# [CHEM 110] - Midterm Exam Guide - Everything you need to know! (17 pages long)

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NIU

CHEM 110

MIDTERM EXAM

STUDY GUIDE

Chapter 1 LearnSmart due Thursday @9PM

Chapter 1 Connect due Friday @Midnight

Units of Measurement

● Units

○ The basic quantity of mass, volume, or whatever quantity is being measured

○ A measurement is useless without its units

● English / Imperial System

○ A collection of functionally unrelated units

■ Difficult to convert from one unit to another

■ Ie. 1ft = 12 inches = 0.33 yards = 1/5280 miles

● Metric System

○ Composed of a set of units that are related to each other decimally, systematic

○ Units related by powers of tens

○ Units

■ Time - metric unit is seconds

■ Mass - the quantity of matter in an object

● Not synonymous with weight

● Standard unit is the gram (g)

● The pound (lb) is the common English unit

● 1lb = 454g

● MUST be measured on a balance (not a scale)

● Balance = removes gravity from equation

● Scale = relies on gravity

● Mass =/= Weight

○ Mass: the quantity of matter in an object

○ Weight: the force of gravity on an object

■ Equation: mass x acceleration

■ Length

● The distance between two points

● Standard unit is the meter (m)

● The yard is the common English unit

○ 1yd - 0.91m

■ Volume

● The space occupied by an object

● Standard unit is the liter (L)

● The quart is the common English unit

○ 1qt = 0.946L

○ Prefixes

■ Basic units are the units of a quantity without any metric prefix

■ Milli = -1000

■ Kilo = 1000

■ 1000g = 1kg

■ 1g = 1000mg

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■ 10^3L = 1kL

■ 1L = 10^3 mL

● The Numbers of Measurement

○ Information-bearing digits or figures in a number are significant figures

○ The measuring device used determines the number of significant figures in a

measurement

○ The degree of uncertainty associated with a measurement is indicated by the

number of figures used to represent the information

○ Recognition of Significant Figures

■ All nonzero digits are significant

● 7.314 has four significant digits

■ The number of significant digits is independent of the position of the

decimal point

● 73.14 also has four sigfigs

■ Zeros located between nonzero digits are significant

● 60.052 has five sigfigs

○ Use of Zeros in sigfigs

■ Zeros at the end of a number (trailing zeros) are significant if the number

containers a decimal point

● 4.70 has three sigfigs

■ Trailing zeros are insignificant if the number does NOT contain a decimal

point

● 100 has one significant digit; 100. Has three

■ Zeros to the left of the first nonzero integer are not significant

■ 0.0032 has two sigfigs

■ How many sigfigs in the follow

● 3.400 - 4

● 3004 - 4

● 300. - 3

● 0.003040 - 4

● Scientific Notation

○ Used to express very large or very small numbers easily and with the correct

number of significant figures, represents a number as a power of ten

○ Example

■ 4300 = 4.3 x 1000 = 4.3 x 10^3

○ Another Example

■ 4300.

■ Move to satisfy factor of 10

■ Move left 3 places

■ 4.3 < 10

■ 10^3 because we moved the decimal 3 places

■ 4.3 x 10^3

■ If moved to the left, then the power will be a negative

○ Uncertainty

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find more resources at oneclass.com