Chapter 2: Matter and How It Can Change

1. Chapter 2: Matter and How It Can Change

2. Types of Matter • Substances: contains only one type of matter and has a uniform and definite composition • Element~ • Composed of just one type of atom. They cannot be separated into simpler substances using chemical means. • They are represented by a chemical symbol (see Periodic Table). • Diatomic elements: 7 of them… start at seven, form a seven and Hydrogen. • For example: Gold (Au), Iron (Fe), Oxygen (O or O2) • Compound~ • Substances composed of two or more different kinds of atoms. The atoms are chemically combined to form a molecule (or formula unit). • They are represented by a chemical formula which shows the elements and relative number of atoms in the compound. • For example: Water, H2O and Salt, NaCl.

3. Types of Matter • Mixtures: a physical blend of two or more substances. • Homogenous~ • Uniform in composition. • Transparent: solutions • Opaque: suspensions • Can be separated by distillation, ion exchange, reverse osmosis • For example: Koolaid, salt water, air, milk and blood • Heterogeneous~ • Opaque, not uniform in composition and appearance • Can be separated by sieving, tweezing and skimming • For example: Sand, bronze, us and the ocean

4. States of Matter • Solid~ • Definite shape and volume • Very slight thermal expansion and almost incompressible • Divided into subclasses of amorphous (or glassy) solids and crystalline solids • Arrangements of atoms or molecules in crystalline solids are repeated regularly over a very long range of millions of atoms • Arrangements in amorphous solids are somewhat random or short range of say some tens or hundreds of atoms. • Liquid~ • Indefinite shape (flows) and definite volume • Moderate thermal expansion and almost incompressible • Gas (Vapor)~ • Indefinite shape and indefinite volume • Great thermal expansion and readily compressible • A vapor is the gaseous form of a substance that is normally solid or liquid at room temperature • Plasma~ • A very hot state of matter where atoms have been ripped apart into their smaller parts, protons and electrons.

5. Animation

6. Properties of Matter • Everything is made of matter • Mass is the amount of matter (grams or kg) • Volume is the space that the matter takes up (cm) • Two main types: • Physical properties: A characteristic of a substance that can be measured or observed without changing the substance’s composition • Intensive-don’t change for a particular sample such as density, melting point, boiling point, color, solubility conductivity, ductility, and specific heat. • Extensive- depend on size of matter such as length, mass, height, volume, and area. • Chemical properties: A characteristic of a substance that describes how it interacts with other substances to become something new.

7. Changes in Matter • Physical Change • An alteration of matter that does not change the chemical composition of the material • For example: freezing or melting, boiling or condensing, cutting, grinding, bending, blending • Chemical Changes • Results in a change in the chemical composition of the substance(s) which is called a reaction. • For example: rusting, composting, tarnishing

9. Practice Identifying Types of Changes in Matter Chemical Physical Physical Chemical Physical Chemical Physical Chemical

10. Chemical Reactions • In a chemical reaction, one or more substances change into new substances by rearranging the atoms • Copper + nitric acid  copper(II) nitrate + nitrogen dioxide + water ReactantsProducts • The ability of a substance to undergo a chemical reaction and form new substances is called a chemical property. • How to tell a chemical reaction has occurred. • Heat is absorbed or given off. • Change in color or odor. • Production of a gas or solid. • Law of Conservation of Mass • During any chemical reaction, mass is neither created nor destroyed. The total mass of the system (products plus reactants) and the mass of each element is unchanged. Chemical Reaction Movies