Matter Properties and Changes

States of matter Solid – Definite shape and volume – Only vibration of atoms Liquid – Flows and has constant volume – Takes shape of the container – Atoms close but can slide past one another Gas – Flows – Takes shape and volume of container – Easily compressed – Atoms far apart move around quickly Moves until hits another atom or side of container – Vapor is the gaseous state of a substance Plasma – In neon lights and lighting – Has electrons stripped

Physical property Density, color, odor, hardness, melting point, boiling point Extensive properties – Dependent on the amount of a substance present Mass is an example Intensive properties – Independent of the amount of substance present Example, the density of a substance Better use to identify substances

Chemical properties The ability of a substance to combine with or change into one or more other substances Must be able to tell the difference between the two Water turns to ice at 273K. Water boils at 373K. If water is in a gaseous state it combines readily with other compounds. End 3-1

Physical Changes A physical change does not change the identity of the substance – Cutting paper – Phase change Solid  gas sublimation Solid  liquid Melting Liquid  gas vaporization Liquid  solid solidification (freezing) Gas  solid deposition Gas  liquid condensing

Chemical change Changing into new substances – Rusting – Burning – Explode Conservation of mass – Mass cannot be created nor destroyed – The mass that goes into a reaction must come out of the reaction. – End 3-2

Mixtures Mixtures are a combination of two or more substances Two types of mixtures – Heterogeneous Does not blend smoothly throughout has individual substances remain – Homogeneous mixture Has constant composition throughout

Solutions Different name for homogeneous mixtures – Can be solids liquids or gasses SystemExample Gas-gasAir in a scuba tank Gas-liquidOxygen dissolved in water Liquid-gasMoisture in the air (humidity) Liquid-liquidWater and fruit juice Solid-liquidSalts dissolved in seawater Solid-solidBronze

Separating mixtures Mixtures can be separating using the physical properties of the substances in the mixture – Filtration Porous barrier to separate a solid from a liquid – Distillation Differences in boiling points – Can boil away water leaving salt behind – Crystallization Pure solid particles form crystals – Rock candy is made this way – Sublimation Separate solid if one sublimates – Chromatography Separate base on substances ability to be drawn up paper or tube – Separate ink this way – End 3-3

Elements and Compounds An element is a substance made of only one type of atom – Always has same properties no matter what the amount – Cannot be separated by physical or chemical means The elements are arranged on the periodic table – Group or families-vertical columns – Periods- horizontal rows A compound is made up of two or more different element combined chemically – Can be broken down into smaller parts

Separating compounds into components Compounds that are natural much harder to break down into elements than non natural – Some medicines in opaque containers because light breaks them down – Water can not be so easily separated Electrolysis – Using electricity to separate compounds » Breaks the bonds – Compounds have different properties than the elements that make them up Table salt a great example

Laws

Problems A 78.0 g sample of an unknown compound contains 12.4 g of hydrogen. What is the percent by mass of hydrogen in the compound? 1.0 g of hydrogen reacts completely with 19.0 g of fluorine. What is the percent by mass of hydrogen in the compound that is formed?

Multiple proportion problems