PHSC 1170 Lecture 1: Chem Unit 1 Notes

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23 Mar 2017
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Chemistry Unit 1 Notes
Science Began 300 years ago
Galileo and Newton
Science Today: Based on experimental evidence
o Scientific Method:
Observe some aspect of nature
Propose an explanation for something observed
Use the explanation to make predications
Test the predictions with experiments or more observations
Modify the explanation as needed
Return to #3 and Repeat
Pseudoscience: misleading and often absurd claims of scientific results
o aka no proof
o Tests of Pseudoscience
Check academic and scientific background of claimant
History of review by scientific peers
Participations in scientific institutions and organizations
Claim published in peer-reviewed journals and independently
validated by others
Explanations and Investigations
o Hypothesis: a tentative explanation for some observation
o Experiment: recreation of an event or occurrence to test a hypothesis
o Controlled Experiment: comparing two situations with all factors alike
except one
Control Group: fixed set for comparison
Experimental group: differs from control group by one
influencing factor
Dependent, Independent, and Controlled Variables
o Independent Variable: variable that is changed or manipulated by the
researcher
o Dependent Variable: the response to the change that is measured
o Controlled Variable: are quantities that the researcher wants to stay
constant
Qualitative vs. Quantitative Observations
o Qualitative Observation: Knowledge that we receive through the
senses remarking a quality or change of the observed parameter
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Observations found using senses
o Quantitative Observation: Knowledge that relates to or expressed in
numeric values
Express observation by numbers
Chemistry: A study of matter and Its Changes
Chemical: a technical term referring to any material with a fixed, specific
composition
o Elements or compounds
Matter: the stuff that makes up all material things
o Anything that occupies space and has mass and volume
o Air is matter because it is made of atoms and can be condensed and
weighed
o Matter is measured in Units
SI Base Units (Metric Units)
Length: meters (m)
o 2 km = 1000 m
o 1 m = 100 cm
o 1 cm = 10 mm
Mass: grams (g)
o 1 kg = 1000 g
o 1 g = 1000 mg
Volume: Liter (L)
Mass vs. Weight
o Mass: a measure of the quantity of matter that an object contains
Does not depend on gravity
o Weight: measures a force
On earth, weight measures the force of attraction b/n our
planet and the mass in question
Depends on gravity
Significant Figures
Zero at beginning: irrelevant
o 0.000321 = 3 sig figs
Zero in middle or at end: counts as a sig fig
o 87.230 = 5 sig figs
Multiplication or Division Answer
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o Answer CANNOT have more sig figs than either of the original
numbers
1.25 (3 sig figs) * 10.20 (4 sig figs) = 0.122 (3 sig figs)
Addition or Subtraction
o Answer CANNOT have more digits to the right of the decimal points
than either of the original numbers
1.23 (2 numbers past decimal) + 0.04136 (5 numbers past
decimal) = 1.27 (2 numbers past)
Density
1. Density Ratio: Ratio of mass and volume
o D= m/v
o M=d*v
o V= m/d
2. Characteristic of a given material
o Pieces of Iron and Gold with the same volume will have different
masses
3. Practice Problem: If you were asked to find the density of milk in a glad,
would you need to use all of the milk in the glass? Give reasons for your
answer.
o No, you just need a certain volume and the mass of that amount
4. What is the density of a metal sample with a mass of 18.96 g and a volume
of 4.31 cm3? (see worksheet)
5. Mercury is a liquid metal with a density of 13.6 g/cm3. What is the mass of
10.0 cm3 of mercury?
6. What is the volume of a rock with a density of 3.00 g/cm3, and a mass of
600 g?
7. A 2.1 kg pile of aluminum cans is melted, then cooled into solid cube. What
is the volume of the cube (density of Al= 2.70 g/cm3).
8. A 10.0 g sample of which of the following substances would have the
greatest volume?
o Hexane (0.660 g/mL)
o Ethyl alcohol (0.789 g/mL)
o Water (1.00 g/mL)
o Magnesium (1.738 g/cm3)
o Copper (8.94 g/cm3)
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