Chapter 1: Matter and Measurements – Study Notes

Chapter 1: Matter and Measurements

Introduction

This chapter introduces the foundational concepts of matter and measurement in chemistry. Understanding how to classify matter, make accurate measurements, and convert between units is essential for all further study in chemistry.

Classification of Matter

Pure Substances vs. Mixtures

• Pure Substance: A form of matter with a constant composition and distinct properties. Examples include elements (e.g., O2, Fe) and compounds (e.g., H2O).

• Mixture: A combination of two or more substances in which each retains its own identity and properties. Mixtures can be homogeneous (uniform, e.g., saltwater) or heterogeneous (non-uniform, e.g., salad).

Physical vs. Chemical Properties

• Physical Properties: Characteristics that can be observed or measured without changing the substance's identity (e.g., color, melting point, density).

• Chemical Properties: Characteristics that describe a substance's ability to undergo chemical changes (e.g., flammability, reactivity with acid).

Physical vs. Chemical Changes

• Physical Change: Alters the form or appearance of matter but does not change its composition (e.g., melting ice).

• Chemical Change: Results in the formation of one or more new substances (e.g., rusting iron).

Elements and the Periodic Table

• There are over 100 known elements, each with unique properties.

• Students should learn the names and symbols of at least 50 common elements.

Measurement in Chemistry

Components of a Measurement

• Every measurement has two components: a numerical value and a unit (e.g., 25.0 mL).

Scientific Notation

Scientific Notation is used to express very large or very small numbers concisely. The format is:

• Number between 1 and 10 multiplied by a power of ten.

For example:

• 4,878,720 inches = $4.87872 \times 10^6$ inches

• 0.000 000 000 000 000 000 000 327 g = $3.27 \times 10^{-22}$ g

Metric Prefixes

Metric prefixes are used to indicate multiples or fractions of base units.

Prefix	Symbol	Multiplier	Example
kilo	k	$10^3$	1 kilogram (kg) = 1,000 g
centi	c	$10^{-2}$	1 centimeter (cm) = 0.01 m
milli	m	$10^{-3}$	1 milligram (mg) = 0.001 g
micro	μ	$10^{-6}$	1 microliter (μL) = 0.000001 L
nano	n	$10^{-9}$	1 nanometer (nm) = 0.000000001 m
pico	p	$10^{-12}$	1 picogram (pg) = 0.000000000001 g

Significant Figures and Measurement Precision

Significant Digits

• Report measurements as accurately as possible, estimating one digit beyond the smallest scale division.

• Significant digits include all certain digits plus one uncertain (estimated) digit.

Certain and Uncertain Digits

• The last digit in a measurement is always uncertain.

• More precise instruments allow for more certain digits.

Volume Measurements: Contained vs. Delivered

• Some glassware measures the volume contained (e.g., graduated cylinder), others the volume delivered (e.g., pipette, syringe).

Significant Figures in Calculations

• Addition/Subtraction: The result should have the same number of decimal places as the measurement with the fewest decimal places.

• Multiplication/Division: The result should have the same number of significant figures as the measurement with the fewest significant figures.

Exact vs. Inexact Numbers

• Exact numbers: Have no uncertainty (e.g., 12 eggs in a dozen, 100 cm in 1 m).

• Inexact numbers: Result from measurements and have some uncertainty.

Rounding Rules

• If the digit after the place to be rounded is less than 5, leave the digit unchanged.

• If the digit is 5 or greater, round up.

Unit Conversions and Dimensional Analysis

Dimensional Analysis

Dimensional analysis is a method for converting one unit to another using conversion factors.

• Set up the calculation so that units cancel, leaving only the desired unit.

• Example: To convert 3 feet to inches, use $3 \text{ ft} \times \frac{12 \text{ in}}{1 \text{ ft}} = 36 \text{ in}$

Common Conversion Factors

Quantity	SI Unit	Metric Unit	Equivalent
Mass	kilogram (kg)	gram (g)	1 kg = 1000 g = 2.205 lb
Length	meter (m)	meter (m)	1 m = 3.280 ft
Volume	cubic meter (m3)	liter (L)	1 m3 = 1000 L = 264.2 gal
Temperature	Kelvin (K)	Celsius (°C)	See temperature section

Steps for Unit Conversion

1. Identify the starting and desired units.

2. Find appropriate conversion factors.

3. Set up the calculation so that units cancel appropriately.

4. Perform the calculation and check units.

Density

Definition and Formula

• Density is the ratio of mass to volume.

Formula:

$\text{Density} = \frac{\text{mass (g)}}{\text{volume (mL or cm}^3)}$

• Density is a physical property and can be used to identify substances.

• Units: g/mL or g/cm3 for solids and liquids; g/L for gases.

• Density depends on temperature.

Temperature and Heat

Temperature Scales

• Fahrenheit (°F): Used mainly in the United States.

• Celsius (°C): Used worldwide; 0°C is the freezing point and 100°C is the boiling point of water.

• Kelvin (K): The SI unit; absolute zero (0 K) is the lowest possible temperature.

Temperature Conversions

• Celsius to Fahrenheit: $^{\circ}F = (1.8 \times ^{\circ}C) + 32$

• Fahrenheit to Celsius: $^{\circ}C = \frac{^{\circ}F - 32}{1.8}$

• Celsius to Kelvin: $K = ^{\circ}C + 273$

• Kelvin to Celsius: $^{\circ}C = K - 273$

Heat and Specific Heat

• Heat is a form of energy, measured in joules (J) or calories (cal).

• 1 cal = 4.184 J

• Specific Heat is the amount of heat required to raise the temperature of 1 gram of a substance by 1°C.

Formula:

$\text{Specific Heat} = \frac{\text{Heat (J or cal)}}{\text{mass (g)} \times \Delta T (^{\circ}C)}$

• Each substance has a unique specific heat value.

Summary Table: Metric Prefixes

Prefix	Symbol	Multiplier
kilo	k	$10^3$
centi	c	$10^{-2}$
milli	m	$10^{-3}$
micro	μ	$10^{-6}$
nano	n	$10^{-9}$
pico	p	$10^{-12}$

Key Equations

• Density: $\text{Density} = \frac{\text{mass}}{\text{volume}}$

• Specific Heat: $\text{Specific Heat} = \frac{q}{m \Delta T}$

• Temperature Conversions:

  • $^{\circ}F = (1.8 \times ^{\circ}C) + 32$

  • $^{\circ}C = \frac{^{\circ}F - 32}{1.8}$

  • $K = ^{\circ}C + 273$

Practice and Application

• Apply these concepts to solve problems involving classification of matter, measurement, significant figures, unit conversions, density, and heat calculations.