Scientific Method

A method by which natural phenomena are explained

How would you describe thunder & lightning?

A mythological being?

A dream?

Or science?

Scientific MethodRules of the Game

1. One assumption: the phenomena to be described are able to be described by natural phenomena.

Steps of the Scientific Method 1. Make observations on something

interesting 2. Form a hypothesis, an educated

guess 3. Perform experiments to disprove

the hypothesis 4. Reevaluate the hypothesis

Conducting an Experiment

Control group– a group in an

experimental study that receives no special treatment

Experimental group– a group receiving

special treatment in an experimental study

So what’s the difference between these two groups anyway?

Independent variable– a variable that is

manipulated or modified in an experiment

– CAUSE

Dependent variable– a variable in an

experimental study that may change as a result of the manipulation of the independent variable

– EFFECT

We’ve got to do what? Graph it?!?!

Independent variable– x axis

Dependent variable– y axis

X

Y

Once the reevaluation is over . .

Theory: a tested explanation of natural phenomena

Law: a concise statement or mathematical equation about a relationship, i.e. E=mc2

Qualitative versus Quantitative

How would you describe this picture?

Possible ways to describe it:

Number of people

Number of decorations

Number of lights

Appearance of people

Type of decorations

Type of wall coverings

What does this mean?

Quantitative–a physical

description involving the numbers of a situation

Qualitative–a physical

description involving the physical appearance of a situation

While it may seem that these two are opposite, they are really the halves of the whole description.

Application to a Candle

What types of observations can we make about a candle? How about in order to describe how a candle is able to keep a flame and give off light?

Candle Activity

The Metric System

History:

Early measurements reflected the size of the king or queen of the land

The problem was that as the king’s size changed so did the basis for measurement

In 1670, Gabriel Mouton devised a system of measurement based upon standards instead of the kings’ features

The Metric System

Metric vs. English

easier to use since “nonexact” measurements are expressed as decimals, not fractions

easier to use since conversions are all based upon powers of 10

Metric Base Units

Metric Prefixes (Greater than)

Metric Prefixes (Less Than)

So how do we use this?

1000 g = 1 kg 100 m = 1 hm .01 m = 1 cm .001m = 1 mm

Metcetera (Wet to Dry Volume)

1.0 cm3 = 1.0 mL 1.0 dm3 = 1.0 L

Conversions

Bigger Base Unit Smaller k, h, da m, l, g d, c, m

Convert

5 dm to cm

5 mm to cm

5 km to dam

5 hm to km

2 step conversions

5 km to mm

4 cm to dam

Measurement Lab

Station 1: Using a ruler– Never measure from the end

Measurement Lab

Station 2: Using a graduated cylinder– Meniscus: the

curved line of liquid that is read for measurement in certain types of glassware

Measurement Lab

Station 3: The Pipette Using a known piece

of glassware to calibrate an unknown piece of glassware

Measurement Lab

Station 4: Using different types of pipettes– Mohr and Volumetric

Measurement Lab

Station 5: Using the buret– Only glassware

that is graduated upside down

Measurement Lab

Station 6: Using a thermometer

Measurement Lab

Station 7: Using a balance– How many

digits do you write down?

Measurement Lab

Station 8: Using a barometer– Used to

measure pressue

– Units: mm Hg

Scientific Notation

Shorthand way of writing numbers without having to use placeholder zeros

1,000,000 = 1 x 106

0.005 = 5 x 10-3

Scientific Notation

Rules:1.The number in front of the decimal must be

between 1 and 9.

2.In order to get only one number in front of the decimal you will need to move the decimal

1. If you move to the right, the exponent is negative

2. If you move to the left, the exponent is positive

Write these in scientific notation:

0.00345

1,002,000,000

0.34

403

Write these in standard notation:

2 x 10-2

3 x 104

5.67 x 10-3

4.56 x 102

Significant Digits

Numbers (digits) that show the degree of accuracy and precision of a measurement

Accuracy: How close a measurement is to the accepted value

Precision: Repeatability of a set of measurements to be similar in value

Atlantic-Pacific Rule

Atlantic:– If the decimal is absent, start counting from

the right (Atlantic Ocean) side with the first nonzero. Once you start counting keep on counting.

– 2040

Atlantic-Pacific Rule

Pacific

– If the decimal is present, start counting from the left (Pacific Ocean) side with the first nonzero. Once you start counting keep on counting.

– 0.034500

How many significant digits are in these numbers?

2,339,009

0.00987

0.005600

203040

Math with Significant Digits

When you add and subtract simply line up the decimals and keep the fewest places after the decimal in your answer.

234.0098 + 3.01 = ?

234.0098 – 30.0 = ?

Math with Significant Digits

When you multiply and divide, your answer should have the fewest digits shown in the original numbers.

2.2 x 3 = ?

2.100 / 7.0 = ?

Density

A ratio of a substance’s mass to it’s volume A constant value for a given substance no

matter how much mass or volume D = m/v Units are a combination of mass and

volume, ex. g/mL or kg/L

A rock with a mass of 25.0 g has a volume of 5.0 mL, as determined by water displacement. What is the density of the rock?

A wooden block with measurements of 2 cm, 3.0 cm, and 0.5 cm has a mass of 9.00 mg, what is the density of the wooden block?

Density Gradient Practical