most are Irreversible
Signs of a Chemical Change
• A Precipitate is formed
• A gas is released
(evolved)
• May be visible or
detected as an
odor
– Solid falls out of solution
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Signs of a Chemical Change
• Color change
– Only chemical if resulting
solution is different color
from ALL of its
components
Signs of a Chemical Change
• Temperature Change
– Can also be light
• Endothermic
– Energy is absorbed by system
– Feels cold
– Ex: ice pack
Signs of a Chemical Change
• A substance
“disappears”
– Is consumed
• Dissolving is NOT a
chemical change
Mixture Separation
• We can separate the components of a mixture
by using their characteristic properties
– Boiling/freezing point, density, solubility, state of
matter, etc.
• Exothermic
– Energy released as heat or light
Mixture Separation
• Decanting
– Pouring off liquid without
disturbing the sediment or other
liquid layers
– Usually used to separate solids
from liquids
– Can be used to separate two
liquids
Mixture Separation
• Decanting
• Use a glass stirring rod
to:
• Keep the solid from
pouring out
• Allow liquid to run
down it and avoid
splashing
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Mixture Separation
• Evaporation
– Used to separate a
solid from a liquid in
a solution
– Solution is heated
until all of the liquid
evaporates and solid
is left behind
Mixture Separation
• Magnetic Properties
– Two substances can
be separated if:
• One substance is
magnetic and the
other is not
– Magnet will attract
one substance but not
the other
Mixture Separation
• Filter
Mixture Separation
• Distillation
• Membrane that allows some
substances to pass through
while blocking others
• Separates insoluble solids
from liquids
• Most common type is Gravity
Filtration
• Another is Vacuum Filtration
Mixture Separation
• Chromatography
• Separates components
of a solution
• Sample of mixture is
placed just past one
end of the
chromatography surface
(usually paper)
• End with sample is
placed in another liquid
(solvent)
• Separates two liquids with
different boiling points
• When liquid boils, it
evaporates and reaches the
condenser
• Water runs along outside of
condenser to cool vapor
• Liquid is collected at other
end
Mixture Separation
• Chromatography
• Solvent is absorbed
and travels up surface
with mixture
• Different components
of mixture travel
different lengths up the
surface
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