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Chapter 2September 14 – October 20
Meme Moment
Meme Moment
Meme Moment
Meme Moment
Meme Moment
Meme Moment
Scientist of the Day
Extra Credit Only!
Scientist of the Day
Margaret Hamilton• Started off as a teacher (math
& French)• Went back to grad school to
learn about programming before it was even a thing
• Computer programmer for Apollo 11 mission
• Software design still used today• Made sure moon landing
happened• Entrepreneur
Scientist of the Day
Colin Raston
• TODAY won an Ig Nobel Prize for unboiling an egg
• Ig Nobel Prizes are for silly research – it’s usually still useful
• Vortex fluidic device• Invented a machine that fixes
proteins
Scientist of the Day
Jonas Salk• Invented polio vaccine• 58000 people used to get
polio in the US each yearo 1/3 of them ended up
partially paralyzedo Iron lung
• Funded by March of Dimes
• Refused to patent invention
• Polio now gone in all but 3 countries
Scientist of the Day
Youyou Tu• Won Nobel Prize with 2
others last weeko William C. Campbello Satoshi Omura
• Isolated artemisinin (malaria drug) from traditional Chinese medicineo 2000 combos triedo Other 2 won for ivermectin
(river blindness)
• Family killed in Cultural Revolution
Scientist of the Day
Dennis Ritchie• Invented C programming
language and Unix OSo With Ken Thompson
• Made them free so people could actually use them
• Like Margaret Hamilton, had to join a company to do PhD computer worko Never officially got his PhD
• Died the same week as Steve Jobs to little fanfare
Measurements
September 15, 2015(2.1 in your books)
Metric System• Replaced weird measurements like “hands” or “cubits”
that vary from place to place, as well as mileso A cubit is the length of your fingertip to your elbow
• Based around water, which is the same everywhere• 1 g of water = 1 cm3 = 1 mL (at 4ºC)• Once you have a unit, you can add a prefix to save
space.o The sun is 150,000,000,000 m away has a lot of 0s to keep
track ofo The sun is 150 billion m away has words in it, so you can’t do
matho The sun is 150 Gm away(gigameters)
Imperial vs Metric
Measurement Imperial Metric
length inches, feet, yards, miles, leagues meter
volume ounces, pints, quarts, gallons liter
mass grains, pounds, stones, slugs gram
Who doesn’t use the metric system?
Prefixes
Symbol Prefix Math 10n Example
k kilo x 1000 x 103 kilogram
h hecto x 100 x 102 hectometer
da deka x 10 x 101 dekaliter
x 1 x 100 liter
d deci x 0.1 x 10-1 decimeter
c centi x 0.01 x 10-2 centimeter
m milli x 0.001 x 10-3 milligram
Different ways of writing the same
thing
6th and 7th grade
PrefixesSymbol Prefix Math 10n Example
k kilo x 1000 x 103 kilogram
h hecto x 100 x 102 hectometer
da deka x 10 x 101 dekameter
x 1 x 100 liter
d deci x 0.1 x 10-1 decimeter
c centi x 0.01 x 10-2 centimeter
m milli x 0.001 x 10-3 milligram
µ micro x 0.000001 x 10-6 microliter
n nano x 0.000000001 x 10-9 nanogram
Different ways of writing the same
thing
8th grade
SI Units• Fancier version of the metric system• “International system of units”
o The acronym doesn’t match because it’s international. o Acronym comes from the French versiono Système International d'Unités
• 7 base quantities – if you know these, you can describe any quantitative measurement.
• Everything we know for certain is based on those 7 types of numbers
• We’ll use other units/descriptions/symbols like “energy” or “density” or “power,” but we can always trace them back to SI unitso Energy = Joules = J = N·m = kg·m2/s2
SI Units
• K = Kelvin = temperature• s = second = time• m = meter = length• kg = mass = how heavy
(ish)• cd = candela = how bright• mol = mole = amount of
stuff• A = ampere = electric
current
LengthLength: distance from one point to another
• SI unit = meter = m
Estimating:• 1 m ≈ 1 yard = 3 feet• 1 cm ≈ the width of your finger• 1 km ≈ 0.6 miles
TimeTime: the period between 2 events
• SI unit = second = s
• Sometimes scientists get lazy and say “hours” or “days” instead of “____ kiloseconds”
• Milliseconds, etc are really popular in sports though!
MassMass: the amount of matter in an object
• Not the same as weight!• SI unit = kilogram = kg
Weight: the pull of gravity on an object. Mass and weight only match on earth.
• In space, objects have 0 weight. • A 5 kg object on earth still has 5 kg mass in space
– just have to measure it differently!
