1.4 Measurements

Significant Figures playlist (DeWitt): https://youtube.com/playlist?list=PL3hPm0ZdYhyy0PQUQ1ka94hxVQPdYGS9m 

Making Measurements in the Chemistry Lab

• Measurement (w/ the Metric System)

• Measuring Length (w/ Precision vs. Accuracy)                                                                           

• Measuring Mass (w/ Significant Figures                                                                                    

  • Exact Numbers

  • Rules of Rounding                                                                                    

  • Calculations with Significant Figures                                               

  • Conversions and the Importance of Units                                      

  • Conversion Factors

• Measuring Volume & Density

• Measuring Temperature

• Measuring Amount (w/ Scientific Notation)

• Measuring 

Measurements

Chemists measure the properties of matter and express these measurements as quantities. A quantity is an amount of something and consists of a number and a unit. The number tells us how many (or how much), and the unit tells us what the scale of measurement is. For example, when a distance is reported as “5 kilometers,” we know that the quantity has been expressed in units of kilometers and that the number of kilometers is 5.

Expressing Numbers - Scientific Notation

Scientific notation is a system for expressing very large or very small numbers in a compact manner. It uses the idea that such numbers can be rewritten as a simple number multiplied by 10 raised to a certain exponent, or power.  Scientific notation expressed numbers using powers of 10.

Expressing Numbers - Significant Figures

Significant figures properly report the number of measured and estimated digits in a measurement. There are rules for applying significant figures in calculations.

The International System of Units

Recognize the SI base units. Combining prefixes with base units creates new units of larger or smaller sizes.

Converting Units

The ability to convert from one unit to another is an important skill. A unit can be converted to another unit of the same type with a conversion factor.

Uncertainty, Accuracy, and Precision in Measurements

Learning Objectives

By the end of this section, you will be able to:

• Define accuracy and precision (1.5)

• Distinguish exact and uncertain numbers (1.5)

• Correctly represent uncertainty in quantities using significant figures (1.5)

• Apply proper rounding rules to computed quantities (1.5)

Mathematical Treatment of Measurement Results

Learning Objectives

By the end of this section, you will be able to:

• Explain the dimensional analysis (factor label) approach to mathematical calculations involving quantities (1.6)

• Use dimensional analysis to carry out unit conversions for a given property (single units) and computations involving two or more properties (derived units). (1.6)

Measurements quantify the micro/macroscopic properties of matter by comparing them to a standard unit.

Measurements provide much of the information that support the hypotheses, theories, and laws describing the behavior of matter and energy involved in both the macroscopic and the microscopic domains of chemistry.

It doesn't matter how beautiful your theory is, it doesn't matter how smart you are. If it doesn't agree with experiment, it's wrong.

-Feynman

1. the size or magnitude of the measurement (a number); 

2. a standard of comparison for the measurement (a unit); and 

3. an indication of the uncertainty of the measurement (±, error)