Observation - What is evidence? Any observation of Natural Phenomena –Qualitative Use your senses...

Observation - What is evidence?• Any observation of Natural Phenomena

– Qualitative• Use your senses

• Ex. Texture, color, smell, taste, sound

– Quantitative• Measured values

• Ex. Weight, volume, length, temperature

• Measurements, Verifiable observations, etc.• This is how we know what we know!

Organization of Matter• Continuous

– Aristotle

• Discontinuous– Democritus

• (470-400 B.C.)

– Dalton • (1808)

– Joseph Gay-Lussac • (1805)

Solid, liquid, and gas states

States of Matter

David Schultz/Getty Images

Water can be found in the solid, liquid, and vapor (gaseous) forms simultaneously.

SOLIDS

• Highly structured - many are crystalline

• High degree of interparticle forces

LIQUIDS

• Not structured - particles flow readily

• Significant degree of interparticle forces

GASES

• Not structured - particles flow rapidly

• Very low degree of interparticle forces

The green color of the Statue of Liberty results from the reaction of copper with the components of air.

Andy Levin/Photo Researchers

Changes of Matter

"Good" versus "Bad" Properties for a Chemical Substance

Changes of Matter• Physical - a change which does

NOT alter the composition of a substance.

• Chemical - a change which alters the composition of a substance.

Physical Change• EX. Cutting, breaking, tearing etc.• EX. Phase changes• EX. Water melts at ~ 0˚C and boils at ~ 100˚C.

– Therefore, water is a ______ at 85˚C.– The change of a substance from one phase to

another involves either a gain or loss of ENERGY from the system.

Physical Changes of Matter

The melting of ice cream is a physical change involving a change of state; solid turns to liquid.

Phil Degginger/Color-Pic

(a) A magnet and a mixture consisting of potassium dichromate (orange crystals) and iron fillings.

(b) The magnet can be used to separate the iron fillings from the potassium dichromate.

Physical Changes

Phase Changes

• Solid to liquid = Melting

• Liquid to solid = Freezing

• Liquid to gas = Vaporization

• Gas to liquid = Condensation

• Solid to gas = Sublimation

• Gas to solid = Deposition

As a result of chemical change, bright steel girders become rusty when exposed to moist air.

Chemical Changes of MatterThe green color of the Statue of Liberty results from the reaction of copper with the components of air.

Properties & Changes of Matter

Organization of Matter

How could the appearance of each type of chemical change?

Outward physical appearance of naturally occurring elements

Hg As S

Bi I2

Mg

Laws of Matter• Law of Conservation of Mass

– Amount of matter does not change during a physical or chemical reaction

• Law of Definite Proportions– In samples of a chemical compound, the masses of the elements

are always in the same ratio

• Ex. H2O

• Law of Multiple Proportions– Two or more elements may form more than one compound.

• Ex. H2O and H2O2

Studying Matter - Chemistry

• Requires a scientific approach– Scientific method– Nature of science

• Requires use of a measurement system and tools for measuring

• Requires displaying and explaining experimental results– Variables (dependent vs. independent)

& controls

Metric System• Be able to measure/calculate mass, volume,

distance, density & temperature

Measuring Length The scale on a

measuring device determines the magnitude of the uncertainty for the recorded measurement.

• Include all certain digits plus one uncertain digit in your measurement!– significant (figures)

digits (sd)

Volume/Space

• Liter (L) 1 L = 1 dm3

• Milliliter (mL) 1 mL = 1 cm3 = 1 cc

• Microliter (L) 1 L = 1 mm3

Measuring Volume

• Note the type of liquid• Indicate which kind of

meniscus it is (concave or convex)– Concave: read the bottom of

the meniscus (WATER)– Convex: read the top of the

meniscus (MERCURY)

• Include all certain digits plus one uncertain digit in your measurement!– sd

Mass/Weight

• A gram is defined as the mass of 1 ml of water at 4˚C. Therefore, water has a density of 1 g/mL at 4˚ C.

Measuring Mass

• Check that the scale is TARED prior to placing anything on it.

• Include all certain digits plus one uncertain digit in your measurement!– sd

Converting between Measurement Units

Conversions 453.6 graham crackers = 1 pound cake

2000 mockingbirds = 2 kilomockingbirds

Distance Conversion

It is experimentally determined that 1 inch equals 2.54 cm, or 1 cm equals 0.394 inch