TemperatureTemperature: energy of molecules moving
• Molecules are always moving!• Lots of moving = high temperature, hot• Almost still = low temperature, cold
• SI unit = Kelvin = K• Metric system also uses Celsius = ºC
• K = 273 + ºC
Temperature Scales
Breaking Down SI Units
• Common measurements like “volume” and “density” don’t have their own SI unit, but we can still trace their metric system name to an SI unit
• Volume = liter = Lo How much 3D space something takes upo Everything is based on water, so 1 mL = 1 cm3
o Going back to SI units, 1 L = 0.001 m3 = 1 dm3
• Density is commonly g/mL or g/cm3
o Depends if you’re talking about liquid or solido 1 g/mL = 1 g/cm3, so they’re really the same thingo Example of “mixing and matching” SI units to make a
new measurement
VolumeVolume: Measures 3D space. Metric unit is liters (L). SI unit is cubic meters (m3).
• Often use milliliters also (mL)
Estimating:• 1 coke can ≈ 350 mL• 1 cup (for baking) ≈ 250 mL• 1 gallon of milk ≈ 4 L
Measuring Volume• Taller/longer is better than
stumpyo Easier to see the
measurements
• Measure at eye level• Real number is at the
bottom of the meniscus (the dip)o Water has a big meniscus
because of adhesion – it likes to stick to other things!
o Glass and mercury have an upside-down meniscus
DensityDensity: how much mass is in a given volume. SI unit = kg/m3
• Combines mass and volume.• Common metric measurements are g/mL and g/cm3
• Things float if they are less dense than the liquid• Things sink if they are more dense• When things are the same substance, they always
have the same density. o Water is always 1 g/mL (at 4ºC)
Density Formula
Density Formula
*just like we love comic sans. Not.
Eureka!• Archimedes was asked to figure out if a crown
was made of real gold and if it was all the gold the king had given to the jeweler. o It weighed the right amount, but what if another metal
had been added to make up the difference?o He couldn’t do the normal tests because that would
break the crown
• He yelled “Eureka!” when he figured out he could use density to test ito He stepped into a bath and it overflowed – displaced
volumeo We still use his method
Unit Conversions1. Find the conversion factor.
1 km = 1000 m2. Write it as a fraction (2 ways to do this).
3. You want the same unit on the top and the bottom.
Reminders• 8th grade Scientist of the
Day presentations begin Monday
• Only presentation part• Need 2 pictures• Half a slide of bullet point
facts• Tell people if they’re right
or wrong about subjective, qualitative, etc
• Turn it into a 2-minute story
8th grade
Egg Engineering
September 18, 2015
Egg Engineering1. Find the mass of your egg.2. Find the volume of your egg. 3. Calculate the density of your egg.
4. On Monday, we’re throwing the eggs out the window! Engineer a capsule so it doesn’t break.
Goals:• Protects the egg• Works more than once (repeated trial/rigor)• You can get the egg out again
Estimates and Averages
October 5, 2015(2.2 in your books)
Accuracy vs Precision
Accurate: close to the real answer
Precise: close together
Scientists want to be accurate AND precise!
Estimates• When we’re working with really big numbers, we often
estimate instead of counting to save time• Scientists do this too! Especially with measurements.
o When we use a beaker, graduated cylinder, etc, we estimate between the smallest marks to get a more accurate number.
50 mL
100 mL
150 mL
200 mL
125 mL estimate – even though there’s no mark here!
Averages• When we have lots of estimates (or
measurements), we often want to find the average.
• The average is usually closest to the accurate (real) number.
3 Types of Averages
• Mean• Median• Mode
Mean• Most common type of average
Mean: the numerical average of a set of data
Math: add up all the numbers, then divide by how many
Computer shortcut: =average(B1:B4)
Median• Often used in geography, etc. “Median income,”
“median home price”
Median: the middle number in an ordered set of data
Math: Put the numbers in order, then find the one in the middle. If you have an even number, find the two middle numbers and divide by 2.
Computer shortcut: =median(B1:B10)
MedianMath: Put the numbers in order, then find the one in the middle. If you have an even number, find the two middle numbers and divide by 2.
Mode• In French, “mode” means fashion! If it’s
fashionable, lots of people have it
Mode: the number that appears most often in a set. You can have more than 1 answer for mode.
Math: have to look with your eyes
Computer shortcut: =mode(B1:B10)
Estimates, Averages, and
Sig FigsOctober 6, 2015
(2.2 in your books)
Percent Error• Another way to evaluate accuracy is with percent
error (% err, % E, PE)• In a good experiment, percent error is < 5%
• Sometimes you’ll see “theoretical” or “actual” instead of “true” – this is still OK
• The top half of the equation is often an absolute value I symbol |
Percent Error
• = 2.38%
RangeRange: the spread of data
Math: biggest # - smallest #
In high school/college you might have a different definition, but use this one for now.
