Lecture 1 and Lecture 2

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Lecture 1 and Lecture 2
Chapter 1, 3
Chapter 1 (Scientific Method) Chapter 3.7
(Density) pg 54

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CHEMISTRY
These notes are also in at the end of Lecture 1
The Study of Matter and its Properties, the
Changes that Matter Undergoes, and the
Energy Associated with those Changes
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Chemistry as the Central Science
Atmospheric Sciences
Physics
Oceanography
Medicine
Biochemists
Inorganic
Chemistry
People
Geology
Biology
Organic
Astronomy
Anthropology
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Figure 1.2
Paper A Polymer called Cellulose
The Polymer cellulose, which consists of
B-D-glucose monomers
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Poly(Vinyl Chloride) (PVC) and Teflon
H H H H H H H H
C C C C C C C C
n
H Cl
H Cl H Cl H Cl H Cl
Vinyl chloride
PVC
F F
F F F F F F F F
C C
C C C C C C C C
n
F F
F F F F F F F F
Teflon
Tetrafluoroethylene
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The Scientific Method
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The Scientific Method
An orderly and systematic approach to gathering
information in order to answer questions about
the world
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Scientific Method

• Observation To observe any phenomenon in nature
  

Qualitative involves quality or kind
Quantitative involves the measurement of
quantity, amount, a number
Qualitative Quantitative
red 700 nm wavelength
far from the earth 300 million light years
microscopic smaller than 1 um
burns quickly burns at 1 cm candle per minute
hot 350 degrees C
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• Quantitative
• observation
• (quantities with understood units)
• humans have 10 fingers
• the speed limit is 55 miles per hour
• class is 1 hour long
• acceleration due to gravity is 9.8 m/s2

• Qualitative observations
• (not as precise, descriptive adjectives)
• humans have many fingers
• the speed limit is fast
• class is long
• acceleration due to gravity is large

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Scientific Method continued

1. Question To formulate questions about the
   phenomenon observed
2. Hypothesis To propose an educated guess as to
   the answer for the question
3. Experiment To test the hypothesis

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3 Types of Variables
Scientific Method continued(4. experiment)

• Variables are changing quantities
• Independent variable that is changed by the
  scientist only one independent variable in an
  experiment
• Dependent - variable that changes in response to
  the change the scientist makes to the independent
  variable.
• Controlled variables - are quantities that a
  scientist wants to remain constant

As the independent variable is being changed, the
scientist observes what happens to the dependent
variable
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Dependent variable

• A researcher is measuring the effect of chocolate
  on happiness
• What is actually being measured in the
  experiment?

What is the dependent variable?
The dependent variable is happiness happiness is
affected by chocolate, or happiness depends on
chocolate.
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Independent variable

• A researcher is measuring the effect of chocolate
  on happiness
• What variable is manipulated to see how it
  affects the dependent variable (happiness)?

What is the independent variable?
The independent variable is chocolate Chocolate
is being manipulated to measure its effect on
happiness, so chocolate is the independent
variable
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The control/experiment group

• Control
• the group that is not being change kept
  constant-business as usual
• the group that gets no chocolate
• control group is not being exposed to the
  "treatment
• Experimental group
• the group that actually receives treatment
  (chocolate)

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Example 1

• A researcher is studying the effect of sleep on
  aggression, thinking that less sleep will lead to
  more aggression. She has some people sleep 6
  hours per night, some people sleep 3 hours per
  night and some people sleep as much as they want.
  She then monitors aggressive behavior during
  basketball games among participants.

