Embed Size (px)
Citation preview
Unit 1 – Tools of Chemistry
Objective: To understand the
fundamentals used throughout a study of
chemistry
Learning Goals O I can describe the scientific method.
O I can determine whether a hypothesis is valid.
O I can create a valid hypothesis.
O I can convert numbers into and out of scientific notation.
O I can convert values in the metric system.
O I can determine the number of significant figures in a value.
O I can round to the appropriate number of sig figs.
O I can calculate the density, mass, and volume of a substance given two of those values.
O I can convert between different measurements.
O I can differentiate between physical and chemical properties and changes of a substance.
O I can evaluate measurements based on accuracy and precision.
O I can determine the percent error of a value.
What is Chemistry?
O The study of matter and it’s changes
O Matter – all the stuff around you
O The stuff that makes up the universe
O Example changes – digesting food, make
synthetic fabrics, burning fuel, producing
medicines
How do we study Chemistry?
O The Scientific Method – a system of making questions, developing explanations, and testing those explanations against the reality of the natural world
O OR: an organized system helping to explain the world around us
The Scientific Method – The “Steps”
1. Identify and state the problem or question
2. Gather information and collect data
3. Make a hypothesis about the problem
1. A tentative, reasonable, TESTABLE explanation of the facts
4. Experiment!
1. Test whether or not your hypothesis is correct
5. Collect and analyze your data
6. Make a conclusion
1. Did your problem get solved or question answered?
1. If not repeat the steps
The Scientific Method – Hypothesis, Theory, or Law
O Hypothesis – a possible explanation or guess at the solution to your problem based on observation O IE: The sun caused the paint to fade more on the west side vs. the north
side of the house.
O What you think might happen in your experiment?
O Theory – summarizes a hypothesis or group of hypotheses that have been supported with repeated testing. O Are accepted as true when there is no evidence to refute it – NOT fact
O IE: Darwin’s Theory of Evolution, Einstein’s Theory of Relativity
O Law – a generalization of a body of observations O There are no exceptions in a scientific law when it is made
O IE: Newton’s Laws of Motion, Ideal Gas Laws
O Do not explain why, they just say what occurs
The Scientific Method – Moving from Hypothesis to Theory
Hypothesis
Theory
1. Identify the Problem
2. Collect Data
3. Hypothesis
4. Experiment
5. Analyze Data
6. Make Conclusions
Warm Up
O SpongeBob loves to garden and wants to grow lots of pink flowers for his pal Sandy. He bought a special Flower Power fertilizer to see if will help plants produce more flowers. He plants two plants of the same size in separate containers with the same amount of potting soil. He places one plant in a sunny window and waters it every day with fertilized water. He places the other plant on a shelf in a closet and waters it with plain water every other day.
O What did SpongeBob do wrong in this experiment? Explain.
O What should SpongeBob do to test the effectiveness of Flower Power fertilizer? Write an experiment.
Tools of Chemistry – Scientific Notation
O A way for people to deal with very large and very small numbers
O Eliminates the need to count zeros
O Takes the form of M x 10n
O 1≤ 𝑀 > 10
O n = # of decimal places
O If n is positive, the number is greater than one and the decimals need to move to the right
O If n is negative, the number is less than one and the decimals need to move to the left
Scientific Notation
O From Scientific Notation to Standard
O 1. Determine M
O 2. Determine n and which direction
O Example: 1.2 x 105
O M = 1.2
O n = 5
O So, move the decimal 5 digits to the right
O120000
Scientific Notation
O From Standard to Scientific Notation
O 1. Determine M (drop all zeros and make the
number between 1 and 10)
O 2. Determine the number of decimals places
you moved (this is n)
O Example: 0.000045
O M = 4.5
O n = -5
O 4.5 x 10-5
Scientific Notation
O Practice
O Convert the following into
Scientific Notation:
1) 98,500,000 =
2) 64,100,000,000 =
3) 0.00000056 =
4) 0.000245 =
O Answers
1. 9.85 x 107
2. 6.41 x 1010
3. 5.6 x 10-7
4. 2.45 x 10-4
Scientific Notation
O Convert the following
to standard
1. 8.9 x 109 =
2. 6.57 x 10-3 =
3. 5.98 x 1010 =
4. 1.25 x 10-5 =
O Answers
1. 8,900,000,000
2. 0.00657
3. 59,800,000,000
4. 0.0000125
Tools of Chemistry – Significant Figures
O Science uses lots of measurements and thus lots of numbers
O Types of Numbers
O Counting numbers – numbers without partial units, cannot be broken up
O Ie: 6 shirts, 5 boys, 17 chickens
O Defined numbers – pre-calculated and/or memorized conversion factors in the form of fractions
O Ie: 12inches in 1 foot = 1/3 yard
O Measured Numbers – numbers with measured units (99% of what is used in chemistry)
O Ie:1.25cm, 5.79mm
Determine the Significant Figures in Numbers
O Significant figures – digits for which actual
measurement took place, includes one
estimated digit
O Counting and Defined numbers –an infinite
number of sig figs
O Measured Numbers
O Digits 1-9 ALWAYS count
O Zeros SOMETIMES count
Determine the Significant Figures in Numbers
O Zeros
O Leading zeros – never count O 0.937 – 3 sig figs
O 00836 – 3 sig figs
O Middle Zero – always count O 101 – 3 sig figs
O .3407 – 4 sig figs
O Trailing zeros – Count IF AND ONLY IF a decimal point is present somewhere in the number O 100.0 – 4 sig figs
O .99400 – 5 sig figs
O 100 – 1 sig figs
O 1000 – 1 sig figs
Sig Fig Practice
O Type of Number?
