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# Scientific Method - PowerPoint PPT Presentation

Scientific Method. -Logical approach to solving problems -not the only method. Scientific Method. State Problem in question form Gather Information Hypothesis Experiment Data Conclusion- answer to the problem. Diet Coke and Mentos Guys. Diet coke and mentos guys I

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### Scientific Method

-Logical approach to solving problems

-not the only method

• State Problem in question form

• Gather Information

• Hypothesis

• Experiment

• Data

• Conclusion- answer to the problem

Diet coke and mentos guys I

• Diet coke and mentos guys II

• Myth busters

• State the problem: What combination of soda and mints will produce the highest fountain?

• Gather info: What you already know or have looked up prior to this exp.

• Hypothesis: If I use ____ soda and ___ mints I will get the highest fountain.

• Experiment: Procedure step by step

• Data: organize and include in your write up = get from moodle

• Conclusion: 1) Restate your hypothesis as valid or not. 2) List sources of error. 3) Suggest ways to improve this experiment. 4) Suggest some other experiments with mints and soda.

• Must have a control (what you compare to)

• Must test only one experimental variable

• Involves an independent variable (the one that is manipulated or changed by the experimenter)

• Involves a dependent variable (results of changing the independent variable)

• An hypothesis is a prediction. Experiments are done to prove or disprove an hypothesis.

• A theory is a broad generalization. It is an explanation based on numerous repeated experiments.

• A model can be used as an explanation of data or phenomena observed over many experiments.

• Quantitative – involves numbers

• Qualitative – involves word descriptions

• A comparison between an unknown quantity and a standard

• Standards kept at the Bureau of Weights and Measurement in Sevres, France and Gaithersburg, Maryland USA

• SI = Systeme Internationale d’Unites

http://physics.nist.gov/cuu/Units/current.html

http://physics.nist.gov/cuu/Units/index.html

http://physics.nist.gov/cuu/Units/kilogram2.html

(kilogram)

• Fundamental or standard units (See pg. 34)

• Derived units - combo of standard units

• examples: density g/cm3, molar mass kg/mol

• SI prefixes: memorize table on pg 35

• A sample of metal has a mass of 8.4 g. The volume of the sample is 3.1 cm3. What is the density?

• Diamond has a density of 3.26 g/cm3. What is the mass of a diamond with a volume of 0.351 cm3?

• What is the volume of a sample of liquid mercury that has a mass of 76.2 g, given that the density of mercury is 13.6 g/cm3?

• The density of gold is 19.3 g/cm3. What is the volume of a sample of gold that has a mass of 0.715 kg?

• 2.7 g/cm3

• 1.14 g

• 5.60ml

• 37.0 cm3

• Percent error = Value exp – Value accept X 100%

value accept

• density of Al = 2.7 g/cm3

• You calculate Al = 1.7 g/cm3

• % error = 1.7 g/cm3 – 2.7 g/cm3 X 100%

2.7 g/cm3

• % error = 37%

• A technique that allows you to use units to solve a problem.

• quantity given X conversion factor = Quantity sought

• See pg 41.

• Precision-degree of exactness

• -depends on tool used

• -estimate last digit

-repeatable

• Accuracy-do results agree with a standard

• -calibrate with a known standard

• -is it the correct answer?

• Tell the precision of the instrument

• The last digit is the estimated digit (that is why the last zero is important!)

• See rules pg 47

• Can only express an answer as the least precise measurement

• Picture a map of the U.S.

• If a decimal point is present, count from the Pacific side.

• Start counting with the first nonzero digit.

• All digits from here to the end, including zeros, are significant.

• 0.00682

• 1.0

• 60.

• 1.0 x 102

• If the decimal point is absent, start counting from the Atlantic side.

• All digits from here to the end, including zeros, are significant.

• 60

• 603

• 6030

The number of sig. figs. is determined by the location of digits in the number with the largest uncertainty, not the number of significant figures in the number.

The least precise number

is 2.02. It has sig. figs.

out to the hundredths

place. Therefore the

out to the hundredths

place.

The least precise # (1.0236)

has decimals carried out 4

places. Therefore the

carried out 4 decimal places.

Rules for Multiplication and Division

The answer contains no more significant figures than the least precise number.

The number with the

least # of sig. figs. has

2 sig. figs. Therefore, the

The number with the least

# of sig. figs. has 3 sig.

figs. Therefore, the

• k= y/x

• Directly proportional

• When y gets bigger so does x

• Create a straight line when graphed

• When rearranged: y=kx

• Which is the formula for a line: y=mx + b

• k= xy

• Inversely proportional

• When x gets bigger y gets smaller

• Graph is a hyperbola

• When converting mm to Hm what is the conversion factor?

• 0.046550 g rounded to two sig figs.

• 0.047 g

• 0.000406 How many sig figs?

• 3

• 0.0450 mm how many sig figs?

• 3

• 3020 cm How many sig figs?

• 3

• When 66.4 is divided by 3.00 How many sig figs will be in the answer?

• 3

• When 1.15 g, 2.667 g and 5.0 g are combined how many decimal spaces will the answer show?

• one

• Find the product of 15 cm and 2.3 cm. Express in proper sig figs.

• 34 cm

• Round to four sig figs 2.3456789 X 105

• 2.346 X 105

• Write in scientific notation 0.00000032 g

• 3.2 X 10-7

• 1.85 X 10-6 divided by 7.8 x 103 expressed to two sig figs is

• 2.4 x 10-10

• Which equation represents a direct proportion?

• A. xy=k

• B. X=k/y

• C. y=k/x

• D. k=y/x

Know the following:

• Steps of Scientific Method

• Qualitative vs. quantitative

• Theory and hypothesis

• SI base units and derived units

• Precision vs. accuracy

• Independent variable vs. dependent variable

• The order of the SI prefixes

• Why are there significant figures?

• Why is density a physical characteristic?

• Calculate: Density and percent error

• Count significant figures, calculate and express answer in proper sig. figs.

• Rounding

• Using conversion factors

• graphs