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1 Steps in the Scientific Method 1.Observations quantitative quantitative qualitative qualitative 2.Formulating hypotheses possible explanation for the.

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Presentation on theme: "1 Steps in the Scientific Method 1.Observations quantitative quantitative qualitative qualitative 2.Formulating hypotheses possible explanation for the."— Presentation transcript:

1 1 Steps in the Scientific Method 1.Observations quantitative quantitative qualitative qualitative 2.Formulating hypotheses possible explanation for the observation possible explanation for the observation 3.Performing experiments gathering new information to decide gathering new information to decide whether the hypothesis is valid whether the hypothesis is valid

2 Copyright©2000 by Houghton Mifflin Company. All rights reserved. 2 Outcomes Over the Long-Term Theory (Model) A set of tested hypotheses that give an A set of tested hypotheses that give an overall explanation of some natural phenomenon. overall explanation of some natural phenomenon. Natural Law The same observation applies to many The same observation applies to many different systems different systems Example - Law of Conservation of Mass Example - Law of Conservation of Mass

3 Copyright©2000 by Houghton Mifflin Company. All rights reserved. 3 Law v. Theory A law summarizes what happens; A theory (model) is an attempt to explain why it happens.

4 Copyright©2000 by Houghton Mifflin Company. All rights reserved. 4 Nature of Measurement Measurement - quantitative observation consisting of 2 parts Part 1 - number Part 2 - scale (unit) Part 2 - scale (unit)Examples: 20 grams 6.63 Joule seconds

5 Copyright©2000 by Houghton Mifflin Company. All rights reserved. 5 International System (le Système International) Based on metric system and units derived from metric system.

6 Copyright©2000 by Houghton Mifflin Company. All rights reserved. 6 The Fundamental SI Units

7 Copyright©2000 by Houghton Mifflin Company. All rights reserved. 7 Uncertainty in Measurement A digit that must be estimated is called uncertain. A measurement always has some degree of uncertainty.

8 Copyright©2000 by Houghton Mifflin Company. All rights reserved. 8 Precision and Accuracy Accuracy refers to the agreement of a particular value with the true value. Precision refers to the degree of agreement among several elements of the same quantity.

9 Copyright©2000 by Houghton Mifflin Company. All rights reserved. 9 Types of Error Random Error (Indeterminate Error) - measurement has an equal probability of being high or low. Systematic Error (Determinate Error) - Occurs in the same direction each time (high or low), often resulting from poor technique.

10 Copyright©2000 by Houghton Mifflin Company. All rights reserved. 10 Rules for Counting Significant Figures - Overview 1.Nonzero integers 2.Zeros leading zeros leading zeros captive zeros captive zeros trailing zeros trailing zeros 3.Exact numbers

11 Copyright©2000 by Houghton Mifflin Company. All rights reserved. 11 Rules for Counting Significant Figures - Details Nonzero integers always count as significant figures has 4 sig figs.

12 Copyright©2000 by Houghton Mifflin Company. All rights reserved. 12 Rules for Counting Significant Figures - DetailsZeros Leading zeros do not count as Leading zeros do not count as significant figures has 3 sig figs.

13 Copyright©2000 by Houghton Mifflin Company. All rights reserved. 13 Rules for Counting Significant Figures - DetailsZeros Captive zeros always count as Captive zeros always count as significant figures has 4 sig figs.

14 Copyright©2000 by Houghton Mifflin Company. All rights reserved. 14 Rules for Counting Significant Figures - DetailsZeros Trailing zeros are significant only Trailing zeros are significant only if the number contains a decimal point has 4 sig figs.

15 Copyright©2000 by Houghton Mifflin Company. All rights reserved. 15 Rules for Counting Significant Figures - Details Exact numbers have an infinite number of significant figures. 1 inch = 2.54 cm, exactly

16 Copyright©2000 by Houghton Mifflin Company. All rights reserved. 16 Rules for Significant Figures in Mathematical Operations Multiplication and Division: # sig figs in the result equals the number in the least precise measurement used in the calculation = (2 sig figs)

17 Copyright©2000 by Houghton Mifflin Company. All rights reserved. 17 Rules for Significant Figures in Mathematical Operations Addition and Subtraction: # sig figs in the result equals the number of decimal places in the least precise measurement = (3 sig figs)

18 Copyright©2000 by Houghton Mifflin Company. All rights reserved. 18 Dimensional Analysis Proper use of unit factors leads to proper units in your answer.

19 Copyright©2000 by Houghton Mifflin Company. All rights reserved. 19 Temperature Celsius scale = C Kelvin scale = K Fahrenheit scale = F

20 Copyright©2000 by Houghton Mifflin Company. All rights reserved. 20 Temperature

21 Copyright©2000 by Houghton Mifflin Company. All rights reserved. 21 Density Density is the mass of substance per unit volume of the substance:

22 Copyright©2000 by Houghton Mifflin Company. All rights reserved. 22 Matter: Anything occupying space and having mass.

23 Copyright©2000 by Houghton Mifflin Company. All rights reserved. 23 Classification of Matter Three States of Matter: Solid: rigid - fixed volume and shape Liquid: definite volume but assumes the shape of its container Gas: no fixed volume or shape - assumes the shape of its container

24 Copyright©2000 by Houghton Mifflin Company. All rights reserved. 24 Types of Mixtures Mixtures have variable composition. A homogeneous mixture is a solution (for example, vinegar) A heterogeneous mixture is, to the naked eye, clearly not uniform (for example, a bottle of ranch dressing)

25 Copyright©2000 by Houghton Mifflin Company. All rights reserved. 25 Pure Substances Can be isolated by separation methods: Chromatography Chromatography Filtration Filtration Distillation Distillation

26 Copyright©2000 by Houghton Mifflin Company. All rights reserved. 26 Element: A substance that cannot be decomposed into simpler substances by chemical means. Compound: A substance with a constant composition that can be broken down into elements by chemical processes.


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