CHEM210 X-rays old-time remedies reading Please read the following article: http://www.bbc.co.uk/news/science-environment-2206… and write a response in
CHEM210 X-rays old-time remedies reading Please read the following article:
http://www.bbc.co.uk/news/science-environment-2206…
and write a response in 1-2 pages (minimum of 300 words, maximum of 600 words, not including the exam question) using the 3-2-1 format described below:
3: Find 3 concepts from within the article and relate them to 3 concepts within CHEM 210 we have discussed in class and cite 3 textbook references using the chapter and page number.
2: Find 2 concepts from within the article that you want to know more about (i.e. muddy points, have questions about, did not quite understand).
1: Write an exam question with the answer about 1 concept discussed from within the article. The exam question must be well thought out and appropriate to the subject matter. Chapter 1. Chemistry:
Matter on the Atomic Scale
1.1
1.2
1.3
1.4
What is Chemistry?
Classification of Matter
Units and Measurement
Unit Conversions
Chapter 1 introduces the fundamental components of matter, the
different types of structures they can make when they join
together, and the types of changes they undergo.
Interactive Figure 1.1.1 – Understand the Scale of Science
• Macroscopic scale
– Matter that can be seen with the naked eye and can be held
• Atomic scale
– Nanoscale and molecular scale
– Processes cannot be seen
2
1.2
The Properties of Matter
All properties of matter are either extensive or intensive.
The measured value of an extensive property depends on the
amount of matter.
Mass is an extensive property.
The value of an intensive property are independent on the
amount of matter.
Density and temperature are intensive properties.
3
Some Chemical Properties of the Elements
Physical Properties: Characteristics that do not
involve a change in a sample’s chemical makeup.
Chemical Properties: Characteristics that do involve a
change in a sample’s chemical makeup.
Temperature Conversions
• Fahrenheit to Celsius
9
T(°F) = T(°C) + 32
5
9
T(°F) = (82.63 °C) + 32 = 180.73 F
5
• Celsius to Kelvin
1K
× T°C + 273.15°C
1°C
1K
= 298.2 K
25.0°C + 273.15°C ×
1°C
T(K) =
5
Density Units
• Density: Physical property that relates the
mass of a substance to its volume
mass
Density =
volume
• Densities of solids and liquids are reported:
– As grams per milliliter (g/mL) or grams per cubic
centimeter (g/cm3) 1 mL = 1 cm3
– At a standard temperature, 25°C, close to room
temperature
6
Density
Example
Determine the mass of 3274 mL of mercury, with a
d = 13.55 g/mL.
m = V x d = 3274 mL x 13.55 g = 4.436 x 104 g
1 mL
Interactive Figure 1.2.5 – Classify Matter
Mixture combo of two or
more substances retain their
distinct identities
Substance definite composition
& distinct properties
Element cannot be separated
into simpler substances by
chemical means
Compound atoms of two or
more elements in fixed ratio.
Homogeneous
uniform throughout
Heterogeneous not
uniform throughout
8
1.3
1.3 Scientific Measurement
SI Base Units
Measured property
Unit name
Abbreviation
Mass
Kilogram
kg
Length
Meter
m
Time
Second
s
Temperature
Kelvin
K
Amount
Mole
mol
Electric current
Ampere
A
Luminous intensity
Candela
cd
9
Units of Measure
Metric prefixes are combined with SI units when reporting physical quantities
Prefix
Abbreviation
Meaning
Example
Giga
G
109 (billion)
1 gigahertz = 1 X 109 Hz
Mega
M
106 (million)
1megaton = 1 X 106 ton
Kilo
k
103 (thousand)
1 kilometer (km) = 1 X 103 m
Deci
d
10-1 (tenth)
1 decimeter (dc) = 1 X 10-1 m
Centi
c
10-2 (onehundredth)
1 centimeter (cm) = 1 X 10-2 m
Milli
m
10-3 (one
thousandth)
1 millimeter (MM)= 1 X 10-3 m
Micro
m
10-6 (one
millionth)
1 micrometer (mm)= 1 X 10-6 m
Nano
n
10-9 (one
billionth)
1 nanometer (nm) 1 X 10-9 m
Pico
p
10-12
1 picometer (pm) =1 X 10-12 m
Femto
f
10-15
1 femtometer (fm)= 1 X 10-15 m
10
Scientific Notation
• Numbers are expressed in a format that
conveys the order of magnitude
– General form: N × 10x
• Converting standard notation to scientific
notation
– Count the number of times the decimal point is
moved to the right or left
3285 ft = 3.285 103 ft
0.00215kg = 2.15 103 kg
1
Precision and Accuracy
• Precision: How close the values in a set of
measurements are to one another
• Accuracy: How close a measurement or a set of
measurements is to a real value
12
1.4
Uncertainty in Measurement
Chemistry makes use of two types of numbers: exact and
inexact.
