Transcript Slide 1

Unit 1- Matter and Measurement
Chapter 1 in text book
Day 1
Qualitative and Quantitative Data
Qualitative- information that describes
• Qualitative Quality
• 5 senses
• Ex- color, texture, smell, taste, sound, etc.
Quantitative- numerical information
• Quantitative Quantity
• Measured
• Ex- mass, speed, height, length, etc.
Accuracy and Precision
• Accuracy
– How close a number is to the correct answer or
value
• On a test, you need to be accurate to get the question
correct.
• Precision
– Having data values that are close to each other
• If you mass a block three times and your values are
5.67g, 5.66g, and 5.69g; your data is precise.
For each dart board,
do the darts have high or low accuracy and precision?
Lets look at some example data!
You measure the length of a piece of wood
three times and record the following data:
76.48cm, 76.47cm, and 76.59cm.
1. Is your data precise?
2. If the label on the wood says it is 76.49cm long,
are your measurements accurate?
Student A
Student B
Student C
Trial 1
1.54 g
1.40 g
1.70g
Trial 2
1.60g
1.68g
1.69g
Trial 3
1.57g
1.45g
1.71 g
Average
1.57g
1.51g
1.70g
Uncertain Digit
• All measurements are uncertain to some
degree
– Basis for significant figures
• The uncertain digit is the guessed digit
Significant Figures (sig figs)
• Meaningful digits in a MEASUREMENT
– The certain numbers and the first uncertain digit.
• Exact numbers are counted, have unlimited
significant figures
• If the number is measured or estimated, it has
sig figs.
Rules for SIG FIGS
1. All non-zero numbers are significant.
–
Example- 5952 – has 4 sig figs
2. All zeros between non-zero numbers are
significant.
–
405 – has 3 sig figs
3. All zeros to the left of the number are not
significant.
–
0.0028 – has 2 sig figs
4. Zeros on the right of the number are only
significant if there is a decimal point.
–
–
–
1590 – has 3 sig figs
8260. – has 4 sig figs
0.0837 – has 3 sig figs
Examples
1.
2.
3.
4.
5.
6.
7.
2801.0
693
950
0.369
0.0570
48020.
62.01400
Doing the math
• Multiplication and division, same number of sig
figs in answer as the least in the problem
• Addition and subtraction, same number of
decimal places in answer as least in problem.
• Example– Calculate the density of an object that has a mass of
102.4 g and a volume of 50.0 mL.
– Add the following measurements and report them
to the appropriate significant figures: 28.0 cm,
23.538 cm, and 25.68 cm
Dimensional Analysis
•
•
•
•
Use conversion factors to change the units
Conversion factors = 1
1 foot = 12 inches (equivalence statement)
12 in = 1 = 1 ft.
1 ft.
12 in
• 2 conversion factors
• multiply by the one that will give you the correct
units in your answer.
Temperature
• A measure of the average kinetic energy
• Different temperature scales, all are talking
about the same height of mercury.
• Derive a equation for converting ºF toºC
Temperature Conversions
9
F  C  32
5
5
C  F  32 
9
K  C  273.15
Temperature Conversions
Density
•
•
•
•
•
Ratio of mass to volume
D = m/V
Useful for identifying a compound
Useful for predicting weight
An intrinsic property- does not depend on
how much of the material there is
Density Problem
• An empty container weighs 121.3 g. Filled
with carbon tetrachloride (density 1.53 g/cm3
) the container weighs 283.2 g. What is the
volume of the container?
Day 2: Matter
What is matter?
• Anything that has mass and takes up space.
– (Has mass and volume)
Element vs. Compound
• Element is composed of only atoms from one
element
– One individual part is an atom
• Compound is two or more atoms bonded together
– Water- H20
– Oxygen Gas- O2
– One individual part is a molecule
Pure Substance
• Matter that doesn’t change and is uniform
• Usually an element or compound
– Water
– Salt
– Carbon
• Not a pure substance
– Salt water
– Hot chocolate
– Trail mix
Mixtures
• Homogeneous
– Appears the same throughout
– A.k.a. a solution
• Example- lemonade, salt water
• Heterogeneous
– the different parts can be seen
• Example- Chocolate chip cookie, salad
Mixtures
• Mixture - combo. of 2 or more pure substances in
which each retains its individual chemical props; ex:
water & sand.
• 2 Types:
– 1. Heterogeneous - doesn't blend uniformly (water & sand);
individual substances remain distinct.
– 2. Homogeneous - aka Solutions (soln) - constant
composition throughout & always has a single phase.
•
Ex: salt & water : will contain the same relative amounts of salt &
water in every drop.
Separating Mixtures
• Distillation - based on different boiling pts
(bpts); mixture is heated until the subst.
w/lowest bpt boils to a vapor which can be
condensed into a liquid & collected.
• Crystallization - when a soln has as much
solute it can hold, one more pinch will cause
the solute to come out of soln & collect as
crystals. (Rock candy)
Separation Techniques
• Filtration- solid part is
trapped by filter paper
and the liquid part runs
through the paper
• Vaporization- where the
liquid portion is
evaporated off to leave
solid
Separation Techniques
• Decanting- when liquid is
poured off after solid has
settled to bottom
• Centrifuge- machine that
spins a sample very
quickly so that
components with
different densities will
separate
Separation Techniques
• Paper
Chromatographyused to separate
mixtures because
different parts move
quicker on paper
than other