Chapter 2 Notes

Matter

anything that has mass and occupies space

extensive properties

property that depends on the amount of matter

intensive properties

property that depends upon the type of matter

Substance

matter that has a uniform and definite composition

Every sample of a given substance has what because of their composition?

Identical intensive properties

Element

The simplest form of matter that has a unique set of properties; pure substances made up of only one kind of atom.

Compound

Substances that contain two or more elements chemically combined in a fixed proportion.

Chemical symbols

Represent elements; one or two letters

Chemical formulas

represent compounds; multiple letters combined with numbers

Physical properties

A quality/condition of a substance that can be observed or measured without changing the substance’s composition

Examples of physical properties

Hardness, color, conductivity, melting/boiling points, physical state at room temperature, and malleability

Solids

A form of matter that has a definite shape and form

Solids description

particles packed tightly together, virtually incompressible, only slightly expands with heat

Liquids

A form of matter that has an indefinite shape, flows, yet has a fixed volume

Liquids description

Particles are not arranged rigidly, particles are in close contact with each other, free flowing, volume does not change as shape of container changes; volume is fixed, almost incompressible, expands slightly when heated

Gas form

A form of matter that takes both the shape and volume of its container

Gas descriptions

great distances and no interactions between particles, easily compressible, have indefinite shape and volume, free flowing

Gas

term used for substances that exists in the gaseous state at room temperature

Vapor

term used for the gaseous state of a substance that is usually a liquid or a solid at room temperature

During physical change what happens to the properties and composition?

The properties of a material change but the composition does not change

Reversible physical changes; examples

A change in the physical state; boiling, freezing, melting, condensation

Irreversible changes examples

break, split, grind, cut, crush

Chemical change

a change that produces matter with a different composition than the original matter

During a chemical change, what happens to the composition of matter?

it always changes

When can the chemical properties of a substance be observed?

When it undergoes a chemical change

Chemical property

The ability of a substance to undergo a specific chemical change.

Reactant

The substances present at the start of the chemical reaction

Product

The substances present at the completion of the chemical reaction

Recognizing Chemical Changes

Production of gas, transfer of energy, formation of a precipitate or a color change

Law of Conservation of Mass

In any physical or chemical, mass is conserved

During a chemical reaction, what is the relation of the mass of the products to the mass of reactants?

Equal to one another

Mass in physical changes

weigh mass before and after change, mass before and after is always the same

Mass in chemical changes

weigh reactants and products, mass of reactants and products should also be the same, but not always

Mixtures

Physical blends of two or more components each of which retains its own properties/identities 

Heterogenous mixture

mixture in which the composition is not uniform throughout

Homogeneous mixture

mixture that has uniform composition throughout

phase

any part of a sample with uniform composition and properties

How many phases in homogeneous mixtures?

1

How many phases in homogeneous mixtures?

2 or more

What do you use to separate the components of a mixture?

Differences in physical properties

Filtration

process that separates a solid from a liquid

Distillation

process that separates a liquid from a liquid or liquids from solids dissolved in them

How to distinguish a mixture from a substance

Use the general characteristics

Substances have a what composition?

fixed composition

Mixtures have a what composition?

Mixture

Can you physically separate mixtures and substances?

You can physically separate mixtures into their component parts but we cannot do so with substances.