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Review of Objective 3 vocabulary for 8th Grade STAAR test.

Atom

smallest particle of an element; contains protons, neutrons, and electrons

Nucleus

the central core of an atom containing protons and neutrons

Protons

located in nucleus; has a positive charge; determine element's identity

Neutrons

located in nucleus; neutral (no) charge

Electrons

located in electron cloud around nucleus; has a negative charge

Valence Electrons

electrons in the outer most energy level of an atom; determine the chemical propeties of an element (ex. reactivity - how elements will react with other elements/compounds)

Elements

pure substances; found on periodic table; represented by chemical symbol

Compounds

made of two or more elements; formed by chemical reaction; represented by a formula

Metal

elements found on the left and center of the periodic table; usually solid, are shiny, conduct electricity, malleable

Nonmetal

elements found on the right of the periodic table; usually gas, are dull, do not conduct electricity, brittle (not malleable)

Metalloid

elements located between metals and nonmetals on the periodic table (along bold stair-step line); have characteristics of both metals and nonmetals

Period

rows in the periodic table; elements in same period have same number of energy levels; elements in same period are not alike in properties

Group

columns in periodic table; also known as "families"; elements in same group have similar physical and chemical properties because they have the same number of valence electrons

Physical Properties of Matter

how matter is described according to physical characteristics; characteristics that can be observed without changing the substance into something else; ex. luster

Chemical Properties of Matter

characteristics that can be observed when a substance interacts with another substance; ability to react; inability to react; usually hidden

Physical Changes in Matter

a change in the form or appearance of a material that does not change it into a new substance; a change in size, shape, or state of matter; no new matter is formed; ex. melting ice, tearing paper, dissolving kool-aid, mixing salt and pepper, muscles of stomach grind food into smaller pieces

Chemical Reaction (Chemical Changes in Matter)

atoms are rearranged to make new substances with new properties different than the original substance; starts with reactants, ends with products; ex. rusting nails, decaying matter, burning wood, digesting food is mixed with acid in digestive systemt to break down protein molecules (carbohydrates broken down into sugars)

Evidence of Chemical Reaction

-production of gas
-formation of precipitate
-change in temperature
-change in color
-change in odor

Chemical Formulas

way of describing elements and number of atoms that make up one molecule of a compound; uses symbols, subscripts and coefficients

Finding Number of Elements in Chemical Formula

count the capital letters

Finding Number of Atoms in Chemical Formula

count the capital letters and numbers

Chemical Equation

way of writing changes in the arrangement of atoms during a chemical reaction; uses symbols, subscripts and coefficients; balanced when equation has the same number of atoms of each element on both sides of the equation

Law of Conservation of Mass

matter can neither be created nor destroyed, it can only change form; the mass of all substances before a chemical reaction must equal the mass of all substances after a chemical reaction

Atomic Number

top number in the element square on the periodic table; identifies the number of protons and electrons in a neutral atom

Mass Number

decimal number found beneath the symbol in the element square on the periodic table; usually rounded off to find the number of neutrons

Finding the Number of Protons or Electrons in an Atom

look at the atomic number on the periodic table

Finding the Number of Neutrons in an Atom

round off the atomic mass to the nearest whole number and subtract the atomic number from it.

Element

a pure substance consisting of only one kind of atom and identified by its' atomic number (which is the number of protons).

Compound

a chemical substance made by bonding atoms of two or more different elements.

Organic Compound

compounds containing carbon, as well as hydrogen and/or nitrogen, sulfur, phosphorous, or oxygen. (Used for life processess, make up nucleic acids, proteins, carbohydrates)

Food web

the pattern of overlapping food chains in an ecosystem

Food Chain

simplified model that shows a single path for energy flow through an ecosystem

energy pyramid

A diagram shaped like a TRIANGLE that shows the loss of energy at each level of the food chain

luster

the quality of giving off light, brightness, glitter, brilliance (shine)

malleability

property of a material to be hammered into various shapes without breaking

ductility

the ability to be stretched into a thin wire

conductivity

The ability of an object to transfer heat or electricity to another object

density

mass of an object divided by its volume

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