Chapter 2Matter and Energy

2.1 Properties of Matter

Extensive Properties depend on the amount of matter in a sample: mass, volume

Intensive properties depend on the type of matter/substance, not the amount: density, color, hardness, conductivity, reactivity, solubility

Identifying properties:Physical: density, color, melting point,

boiling pointChemical: reactivity

States of Matter

Solid: definite shape and volume, lowest energy, particles are closest together and vibrate

Liquid: definite volume, particles slide across each other

Gas: takes the shape and volume of their container, highest energy, particles are most spread out. Vapor is the gaseous form of what are normally solids and liquids at room temperature,

Physical Changes Composition of the material does not change,

although some of the physical properties may change

Changes of state: boiling, freezing, melting, condensing

Irreversible changes such as breaking, splitting, grinding, cutting and crushing

2.2 Mixtures

A mixture is a physical combination of 2 or more substances. Examples:

Heterogeneous: a mixture that is not uniform throughout. Examples:

Homogeneous: the composition of materials is uniform throughout. Also called a solution. Examples:

Separating mixtures: differences in physical properties enable us to separate mixtures

Filtration can be used to separates solid from a liquid in a heterogeneous mixture

Distillation is the boiling of a mixture of liquids with different boiling points

2.3 Elements and Compounds

Elements

Simplest form of matter that has a unique set of properties

Cannot be broken down into simpler substances

Examples:

Compounds A substance that

contains 2 or more elements

Chemically combined

Fixed proportion of elements such as: water always has 2 atoms of hydrogen for every one oxygen

Can be broken down into simpler substances by chemical means

Examples:

Compounds

Physical methods that are used to break down mixtures CANNOT be used to separate the substances in a compound.

Chemical changes are required to break down a compound into its components such as: heating (not just boiling) and electricity

Pure Substance or Mixture?Substances

Composition can vary

Cannot be separated physically

Element or compound

Examples:

Mixture Composition is fixed

Can be separated by physical means

Physical combination of 2 or more substances

Examples:

The Periodic Table An arrangement of elements

into groups based on a set of

repeating properties

Permits the comparison of properties of one element to another

Horizontal rows of the table are called periods and properties vary as you move across a row and and that pattern repeats in the next row.

Vertical columns of the table are called groups (or family) and elements in groups have similar chemical and physical properties.

Symbols represent elements

Chemical Formulas represent compounds

2.4 Chemical Reactions (or chemical changes) A chemical property describes the ability of a

substance to undergo a chemical change. While it can help identify a substance, the substance actually undergoes a chemical change and thus becomes a new substance.

Reactants are present at the start of a reaction.

Products are the substances produced from a reaction.

Evidence: transfer of energy (sound, light, heat, electricity) color change, production of gas, formation of a precipitate (a solid that forms and settles out of a liquid mixture)

Conservation of Mass

During any chemical reaction, the mass of the products is always equal to the mass of the reactants

AKA: The Law of Conservation of Mass states that in any physical or chemical reaction, mass is conserved.

Understanding this law and its application is very important to chemistry!!!!!