We also need to know the “true” value to determine accuracy.

Let’s assume the actual value for this object was 7.4413g.

Are we Accurate?

**Chapter 1**

Chemistry: Matter and Measurement

Chemistry: Matter and Measurement

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LDL is the bad cholesterol because it keeps blood

cholesterol circulating in your bloodstream, leaving plaque on artery walls along the way.

HDL is the good cholesterol because it acts like waste removal carriers moving cholesterol from blood and arteries to your liver for removal from your blood.

Cholesterol and Density

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No! We often interchange the two terms creating a language problem.

For example, when a person goes to the moon.

Mass does NOT change, but the person becomes almost weightless!

When on Earth the two terms are often interchanged.

Are Mass and Weight the same thing?

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Base Units

19

Number in Number in

Object Standard Format Scientific Notation

Avogadro’s number 602,000,000,000,000,000,000,000 molecules 6.02 x 1023 molecules

Mass of a human 68 kg 6.8 E 1 kg

Length of a pox virus 0.000 03cm 3 E -5cm

Standard Format and Scientific Notation examples

Dimensional analysis: A method that uses a conversion factor to convert a quantity expressed in one unit to an equivalent quantity in a different unit

Conversion factor: Expresses the relationship between two different units

Calculations: Converting from One Unit to Another

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If we compare the actual value to our average value they are the same meaning we have very good accuracy as well.

Average = (7.4413 g + 7.4413 g + 7.4414 g)/3 = 7.4413 g

We must calculate the average (or mean) of the three trials.

Average = Sum of trials / Number of trials

To determine Accuracy

All three trial values are within +- 0.0001 g of each

other meaning there is very good precision for these measurements.

Suppose you weigh an object three times and record

the information in the following table.

Volume and Its Measurement

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© 2012 Pearson Education, Inc.

Meter

1790: One ten-millionth of the distance from the equator to the

North pole along a meridian running through Paris, France

1889: Distance between two thin lines on a bar of platinum-iridium

alloy stored near Paris, France

1983: The distance light travels in a vacuum in 1/299,792,458 of a second

Length and Its Measurement

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18

Numbers written in scientific notation have three parts:

coefficient power of 10 unit

Scientific Notation and Calculators

Number to enter: 4 x 10^6

Enter: 4 EXP (EE or 10^x) 6

Display: 4 06 or 4 x 10^6 or 4 E06

Number to enter: 2.5 x 10−4

Enter: 2.5 EXP (EE or 10^x) +/− 4

Display: 2.5 −04 or 2.5x 10^04 or 2.5 E−04

Scientific Notation

Copyright © Houghton Mifflin Company. All rights reserved.

The Various Parts of the Scientific Method

Zeros in the middle of a number are like any other digit; they are always significant.

Rules for counting significant figures (left-to-right):

4.803 cm 4 SF

Accuracy, Precision, and Significant Figures in Measurement

© 2012 Pearson Education, Inc.

© 2012 Pearson Education, Inc.

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Heat and its Measurement

Derived Units

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Mass and Its Measurement

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If the first digit you remove is less than 5, round down by

dropping it and all following numbers.

If the first digit you remove is 6 or greater, round up by adding 1 to the digit on the left.

If the first digit you remove is 5 and there are more nonzero digits following, round up.

Rules for rounding off numbers:

5.664 525 = 5.665

Rounding Numbers

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If the first digit you remove is less than 5, round down by dropping it and all following numbers.

Rules for rounding off numbers:

5.664 525 = 5.66

Rounding Numbers

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Rules for counting significant figures (left-to-right):

34,200 m ? SF

Zeros at the end of a number and before the decimal point may or may not be significant.

Accuracy, Precision, and Significant Figures in Measurement

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Zeros at the beginning of a number are not significant (placeholders).

Rules for counting significant figures (left-to-right):

0.006 61 g 3 SF (or 6.61 E-3 g)

Accuracy, Precision, and Significant Figures in Measurement

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Mass of a Tennis Ball

(True Mass = 54.441 778 g)

poor accuracy

poor precision

Accuracy, Precision, and Significant Figures in Measurement

© 2012 Pearson Education, Inc.

All other units are derived from these fundamental units.

Système Internationale d´Unités

Experimentation and Measurement

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5.664 525 = 5.664 52

If the first digit you remove is less than 5, round down

by dropping it and all following numbers.

If the first digit you remove is 6 or greater, round up by adding 1 to the digit on the left.

If the first digit you remove is 5 and there are more nonzero digits following, round up.

If the digit you remove is a 5 with nothing following, round down.

Rules for rounding off numbers:

Rounding Numbers

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If the first digit you remove is 6 or greater, round up by adding 1 to the digit on the left.

Rules for rounding off numbers:

5.664 525 = 5.7

Rounding Numbers

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Zeros at the end of a number and after the decimal point are always significant.

Rules for counting significant figures (left-to-right):

55.220 K 5 SF

Accuracy, Precision, and Significant Figures in Measurement

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Mass of a Tennis Ball

(True Mass = 54.441 778 g)

good accuracy

poor precision

Accuracy, Precision, and Significant Figures in Measurement

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good accuracy

good precision

Accuracy, Precision, and Significant Figures in Measurement

Mass of a Tennis Ball

(True Mass = 54.441 778 g)

© 2012 Pearson Education, Inc.

Density and Its Measurement

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Math rules for keeping track of significant figures:

2 decimal places

3.19 315

2 decimal places

5 decimal places

3.18

+ 0.01 315

3.19

Addition or subtraction: The answer can’t have more digits to the right

of the decimal point than any of the original numbers.

Rounding Numbers

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converts

in to m

converts

m to in

1 m

39.37 in

or

39.37 in

1 m

Relationship:

Conversion factor:

1 m = 39.37 in

Calculations: Converting from One Unit to Another

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Multiplication or division: The answer can’t have more significant figures

than any of the original numbers.

Math rules for keeping track of significant figures:

= 23.760 684 mi/gal

3 SF

3 SF

4 SF

= 23.8 mi/gal

278 mi

11.70 gal

Rounding Numbers

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K = oC + 273.15

oF =

5 oC

9 oF

oC + 32 oF

oC =

9 oF

5 oC

(oF - 32 oF)

Temperature and Its Measurement

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**Conversion Factor**

**Given Unit**

**Needed Unit**

**x**

**= 1.77 m**

**69.5 in**

**1 m**

**39.37 in**

**Calculations: Converting from One Unit to Another**

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Know!

Energy - The ability to do work or supply heat

Units: Joule, calorie, Calorie

Types: Kinetic and Potential

Kinetic energy - energy of motion

E_k_ = (1/2) mv^2

Potential energy- stored energy

E_p_ = mgh

Joule (J) - relatively small unit; often use kJ in our measurements

calorie - amount of energy necessary to raise the temperature of 1g of water by 1 degree Celsius

Calorie - Nutritional Food Calorie

1000 J = 1kJ

1 cal = 4.184 J

1 Cal = 1000 cal = 1 kcal