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Welcome to: CHEMISTRY. The Study of the Universe!. When Doing Labs. Use the Scientific Method – accepted method for scientists to explain how things work Steps: State Problem and Collect Data Formulate Hypothesis Perform Experiments. - PowerPoint PPT PresentationTRANSCRIPT
The Study of the Universe!
When Doing Labs• Use the Scientific Method – accepted
method for scientists to explain how things work
• Steps:
1.State Problem and Collect Data2.Formulate Hypothesis3.Perform Experiments
Step 1: Collecting Data [Two Types]Quality vs. Quantity?Qualitative (Quality)
NO NUMBERS involved
Ex. The sky is blue
Ex. The solution is cloudy
Quantitative (Quantity)
NUMBERS involved
Ex. The solution is 34.50 grams
Ex. Water boils at 100 degrees
Step 2: Hypothesis• Hypothesis – a
POSSIBLE explanation for why something happens
• Observations are NOT hypotheses
• Ex. the solution is cloudy (observation)
• Ex. the solution is cloudy because it is contaminated (hypothesis)
Step 3: ExperimentsUse controls and
variables
Control – the constant
Variable – the thing that changes in the experiment
Lake vs. Ocean
Perform multiple Trials – attempts at experiment
When Measuring Liquids…Meniscus – curve at
upper surface of liquid
Measure liquids HERE
Quick Quiz #1The scientist notes that there are 42 eggs in
the basket. Is this a qualitative or quantitative measurement?
What is a variable?
When measuring volumes of liquids, what is the curved line that you use?
Types of ChemicalsFlammables and Combustibles –
chemicals that can catch on fire
Corrosives – things that damage/burn through skin tissue
Pressure – chemicals that are dangerous at different pressures
FlammablesEx. Bunsen Burners
(used in this lab!)
Precaution: WEAR GOGGLES!
Similar but NOT the same as COMBUSTABLES – catch fire at HIGH temperatures
Handling Boiling/Hot ChemicalsDON’T TOUCH
WITH BARE HANDS!
USE TONGS or “Hot Hands”
CorrosivesCorrosives = acids
and bases that can damage skin
Precautions: WEAR GLOVES, PROTECTIVE CLOTHING (long-sleeves) AND GOGGLES
If Corrosive Chemicals Get On Skin…RINSE
IMMEDIATELY
continuous running water (NOT SOAP)
Eyes – RINSE IMMEDIATELY for at least 5 minutes under eye wash.
Broken GlassAccidents happen (no,
really)
Broken glass (beakers, test tubes, thermometers, etc) LET ME KNOW ASAP!
Move away from station until glass is cleared
Warm Up #5
Converting Units
Amurrica vs. The WorldAmurrica The Rest of the World
Distance: Inches, Feet, Miles
Volume: Cups, Quarts, Gallons
Mass: Ounces, Pounds, Tons
WHY DOES THIS STILL EXIST?
Distance: Millimeters, Meters, Kilometers
Volume: Milliliters, Liters, Kilometers
Mass: Milligrams, Grams, Kilograms
THIS IS WAY EASIER.
The Metric System Prefixes
Going from BIG to smallEx: 145.8 Decimeters (dm) into Kilometers
(km)
FOUR decimal places from DECI to KILO
Move Decimal FOUR PLACES LEFT
145.8 dm = 0.01458
Quick Quiz #3Convert the following:
34.67 mL = ____ L?
4.903 hg = _____ dg?
John travelled a distance of 290480000 millimeters. How many kilometers is that?
Density and SpeedDensity: Concentration
of a substance in a given space
Mass over Volume (m/v)Ex. g/mL, kg/L, etc.
Speed: rate at which an object moves
Distance over Time (d/t)Ex. m/s, km/hr, etc.
Dimensional Analysis Intro.Problem #1: Karla has a substance with a
density of 4.68 g/mL. How many g/cL is that?
Problem #2: James was measuring the speed of a car in meters per second. If he found that a car was moving at the speed of 5.50 m/s, how many km/hr is that?
On your Calculator:500 x 500 = 250000. (that’s a
big number!)
.005 x .005 = 2.5-05 (WTF?)
