Classification of Matter

Types of Matter

Chemistry is the study of matter and the changes it undergoes. Matter is anything that occupies space and has mass. It can be classified into three main types:

• Element: The simplest type of matter, composed of only one kind of atom. Examples include gold (Au) and oxygen (O2).

• Compound: Matter composed of two or more different elements that are chemically bonded together, such as water (H2O).

• Mixture: Matter composed of elements and/or compounds that are physically mixed together, such as air or salad.

Pure substances include elements and compounds, while mixtures can be homogeneous (uniform composition, e.g., saltwater) or heterogeneous (non-uniform, e.g., salad).

Practice and Examples

• Compounds can only be broken down by chemical means.

• Milk is an example of a heterogeneous mixture.

• Gold bar is an element; ammonia (NH3) is a compound; orange juice and wine are mixtures.

Physical and Chemical Changes

Physical Changes

Physical changes alter the state or appearance of matter without changing its composition. Examples include melting, freezing, dissolving, and tearing.

• Example: Dissolving sugar in water is a physical change.

Chemical Changes

Chemical changes result in the formation of new substances with different properties. This involves making or breaking chemical bonds.

• Example: Iron rusting or wood burning are chemical changes.

Reversible vs. Irreversible Changes

• Reversible changes: Can be undone (e.g., melting and freezing).

• Irreversible changes: Cannot be undone (e.g., burning, cooking).

Chemical and Physical Properties

Chemical Properties

Chemical properties describe a substance's ability to undergo chemical changes, forming new substances. Examples include flammability, reactivity with acids, and radioactivity.

Physical Properties

Physical properties can be observed or measured without changing the substance's chemical identity. Examples include color, mass, density, melting point, and state of matter.

• Example: Mercury is a silvery liquid at 25ºC (physical property).

Intensive vs. Extensive Properties

Intensive Properties

Intensive properties do not depend on the amount of substance present. They are useful for identifying substances.

• Examples: Density, melting point, color, luster.

Extensive Properties

Extensive properties depend on the amount of substance present.

• Examples: Mass, volume, energy.

Temperature and Heat

Thermal Energy, Temperature, and Heat

• Thermal energy: Total kinetic and potential energy of particles in a substance.

• Temperature: Average kinetic energy of particles; measured in Celsius (ºC), Fahrenheit (ºF), or Kelvin (K).

• Heat: Transfer of thermal energy from a hotter object to a cooler one.

Temperature Conversions

Scientific Notation

Format and Conversion

• Scientific notation expresses numbers as , where and is an integer.

• Positive exponents indicate large numbers; negative exponents indicate small numbers.

SI Units and Metric Prefixes

SI Base Units

• Mass: kilogram (kg)

• Length: meter (m)

• Time: second (s)

• Temperature: kelvin (K)

• Amount of substance: mole (mol)

• Electric current: ampere (A)

• Luminous intensity: candela (cd)

Metric Prefixes

• kilo- (), centi- (), milli- (), micro- (), nano- (), etc.

Significant Figures

Rules for Counting Significant Figures

• All nonzero digits are significant.

• Zeros between nonzero digits are significant.

• Leading zeros are not significant.

• Trailing zeros are significant if there is a decimal point.

Significant Figures in Calculations

• Multiplication/Division: Result has the same number of significant figures as the value with the fewest significant figures.

• Addition/Subtraction: Result has the same number of decimal places as the value with the fewest decimal places.

Conversion Factors and Dimensional Analysis

Conversion Factors

Conversion factors are ratios that relate different units and are used to convert from one unit to another.

• Example:

Dimensional Analysis

Dimensional analysis is a systematic approach to problem-solving that uses conversion factors to move from one unit to another.

• Set up the problem so that units cancel appropriately, leaving the desired unit.

Density

Definition and Formula

Density is the amount of mass per unit volume. It is a useful property for identifying substances and solving problems involving mass and volume.

Units

• Solids/Liquids: g/cm3 or kg/L

• Gases: g/L

Water Displacement

Water displacement is used to determine the volume of irregularly shaped objects by measuring the change in water level when the object is submerged.

Geometric and Non-Geometric Objects

Volume Formulas

• Cube:

• Sphere:

• Cylinder:

Application

Given the mass and volume (or dimensions), density can be calculated for both geometric and non-geometric objects.