Scientific Method and the Metric System

The Scientific MethodScientific method: a logical approach to solving problems by observing and collecting data, formulating hypotheses, and formulating theories that are supported by data

Observing and Collecting Data

Observing: the use of the senses to obtain information Qualitative-descriptive Quantitative-numerical

System: a specific portion of matter in a given region of space that has been selected for study during an experiment or observation

Formulating Hypotheses Hypothesis: A testable statement

Serves as a basis for making predictions and for carrying out further experiments

Often “if-then” statements Logic

Testing Hypotheses Requires experimentation that provides

data to support or refute a hypothesis or theory

If the data does not support the predictions, then the generalizations on which the predictions were based must be discarded or modified

Theorizing When the data from experiments confirm the

hypothesis, scientists use models to explain what they observed

Model: in science is more than a physical object: it is often an explanation of how phenomena occur and how data or events are related. If a model successfully explains a phenomena, it

may become part of theory Theory: broad generalizations that explains a

body of facts or phenomena

Scientific Method is NOT…

LINEAR!!! It IS….complicated and messy

Versions of the scientific method

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More versions of the scientific method

Important!

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Units of Measurement You are constantly measuring things

(whether you realize it or not)- what units are you most familiar with?

A few ideas

Height- feet/inches (5’8”) Temperature- F not Celsius Baking- 1 cup, 1 tablespoon, 1 teaspoon Drinks- 12 ounces (can of soda) Weight- pounds (???lbs) Distance- miles

SI Measurement SI- a single measurement system

adopted in 1960 by the General Conference on Weights and Measurements Contains 7 base units and many derived

SI Base Units

QuantityQuantity Symbol

Unit name

Unit abbreviation

Length l meter mMass m kilogram kgTime t second sTemperature T kelvin kg

Amount of substance n mole molElectric current I ampere ALuminous Intensity Iv candela cd

Mass Mass- measure of the quantity of matter SI unit-kilogram Weight- measure of the gravitational pull

on matter Mass does not depend on such as attraction Which is why your WEIGHT changes if you

go to the moon (1/6 to be exact)

Mountain Dew Mass Demo

Who drank a soda yesterday

What was it?Did you notice the sugar content?

What was the unit of measure in?

Can you visualize how much sugar you are actually consuming in a 12oz of soda?

Length SI unit- meter United States-miles Everyone else-kilometers

How tall are you in meters?!

1 foot = 0.3048 meters

If you are 5’4” so in meters you are 1.6256m

Derived SI Units Derived units- combinations of SI base

units

QuantityQuantity

Symbol Unit nameUnit abbreviation Derivation

Area A square meter m2 length x widthVolume V cubic meter m3 length x width x height

Density Dkilograms per cubic

meter kg/m3 mass/volume

Molar mass M kilograms per mole kg/molmass/amount of

substance

Concentration c moles per liter m3amount of

substance/volume

Molar Volume Vm

cubic meters per mole m3/mol

volume/amount of substance

Energy E  Joule J force x length

Volume Volume: the amount of space occupied

by an object SI unit-m3

Non-SI unit-Liters 1000mL=1L 1000cm3=1Liter 1L=1000mL=1000cm3

Density Always remember:

I DENSITY!!!!

Density=Mass/Volume

Density Density: the ratio of mass to volume or

mass/volume SI derived units: mass (kg) and volume (cubic

meter) kg/m3

Characteristic physical property of a substance Density varies with temperature; generally

density decreases with increasing temperature

SI prefixes

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Conversion Factors Conversion factor: a ratio from the

equality between two different units that can be used to convert from one unit to the other

How many minutes are in a day?

1440 minutes

How did you do it?

Minutes in a day _____ minutes per day= 60 minutes/1

hour x 24 hours/ day Answer: 1440 minutes/day

Handy equation Quantity sought= quantity given x

conversion factor

Derive conversion factors Derive conversion factors if you know the

relationship between the unit you HAVE and the unit you WANT

Example: Express a mass of 5.712 grams in milligrams and in kilograms

Hint:1gram=1000mg1kg=1000 grams

Answer 5.712 grams x

1000mg/1gram=5712milgrams

5.712grams x 1 kg/1000grams =.005712kg

Practice makes perfect Complete the following conversions: 10.5g=____kg 1.57km=____m 1.2L=_____mL 358cm=_____m 3548.6mL=_____cm3

answers Complete the following conversions: 10.5g=.0105 kg 1.57km= 1570 m 1.2L=1200 mL 3548.6mL= 3548.6 cm3

Density problem The density of gold is 19.3g/cm3. What is the volume, in cm3, of a sample

of gold with mass .715kg?

Answer 37.05cm3

____cm3=.715kg x 1000g/1kg x 1cm3/19.3g