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Classification and Properties of Matter













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Advanced Placement Chemistry

Lesson Plan #1

1 class period

Classification and Properties of Matter

States of Matter

Gas

    • No fixed volume

    • No fixed shape

    • Conforms to the volume and shape of container

    • Can be compressed to a smaller volume

    • Can expand to a larger volume

Liquid

    • Has a distinct volume independent of its container

    • No specific shape

    • Assumes shape of the portion of the container it occupies.

    • Can not be compressed to any appreciable extent.

Solid

    • Has definite shape

    • Has definite volume

    • It is rigid

    • Can not be compressed to any appreciable extent.

On the Molecular Level:

Gas

    • Molecules are far apart

    • Moving at high speeds

    • Colliding repeatedly with each other and walls of container

Liquid

    • Molecules packed more closely together

    • Still move rapidly

    • Allowed to slide over each other

    • Liquids pour easily

Solid

    • Molecules held tightly together

    • Usually in definite arrangements

    • Molecules can wiggle only slightly

    • Solids have rigid shapes.

Pure Substances and Mixtures

Pure substance

    • Has fixed composition

    • Has distinct properties

Elements

    • Substances that cannot be decomposed into simpler substances

    • Composed of only one kind of atom

Compounds

    • Composed of two or more elements

    • Contain two or more kinds of atoms

Mixtures

    • Combinations of two or more substances in which each substance retains its own chemical identity and its own properties

    • Two types of mixtures

    • Heterogeneous mixtures

    • Homogeneous mixtures

Heterogeneous mixtures

    • Do not have the same composition, properties, and appearance throughout the mixture.

    • Examples: sand, rocks, and wood

Homogeneous mixtures

    • Uniform throughout the mixture

    • Examples: air, salt, sugar, and many other substances dissolved in water to form homogeneous mixtures.

    • Also called solutions

    • Air is a gaseous solution; gasoline is a liquid solution; brass is a solid solution

Separation of Mixtures

Here is a way to determine what a substance is.

Matter

|

Is it uniform throughout?

No                   Yes

Heterogeneous    Homogeneous

|

homogeneous

|

Can it be separated by physical means?

NO                YES

Pure Substance homogeneous mixture (solution)

|

|

|

Can it be decomposed into other substances by chemical processes?

NO                         YES

Element                 Compound

Elements

    • 122 known at present

    • vary widely in abundance

    • over 90% of Earth's crust consists of only 5 elements:

    • oxygen

    • silicon

    • aluminum

    • iron

    • calcium

    • in contrast, just three elements account for over 90% of the mass of the human body

    • oxygen

    • carbon

    • hydrogen

    • symbol for each element consists of one or two letters, with the first letter capitalized (exception: three letters for elements in which name has not been uniformly adopted)

Compounds

    • Law of constant composition (or the Law of definite proportions)

    • French chemist Joseph Louis Proust in about 1800

    • A pure compound has the same composition and properties regardless of its source

Properties of Matter

    • Every substance has a unique set of properties - characteristics that allow us to recognize it and to distinguish it from other substances

    • Physical properties - can be measured without changing the identity and composition of substance.

    • Examples: color, odor, density, melting point, boiling point, and hardness

    • Chemical properties - describe the way a substance may change or react to form other substances

    • Example is flammability, the ability of a substance to burn in the presence of oxygen

    • Intensive properties are useful in chemistry, can be used to identify substances

    • Examples are temperature, melting point, and density

    • Do not depend on the amount of sample being examined

    • Extensive properties

    • Depend on the quantity of the sample

    • Include measurements of mass and volume

    • Relates to the amount of substance present

Physical and Chemical Changes

    • Physical changes

    • Substance changes its physical appearance but not its composition

    • Example is evaporation of water

    • All changes of state (for example, from liquid to gas or from liquid to solid) are physical changes

    • Chemical changes

  • Also called a chemical reaction

  • Substance is transformed into a chemically different substance

  • Example: when hydrogen burns in air, it undergoes a chemical change in which it is converted into water