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Scientific Method and the Metric System

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Scientific Method and the Metric System

The Scientific Method

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

- Hypothesis: A testable statement
- Serves as a basis for making predictions and for carrying out further experiments
- Often “if-then” statements
- Logic

- 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

- 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

- LINEAR!!!
- It IS….complicated and messy

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Important!

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

- 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- a single measurement system adopted in 1960 by the General Conference on Weights and Measurements
- Contains 7 base units and many derived

- 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)

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?

- 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 units- combinations of SI base units

- Volume: the amount of space occupied by an object
- SI unit-m3
- Non-SI unit-Liters
- 1000mL=1L
- 1000cm3=1Liter
- 1L=1000mL=1000cm3

- Always remember:
- I DENSITY!!!!

Density=Mass/Volume

- 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

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- 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 per day= 60 minutes/1 hour x 24 hours/ day
- Answer: 1440 minutes/day

- Quantity sought= quantity given x conversion factor

- 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=1000mg

1kg=1000 grams

- 5.712 grams x 1000mg/1gram=5712milgrams
- 5.712grams x 1 kg/1000grams =.005712kg

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

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

- The density of gold is 19.3g/cm3.
- What is the volume, in cm3, of a sample of gold with mass .715kg?

- 37.05cm3
- ____cm3=.715kg x 1000g/1kg x 1cm3/19.3g