Properties of Matter

 chemists use characteristic properties to tell substances apart and to separate them  some properties define a group of substances

Types of Properties  Extensive- a property that depends on the amount of matter  Ex: volume, mass, amount of energy  Intensive- a property that does not depend on the amount of matter  Ex: density, boiling point, ability to conduct electricity

A. Extensive vs. Intensive  Examples: boiling point volume mass density Conductivity temperature intensive extensive intensive

Types of Properties  Physical property- characteristics that can be observed or measured without changing the identity of a substance  Chemical property- relates to a substance’s ability to undergo changes that transform it into a different substance  Easiest to see when a chemical is reacting

B. Physical vs. Chemical  Examples: melting & boiling point flammable density magnetic tarnishes in air physical chemical physical chemical

Physical Changes in Matter  change in a substance that doesn’t change the identity of the substance  Ex. grinding, cutting, melting, boiling  Includes all changes of state (physical changes of a substance from one state to another)

Solid  definite volume  definite shape  atoms are packed together in fixed positions  strong attractive forces between atoms  only vibrate in place

Liquid  definite volume  indefinite shape  atoms are close together  atoms can overcome attractive forces to flow

Gases  indefinite volume  indefinite shape  atoms move very quickly  atoms are far apart  pretty weak attractive forces

Chemical Changes in Matter  A change in which a substance is converted into a different substance  Also known as a chemical reaction  Doesn’t change the amount of matter present (Law of Conservation of Mass)  reactants- substances that react  products- substances that are formed

mercury + iodine  mercuric iodide

Signs of a Chemical Change  Heat is released (gas is given off) or absorbed (feels cold)  Bubbles form without heating  Color change without an apparent cause

B. Physical vs. Chemical  Examples: rusting iron dissolving in water burning a log melting ice grinding spices Decomposing tree chemical physical chemical physical Physical chemical

Physical vs Chemical Color Change  What is the difference between the cause of color change in the two pictures below?

What types of matter are there?  Element  Compound  Homogeneous Mixture  Heterogeneous Mixture

Atom- smallest unit of an element that keeps the properties of element Evolution of the atom

Element- pure substance made of only one type of atom

Compound- substance made of 2 or more types of atoms that are chemically bonded TNTSalt Sugar Caffeine

Pure Substances  every sample has same: characteristic properties composition  are made of: one type of atom: element  Ex: iron, gold, oxygen 2 or more types of atoms: compound  Ex: salt, sugar, water

Which are pure substances?

Mixtures  blend of 2 or more types of matter  each component keeps its own identity and properties  the components are only physically mixed  can be separated using physical means  properties of the mixture are a combination of the properties of the componenent’s properties

Homogeneous Mixtures  also called solution  uniform in composition  no visible parts Ex:  vinegar  clear air  salt water  brass

Heterogeneous Mixtures  not uniform in composition  visible parts Ex:  soil  concrete  blood  chocolate chip cookies  sand in water  iced tea with ice

Mixtures

Practice Determine whether each of the following is element, compound, homogeneous mixture or heterogeneous mixture.  air  wood  chlorine  granite  aluminum  sugar in water  blood  sucrose  stainless steel  sodium chloride  brass  whole milk  apple  table salt  soft drinks  vinegar  concrete  sodium  baking soda (NaHCO 3 )  gravel