Chapter 2 Matter and Change Hingham High School Mr. Clune

What is Matter? Matter is anything that takes up space and has mass. Mass- amount of material or “stuff” in an object Weight is due to gravity, and changes from location to location; mass is always constant.

Mass or Weight

Types of Matter Substance- a particular kind of matter - pure; is uniform (all the same) and has a definite composition (examples are elements & compounds) water; gold; lemonade? Mixture- more than one kind of matter; has a variable composition

Substance or Mixture???

Properties Words that describe matter (adjectives) Physical Properties- a property that can be observed and measured without changing the composition. Examples- color, hardness, m.p., b.p. Chemical Properties- a property that can only be observed by changing the composition of the material.

Properties Words that describe matter (adjectives) Physical Properties- a property that can be observed and measured without changing the composition. Examples- color, hardness, m.p., b.p. Chemical Properties- a property that can only be observed by changing the composition of the material.

Properties????

States of matter Solid- matter that can not flow (definite shape) and has definite volume. Liquid- definite volume but takes the shape of its container (flows). Gas- a substance without definite volume or shape and can flow. Vapor- a substance that is currently a gas, but normally is a liquid or solid at room temperature. (water vapor?)

States of matter

States of Matter Definite Volume? Definite Shape? Temp. increase Com-pressible? Small Expans. Solid YES YES NO Small Expans. Liquid NO NO YES Large Expans. Gas NO NO YES

Condense Freeze Melt Evaporate Solid Liquid Gas

Physical Changes A change that changes appearances, without changing the composition. Ex. Boil, melt, cut, bend, split, crack Boiled water is still water.

O2 + Fe Fe2O3 Chemical Changes Chemical changes - a change where a new form of matter is formed. Ex. Rust, burn, decompose, ferment O2 + Fe Fe2O3

Mixtures Physical blend of at least two substances; variable composition Heterogeneous- mixture is not uniform in composition Chocolate chip cookie, gravel, soil.

Mixtures Homogeneous- same composition throughout; called “solutions” Kool-aid, air, salt water Every part keeps it’s own properties.

Mixtures Heterogeneous Homogeneous

Solutions Homogeneous mixture Mixed molecule by molecule Can occur between any state of matter gas in gas; liquid in gas; gas in liquid; solid in liquid; solid in solid (alloys), etc.

Solutions Like all mixtures, they keep the properties of the components. Some can be separated easily by physical means: rocks and marbles, iron filings and sulfur Other methods: distillation- takes advantage of different boiling points

Distillation

Filtration

Water Filtration

Homework Worksheets Section 2-1 Section 2-2

Section 2.3 Elements and Compounds

Substances Hg Cu H Au NaCl H2O CO2 Elements Compounds

Elements Element A pure substance that cannot be made simpler by known chemical means Examples: hydrogen, oxygen, nitrogen, carbon, phosphorus, sodium, potassium and chlorine

Elements Each element is represented by a symbol that usually consists of one or two letters Hydrogen (H), Oxygen (O), Carbon (C), Chlorine (Cl), Sodium (Na)

Pure substances produced from the chemical combination of elements Compounds Pure substances produced from the chemical combination of elements Examples: water (H2O) is a compound of hydrogen and oxygen, sodium chloride (NaCl) is a compound of sodium and chlorine.

Compounds Has a fixed composition Has its own characteristic properties H2 is a combustible gas, O2 is a gas helps burning but H2O is a liquid that is used to extinguish fire.

Compound or Mixture Compound Mixture Made of one kind of material Made of more than one kind of material Made by a physical change Made by a chemical change Definite composition Variable composition

Which is it? Mixture Compound Element

Chemical Symbols & Formulas

Chemical Symbols & Formulas Currently, there are 116 elements Each has a 1 or two letter symbol First letter always capitalized; the second never; chemical “shorthand” Some from Latin or other languages;

Practice Problems: 18,19 Page 51 Section Assessment 20-27 Page: 52 Homework 2.3 Practice Problems: 18,19 Page 51 Section Assessment 20-27 Page: 52 Due: 9/24/04

Chemical Reactions Yields H20 H2 + O2 Reactants } Products }

Chemical Reactions When one or more substances are changed into new substances. Reactants- stuff you start with Products- What you make

Chemical Reactions Ability to undergo chemical reaction is called a chemical property Products have NEW PROPERTIES Arrow from reactants to products

Indications of a chemical reaction: Energy absorbed or released (temperature changes hotter or colder) Color change Gas production (bubbling, fizzing, or odor change)

Indications of a chemical reaction: Formation of a precipitate- a solid that separates from solution (won’t dissolve) Irreversibility- not easily reversed

Law of Conservation of Mass Mass can not be created or destroyed in ordinary (not nuclear) chemical reactions or physical change

Law of Conservation of Mass All the mass can be accounted for. Burning of wood results in products that appear to have less mass as ash; where is the rest?

Law of Conservation of Mass H20 H2 + O2 2 2 Products } Reactants } 10g 10g

Homework Worksheets 2.3 & 2.4 Due: 9/20/05 Test: 9/21/05