Transcript Chemistry

Chemistry: Ch 1
Matter and Change
Golden Rod Demo Notes
Welcome to
Chemistry!!!!!
What is Chemistry?
Activity: Insta-Snow
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Observing
Asking Questions
Looking for Answers
Asking More Questions
Experimenting
More Observing
What we’re doing-playing with stuff like 8-yearolds...is the root of modern science.
• Observing the world and trying to figure out what
it means is the core of science. We invent theories
to explain what we see, hear, and smell.
• Chemistry (Science) is a process of observing,
educated guessing, and testing.
Chemistry is Everywhere
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Everything you hear, see, smell,
taste, and touch involves
chemistry and chemicals.
Chemistry is the study of matter
and the changes it can undergo.
Chemistry is about composition,
structure, function, and
interaction of matter.
Everything has composition,
structure, function, and interaction
Matter is anything that has mass
and occupies space.
All matter is composed of various
combinations of elements. The
wonder of chemistry is that when
these basic particles are
combined, they make something
new and unique.
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Chemistry helps us understand
the world around us.
Understanding the basic
properties of matter and learning
how to predict and explain how
they change when they react to
form new substances is what
chemistry and chemists are all
about.
Chemistry is not limited to beakers
and laboratories. It is all around
us, and the better we know
chemistry, the better we know our
world.
All other sciences (biology,
physics, geology, etc) have their
basis in chemistry.
Chemicals (Substances)
• Matter with definite composition
• Either Elements or Compounds
• Elements: One type of atom
• Oxygen (O2)
• Ozone (O3)
• Copper
• Compounds: Two or more types of atoms
• Sodium chloride (table salt) NaCl
• Ethyl alcohol
• H 2O
Topics in Chemistry: ABC Chart
How does this photo illustrate what
chemistry is all about?
• Chemical reactions of rusting/weathering/maybe a fire in
the fireplace
• Physical states of water
• Different types of materials: glass, wood, living material,
brick, snow
The Study of Matter
and Change
What is Matter?
Anything that has
mass and takes up
space (volume)
Stuff
Not Matter
Light
Energy
Emotions or Feelings
Thoughts
Electricity
Sound
Submicroscopic and Macroscopic
Submicroscopic
• Atomic Level
• What happens here
determines the
macroscopic
Macroscopic
• What we observe
• Determined by the
submicroscopic (atomic)
• Chemist are interested
in how the atomic level
determines the
macroscopic
Observation of a Burning Candle
Mystery Light Block
The Scientific Method
• The scientific method is a systematic approach used in
scientific study, whether it is chemistry, physics, biology,
or another science.
• To solve problems
• Not a set of rigid steps
• It is an organized process used by scientists to do
research, and provides methods for scientists to verify
the work of others.
Observations
• Gathering Information (Data) using the five senses
• No trivial or unimportant observations
• Don’t make inferences or assumptions when you
observe
– Qualitative data is obtained through
observations that describe color, smell, shape,
or some other physical characteristic that is
related to the five senses.
– Quantitative data is obtained from numerical
observations that describe how much, how
little, how big or how fast.
Controlled Experiment
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A test of a hypothesis
Making observations under controlled conditions
Where only one variable at a time is changed
Systematic approach to test a hypothesis
Parts of An Experiment
• Variables: A condition changed in an experiment
• Independent
• Dependent
• Constants: any factor not changed in an experiment
• Control: Group/set up that has no changes made to it
• Conclusion: A judgment based on the observations made in a
controlled experiment
Independent Variable
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Changed by the experimenter
Allowed to change
The Cause in Cause and Effect
Manipulated Variable
Happens First
• The water’s temperature increased as more heat was
applied.
• The temperature of the solid caused the density of
the solid to change
• An increase in phosphorous helped the plants to grow
taller.
Dependent Variable
• Changes in response to the change in the independent
variable
• Responding Variable
• Happens second
• The boiling point increased as salt was added to the
water
• The hamster grew two inches with an increase in the
hormone.
Control
• A point of comparison in an experiment
• The group that does NOT receive the treatment
Constants
• Specifics that remain the same between the control
group and the experimental group
• Only the independent variable should be changed by the
experimenter
Examples of Constants:
Conclusion
• A conclusion is a judgment based on the information
obtained from the experiment
Identify the following
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Independent Variable
Dependent Variable
Control
Constants
Possible conclusion
Another hypothesis
Experiment
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Kate noticed that she could dissolve more sugar in the tea when it was
warm than when it was ice cold. She wondered if this was true for all
solids. She decided to design an experiment to see if water temperature
effects how much salt can be dissolved.
She chose table salt as her solid to test. She used water as her solvent.
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Hypothesis: An increase in the temperature of the water will allow
more salt to dissolve,
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She placed 100 mL of water in each of 10 250 mL beakers.
She cooled the water in beaker # 1 to 10 degrees C.
The water in beaker #2 was 25 degrees C.
Beaker # 3 water was heated to 35 degrees C.
Beaker # 4 water was heated to 45 degrees C.
Beaker # 5 was heated to 55 degrees C.
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Beaker # 6 65 degrees C
Beaker # 7 75 degrees C
Beaker # 8 85 degrees C
Beaker # 9 95 degrees C
Beaker # 10 100 degrees C
• She added salt to each beaker while using a magnetic
stirrer which provided constant and uniform stirring until
no more salt would dissolve.
