# Unit 2 (Materials: Structure and Uses): Section A

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Unit 2 (Materials: Structure and Uses): Section A

Some Review Definitions
Mass is a measure of the amount of matter in a material. Matter is anything with mass that takes up space. Weight is a measure of the gravitational pull on an object. Weight can change from place to place, mass is constant.

Basic Building Blocks of Matter
An atom is the smallest unit of an element that has the same properties of that element. An element is a pure substance composed of only one kind of atom. Example: Gold = Au A compound is a substance that is made of two or more elements that are chemically bonded together. Example: Water

Properties and Changes in Matter
Every substance has properties that make it different from other substances, and these properties can be used to identify a substance. Extensive Properties depend on the amount of matter that is present. (mass, volume) Intensive Properties do not depend on the amount of matter that is present. (color, density)

Physical Properties and Changes
A physical property is a characteristic that can be observed or measured without changing the identity of the substance. These properties are used to describe the substance. A physical change is a change in the substance that does not result in a change in the substance’s identity.

Changes of State Changes of state is a physical change of a substance from one state to another. States of matter Solid – definite volume and definite shape Liquid – definite volume and indefinite shape Gas – indefinite volume and indefinite shape Plasma – high temperature state of matter in which atoms lose their electrons.

Chemical Properties and Changes
A chemical property relates to a substance’s ability to undergo changes that transform it into different substances. A chemical change or chemical reaction (rxn) is a change in which one or more substances is transformed into one or more different substances. The substances that react together in a chemical rxn are called the reactants. The substances that are formed from a chemical rxn are called the products.

Periodic Table The periodic table is a grouping of elements in order of increasing atomic number. Vertical columns on a periodic table are called groups or families. Horizontal rows on a periodic table are called periods. The periods are numbered Period 1 to 7.

Periodic Table Families
Group 1 – Alkali Metals Group 2 – Alkaline Earth Metals Groups 3-12 – Transition Metals Group 13 – Boron Family Group 14 – Carbon Family Group 15 – Nitrogen Family Group 16 – Chalcogens Group 17 – Halogens Group 18 – Noble Gases

Metals vs. Nonmetals vs. Metalloids
Metals are on the left side of the periodic table, and they are good conductors of heat and electricity. They are also malleable (can be hammered into sheets) and ductile (rolled into wire). Nonmetals are on the right side of the periodic table, and they are poor conductors of heat and electricity. They can be gases or brittle solids. Metalloids have properties of metals and nonmetals.

Noble Gases The Noble Gases are group 18 on the periodic table. They are very stable, and they do not like to react with anything. Most of the Noble Gases are used in lighting (fluorescent lights), and helium is used to inflate balloons so that they float.