Chemistry basics Do they matter?. O Qualitative observations are observations made with words… O...
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Transcript of Chemistry basics Do they matter?. O Qualitative observations are observations made with words… O...
Chemistry basicsDo they matter?
O Qualitative observations are observations made with words…O The reaction smells like pumpkin pie.O The solution is royal blue.
O Quantitative observations are those that are made with numbers (measurements). O Scientists seem to prefer these if at
all possible.O The table is 47.2 inches long.
Observations:Statements of fact about what you see, feel,
smell, taste, hear.
O Observation: The man is frowning.O Inference: The man is unhappy.O Observation: The reaction is
producing a gas.O Inference: The gas being produced is
hydrogen.
Inferences: What you believe to be true, based on your observations.
Whatsamatter?O Matter is stuff. It’s anything that has
mass and volume. Some examples of matter are:
O CheeseO Badgers!!!
O An idea isn’t matter since it doesn’t have mass
Matter comes in different states
O Alaska?O No!O Minnesota?O No!!O Arizona (A very
warm place)?O No!!!
The three main states (phases) of matter are:
O Solid: Definite shape and volume.O This is because the molecules are tightly
packed and vibrating in place.O Liquid: Indefinite (changeable) shape but
definite volume.O This is because the molecules can move in
relation to one another but are still pretty tightly packed.
O Gas: Indefinite shape and volume.O Molecules are spaced out and can move
freely.
You may be wondering about that fourth state…
O It is not Utah!O It is…O Plasma!!!
Substances can be changed from one state to another.O Melting
O The change from solid to liquid. O Evaporation
O The change from liquid to gas.O Condensation
O The change from gas to liquid.O Freezing
O Liquid to solid.O Sublimation
O The change from a solid directly to a gas
When a substance changes state or shape…
O It’s still the same substanceO These changes are called physical
changes. So…O A physical change is one that
changes the shape or state of a substance without changing the nature of the substance itself.O Cutting, tearing, crumbling…O Physical changes are usually
reversible
Chemical ChangesO Chemical changes are those that
cause a reorganization of atoms and result in the formation of new substances.
O Chemical reactions result in chemical changes.
Evidences of chemical change
O OdorO Color
changeO Gas
producedO Temperatur
e changeO PrecipitateO Light
Mixtures: Substances are often found mixed with other
substances.O Mixtures fall into one of two categories.O Homogeneous mixtures have the same
composition (make-up) throughout.O SodaO Air
O Heterogeneous mixtures have a make-up that is not the same throughout.O Oil and vinegar dressingO Dirt
Remember this?O Homo = SameO Hetero = Different
Different ways to separate mixtures:
O Filtration allows some particles through a membrane (Remember your cells have a semi-permeable membrane?) and keeps others out.
O Distillation uses differing boiling points to boil off and separate different parts of a mixture.
O Chromatography uses differing polarity and solubility to separate mixtures
Measuring VolumeO Graduated cylinders are used to
measure specific volumes of liquids. The glass cylinder has marks to indicate volumes, a pouring lip, and quite often, a plastic bumper to prevent breakage.
What is A Meniscus?O A meniscus is what happens when
you put a liquid into a container. When you put water in a beaker or test tube, you see a curved surface.
Reading the Meniscus
The Meniscus: Practice #1
ANSWERO73.0 mL
10 mL graduated cylinder: Practice #2
ANSWERO6.62 mL
100 mL graduated cylinder: Practice #3
ANSWERO52.8 mL
25 mL graduated cylinder: Practice #4
ANSWERO11.52 mL
100 mL graduated cylinder: Practice #5
ANSWERO52.8 mL
What We’ve DoneO White Powder Lab
O I can use scientific methods to determine the identity of an unknownO Solubility is a physical propertyO Color change is a signal of a chemical
changeO Bubbling is a signal of a chemical
change
What We’ve DoneO Marshmallow Challenge
O I can cooperate with team members in order to complete a design challenge.O The scientific method is what
kindergarteners use to succeed.O Skills are needed first in order to
succeed in high stakes environments.O Don’t make assumptions
What We’ve DoneO Measurement worksheet
O I can provide accurate measurementsO Scientific measurements have certain
digits and estimated digits.O The marked numbers on a measuring
tool are the certain digits in a measurement
O The last digit is an estimated digit.
What We’ve DoneO Matchstick Rockets
O I can use the scientific method to design a matchstick rocketO The scientific method is a method, not
just random trialsO Learn from mistakes!O We take multiple measurements and
average measurements to:O Reduce errorO Increase reliability
What We’ve DoneO Notes on science basics
O I can identify physical and chemical properties/changesO Signs of chemical changeO States of matterO Types of observationsO Types of mixturesO Measuring
What We’ve DoneO Soda Density Lab
O I can use density to determine the identity of an unknown soda.O Density = mass/volume
Individual substances fall in two categories
O ElementsO Elements are the simplest form of matter
with unique properties. You cannot break up elements any further (easily).
O CompoundsO Compounds are substances made of two
or more elements, chemically combined.O A mixture could be made of two or more
elements, but they aren’t chemically combined!
Symbols and formulasO Each element has a symbol, kind of like
each state has an abbreviation…O The symbols make it easier to write out
chemical formulas for things like…O Water
O H2O
O MethaneO CH4
O GlucoseO C6H12O6
Chemical formulas tell you what elements are in the compound and the proportions of atoms of
each element.O H2O
O 2 hydrogen atoms, 1 oxygen atomO CH4
O 1 carbon atom, 4 hydrogen atomsO C6H12O6
O 6 carbon atoms, 12 hydrogen atoms, 6 oxygen atomsO C2H6O
O 2 carbon atoms, 6 hydrogen atoms, 1 oxygen atom
3HNO3 + C6H10O5 → C6H7(NO2)3O5 + 3H2O
O Some rules for reading chemical formulasO The symbol tells you the element.O If the is no subscript it means there is one atom.
O There is one atom of hydrogen in HNO3
O Any other subscript tells you that there are that number of atoms. O There are 10 atoms of hydrogen in C6H10O5
O A subscript outside parentheses means there are that many of the thing in the parentheses.O There are 3 NO2 units in C6H7(NO2)3O
O A coefficient (number in front) means there are that number of molecules of a compound.O There are 3 molecules of H2O
So let’s count the atoms in3HNO3 + C6H10O5 → C6H7(NO2)3O5 + 3H2O
O 3 HNO3
O 3 HO 3 NO 9 O
O C6H10O5
O 6 CO 10 HO 5 O
O C6H7(NO2)3O5
O 6 CO 7 HO 11 OO 3 N
O 3 H2OO 6 HO 3 O
Counting up those atoms brings up a nifty law…
O The law of conservation of mass.O During any chemical reaction, the
mass of the products is always equal to the mass of the reactants
O Reactants are what goes into the reaction
O Products are what comes out of the reaction.3HNO3 + C6H10O5
Reactants
C6H7(NO2)3O5 + 3H2O
Products
Remember our copper chloride reaction with aluminum?
O Al + CuCl2 + H2O Al(OH)3 + AlCl3 + Cu + H2
