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Measurement & Scientific Tools

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Biblical Reference He measured its wall and it was 144 cubits thick, by man's measurement, which the angel was using. Revelation 21:17

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Description & Explanation A description is a spoken or written summary of observations. An explanation is an interpretation of observations. When you explain something, you try to interpret your observations, which can lead to a hypothesis.

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The International System of Units The International System of Units (SI) is an internationally accepted system for measurement. All SI units are derived from seven base units.

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SI Prefixes A prefix can be added to a base unit’s name to indicate either a fraction or a multiple of that base unit. Prefixes are based on powers of ten, such as 0.01 and 100.

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Converting Among SI Units To convert from one SI unit to another either multiply or divide by a factor of 10. Example: Convert a driving distance of 8,975 m into km.

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Accuracy vs. Precision For a single measurement: Accuracy - An indication of how close a measurement is to the accepted value Precision - An indication of the degree of exactness of a measurement For multiple measurements: Accuracy - An indication of how close the average measurement is to the accepted value Precision - An indication of the agreement among a number of similar measurements

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The data taken by student A are more accurate because each value is close to the accepted value. The data taken by student C are more precise because the data are similar.

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Percent Error The expression of error as a percentage of the accepted value.

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Percent Error

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Measurement & Accuracy All measurements have some uncertainty. The tools used to make measurements limit the accuracy of the measurements.

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Significant Digits Significant digits are the number of digits in a measurement that are known with a certain degree of reliability. The significant digits in a measurement include all digits you know for certain plus one estimated digit.

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Rounding Rules If the last number is less than 5, round down. If the last number is 5 or greater, round up. Examples: 6.14 rounded to the nearest tenth is 6.1 6.145 rounded to the nearest hundredth is 6.15

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Mathematical Operations Rounding with Addition and Subtraction –Round to the least number of decimal places Example: 6.7 + 4.321 = 11.0 Rounding with Multiplication and Division –Round to the same number of significant figures as the measurement with the least number of significant figures Example: 540. g / 62 ml = 8.7 g/ml

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Scientific Notation A method of writing or displaying very small or very large numbers in a short form. Examples: –The U.S. has a total of 1.2916 X 10 7 acres of land reserved for state parks. –The nucleus of a human cell is about 7.0 X 10 -6 meters in diameter.

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Rules for Scientific Notation 1)Write the original number a)12,916,000 acres b)0.0000070 m 2)Move the decimal point to the right or left to make the number between 1 and 10. Count the number of decimal places. a)1.2916000 = 7 places to the left b)7.0 = 6 places to the right

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Rules for Scientific Notation 3)Rewrite the number, deleting all extra zeroes except if it is just to the right of the decimal a)1.2916 b)7.0 4)Write a multiplication symbol and the number 10 with an exponent equal to the number of places you moved to the left (positive) or right (negative). a)1.2916 x 10 7 acres b)7.0 x 10 -6 m

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Converting to Standard Form 1)Write the original number a)1.2916 x 10 7 acres b)7.0 x 10 -6 m 2)Move the decimal point to the right (positive exponent) or left (negative exponent) the value of the exponent. a)12,916,000 = 7 places to the right b)0.0000070 = 6 places to the left

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Scientific Tools Science journals are used to record descriptions, explanations, plans, and steps used in scientific inquiry. A triple-beam balance or digital balance is used by scientists to measure mass.

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Scientific Tools A thermometer measures the temperatures of substances. A graduated cylinder is used to measure the volume of a liquid.

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Scientific Tools Flasks, beakers, petri dishes, test tubes, and specimen jars are used as containers.

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Scientific Tools Dissecting and compound light microscopes enable scientists to observe small objects that they cannot observe with just their eyes. A magnifying lens is a hand- held lens that magnifies, or enlarges, an image of an object.

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Scientific Tools Scientists use dissecting tools, such as scalpels and scissors, to examine tissues, organs, or prepared organisms. A pipette is a small glass or plastic tube used to draw up and transfer liquids.

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Scientific Tools Scientists use computers to compile, retrieve, and analyze data for reports. Scientists use calculators to perform mathematical computations.

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Scientific Tools Scientists use pH paper to quickly estimate the acidity of a substance. A hot plate is a small heating device that can be placed on a table or desk.

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Scientific Tools Scientists use stopwatches to measure the time it takes events to occur. A spring scale measures the weight or amount of force applied to an object.

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A.accuracy B.explanation C.precision D.significant digit Which term refers to a description of how close a measurement is to an accepted or true value? Pop Quiz

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A.SI unit B.significant digit C.prefix D.description Which can be added to a base unit’s name to indicate either a fraction or a multiple of that base unit? Pop Quiz

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A.microscope B.petri dish C.thermometer D.triple-beam balance Which of these is used by scientists to measure mass? Pop Quiz

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