BackChapter 1: Measurement, Physical and Chemical Change – General Chemistry Study Notes
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Chapter 1: Measurement, Physical and Chemical Change
Chemical Changes and Physical and Chemical Change
Chemistry is the scientific discipline that seeks to understand the properties and behavior of matter by studying the atoms and molecules that compose it. Matter can undergo two main types of changes: physical changes and chemical changes.
Physical properties: Characteristics that can be observed or measured without changing the substance's chemical composition (e.g., melting point, boiling point, density).
Chemical properties: Characteristics that describe a substance's ability to undergo a specific chemical change (e.g., flammability, reactivity with oxygen).
Physical change: A change that alters the state or appearance of matter without changing its composition (e.g., melting ice, boiling water).
Chemical change: A change that alters the composition of matter, resulting in the formation of one or more new substances (e.g., rusting of iron, combustion of gasoline).
Example: Boiling water is a physical change (liquid to gas), while rusting iron is a chemical change (iron reacts with oxygen to form iron(III) oxide).
Energy: A Fundamental Part of Physical and Chemical Change
Physical and chemical changes are often accompanied by changes in energy. The total energy of an object is the sum of its potential energy and kinetic energy.
Potential energy: Energy associated with position or composition.
Gravitational potential energy
Elastic potential energy
Chemical potential energy (stored in chemical bonds)
Kinetic energy: Energy associated with motion.
Movement of atoms, molecules, or electrons
Heat (thermal energy)
Mechanical energy
Law of Conservation of Energy: Energy is neither created nor destroyed, but can be transferred or transformed from one form to another.
Substances with high potential energy tend to undergo changes that lower their potential energy, often releasing energy in the process (e.g., combustion of hydrocarbons).
Example: Gasoline (high potential energy) combusts to form exhaust gases (lower potential energy), releasing energy that can do work (e.g., move a car).
