Introduction to Chemistry: Matter, Properties, and Measurement

Chemistry & Matter

Central Role of Chemistry

Chemistry is the study of matter, its properties, the changes it undergoes, and the energy associated with those changes. Chemistry connects to many scientific fields, including biology, physics, geology, medicine, and environmental science.

• Definition: Chemistry investigates the composition, structure, properties, and reactions of matter.

• Applications: Chemistry is involved in daily life (e.g., cooking, cleaning, medicine, environmental processes).

• Scientific Models: Tangible items, pictures, or mathematical equations used to represent invisible processes (e.g., Bohr model, carbon cycle, equations).

Matter and Its Properties

Definition of Matter

Matter is anything that has mass and occupies space (volume).

• Mass: The measure of the amount of matter in an object.

• Weight: The measure of the gravitational force on the matter in an object (on Earth, often used interchangeably with mass).

Physical Properties of Matter

Physical properties can be observed or measured without changing the substance's chemical identity.

Property	Examples
Temperature	0°C for ice water, 100°C for boiling water
Mass	A nickel weighs 5 g, a penny weighs 2.5 g
Color	Sulfur is yellow, bromine is reddish-brown
Taste	Acids are sour, bases are bitter
Odor	Benzyl acetate smells like jasmine
Boiling point	Water boils at 100°C, ethyl alcohol at 78.5°C
Hardness	Diamond is exceptionally hard
Density	1.00 g/mL for water, 19.3 g/cm³ for gold

Physical Changes

Physical changes are changes in which the chemical identity of the substance is not changed (e.g., melting, freezing, dissolving).

Chemical Properties of Matter

Chemical properties can only be observed by changing the chemical identity of a substance (i.e., forming new substances).

Substance	Typical Chemical Property
Iron	Rusts (combines with oxygen to form iron oxide)
Carbon	Burns (combines with oxygen to form carbon dioxide)
Silver	Tarnishes (combines with sulfur to form silver sulfide)
Nitroglycerin	Explodes (decomposes to produce a mixture of gases)
Carbon monoxide	Is toxic (combines with hemoglobin, causing anoxia)
Neon	Is inert (does not react with anything)

Chemical Changes

Chemical changes are changes in which the chemical identity of the substance does change (e.g., rusting, burning, decomposing).

• Example: A bicycle left outdoors begins to rust (iron reacts with oxygen to form iron oxide).

Classification of Matter

States of Matter

• Solid: Definite shape and volume.

• Liquid: Definite volume but no definite shape.

• Gas: Neither definite volume nor definite shape.

Elements

Elements are composed of one type of atom (same number of protons). Atoms are the smallest particle of an element. Elements are represented by chemical symbols (e.g., H for hydrogen, O for oxygen, Na for sodium).

Compounds & Molecules

• Compounds: Made of two or more elements chemically combined in fixed ratios (e.g., NaCl, H2O, C6H12O6).

• Molecules: Groups of atoms bonded together as a unit. Includes compounds and diatomic elements (e.g., O2, N2).

Mixtures

• Mixture: A physical blend of two or more substances.

• Homogeneous mixtures: Uniform in composition (e.g., salt water, air).

• Heterogeneous mixtures: Not uniform in composition (e.g., soil, granite).

Types of Matter

Type	Example
Element	Gold (Au)
Compound	Water (H2O)
Homogeneous mixture	Rose gold (gold & copper)
Heterogeneous mixture	Rose gold, white gold (mixture of metals)

Measurement of Matter

SI Base Units

Physical Quantity	Name of Unit	Symbol
Length	meter	m
Mass	kilogram	kg
Time	second	s
Temperature	kelvin	K
Amount of substance	mole	mol
Electric current	ampere	A
Luminous intensity	candela	cd

Volume: The SI base unit of volume is the cubic meter (m3).

Numerical Prefixes

Exponential Expression	Decimal Equivalent	Prefix	Symbol
109	1,000,000,000	giga	G
106	1,000,000	mega	M
103	1,000	kilo	k
10-3	0.001	milli	m
10-6	0.000001	micro	μ
10-9	0.000000001	nano	n

Scientific Notation

• Exponential notation: Writing a number as the product of a coefficient and a power of 10.

• Scientific notation: Coefficient has a value between 1 and 10 or -1 and -10.

Examples:

• $5.47 \times 10^{10}$ for 54,700,000,000

• $1.7 \times 10^{-4}$ for 0.00017

• $-1.8 \times 10^{4}$ for -18,000

• $4.30 \times 10^{3}$ in standard notation is 4,300

Density

Density is the mass of a substance per unit volume.

• Formula: $d = \frac{m}{V}$

• Units: g/cm3 or kg/m3

• Example: Water has a density of 1.00 g/cm3; gold has a density of 19.3 g/cm3.

Energy and Temperature

Energy

Energy is the ability to change matter, either physically or chemically ("ability to do work").

• Potential energy: Stored energy.

• Kinetic energy: Energy in motion.

Heat vs Temperature

• Heat: Energy transferred from hotter objects to cooler objects.

• Temperature: Average kinetic energy of the atoms or molecules in an object.

Units of Heat

• Heat energy is measured in calories or joules.

• 1 calorie (cal) is the amount of heat required to change the temperature of 1.00 g of water by 1.00°C.

• 1 calorie = 4.184 joules (J)

Temperature Scales

• Celsius (°C): Freezing point of water is 0°C, boiling point is 100°C.

• Kelvin (K): Absolute zero is 0 K; K = °C + 273.15.

• Fahrenheit (°F): Freezing point of water is 32°F, boiling point is 212°F.

Example: Room temperature is 25°C. In Kelvin: $K = 25 + 273.15 = 298.15$ K

Summary Table: Types of Matter

Type	Description	Example
Element	One type of atom	Gold (Au)
Compound	Two or more elements chemically combined	Water (H2O)
Homogeneous mixture	Uniform composition	Salt water
Heterogeneous mixture	Non-uniform composition	Granite

Additional info: These notes are based on introductory lecture slides for a college-level Introduction to Chemistry course, covering foundational concepts in matter, properties, classification, and measurement.