Scientific method
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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

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Scientific method

Scientific Method

-Logical approach to solving problems

-not the only method


Scientific method1

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

Diet coke and mentos guys I

  • http://www.youtube.com/watch?v=hKoB0MHVBvM

  • Diet coke and mentos guys II

  • http://www.youtube.com/watch?v=I48hAOh3zJY&safe=active

  • Myth busters

  • http://www.youtube.com/watch?v=LjbJELjLgZg


Write up

Write up

  • 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.


Experiment

Experiment

  • 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)


Hypothesis vs theory

Hypothesis VS. Theory

  • 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.


Observations

Observations

  • Quantitative – involves numbers

  • Qualitative – involves word descriptions


Measurement

Measurement

  • 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 units

SI UNITS

  • 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

  • http://www.i-am-bored.com/bored_link.cfm?link_id=47378


Bellwork podcast

Bellwork podcast

http://www.youtube.com/watch?v=xbcn7FR3pdg&feature=player_embedded


Density mass volume

Density= mass/volume

  • 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?


Answers

Answers:

  • 2.7 g/cm3

  • 1.14 g

  • 5.60ml

  • 37.0 cm3


Percent error

Percent error

  • 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%


Dimensional analysis

Dimensional Analysis

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

  • quantity given X conversion factor = Quantity sought

  • See pg 41.


Scientific method

  • 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?


Significant figures

Significant figures

  • 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


Determining the number of sig figs in a number

Determining the number of sig. figs. in a number.

  • 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.


Examples

Examples:

Answer: 3

  • 0.00682

Answer: 2

  • 1.0

Answer: 2

  • 60.

Answer: 2

  • 1.0 x 102


Scientific method

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

  • Start with the first nonzero digit.

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


Examples1

Examples:

Answer: 1

  • 60

Answer: 3

  • 603

Answer: 3

  • 6030


Rules for addition and subtraction

Rules for Addition and Subtraction

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.


Examples2

Examples:

The least precise number

is 2.02. It has sig. figs.

out to the hundredths

place. Therefore the

answer will have sig. figs.

out to the hundredths

place.

The least precise # (1.0236)

has decimals carried out 4

places. Therefore the

answer will have sig. figs.

carried out 4 decimal places.


Significant figures in calculations

Significant Figures in Calculations:

Rules for Multiplication and Division

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


Examples3

Examples:

The number with the

least # of sig. figs. has

2 sig. figs. Therefore, the

answer must have 2.

The number with the least

# of sig. figs. has 3 sig.

figs. Therefore, the

answer must have 3.


Powers of ten

Powers of Ten

http://www.youtube.com/watch?v=0fKBhvDjuy0&feature=youtu.be


Graphs

graphs

  • 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


Graphs1

graphs

  • k= xy

  • Inversely proportional

  • When x gets bigger y gets smaller

  • Graph is a hyperbola


Practice test

Practice Test

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

  • Answer 1Hm/100,000mm


Practice test1

Practice Test

  • 0.046550 g rounded to two sig figs.

  • 0.047 g

  • 0.000406 How many sig figs?

  • 3


Practice test2

Practice Test

  • 0.0450 mm how many sig figs?

  • 3

  • 3020 cm How many sig figs?

  • 3


Practice test3

Practice Test

  • 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


Practice test4

Practice Test

  • 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


Practice test5

Practice Test

  • 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


Practice test6

Practice Test

  • Which equation represents a direct proportion?

  • A. xy=k

  • B. X=k/y

  • C. y=k/x

  • D. k=y/x

  • Answer D


Test review

Test Review

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


Test review1

Test Review

  • 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


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