Anomalous Data• Sometimes you make a data set and one number
looks really weird• This is anomalous data• Anomalous data is useful – it can tell you if your
equipment isn’t working right, or maybe you forgot to control for a variable
• If your averages and percent error are strange, look for anomalous data
Significant Figures• Significant figures = sig figs• How scientists tell each other
how precise a number is.• Sig figs are made up of all the
measured values (increments) + one that we estimateo Like how we measured volume in a
beaker, then estimated in between the smallest marks
• From now on, all answers must be in sig figs!
Sig the Fig
Zeroes in Sig Figs• A number that isn’t zero always counts• Zeroes in the middle always count• Zeroes at the start don’t count• Zeroes at the end don’t count unless there’s a
decimalNumber Significant
Parts# Sig Figs
45357 45357 5
405 405 3
200 200 1
200.00 200.00 5
200.5 200.5 4
0.0045 0.0045 2
10. 10. 2
More Sig Figs!
Number Significant Parts # Sig Figs
2502757 2502757 7
14.058000 14.058000 8
0.000450 0.000450 3
10000 10000 1
67 67 2
0100 0100 1
2.000 2.000 4
2.00200 2.00200 6
3850 3850 3
Adding/Subtracting Sig Figs
• Use the smallest number of decimal places (or tens, hundreds, thousands, etc)
• Round to that number!
Multiplying/Dividing Sig Figs
• Use the smallest number of sig figs• Round to that number!
More Stuff• If you are using a conversion factor like “1000 g/
1 kg” you have unlimited sig figs
• If you are using a counting number like “2 people,” you have unlimited sig figs
Homework• Worksheet! It’s double-sided and due Friday.
• All answers must be in sig figs.
• Worksheet covers 2.1 and 2.2.
GraphsOctober 12, 2015
(2.3 in your books)
More Stuff about Sig Figs
• If you are using a conversion factor like “1000 g/ 1 kg” you have unlimited sig figs
• If you are using a counting number like “2 people,” you have unlimited sig figs
Anomalous Data• Sometimes you make a data set and one number
looks really weird• This is anomalous data• Anomalous data is useful – it can tell you if your
equipment isn’t working right, or maybe you forgot to control for a variable
• If your averages and percent error are strange, look for anomalous data
• Graphs can help you spot anomalous data!
GraphsGraph: a picture of data that displays and compares information
Axis/Axes: the straight lines in a graph that you plot data on
*Outlier: a piece of data that doesn’t “fit” – often anomalous data
Not these axes
Types of Graphs• Bar graph
o Vertical or horizontalo Can have more than one series at a time (use a
legend/key if you have more than 1)o Good for counting and comparisons
• Line grapho Good for tracking changes
• Circle graph/pie charto Good for comparing parts of a wholeo Each section has to add up to 100%
Features of a Good Bar/Line Graph
• Title• X-axis• Y-axis• X-axis subtitle• Y-axis subtitle• Units• Key/legend• Scale
Features of a Good Circle Graph/Pie Chart• Title• Labels• Key• Different colors• Adds up to 100%
• What’s missing from this graph?
What does this chart tell you?
Linear vs Nonlinear
linear nonlinearNeither linear nor nonlinear
All of these are line graphs (lines connect & compare)
There’s something wrong with each of these graphs. What is it each time?
Models and Systems
October 19, 2015(2.4 in your books)
Models• Scientists and regular people use model differently
Normal person: pretty person showing off clothes OR the best example OR a representation of an object or process
Science: a representation of an object or process
Models• A good model is different from symbolism (like
in LA) because the representation has to work similarly to the real thing
• Models are used to test ideas that can’t be observed directlyo Either because of cost, ethics, time, real thing is too big,
have to test multiple ideas at once...
• What are some examples of hypotheses that must be tested with a model?
SystemsSystem: a group of parts that work together to do something
Input: thing that go into a system (material or energy)
Process: action that happens inside the system
Output: thing that comes out of a system (material or energy)
Feedback: output that changes the system in some way (because it’s being input again)
Model/System
System
Atomic Models• The atomic model
changed a lot over 100 years, but it got a little better each time
• The cloud model in your books is incompleteo Atoms have more
complicated shapes than spheres around them
o Cloud model still works to explain most concepts
What does this chart/model tell you?
Old Questions• What is the most dangerous big cat?
• What is the most dangerous fish apart from sharks?
• What kinds of water snakes are venomous?• Where is West Nile virus and what does it do?• Picture of largest snake?• How many scientific laws are there?• What is fugacity?• How do spitting cobras work?
