Allied health Chemistry exam #1

examples of matter

matter is anything that has mass and takes up space. air, salt, water, etc.

what is a physical change

A physical change is when a substance changes in size, shape, or state without changing its chemical composition.

chemical change

A chemical change is when a substance undergoes a reaction that forms one or more new substances with different chemical compositions. ex iron rusting.

which statement describes the size and shape of a sample of gas?

volume and shape cannot be discribed.

which factor determines the state of matter in which a substance excists?

tempature, can be a solid, liquid, or gas

what is a pure substance?

a substance that always has the same elemental compound. ex. distilled water (H₂O), because it contains only one type of molecule and has a uniform composition throughout.

an exsample of a pure compound is?

sugar, C12H22Oll

The formula for phosphorus pentafluoride is

PF5.

A chemical bond formed when two atoms share one pair of electrons is a_____bond; its best described by___.

single; covalent

In a Lewis dot structure the electrons which complete an octet but are not located between two atoms are referred to as

one pair

Which representation of a methane molecule is not correct? (A methane molecule is composed of one carbon atom and four hydrogen atoms.)

least electromagnetic goes from which way

left to right

A bond where the electrons are shared equally is called a(an)________bond.

Covalent

An atom with 3 valence electrons will most likely_____to attain an octet of valence electrons

lose 3 electrons

ionic bond

formed by transferring between metals and non metals

diatomic molecules

most of the time gases(halogens) are diatomic

the number of valence electrons in a main group is given by

group number

A positively charged particle formed by loss of one or more electrons from an atom is called a(an)

cation

A small negatively charged particle formed when an atom gains one or more electrons is called

anion

Which chemical symbol represents a metallic element?

Ca

Which chemical symbol represents a metalloid?

Ga