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 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.

Mixtures can be further classified as homogeneous (uniform composition, e.g., saltwater) or heterogeneous (non-uniform composition, e.g., salad).

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.

Chemical Changes

Chemical changes result in the formation of new substances with different chemical properties. Examples include burning, rusting, and digestion.

Chemical and Physical Properties

Chemical Properties

Chemical properties describe a substance's ability to undergo chemical changes, forming new substances. These are observed during chemical reactions.

• Examples: Flammability, reactivity with acids, toxicity, and radioactivity.

Physical Properties

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

• Examples: Color, mass, volume, density, melting point, boiling point, hardness, and luster.

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, color, melting point, boiling point, luster.

Extensive Properties

Extensive properties depend on the amount of substance present. They change when the size of the sample changes.

• Examples: Mass, volume, length, total charge.

Temperature and Heat

Thermal Energy, Temperature, and Heat

Thermal energy is the total kinetic and potential energy of all atoms in an object. Temperature is the average kinetic energy of particles, while heat is the transfer of thermal energy from a hotter object to a cooler one.

Scientific Notation and Significant Figures

Scientific Notation

Scientific notation expresses very large or small numbers in the form , where and is an integer.

• Example:

Significant Figures

Significant figures reflect the precision of a measured value. Rules for counting significant figures include:

• 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.

SI Units and Metric Prefixes

SI Base Units

The International System of Units (SI) uses seven base units for fundamental quantities:

Metric Prefixes

Metric prefixes indicate multiples or fractions of base units. For example, kilo- (k) means , milli- (m) means , and micro- (μ) means .

Density

Definition and Formula

Density is the amount of mass per unit volume. It is calculated as:

• For solids and liquids: units are typically g/cm3 or kg/L.

• For gases: units are typically g/L.

Density of Geometric and Non-Geometric Objects

For regular shapes, use geometric formulas to find volume. For irregular objects, use water displacement to determine volume.

Dimensional Analysis and Conversion Factors

Dimensional Analysis

Dimensional analysis is a systematic approach to converting between units using conversion factors. Set up the problem so that units cancel, leaving only the desired unit.

• Example: To convert 10 inches to centimeters, use the conversion factor 2.54 cm/1 inch.

Summary Table: Properties of Matter