Transcript Introduction to Chemistry

Warm Up #1.1
1. The following data was collected.
The volume of the gas is known to be
2.20 L. Use the words Precise and
Accurate to describe the data.
2. How old are you in seconds?
Warm Up #1.1 Answer
Is precise but not accurate
2. Givens: xx years old
Want: ? Seconds
Need: 1 year = 365 days; 1 day = 24 hours;
1.
1 hour = 60 minutes; 1 minute = 60seconds
Graphing Data
Homework Worksheet
Variables
Independent Variable: causes a change
Dependent Variable: depends on
independent
Ex. Time is always independent…
always changes
Speed depends on the time  it’s dependent
X axis : Independent variable
Y-axis: Dependent variable
Slope: Rise/Run
Graph 1: Mass-Volume
Slope: 2.70 g/cm3
Independent:
Volume
Dependent:
Mass
Observations: its straight, one variable increases the
other variable increases
Graph 2: Pressure- Volume
Slope: varies
Independent:
Volume
Dependent:
Pressure
Observations: opposite; one variable increases the
other variable decreases
Conclusion:
What are differences in graph 1 & 2
Graph 1: is a direct relationship
Graph 2: is a opposite (inverse) relationship
Graph 1 is…..
Directly Proportional
Graph 2 is ….
Inversely Proportional
Practice: graph the data below
Table 3: Cesium-137 Half- life
Amount of sample (kg)
Time (years)
1.00
30.2
0.5
60.4
0.25
90.6
0.125
120.8
0.0625
151
Graph 3: Cesium 137 Half Life
Cesium 137 Half Life
Amount of Sample (Kg)
1.2
0.8
Slope: varies
Independent:
0.6
Time
1
Dependent:
0.4
Amount
0.2
0
0
20
40
60
80
100
Time ( years)
120
140
160
Units
Units of Measurement

ALL measurements must include:
#
&
unit
SI Units





(International System of Units)
Length= meter (m)
Mass= kilogram (kg)
Time= seconds (s)
Temperature= Kelvin (K) ***
K = C + 273
Pressure= pascal (Pa)
Prefixes
Prefix
Symbol
Value
Giga
G
Mega
M
Kilo
k
Hecto
H
Deka
Da
109
106
103
102
101
Base Unit: g, L, m, s
Deci
d
Centi
c
Milli
m
Micro

Nano
n
10-1
10-2
10-3
10-6
10-9
Great
Many
Kids
Have
Dropped
Over
dead
converting
metrics
many
nights
Significant Figures and
Scientific Notation
Volume is?
Length is?
Uncertainty in Measurements
When reading an instrument…
write all #s you see
+ 1 more that you estimate
Rules for Significant Figures (sig figs)
1. Count all non-zero # s
ex: a. 1234
= 4 sig figs
b. 100
= 1 sig figs
2. Count zeros that are in b/w non-zero #s
ex: a. 708
= 3 sig figs
b. 1008
= 4 sig figs
3. If # is less than one, count all # after the
first non-zero # (do not count the zeros to the
left of the first non-zero #)
ex: 0.000987
= 3 sig figs
0.009870
= 4 sig figs
4. If # is greater than zero & a decimal point is
present, count all #s
ex: a. 101.2
= 4 sig figs
b. 1000.000
= 7 sig figs
Adding and Subtracting



add or subtract the numbers
keep all whole numbers
round the decimal to the least number of
decimal places
-
5.00 cm
4.352 cm
0.648 cm
0.65 cm
Multiplying and Dividing
multiply or divide # s
 count the TOTAL number of sig figs in each
 Round to the least # of TOTAL sig figs

6.7 cm
x 1.1 cm
7.37 cm2
7.4 cm2 is the correct answer in sig figs
Practice
1.
2.
3.
4.
708.0 – 89.49 = 618.51 =
8.4 x 6.12345 = 51.43698 =
6.8947 x 200 = 1378.94 =
5.43 + 4.1 = 9.53 =
Scientific Notation
In chemistry we often use very large or very small
numbers.
54, 000
0.000008765
Mistakes are made with all these zeros so…..
We use scientific notation.
Scientific Notation
1. Make the # <10
2. Count # of places decimal moves = exponent
Ex: 54 000 = 5.4 x 104
3. If original # <1 the exponent is negative
Ex: 0.000008765= 8.765 x 10-6
Practice
1. 73,200 =
2. 23.21 =
3. 4, 713, 000, 000=
4. 0.00000000000043791=
Dimensional Analysis
See Yellow Note Sheet
Dimensional Analysis
1. uses numbers in the form of fractions.
2. enables us to convert from one type of unit
measurement to another.
Dimensional Analysis
In order to convert from one quantity to
another, we must use known quantities
called Conversion Factors
Fractions = Conversion Factors
Any number or any relationship can be made
into a FRACTION, which is called a
conversion factor in dimensional analysis.
ex. 12 eggs in one dozen:
12 eggs = 1 dozen
or
12 eggs
1 dozen
or
1 dozen
12 eggs
Canceling Units
If a unit appears in the numerator and
the same unit appears in the
denominator, it can be cancelled/
removed. Sometimes we need to invert to
make this happen.
Set Up of Problems
Must determine:
1. What is your GIVEN
2. What do you WANT
3. What do you NEED (conversions)
(1)GIVEN (2)Conversion (3)what you WANT
factor (s)
Prefixes
Prefix
Symbol
Value
Giga
G
Mega
M
Kilo
k
Hecto
H
Deka
Da
109
106
103
102
101
Base Unit: g, L, m, s
Deci
d
Centi
c
Milli
m
Micro

Nano
n
10-1
10-2
10-3
10-6
10-9
Great
Many
Kids
Have
Dropped
Over
dead
converting
metrics
many
nights
Warm Up 1.2- Round answer using sig
fig rules






16.5 + 8 +4.37 = 28.87=
25.37 +6.850+15.07+ 8.056 = 55.346=
350.0 – 200 = 150=
0.58/ 2.1 = 0.2761904761904762=
6.54 x 0.37= 2.4198 =
0.0085 x 0.050 x 0.655= 0.655425=
Now you practice…
1. 0.56kg = ? mg
0.56 kg
_______ g _______ mg = __________ mg
kg
g
2) 1.2ng = ? g
1.2 ng____
____g = ___________ g
ng
Now you practice…
1. 0.56kg = ? mg
0.56 kg
_______ g _______ mg = __________ mg
kg
g
2) 1.2ng = ? g
1.2 ng____
____g = ___________ g
ng
3) 2.0 in = ? mm (1in = 2.54 cm)
2.0 in _______cm ______
in
m ______ mm = ______ mm
cm
m
4) 500ft = ? M
500 ft _______ in _________ cm _________ m = __________ m
ft
in
cm
5) 10μL = ? cc (1mL = 1cm3 = 1 cc)
10μL _________L ________
μL
mL _________ cc = _________ cc
L
mL
6) 3 wk = ? min
3 wk ___________ _____________________ = _______ min
7) 50mL = ? cups (1L = 4.226cups)
50mL __________ _____________ = __________ cups
8) 5.33km = ? dm
5.33 km ____________ __________= ___________ dm
9) 123.0 ng = ? Mg
123.0ng _____________ _____________ = ____________ Mg
10) 3yds = ? in (1 yd = 3ft)
3 yds ___________ _____________ = ______________ in