chemistry notes. what is chemistry? study of matter and its properties

Chemistry Notes

What is chemistry?

Study of matter and its properties

Why study chemistry?Used in career fields like doctor,

nurse, pharmacist, engineer, rocket scientist, etc

Can help you stay healthier – helps explain reactions in your body and certain diseases and their treatments

Matter’ definitionIt has to have 2 things

Has to have mass and volume

How to describe matter? Physical Properties - properties you can

test for or sense without changing the substance

Examples:density color tastepH magnetism boiling pointmelting point odor

Chemical properties Chemical properties – property in

which you test how it reacts with another substance, and the substance being tested is changed

Reaction with baking soda Flammability Decompose with heat

State of Matter and Their Properties

All matter can exist as a gas, solid, or liquid at the proper temperature and pressure

Solid

Particles are close to one another and don’t move

Fixed shapeDoesn’t fill container necessarilyHigh densityNot very compressible

Examples: steel, copper, plastic, ice

Gases Particles are far apart and moving

fast Always fills container Takes shape of container Least density Compressible

Examples: air, natural gas, water vapor

Liquid Particles can move past each other Can fill a container Takes shape of a container Medium density Slightly compressible

Examples: liquid water, milk 

Two major classifications  

Two major classifications

Pure substanceMixture

Two kinds of pure substances Element

Definition – pure substance that can’t be broken down into simpler substances by chemical or physical means

   #’s – approximately 118  The substances on the periodic table

Examples: gold, iron, hydrogen, oxygen 

Compound Definition – pure substance made up of

two or more different elements chemically combined

  #’s – millions  Examples: salt, water, sugar  

Mixture Mixture – two or more pure substances

physically combined Gaseous mixtures – like air

Solid mixtures – like alloys such as brass and stainless steel

Liquid mixtures – milk, salt water

Mixtures with more than one phase

Carbonated beverages 

Separating or purifying matter

Mixtures – can be separated by physical means

Separate a mixture of any two pure liquids

Distillation Separate the water in salt water from the

saltsBoil off the water and salts will remain

Separate a mixture of gasesCool them – they will condense at different temperatures

Compounds Can only be separated by chemical means

Decomposition – Heat to high temperature:Ex. copper oxide ore from the earth – drive off the oxygen by heating to a high temperature

Electrolysis Pure water can be separated into

hydrogen and oxygen gases by using an electric current

Elements Can’t be purified any further or broken apart by chemical or physical means

Chemical Changes

Definition – change in which a substance changes its chemical identity

Examples 

Burning propaneReaction between vinegar and baking

soda

Also called a chemical reaction

Physical changes 

Definition – change in which a substance changes its physical properties without changing its identity.    Examples 

Cutting woodTearing up a piece of paperMelting iceBoiling water