Matter & Change

What is Chemistry?

• The study of the composition, structure, and properties of matter and the changes it undergoes

Why Study Chemistry?• Chemistry is central to our understanding of

other sciences.• Chemistry is also encountered in everyday

life.

Branches of Chemistry

• Organic – carbon – containing compounds

• Inorganic – anything not organic• Physical – relationship between energy &

matter• Analytical – identification of components

and composition• Biochemistry – substances & processes

occurring in living things• Theoretical – use math & computers to

predict properties of new compounds

Types of Research

Basic – carried out for the sake of increasing knowledge, such as how and why a specific reaction occurs

- chance discoveries are sometimes the result

Applied – generally carried out to solve a problem

- develop new compounds to replace refrigerants that are suspected of destroying ozone layer

Technological development – involves the production and use of products

What is Matter?

Must Fulfill Two RequirementsHave Mass - amountHave Volume - space

States of Matter

• Matter can be a gas, a liquid, or a solid.• Gases have no fixed shape or volume.• Gases can be compressed to form liquids.• Liquids have no shape, but they do have a

volume.• Solids are rigid and have a definite shape

and volume.

 

The Three States of Matter

Building Blocks of Matter

• Atom – smallest unit of an element that maintains the properties of that element

• Element – pure substance made of only one kind of atom

• Compound – atoms of two or more elements chemically combined

Properties

• A characteristic that defines substance

• Two classes– Extensive – dependent on the amount

of matter present (volume, mass, energy)

– Intensive – is not dependent on amount (melting point, boiling point)

Physical Properties & Changes

A change in the substance that does not involve a change in the identity

Eg: change of state

Chemical Properties & Changes

Substance’s ability to undergo changes that transform it into different substances

Reactants Products

Chemical Change Evidence

•Production of a gas•Production of a precipitate•Heat•Light

Energy & Change

• Energy is almost always involved in both chemical and physical changes.

• Law of Conservation of Energy (and Mass)

• Energy is put in – endothermic• Energy given off - exothermic

Classification of MatterMatter

Can it be separated?Yes No

Pure Substances

Mixtures

Is composition uniform?

Homogeneous Heterogeneous

Yes No Can it be decomposed by ordinary chemical means?Yes No

Compounds Elements

Blend of two or more kinds of matter, each of which retains its own identity and properties

Has a fixed composition; has exactly the same properties throughout; has exactly the same composition

Pure Substances and Mixtures

• Atoms consist of only one type of element.• Molecules can consist of more than one

type of element.– Molecules can have only one type of atom (an

element).– Molecules can have more than one type of

atom (a compound).• If more than one atom, element, or

compound are found together, then the substance is a mixture.

Pure Substances

and Mixtures

Pure Substances and Mixtures• If matter is not uniform throughout, then it is a

heterogeneous mixture.• If matter is uniform throughout, it is

homogeneous.• If homogeneous matter can be separated by

physical means, then the matter is a mixture.• If homogeneous matter cannot be separated by

physical means, then the matter is a pure substance.

• If a pure substance can be decomposed into something else, then the substance is a compound.

Mixtures

• Heterogeneous mixtures are not uniform throughout.

• Homogeneous mixtures are uniform throughout.

• Homogeneous mixtures are called solutions.

Periodic TableGroups

Periods

Metalloids

Noble Gases

Elements• If a pure substance cannot be decomposed into

something else, then the substance is an element.• There are 114 elements known.• Each element is given a unique chemical symbol

(one or two letters).• Elements are building blocks of matter.• The earth’s crust consists of 5 main elements. (O, Si,

Al, Fe, Ca)• The human body consists mostly of 3 main

elements. (O, C, H)

Elements

Elements• Chemical symbols with one letter have that letter

capitalized (e.g., H, B, C, N, etc.)• Chemical symbols with two letters have only the first

letter capitalized (e.g., He, Be).

C U Cu

Na