MATTER

CHANGE

AND

Chemistry:

The study of matter and the changes it undergoes.

Matter

Anything that has mass and takes up space

Alchemical view of matter

Matter• Atoms are the building blocks of matter

Matter

“Space-filling” models of molecules

Matter

Each element is made of the same kind of atom

Oxygen

Hydrogen

Each element is made of the same kind of atom with unique set of properties

Carbon

Graphite

Uncut diamond

Uncut diamond

with impurities

STATES OF MATTER: Solid, Liquid, Gas

(a) Particles in solid (b) Particles in liquid (c) Particles in gas

STATES OF MATTER

• SOLIDS– Definite shape and

volume– Particles of a solid

packed tightly together– NOT easily

compressed

SOLIDS

STATES OF MATTER

• LIQUIDS– Particles in close

contact but arrangement is not orderly or fixed

– Definite volume– NOT easily

compressed

Liquid

H2O(l) Water

Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 31

In a liquid• molecules are in constant motion

• there are appreciable intermolecular forces

• molecules are close together

• Liquids are almost incompressible

• Liquids do not fill the container

STATES OF MATTER

• GAS– Particles NOT in close

contact and are constantly moving

– No definite volume

Some Properties of Solids, Liquids, and Gases

Property Solid Liquid Gas

Shape Has definite shape Takes the shape of Takes the shape the container of its container

Volume Has a definite volume Has a definite volume Fills the volume of the container

Arrangement of Fixed, very close Random, close Random, far apartParticles

Interactions between Very strong Strong Essentially noneparticles

How to describe matter…

• Extensive properties– Depends on the

AMOUNT of matter in a sample

• Mass• Volume

• Intensive properties– Depends on the TYPE

of matter in a sample• Color• Temperature• Density

SUBSTANCE

• Matter that has a uniform and definite composition

• Every sample of a given substance has identical intensive properties because every sample has the same composition

• Elements CANNOT be broken down into simpler components

• Compounds CAN be broken down into elements

Examples of pure substances

GOLD ALUMINUM

Compounds• Made of two or more different kinds of elements

chemically combined in a fixed proportion.– for example:

• Common table salt is a one to one combination of sodium atoms (Na) and chlorine atoms (Cl) = NaCl

What do we mean by “chemically combined”?

• Elements in compounds are joined by chemical bonds.– Examples of chemical bonds:

• Ionic bond (electrostatic attraction that binds oppositely charged ions)

– Usually composed of metal and nonmetal atoms

• Covalent bond (bond that forms by the sharing of electrons between atoms)

– Usually composed of carbon atoms bonded to elements such as hydrogen, oxygen, nitrogen and sulfur

Properties of Compounds

• Compounds can be broken down into simpler substances by chemical means but elements cannot.

• Compounds and the elements from which they are formed have different properties

Examples of Compounds

• Sugar (sucrose)– Composed of carbon, hydrogen and oxygen

• Sugar a sweet-tasting white solid but carbon is a black, tasteless solid; Hydrogen and oxygen are odorless gasses

Sugar Carbon + Water

http://www.youtube.com/watch?v=A_jtOpAYG70

Sugar (sucrose)

Sugar (sucrose)

Properties of Matter

• Physical properties:– Can be observed without changing a

substance into another substance• Boiling point, density, mass, volume, magnetic

Properties of Matter

• Physical changes– Changes in matter that do NOT change the

composition of a substance• Changes of state (liquid to a gas), temperature

(melting point), volume, crush, grind

• Chemical changes– Changes that result in a new substance

• Combustion, oxidation, decomposition

Mixtures

• Physical blend of two or more components

• Heterogeneous = composition is variable throughout the sample

• Homogeneous = composition is uniform throughout the sample

Classification of Matter