Exact numbers include numbers with defined values with
infinite significant figures, such as
2.54 in the definition 1 inch (in) = 2.54 cm
1000 in the definition 1 kg = 1000 g
12 in the definition 1 dozen = 12 objects.
Numbers measured by any method other than counting are
inexact.
13
1.4
Uncertainty in Measurement
An inexact number must be
reported in such a way as to
indicate the uncertainty in its value.
Significant figures are the
meaningful digits in a reported
number.
14
Counting Significant Figures
Rule
Example
Number of significant
figures
1256
4
All zeros between non-zero
numbers are significant-captive
zeros
1056007
7
Leading zeros are NEVER
significant (zeros to the left of your
first non-zero number)
0.000345
3
0.00046909
5
1780
3
770.0
4
0.08040
4
All non-zero numbers are
significant
Trailing zeros are significant ONLY
if a decimal point is part of the
number (zeros to the right of your
last non-zero number)
1
1.3
Uncertainty in Measurement
Significant Figures
To avoid ambiguity in such cases, it is best to express such
numbers using scientific notation [Appendix 1].
1.3 × 102 two significant figures
1.30 × 102 three significant figures
50
Rounding Numbers
• Find the last digit that is to be kept
• Check the number immediately to the right
– If that number is less than 5 leave the last digit
alone
2.543 round down to 2.54
– If that number is 5 or greater increase the
previous digit by one
2.546 round up to 2.55
1
Round to Two Significant Figures
Find the
last digit
that is to be
kept
Check
number
to the
right
Is digit to
the right
less than
5?
Is digit to
right 5 or
greater?
Rounded
number
1056007
1056007
No
Yes
1100000
0.000345
0.000345
No
Yes
0.00035
1740
1740
Yes
No
1700
1
1.3
Uncertainty in Measurement
Calculations with Measured Numbers
Addition and Subtraction, the answer cannot have more
digits to the right of the decimal point than the original
number with the smallest number of digits to the right of
the decimal point
If the leftmost digit to be dropped is less than 5, round down.
If the leftmost digit to be dropped is equal to or greater than
5, round up.
55
1.3
Uncertainty in Measurement
Calculations with Measured Numbers
Multiplication and Division, the number of significant figures
in the final product or quotient is determined by the original
number that has the smallest number of significant figures.
2 SF
4 SF
2 SF
56
1.3
Uncertainty in Measurement
Addition and Subtraction with Multiplication and Division,
the number of significant figures in the final answer is based
on the Order of Operations and the corresponding rule
needed.
2.54 cm x (147.9 inch – 145.900 inch) = ??
inch
Do () math 1st:
147.9 inch
– 145.900 inch 2 SF
2.000 inch ~ 2.0 inch
3 SF
2 SF
3 SF
2 SF
Then multiply: 2.54 cm x (2.0 inch) = 5.08 cm ~ 5.1 cm
inch
56
1.3
Using Units and Solving Problems
A conversion factor is a fraction in which the same quantity is
expressed one way in the numerator and another way in the
denominator.
Both forms of this conversion factor are equal to 1, we can
multiply a quantity by either form without changing the value
of that quantity.
72
Dimensional Analysis
Useful US units to Metric Unit Conversions
• 1 in = 2.54 cm
• 1 lb = 453.6 g
• 1 oz (mass) = 28.3459231 g (mass)
• 1 oz (fluid) = 29.5735 mL (fluid)
FOLLOW THE UNITS!
2
Example of Conversion Factors
• Conversion factors – Used to make the
conversion between units
– The resulting quantity is equivalent to the original
quantity, it differs only by the units
Unit (1) ×conversion factor = unit (2)
– Example – Metric to metric equalities
1 m = 100 cm
1m
102 cm
or
2
10 cm
1m
• Use of exact conversion factors will not affect the
significant figures in a calculation
24
1.6
Using Units and Solving Problems
The use of conversion factors in problem solving is called
dimensional analysis or the factor-label method.
A proportionality (or conversion) factor was used.
known units x desired units = desired units
known units
FOLLOW THE UNITS!
Make sure UNITS Cancel Out before doing the math!
74
1.6
Using Units and Solving Problems
The speed of light in a vacuum is 2.998 x 108 m/s, what is
the speed in cm/min?
2.998 x 108 m x 100 cm x 60 s = 1.799 x 1012 cm
s
1m
1 min
min
FOLLOW THE UNITS!
Make sure UNITS Cancel Out before
doing the math!
74
Exercise: How Many Picometers Are in 25.4 nm?
Given: 25.4 nm
Find: pm
Roadmap:
Factors:
Solve:
nm m pm
1 m 1012 pm
;
9
10 nm 1 m
1m
1012 pm
25.4nm × 9
×
= 2.54 ×10 4 pm
10 nm
1m
FOLLOW THE UNITS!
Make sure UNITS Cancel Out before doing
the math!
Check: We would expect a greater number of pm and that is what we have
27
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