Measurement & Scientific Tools

Biblical Reference

He measured its wall and it was 144 cubits thick, by man's measurement, which the angel was using.

Revelation 21:17

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.

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.

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.

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.

kmm

kmm 975.81000

18975

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

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.

Percent Error• The expression of error as a percentage of

the accepted value.

%100_

___%

ValueTrue

ValueTrueValueExpError

Percent Error

%16.0%100185

1857.184_

AStudent

%97.0%100185

1858.186_

BStudent

%84.1%100185

1856.181_

CStudent

Measurement & Accuracy

• All measurements have some uncertainty.

• The tools used to make measurements limit the accuracy of the measurements.

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.

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

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

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 107 acres of

land reserved for state parks.– The nucleus of a human cell is about 7.0 X 10-6

meters in diameter.

Rules for Scientific Notation1) 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

Rules for Scientific Notation3) 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 107 acres

b) 7.0 x 10-6 m

Converting to Standard Form1) Write the original number

a) 1.2916 x 107 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

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.

Scientific Tools

A thermometer measures the temperatures of substances.

A graduated cylinder is used to measure the volume of a liquid.

Scientific Tools

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

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.

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.

Scientific Tools

Scientists use computers to compile, retrieve, and analyze data for reports.

Scientists use calculators to perform mathematical computations.

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.

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.

A. accuracyB. explanation C. precision D. significant digit

Which term refers to a description of how close a measurement is to an accepted or true value?

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A. SI unitB. significant digitC. prefixD. description

Which can be added to a base unit’s name to indicate either a fraction or a multiple of that base unit?

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A. microscope B. petri dishC. thermometerD. triple-beam balance

Which of these is used by scientists to measure mass?

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