• She measured and recorded the amount of salt that
dissolved in each beaker.
• Her data is shown below.
Data
Amount of water Temp of Water
100 mL
(degrees C)
Grams of salt
dissolved
1
10
37
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25
37
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35
38
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45
38
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55
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65
38
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75
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85
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9
95
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100
40
Hypothesis and Experiment
• Hypothesis: A tentative explanation of observations
• A tentative answer
• A statement to be tested by an experiment
Example: If I give the fish more hormone then they will
grow longer.
• Experiment: The test of a hypothesis
• A controlled set of steps to test a hypothesis
Theory Vs Hypothesis
• A theory is a hypothesis that has stood the test of
repeated experiments
• An explanation of results
• Never proven
• Can be disproven
• All theories are hypotheses . (True)
• All hypotheses can become theories. (True)
• All hypotheses are theories. (False)
Scientific Law Vs Theory
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Observable Fact
True: Always observed
No known exceptions
No explanation
• Explanation
• Tentative
• Can be disproven
Development of a Theory
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Start with an observation that evokes a question: Broth spoils when
I leave it out for a couple of days. Why?
Using logic and previous knowledge, state a possible answer,
called a Hypothesis: Tiny organisms floating in the air must fall into
the broth and start reproducing.
Perform an experiment or Test: After boiling some broth, I divide it
into two containers, one covered and one not covered. I place them on
the table for two days and see if one spoils. Only the uncovered broth
spoiled.
Then publish your findings in a peer-reviewed journal. Publication:
"Only broth that is exposed to the air after two days tended to spoil. The
covered specimen did not."
Other scientists read about your experiment and try to duplicate it.
Verification: Every scientist who tries your experiment comes up with
the same results. So they try other methods to make sure your
experiment was measuring what it was supposed to. Again, they get the
same results every time.
In time, and if experiments continue to support your hypothesis, it
becomes a Theory: Microorganisms from the air cause broth to spoil.
Useful Prediction: If I leave food items open to the air, they will spoil. If
I want to keep them from spoiling, I will keep them covered.
Notes for Demo Penny in Nitric Acid
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copper solutions/compounds are blue
colored gases are poisonous
strong acids are corrosive
Copper reacts with nitric acid HNO3
Indicators of a Chemical Change
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Production of a gas
Production of a solid
Temperature change
Color change
Chemistry is traditionally broken into
branches that focus on specific areas such
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Organic chemistry
Inorganic chemistry
Physical chemistry
Analytical chemistry
Biochemistry
Environmental chemistry
Industrial chemistry
Polymer chemistry
Theoretical chemistry
Thermochemistry
This Class
HS General Chemistry is Inorganic
• Inorganic Chemistry: the study of non-carbon
based compounds
• Organic Chemistry: Study of matter that
contains carbon
Technology
• Application of Science for human benefit
• Good and Bad
• Nuclear Technology
• Good: Energy
Bad: Waste
• Computer Technology
• Good: Communication Bad: Wasted Time
Pure Science Vs Applied Science
• Pure Science: For the sake of the knowledge
• Studying butterflies just to know more
• Researcher lives on a remote island to daily study the
jungle trees
• Studying ape behavior
• Applied Science: Using science to solve a particular
problem
• Scientist studying corn in fields to increase the yield
for farmers
• Scientist searching for a cancer cure
Why is Pure Research Important?
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A Base of knowledge when needed
Keeps us current
General not specific and possible commercial
Accidental Discoveries
Mass Vs Weight
Mass
• Not influenced by gravity
• Changes only when
amount of matter
changes
• Kilograms or grams
Weight
• Affected by gravity
• W = mg
• g= 9.8 m/s2
Your Mass
Earth
• M ass = 60 kg
Moon
• Gravity = 1/6th the
gravity on Earth
• Mass = 60 kg
• Not affected by gravity
Weight
Earth
• m = 60 kg
• W = mg
• W = (6o kg)(9.8m/s2)
• W = 588 Newtons
Moon
• m = 60 kg
• W = mg
• g = 9.8m/s2/6 = 1.63
m/s2
• W = (60 kg)(1.63m/s2)
• W = 98 Newtons
Environment with No Gravity
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Weight only would change
You would weigh less
Amount of Matter is not affected
Mass stays the same
Chance Discoveries
• Discoveries made by accident
• Not trying to find an answer
• Examples
• Velcro
• Penicillin
• Teflon
• Chocolate Chip Cookies
• The Microwave Oven
• Artificial Sweeteners
• Curiosity Drives Discovery
Tuesday and Wednesday
• Pre-Assessment: Password is
• Lab: Dissolving Salt
• Electronic Balance
• Graduated Cylinder
• Post Lab Q’s: Add One: Do you think particle size affects
the rate of a chemical reaction? Why?
• Lab Equipment Review Using
• The Presentation: Lab Equipment from my website
• This Electronic Quiz:
http://www.sciencegeek.net/Chemistry/taters/labequipment.htm
• Vocabulary Review/Practice Using Online Resources
• HW) Equipment Test 25, 27, 31, 33-38, 39-45, 48-51