Matter & Energy: Classification, Properties, and Changes (GOB Chemistry Study Notes)

Matter & Energy

Introduction

This study guide covers the foundational concepts of matter and energy as presented in a GOB Chemistry course. Topics include the classification of matter, physical and chemical properties, specific heat calculations, and changes of state. Understanding these concepts is essential for further study in chemistry and its applications in health sciences.

Classification of Matter

Definition and States of Matter

• Matter is anything that has mass and occupies space.

• On Earth, matter exists in three physical states: solid, liquid, and gas.

Types of Matter

• Pure substances: Have a fixed or definite composition.

• Mixtures: Contain two or more different substances physically mixed but not chemically combined.

Classification Table

Type	Subtypes	Examples
Pure Substances	Elements, Compounds	Copper (Cu), Water (H2O)
Mixtures	Homogeneous, Heterogeneous	Brass (Cu & Zn), Water & Copper

Elements & Compounds

• Element: A pure substance composed of one type of atom (e.g., Copper, Cu; Lead, Pb; Aluminum, Al).

• Compound: A pure substance composed of two or more elements chemically combined in a definite ratio (e.g., Hydrogen peroxide, H2O2; Table salt, NaCl; Sugar, C12H22O11; Water, H2O).

Mixtures

• Mixture: Two or more substances physically mixed, not chemically combined; can be separated by physical methods.

• Classified as homogeneous (uniform composition, not visible parts; e.g., sugar water, brass) or heterogeneous (composition varies, visible parts; e.g., peach pie, water & copper).

Physical States of Matter

Properties of Solids, Liquids, and Gases

• Solids: Definite shape and volume; particles held close together in a rigid pattern; very slow movement.

• Liquids: Definite volume, no definite shape; take the shape of their container; particles move slowly in random directions.

• Gases: Indefinite shape and volume; take the shape and volume of their container; particles are far apart and move rapidly.

Physical States Comparison Table

Characteristic	Solid	Liquid	Gas
Shape	Definite	Container shape	Container shape
Volume	Definite	Definite	Fills container
Arrangement of Particles	Fixed, very close	Random, close	Random, far apart
Interaction between Particles	Very strong	Strong	Essentially none
Movement of Particles	Very slow	Moderate	Very fast
Examples	Ice, salt, iron	Water, oil, vinegar	Water vapor, helium, air

Physical and Chemical Properties

Physical Properties

• Characteristics observed or measured without changing the identity of a substance (e.g., shape, state, boiling/freezing point, density, color).

• Example: Copper (Cu) is reddish-orange, shiny, and an excellent conductor of heat and electricity.

Physical Changes

• Occur when matter undergoes a change of state, but its composition remains the same (e.g., water as ice, liquid, or steam).

• Physical appearance can change (e.g., salt dissolving in water).

Chemical Properties & Changes

• Describe the ability of a substance to interact with other substances or change into a new substance.

• During a chemical change, a new substance forms with new composition and properties (e.g., iron rusting, sugar caramelizing).

Physical vs. Chemical Changes Table

Physical Changes	Chemical Changes
Water boils to form vapor	Silver reacts in air to form a black coating
Copper drawn into wires	Wood burns to form ash, CO2, and water vapor
Sugar dissolves in water	Heating sugar forms caramel
Paper cut into confetti	Iron combines with oxygen to form rust

Specific Heat and Heat Calculations

Specific Heat

• Specific heat (SH) is the amount of heat needed to raise the temperature of 1 g of a substance by 1°C.

• Units: J/g°C (SI) or cal/g°C (metric).

• Different substances have different specific heats.

Formula:

$SH = \frac{\text{heat}}{m \times \Delta T}$

For water: $SH_{H_2O(l)} = 1.00 \frac{cal}{g \cdot ^\circ C} = 4.184 \frac{J}{g \cdot ^\circ C}$

Calculating Specific Heat

• Given mass, heat absorbed, and temperature change, calculate SH.

• Example: 24.8 g metal absorbs 275 J, temperature rises from 20.2°C to 24.5°C.

$\Delta T = 24.5^\circ C - 20.2^\circ C = 4.3^\circ C$

$SH = \frac{275\ J}{24.8\ g \times 4.3^\circ C} = 2.6\ J/g^\circ C$

Heat Equation

• Calculate heat lost or gained: $\text{Heat} = m \times \Delta T \times SH$

• Example: Heat needed to raise 255 g copper from 24°C to 185°C:

$\Delta T = 185^\circ C - 24^\circ C = 161^\circ C$

$SH_{copper} = 0.385\ J/g^\circ C$

$\text{Heat} = 255\ g \times 161^\circ C \times 0.385\ J/g^\circ C = 15.8\ kJ$

Changes of State

Types of Changes

• Melting: Solid to liquid at melting point (mp).

• Freezing: Liquid to solid at freezing point (fp).

• Sublimation: Solid to gas without passing through liquid state.

• Deposition: Gas to solid.

• Evaporation: Liquid to gas at surface.

• Boiling: Liquid to gas throughout the liquid at boiling point.

• Condensation: Gas to liquid as molecules lose energy.

Heating and Cooling Curves

• Heating curve: Diagonal lines show temperature changes; horizontal lines (plateaus) show changes of state.

• Cooling curve: Diagonal lines show temperature decreases; plateaus show changes of state as heat is removed.

Summary Table: Physical vs. Chemical Changes

Property	Physical	Chemical
Definition	Color, shape, odor, luster, size, melting point, density	Ability to form another substance (e.g., paper can burn, iron can rust)
Change	Retains identity (change of state, size, shape)	Converted to new substance (paper burns, iron rusts)

Key Equations

• $SH = \frac{\text{heat}}{m \times \Delta T}$

• $\text{Heat} = m \times \Delta T \times SH$

Examples & Applications

• Classification: Air is a mixture; aluminum foil is a pure substance.

• Physical change: Ice melting; cutting pizza.

• Chemical change: Iron rusting; burning a candle.

Additional info:

• These notes are based on Timberlake, K. (2018). Chemistry: Introduction to general, organic and biological chemistry (13th ed.). Pearson Education.