Transcript Mass - RCSD

Chapter 2
2.1 Mass and Volume
• Mass describes the amount of matter in an object.
o Matter – anything that has mass and takes up space.
o SI unit for mass is the kilogram.
 1 kg = 2.2 pounds
 1 gram = 0.001 kilogram
o Mass is measured with a triple-beam balance or
electronic scale.
o Mass is not the same as weight.
• Weight measures the pull of gravity on an object.
o English unit is the slug or pound.
o Related to mass because more mass = more weight.
o Weight changes with gravity.
< gravity = < weight
> gravity = > weight
• Volume – amount of space an object takes up.
o Basic unit is the m3 - cubic meter.
o Can also be cm3 or cc.
o 1 cm3 = 1 mL
• Volume can be measured using 3 different methods.
1. Graduated cylinder - used to measure liquid volume in mL
 To read a graduated cylinder:
 Place on flat surface
 Read at eye level
 Read at center – bottom of meniscus – curve of liquid
 Report measurement to one place value past
the value represented by lines on cylinder
3
2. Regular, Solid Shape – geometric formulas
 Cube or rectangle – length x width x height
 Answer will have length units cubed: cm3, m3,
dm3
6.2 cm long
2.0 cm wide
1.0 cm tall
6.2 cm x 2.0 cm x 1.0 cm = 12.4 cm3
 1 cm3 = 1 mL
3. Displacement Method
Place a volume of water in a graduated
cylinder. Make sure the cylinder will hold your
object and the water will cover the object.
Measure the water
Carefully slide the object into the cylinder
Make a new measurement of the height of the
water
Subtract the 2 measurements –
the difference is the volume of
the object!
• Calculate the volume
of the object in mL
Complete the Chapter 2, Section 1 Worksheet
2.2 Density
• Mass is not proportional to size – a large object
does not always have a large mass. A small object
can contain more mass than a large object.
Ex: compare a loaf of bread to a brick
• Density describes how much mass is in a given volume
of a material. (how tightly matter is “packed”)
o Stated as a ratio of mass to volume
o Units can be grams/milliliter; grams/cm3; kilograms/liter
o Density of pure water is 1 g/1 mL
o Density of a material is the same no matter what the
size or shape of the material.
 Ex: the density of a steel nail and a steel cube are
the same because they are both made of steel.
Exception: water – ice has less density than liquid
water
• Density formula
Density = mass / volume
D= m
V
• Ex: A solid wax candle has a volume of 1700 mL.
The candle has a mass of 1500 g. What is the
density of the candle?
D = 1500 g = 0.88 g/mL
1700 mL
Calculate (in your notes)
1. A student measures the mass of five steel
hex nuts to be 96.2 g. The hex nuts displace
13 mL of water. Calculate the density of the
steel in the hex nuts.
2. A 31.2 g piece of granite measures 2.00 cm x
2.00 cm x 3.00 cm. What is its density?
3. What is the density of ice that has a mass of
100.0 grams and a volume of 92 cm3.
Turn in on Paper
1. Calculate the density of your
objects.
2. Show all measurements and
calculations.
3. Record your densities on the class
chart.
4. Copy the class chart, calculate the
average densities and turn in.
Group
1
2
3
4
5
6
7
8
9
10
11
12
Class Average
Hex Nut
Clay Object
2.3 Graphing
• A graph is a visual way to organize data.
o Circle graph (pie graph)
o Bar graph
o Line graph (scatterplot, XY graph)
• Circle graph (pie graph) - shows percentages
• Bar graph – compares data, often 1 of the
variables is not a number
• Line graph – compare 2 sets of number data
where one variable is thought to cause a
change in the other
• Line graphs can compare 2 sets of data
• Easier to read if 2 different colors!!!! Create a
legend.
Requirements
• Independent variable (variable you think will influence
another variable) is on X
• Dependent variable (variable that might be changed by
independent variable) is on Y
• Paper turned so variable with largest spread has more
room
• Covers most of the paper (2/3)
• Number lines have equal intervals and equal spaces
between all numbers – DO NOT have to start with 0 on
both axes
• Axes are labeled with what was measured AND units
• Points are correctly plotted
• Best-fit line (NOT connect the dots)
• Graph has title that relates relationship of information
measured
Scientists studying the effect of pH on tadpole populations,
collected samples of pond water from 6 local ponds and
counted tadpoles in each pond. The data is recorded in
this chart.