1. 12 people
2. 5.34 gram
3. 16 tbsp in 1 cup
4. 6 cans
5. 4 qrts in l gallon
6. 3 feet in 1 yard
7. 14.75 in
8. 2.25cm
O Answers
1. Counting
2. Measured
3. Defined
4. Counting
5. Defined
6. Defined
7. Measured
8. Measured
Sig Fig Practice
O Type of Zero and Number of Sig Figs
1. 0.031cm
2. 6.00cm
3. 107.050g
4. 2.350 x 10-3mg
5. 12.05mL
6. 0.14cm
7. 5790L
O Answers
1. Leading, 2
2. Trailing, 3
3. Middle/trailing, 6
4. Trailing, 4
5. Middle, 4
6. Leading, 2
7. Trailing, 3
Sig Figs in Calculations
O Addition and Subtration
O Answer goes by the least number of sig figs in the given numbers
O Multiplication and Division
O Answer goes by the number of sig figs
O Examples
O 12.0cm + 2.45cm =
O =14.45cm
O 14.5cm
O 111cm x 22cm =
O = 2442cm
O 2440cm
Warm Up O Convert the following into
scientific notation:
1. 12000
2. 0.0025
3. 42500
4. 0.0000256
O Convert the following into standard notation
1. 1.2 x 105
2. 5.25 x 10-3
3. 2.6 x 10-3
4. 4.2 x 104
O Round the following
to 3 sig figs:
1. 125006
2. 0.0025467
3. 1.2567 x 109
4. 87964
Warm Up
O Round the following to three sig figs
1. 1.25678
2. 0.0025647
3. 0.0002389
4. 654980000
5. 456789
Tools in Chemistry – Metric Measurement
O Metric is the standard measurement system
in chemistry (and the only one we’ll use)
O SI unit (Standard Internation Unit)
O Time: s – seconds
O Length: m – meter
O Mass: kg – kilogram
O Volume: m3 – meters cubed (rarely used)
O Temperature: K – Kelvin
O Also KNOW: °C – Celcius
Met
ric
pre
fixe
s Prefix Symbol Meaning Multiplier Multiplier
Mega M Million 1,000,000 1 x 106
-
-
Kilo k Thousand 1,000 1 x 103
Hecto h Hundred 100 1 x 102
Deka da Ten 10 1 x 101
Base unit (Suffix – gram, meter, liter)
Deci d Tenth 0.1 1 x 10-1
Centi c Hundreth 0.01 1 x 10-2
Milli m Thousandth 0.001 1 x 10-3
-
-
Micro μ Millionth 0.000 001 1 x10-6 -
-
Nano n Billionth 0.000 000 001 1 x 10-9
-
-
Pico p Trillionth 0.000 000 000 001 1 x 10-12
Converting Between Units 1. Start with what you are given
2. Place the unit you want to convert to on the top of the next section and where you are converting from on the bottom
3. Set the larger unit equal to 1 1. The farther up the list the larger the unit
4. Set the smaller unit equal to 1with x number of zeros 1. X = The number of steps between the units
5. Multiply across the top and bottom
6. Divide the two answers
5cm = ______km
= 5 x 10-5km =
=
5cm
cm
km 1
100000
5 km
100000
Conversion Practice
1. How many grams are in
4kg?
2. How many millimeters
are in 2 meters?
3. The name equivalent
of 0.001m is what?
Warm Up
O Convert the following: (Show your work)
O 1.25mm = ____________ dam
O 150cL = _______________nL
O 458kg = _______________g
O 879.0µm = ______________dm
Derived Units
O Units that are made when two other units
are put together
O Ie: miles per gallon
O Types:
O Volume – 1mL = 1cm3
O Density
O Mass/volume = g/cm3 or g/mL
Density O How much matter (stuff) in a certain volume of a
substance O Ie: marshmallows are less dense, than lead
O More gaps between the matter
O Density = mass/volume O D = m/V
O Densities for solids are reported in grams per cm3, mL, or L
O Densities for liquids are reported in grams per mL or cm3
O 1mL = 1cm3
O The density of water is 1.00g/mL. O You can quickly approximate the mass of water or
something in water when the volume is known
O Ice floats b/c it has a density less than 1.00g/mL
Examples O A gold colored ring has a mass of 18.9grams and
a volume of 1.12mL. What is its density?
O What volume would a 0.871 gram sample of air occupy if the density of air is 1.29g/L?
O Pumice is volcanic rock that contains many trapped air bubbles. A 225 gram sample occupied 236.6mL. Will pumice float on water?