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aggression depends on the amount of sleep

• dependent variable
• Aggression
• independent variable
• amount of sleep (manipulated)

Practice Determining Independent/Dependent
Variables
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Scientific Method continued

• Data/results To gather and interpret
  information obtained from the experiment
• Conclusion -To make a decision as to whether your
  results support or do not support your
  hypothesis.
• Theory - A well-tested explanation for
  experimental data based on a set of hypothesis
• theory is not always included at one of the
  steps in the scientific method

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• Hypothesis
• educated guess based upon observation rational
  explanation of a single event/phenomenon based on
  observations has not been proved.
• Theory
• A set of tested hypothesis that gives an overall
  explanation of some natural phenomenon.
• Subject to change as more information becomes
  available
• evolution
• Scientific Law
• a statement of fact meant to explain, in concise
  terms, an action or set of actions accepted to
  be true and universal
• Often expressed as a single mathematical equation
  the law of gravity, the law of thermodynamics

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Density

1. Mass is the amount of matter an object has.
2. Volume is the amount of space an object occupies.

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Density

• a measure of mass per unit of volume
• Density Mass/Volume
• D M
• V
• mass of the liquid (grams, g)
• Volume of the liquid (milliliters, mL)

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Problem

• You are given two unknown liquids and must
  identify the liquid based on its density.

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Materials

• 100ml graduated cylinder
• Electrical Balance
• Calculator
• 2 unknown liquids

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Procedure

• Find the mass of the empty graduated cylinder.
• Pour unknown liquid 1 into the graduated
  cylinder to the 50 ml. level.
• Find the mass of the graduated cylinder with 50ml
  of unknown liquid 1.
• Repeat steps 1-3 for unknown liquid 2.

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Liquid 1

• Mass of grad. cylinder 78 grams
• Mass of grad. cylinder Liquid 1 128 grams.
• Find
• Mass of just the liquid ____
• Volume of liquid_____
• c) Density of liquid 1 ____

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Liquid 2

• Mass of grad. cylinder 78 grams
• Mass of grad. cylinder Liquid 1 117.5 grams.
• Find
• Mass of just the liquid ____
• Volume of liquid_____
• c) Density of liquid 2 ____

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Identify your Unknown
Substance Density (gm/mL)
Water 1.00
Cooking oil 0.92
Sea Water 1.025
Carbon tetrachloride 1.58
Benzene 0.87
Glycerin 1.26
Methanol 0.79
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Liquid 1

• Mass of grad. cylinder 78 grams
• Mass of grad. cylinder Liquid 1 128 grams.
• Find
• Mass of just the liquid ____
• Volume of liquid_____
• c) Density of liquid 1 ____

128 78 50 g
50 mL
50 g/50 mL 1.0 g/mL
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Liquid 2

• Mass of grad. cylinder 78 grams
• Mass of grad. cylinder Liquid 1 117.5 grams.
• Find
• Mass of just the liquid ____
• Volume of liquid_____
• c) Density of liquid 2 ____

117.5 78 39.5g
50 mL
39.5 g/50 mL 0.79 g/mL
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Identify your Unknown
Substance Density (gm/mL)
Water 1.00
Cooking oil 0.92
Sea Water 1.025
Carbon tetrachloride 1.58
Benzene 0.87
Glycerin 1.26
Methanol 0.79
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(No Transcript)
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A rock has a mass of 210 grams and occupies a
volume of 70 mL.
What is its density?

•  3 g/mL

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Practice
1 mL 1 cm3

• A rectangular solid of unknown density is 5 cm
  long, 2 cm high  and 4 cm wide.  The mass of this
  solid is 30 grams.  Given this information for
  this homogeneous (alike throughout)
  material, calculate its density.

Volume L x W x H
0.75 g/cm3
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Practice

• A rock has a density of 4 g/ml and a mass of
  16 grams.  What is the volume this rock occupies?

Solve D M/V for V V M/D
V 16/4 4 mL
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Practice

• An unknown substance from planet X has a density
  of 10 g/ml.  It occupies a volume of 80 ml.  What
  is the mass of this unknown substance?

Solve D M/V for M M DV
M 10 x 80 800 g
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Using Puzzlemaker.com

• Prepare word document
• Write the word/phrase without any spaces allow
  one space and type in the clue
• Go to http//puzzlemaker.school.discovery.com/
• Choose criss-cross puzzle
• Copy and paste word document into puzzlemaker

http//puzzlemaker.school.discovery.com/
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The End