Create a line graph of the data following the rules you
were given.
pH of water
Number of Tadpoles
5.5
6.0
6.5
7.0
23
43
88
78
7.5
69
8.0
45
Check Your Work
Did you:
Place pH on the X axis? Tadpoles on Y axis? 10 pt
Turn your paper so tadpole numbers have the longest part of
the paper? 10 pt
Cover 2/3 of your paper? 10 pt
Space your number intervals correctly and equally? 10pt
Label Axes with what was measured? 10 pt
Correctly plot values? 30 pt.
Best-fit line? 10pt
Create an acceptable title? 10 pt.
A clam farmer has been keeping records concerning
the water temperature and the number of clams
developing from fertilized eggs. Make a line graph of
the data.
Water Temperature in Number of developing
oC
clams
15
75
20
90
25
120
30
140
35
? Oops, forgot to
record!
40
40
45
15
50
0
Answer on the bottom of your graph.
1. What is the dependent variable?
2. What is the independent variable?
3. What is an estimate of the number of clams at 35 oC?
4. What is the optimum (best) temperature for
clam development?
Identifying graph relationships
• In a direct
relationship,
when one
variable
increases, so
does the
other.
The speed and distance variables show a direct relationship.
• In an inverse
relationship,
when one
variable
increases, the
other
decreases.
Interpolation
Method of determining a new data point that
exists between a set of known data points
Scientific Notation
• Simple way of writing numbers with many digits
• Number x 10 to a specific power
Ex: 602 200 000 000 000 000 000 000
6.022 x 1023
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Scientific Notation
• The exponent of 10 tells the person reading the
direction the decimal must be moved to obtain the
number written in long notation
• Example:
65 000 km = 6.5 x 104 km
0.000 12 mm = 1.2 x 10-4 mm
• A positive exponent means “ x10” to that power
• A negative exponent means “dividing by 10” to that
power
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Expressing Scientific Notation in Full Form
• Rewrite the number in front of “x10”
• Determine if decimal should be moved left or
right.
– Negative exponent tells reader to move left
– Positive exponent tells reader to move right
• If adding zero’s on end – DO NOT add decimal
to full number!
• If adding leading zero’s – add the decimal.
Remember, leading zero’s are not sig fig’s
• Ex: 7 x 104 =
• Ex: 2.31 x 10-7 =
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Expressing Scientific Notation in Full Form
• 1.56 x 104
• 2.59 x 105
• 5.6 x 10-2
• 4.59 x 10-5
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Expressing a number in Scientific Notation
1. Rewrite numbers leaving off zero’s on the end or
zero’s in front of first “non-zero”.
2. Place a decimal after the first number - only 1 number
allowed in front of the decimal
3. State “x 10” . To determine how many places the
decimal should be moved – count how many place
values to where the decimal started.
4. If the decimal needs to be moved right, exponent is
“positive”. If the decimal needs to be moved left,
exponent is “negative”.
• Ex: 4 325 000 =
• Ex: 0.000 003 61 =
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Expressing a Number in Scientific Notation
• 0.000 000 451
• 114 000 000
• 0.007 81
• 1 003 040 000
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Complete and Turn in
Convert into scientific notation:
1.
2.
3.
4.
680 m
0.00560 mm
250 800 L
267.80 g
Convert into full notation:
1.
2.
3.
4.
5.
2.86 x 103
3.440 x 10 3
2.6130 x 10-4
2.508 x 105
4.80 x 10-7
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Make up
• State the following numbers in scientific notation
1)
2)
3)
4)
5)
0.000 000 786
3 940
407 000
1 260 000
0.06
• State the following scientific notation in standard form
6)
7)
8)
9)
10)
6.17 x 10 3
7 x 10 4
7.31 x 10 6
6.7 x 10 -3
9.59 x 10 -5