Chapter 1 Chem Terms

Chemistry

Measuring and analyzing matter and how it changes. Also interested in the energy associated with these changes

Matter

Has mass and takes up space

Atom

Smallest building block of matter

Molecules

Two or more atoms bonded together

Gas

Has no fixed shape and no fixed volume. Does conform to a container and somewhat fills it. Atoms and molecules are far apart and disorganized

Liquid

No fixed shape but has a fixed volume. Does conform to a container and somewhat fills it. Atoms and molecules are close together and disorganized.

Solid

Have a fixed shape and have fixed volume. Does not conform to container nor fills it. Atoms and molecules are closely packed and rigid/organized.

Pure Substances

Have distinct properties and a fixed composition. Composition does not vary from sample to sample. An element or compound/ a material that only contains one element or compound. Opposite of a mixture basically.

Elements

Cannot decompose into anything smaller. 118 known, 90 natural. Represented by 1 or 2 letters. (Carbon- C, Oxygen- O, Cobalt- Co) CO- cardon monoxide (compound). One type of atom.

Atomic Elements

Elements made up of one individual atom. Each atom is separate from the others.

Molecular Elements

A few elements exist as molecules. Similar atoms bonded together. (More than two but must be the same element)

Diatomic Molecules

Two of the same atoms attached. Only 7 exist and are gases. H2, N2, O2, F2, Cl2, Br2, and I2.

Ozone

O3

Tetraphosohorus

P4

Sulfur

S8

Compounds

Molecules of two or more different elements that are connected. Combined in a fixed ratio (H2O, H2O2) Able to decompose into respective elements. All pure substances. 2 types of atoms

Mixture

Combination of two or more substances. Are not pure but are made up of pure substances. Each substance keeps its original properties, can separate each substance, no fixed composition, varies sample to sample.

Homogeneous Mixture/Solutions

Uniform appearance and composition. (Air, sugar water)

Heterogeneous Mixture

Not Uniform composition and appearance. (Sedimentary rocks, mixing oil and water)

Physical Properties

Describes appearance and can be observed without changing composition

Intensive property

Does not depend on how much of the sample is present. Ex.) color, luster, hardness, melting point, density, conductivity, phase/state.

Extensive property

Does depend on how much of the sample is present. Ex.) mass, volume, length, thickness.

Chemical properties

describes interactions with other substances. How a substance changes/reacts to form a new substance. Ex.) corrosiveness, flammability, reactivity towards acids and bases.

Physical changes

Alters the form of a substance but not the identity. Same substance before and after. Ex.) a change in state and is reversible. H2O (l) → H2O (g)

Chemical changes/reactions

Starting substance converted to new substance(s). A different substance before and after. Usually associated with bubbles, flame, or color change. H2O (l) → 2H (g) + O2 (g)