O A cup of sugar has a volume of 237mL. What is the mass of the cup of sugar if the density is 1.59g/mL?
Warm Up
O If the density of a gas is 0.24g/cm3 and
occupies a space of 250mL, what is the
mass of the gas?
O If a marshmallow has a mass of 15.24g and
a volume of 150.0mL, what is the density of
the marshmallow?
Chemistry Tools – Dimensional Analysis
O In science, sometimes we need to convert from a given unit into desired units
O Dimensional Analysis is just a fancy (and MUCH) easier way to set up this conversion
O Same process as when we converted metric units
O Uses conversion factors
O Ratio of two equivalent quantities using different units
O 1 hr = 60 min or 1 hour/60min or 60min/1hr
Conversion Factors O Length
O 1inch (in) = 2.54cm
O 1foot (ft) = 12 in
O 1 yard (yd) = 3ft
O 1mile (mi) = 1,760yd
O 1mile = 1.609km
O 1mile = 5,280
O Time
O 1minute (min) = 60 seconds (s)
O 1 hour (hr) = 60 min
O 1 day = 24 hr
O 1year (yr) = 365 days
O Volume
O 1 cup (c) = 16tbsp.
O 1pint (pt) = 2c
O 1quart (qt) = 2pt
O 1gallon (gal) = 4qt
O 1gal = 3.78L
O Mass
O 1 pound (lb) = 16 ounces (oz)
O 1oz = 28.35grams
O 2.2lb = 1kg
O 1ton = 2,000lb
Steps O Place the given quantity on the top of the ladder
O Place the unit you want to convert to on the top and the unit you want on the bottom
O What is the conversion factor between the two units?
O Cross out the units that cancel
O Multiply across the top and bottom
O Divide the top from the bottom
2.5 hours = ? minutes
2.5 hr min
hr
60
1
=
=
150 min
1 = 150 min
Helpful Hints
O Figure out what unit(s) you are converting to and
from
O Write them down
O Set up the problem using your units first
O Don’t forget, you can do this in several steps, if
you don’t have a conversion factor between two
units find a unit they have in common
O If the units don’t cancel and leave you with your
desired unit, something is wrong
Practice
1. If your heart beats at a rate of 72 beats per minute, how many times will your heart beat each year?
2. Basketball player Shaquille O’Neal weighs 310pounds. What is his weight (mass) in kilograms?
3. How many days would it take you to count 200,000 items assuming you count one item every second, without stopping?
4. Since 5280ft = 1 mile, and 12in = 1ft, how many inches are in 3.5miles?
Evaluating Measurement O Percent Error – how far away from the accepted value
O %error = 𝑎𝑐𝑐𝑒𝑝𝑡𝑒𝑑 𝑣𝑎𝑙𝑢𝑒 −𝑒𝑥𝑝𝑒𝑟𝑖𝑚𝑒𝑛𝑡𝑎𝑙 𝑣𝑎𝑙𝑢𝑒 𝑥 100
𝑎𝑐𝑐𝑒𝑝𝑡𝑒𝑑 𝑣𝑎𝑙𝑢𝑒
O Qualitative Measurement – a description without any
measurement tools
O Color, shape, texture, etc
O Quantitative Measurement – a description of an
object with numbers using units
O Length, density, mass, etc
O Something you can place on a graph
Evaluating Measurement
O Accuracy – the Closeness of a quantitative
measurement to its accepted value
O Precision – the closeness of a set of values
in relationship to each other
Uncertainty in Measurement
O Using Sig Figs, sometimes accuracy and precision are lost
O IE: two population signs say the follow
O Littleton – Population 784
O Largeton – Population 6100
O Which of these is a more precise reporting of the population based on sig figs?
O The same rules apply to measurement in chemistry
O You need to measure in the number of sig figs the tool is graduated in plus one estimated unit
Uncertainty in Measurement O To determine the estimated digit
O When measuring and the measurement isn’t
directly on a line, you must round to the next
closest significant figure
O This means you must determine what the
increments stand for and what the next
increment will tell you
Measurement Uncertainty
O When measuring volume, you eye level
should be looking squarely at the bottom of
the meniscus
O The crescent shaped liquid surface caused
by the attraction of the liquid to the container
Chemistry Basics– Physical & Chemical
O Physical Properties – properties of an object
that can be changes WITHOUT changing the
objects chemical components
O Temperature, state, length, mass, volume,
pressure, velocity, area, color, texture
O Physical Change – an alteration of a
substance that DOES NOT change into
something new
O Heating, shaping, cutting, changing state,
O Chemical Properties – describe the ability of an object to undergo a chemical change (rxn) forming something completely new
O Reactivity, toxicity, preferred type of chemical bonds, oxidation state, flammability
O Chemical Changes – reactions (this is the fun lab work of actually changing an object into something new)
O Digestion, combustion, explosions,
O Clues to a chemical change: color change, productions of a new substance (solid, liquid or gas), energy absorbed or released, not easily reversed
Chemistry Basics– Physical & Chemical
