Transcript Turn in Homework to the front! 9/7 Warm Up

Turn in Homework to the front!
9/5 Warm Up
1. Explain the difference between a
physical and chemical change.
2. Explain the difference between
homogenous and heterogeneous
mixtures.
3. What are 3 ways that a mixture can be
separated?
2.2 & 2.3 & 2.4 Notes
Element vs. Compound
• Simplest form of matter
• Can NOT be separated
into simpler substances
by chemical means
• Building blocks of other
substances
• Examples: oxygen,
hydrogen, etc
• 2 or more elements
combined
• Substance that can
be separated into
simpler substances
by chemical means
• H2O
Properties of compounds
compared to the elements
• Sugar, C6H12O6: sweet, white, edible
– Carbon, C: black, tasteless solid
• Other interesting examples
– Salt, NaCl
2 Na +
Cl2
= 2 NaCl
Symbols and Formulas
• Chemical Symbol: a one or two letter
symbol for the name of an element
• Element symbols that you must
memorize the name!!!!
C
H
He N
O P
S
Na Mg K
Ca Cl F
Al
Fe Cu Ag Au Hg Pb Sn
Chemical Reactions:
Chemical Change
• Changing reactants to products
– Reactants: starting substances
– Products: substances that are formed
• Equation example
– Reactants  Products
– H2 + I2  2 HI(g)
Journal #4 : Write down the
following chemical reaction
• NH4NO3  N2 + O2 + H2O
• Label the reactants and products
Conservation of Mass
• Mass is neither created nor destroyed
• Total mass of reactants = total mass of products
Journal # 5
NH4NO3  N2 + O2 + H2O
• When 20 grams of ammonium nitrate
(NH4NO3) break down, 7 grams
nitrogen (N2) and 4 grams of oxygen
(O2) form.
• How many grams of water are formed?
Journal # 5 Answer
• NH4NO3  N2
+ O2 + H2O
20 grams = 7 g + 4 g + X g
• When of ammonium nitrate (NH4NO3) break
down, 7 grams nitrogen and 4 grams of
oxygen form. How many grams of water are
formed?
• X = 20 - 7- 4 = 9
• During any chemical reaction, the
amount of matter is unchanged!!!
• Mass is neither created nor destroyed
• Matter is neither created nor destroyed
3.1 The Importance of
Measurement
Scientific Notation
• Mathematical abbreviation for measured
values
– Coefficient x 10n
– The coefficient is greater than or equal to one and
less that 10.
– Example:
67,500,000,000,000.0
Decimal moves 13 places to the left
6.75 x 1013
• Example:
0.00000489
Decimal moves 6 places to the right
4.89x10-6
Journal
Now its your turn!!!!
Convert the following values into scientific
notation:
a. 86700000
b. 0.00000052
c. 63100
Journal
Now its your turn!!!!
Convert the following values into scientific
notation:
a. 86700000 = 8.67 x 107
b. 0.00000052 = 5.2 x 10-7
c. 63100 = 6.31 x 104
Accuracy
• Measure of how close a measurement
comes to to the actual or true value of
whatever is measured
Precision
• Measure of how close a series of
measurement are to one another
– Depends on more than one measurement!
Error
• Error = accepted value - experimental value
• Percent error = ___|error | ___
accepted value
x 100
Journal
• Error = accepted value - experimental value
• Percent error = ___|error | ___
accepted value
x 100 %
You measured the diameter of a ball to be
0.489 m. The package states that the ball has
a diameter of 0.5 m. Identify the error and
percent error of your measurement.
• You measured the diameter of a ball to be
0.489 m. The package states that the ball has
a diameter of 0.5 m
• Error:
0.5 - 0.489 = 0.011
• Percent error = 0.011
0.5
x 100 = 2.2 %
Significant Figures
How do we round in Chemistry???
Significant Figures give the reader an idea of how well you could
actually measure/report your data.
Rules for significant figures.
1) ALL non-zero numbers (1,2,3,4,5,6,7,8,9) are ALWAYS
significant.
2) ALL zeroes between non-zero numbers are ALWAYS significant.
3) ALL zeroes which are SIMULTANEOUSLY to the right of the
decimal point AND at the end of the number are ALWAYS
significant. (2.400)
4) ALL zeroes which are to the left of a written decimal point and
are in a number >= 10 are ALWAYS significant. (300.0)
How Many sig figs?
•
•
•
•
•
•
•
•
49,582 has 5 sig figs
3.967 has 4 sig figs
9.006 has 4 sig figs
0.0004 has 1 sig fig
8.1000 has 5 sig sig figs
501.040 has 6 sig figs
3,000,000 has 1 sig fig
10.0 has 3 sig figs
Using rounding in calculations
• Addition/Subtraction: The answer to
an addition or subtraction problem
should be rounded to the same number
of decimal places as the measurement
with the least number of decimal places.
– Example: 900.049 + 2.2 = 902.249
needs to be rounded to 902.2
• Multiplication/Division: answer needs
to be rounded to the same number of
significant figures as the measurement
with the least number of significant
figures
– Example: 200 x 4.579 = 915.8
needs to be rounded to contain only 1
significant figure so your answer is 900
The End