Why does the second answer look like this?
Scientific NotationScientific Notation – way of
making REALLY big or REALLY small numbers easy to read.
General Form:
M x 10n
M = number between 1 and 10n = number of decimal places
you move
2 500 000 000.9 8 7 6 5 4 3 2 1
Step 1: Insert an understood decimal pointStep 2: Decide where the decimal must end up so that
one number is to the leftStep 3: Count how many places you bounce the
decimal pointStep 4: Re-write in the form M x 10n
2.5 x 109
The exponent is the number of places we moved the decimal TO THE LEFT.
Quick Quiz #1Multiply 123456 x 7890 on your calculator
1.What was your answer?2.Write your answer in scientific notation.
Do the same for the following problems:
1.98765 x 43210 = ?2.10000 x 892800 = ?3.90 x 9 = ?
0. 0 0 0 0 2 5 0. 0 0 0 0 2 5 1 2 3 4 5 1 2 3 4 5
WITH NUMBERS SMALLER WITH NUMBERS SMALLER THAN ONETHAN ONE……
2.5 x 10-5
The exponent is negative because the number we
started with was less than 1.
Review:WITH NUMBERS WAY BIGGER THAN 1
MOVE DECIMAL TO THE LEFTn VALUE WILL BE A POSITIVE NUMBER
WITH NUMBERS WAY SMALLER THAN 1
MOVE DECIMAL TO THE RIGHTn VALUE WILL BE A NEGATIVE NUMBER
Part 1
What does that mean?Dimensional Analysis– Converting one thing to another
Used in chemistry (converting units of mass/distance/volume)
BUT YOU DO THIS IN REAL LIFE ALL THE TIME
Convert the following:How many seconds in a
minute?1 minute = ___ seconds
How many quarters in a dollar?1 dollar = ___ quarters
How many points do you score in a touchdown?1 touchdown = ___
points
OR
OR
OR
1 min.
1 min.60 sec.
60 sec.
$1
$1
Example ProblemJulia measured the length of Catherine’s hair.
She found out that her hair was 24 inches long. How many feet is that?
First ask yourself:What is your starting amount?What are you converting to?How many inches are in a foot?
Reminder: UNITSDO NOT LEAVE ANY NUMBER NAKED!
IT NEEDS A UNIT.
GOAL: CANCELLING OUT UNITS
One unit label on top, the other on bottomFeet will cancel out (Feet x Feet) = Feet2
Feet
System to Do This:DIMENSIONAL ANALYSISStarting amount, draw
a line underneath it.
Draw a vertical line next to it.
One unit on top, other on bottom
Multiply stuff on topMultiply stuff on
bottomDivide Top and Bottom
Quick Quiz #2Convert the following using Dimensional
Analysis:
12 feet = ___ inches? (1 foot = 12 inches)
9 touchdowns = ___ points? (1 TD = 6 points)
4 apples = ___ oranges? (1 apple = 3 oranges)
Word ProblemsRead the problems carefully
Underline important information (things with numbers)
Know what units you start with
Know what units you need to end with
Example ProblemSteven was REALLY thirsty, so he wanted to buy some water bottles from Mr. Lockett. He ended up buying 4 water bottles. If each water bottle costs $2, how much money (in dollars) did he spend?
Underline Important Info.Steven was REALLY thirsty, so he wanted to buy some water bottles from Mr. Lockett. He ended up buying 4 water bottles. If each water bottle costs $2, how much money (in dollars) did he spend?
Solve Using Dimensional Analysis
4 Water Bottles
1 Water Bottle
2 Dollars
Starting Materials (INCLUDE UNITS)
=
Convert One Thing to Another
4 x 2
1
= 8 Dollars
Quick Quiz #3: SOLVE USING DIMENSIONAL ANALYSIS
1. Guadalupe was bored and wanted class to be over. Mr. Lockett said class was over in 90 minutes. How many hours is that? (1 hour = 60 minutes)
2. For some reason Esteban really wanted quarters. He gives the cashier a 5 dollar bill. How many quarters will he get from this 5 dollar bill? (1 dollar = 4 quarters)