chapter 2 matter and change p. 38. describing matter properties: 1)extensive 1)extensive depends on...

Chapter 2Chapter 2“Matter and Change”“Matter and Change”p. 38p. 38

Describing MatterDescribing MatterProperties:Properties:

1)1) ExtensiveExtensive – depends on amt of matter in sample

- ex’s. mass, volume, calories, magnetism

2)2) IntensiveIntensive – depends on type of matter, not amt.

- Hardness, Density, B.P.- All samples of same substance have

same intensive prop’s. (same composition)

Identifying SubstancesIdentifying SubstancesPhysical Properties- observed & measured w/o changing composition◦color, hardness, m.p., b.p.

Chemical Properties- observed by changing comp of material ◦ability to burn, decompose, ferment, react w/, etc.

States of matterStates of matter1) Solid- cannot flow (definite shape &

volume)2) Liquid- definite vol - takes shape of

container (flows)3) Gas- w/o definite vol or shape & flows

◦ Vapor- gaseous but normally liquid or solid @ room temp

water “gas”, or water “vapor”?

Three Main Phases – page 41Three Main Phases – page 41

States of MatterStates of Matter

Solid

Liquid

Gas

Definite Volume?

YES

YES

NO

Definite Shape?

YES

NO

NO

Result of a Temperature Increase?

Small Expans.

Small Expans.

Large Expans.

Will it Compress?

Not easily

YES

Not easily

44thth state: state: PlasmaPlasma - - formed at hi formed at hi temps; ionized phase of matter temps; ionized phase of matter (Sun)(Sun)

Solid Liquid Gas

Melt Evaporate

CondenseFreeze

Sublime

Physical vs. Chemical Physical vs. Chemical ChangeChange

Physical changePhysical change changes visible appearance w/o changing comp of material◦Boil, melt, cut, bend, split, crack◦Is boiled water still water?

Reversible, or irreversibleChemical changeChemical change - change where new substance formed◦Rust, burn, decompose, ferment

Section 2.2 MixturesSection 2.2 Mixturesp. 44p. 44

Mixtures - physical blend of 2+ substances & have variable comp.

1) Heterogeneous – not uniform in comp

• Chocolate chip cookie, gravel, soil2) Homogeneous - same comp thruout

called “solutions”• Kool-aid, air, salt water

Every part keeps own prop’s.

Solutions - homogeneous mixturesSolutions - homogeneous mixturesMixed molecule by molecule, so too small to see diff pts

occurs btwn any state of matter: gas-gas; liquid-gas; gas-liquid; solid-liquid; solid-solid (alloys), etc.

Classified based on distribution of their components

Phase?Phase?“phase” describes any pt of sample w/ uniform comp of properties

A homogeneous mixture consists of a single phase

A heterogeneous mixture consists of two or more phases.

Note Figure 2.6, page 45

Separating MixturesSeparating MixturesSome by physical means: rocks & marbles, iron filings & sulfur (magnet)

Differences in physical props used to separate mixtures

Filtration - separates solid from liquid in hetero mix. (by size) – Figure 2.7, page 46

Separation of a MixtureSeparation of a MixtureComponents of dyes such as ink may be separated by paper chromatography.

Separation of a MixtureSeparation of a MixtureDistillation: takes advantage of different boiling pts.

NaCl boils at 1415 oCH2O boils at 100 oCMg boils at 1107 oC

Sec 2.3 Elements & Sec 2.3 Elements & Compounds p. 48Compounds p. 48

Substances are either:a) elements, orb) compounds

Elements- simplest kind of matter◦cannot be broken down & still have props of that element!

◦all one kind of atomCmpds - broken down only by chemical

methods◦when broken down, pieces have diff. props. than original cmpd

◦made of 2+ atoms, chemically combined (not just a physical blend!)

Compound vs. MixtureCompound vs. MixtureCompound Mixture

Made of one kindof material

Made of more thanone kind of material

Made by a chemical change

Made by a physical change

Definitecomposition

Variablecomposition

Which is it?Which is it?

ElementCompoundMixture

Elements vs. CompoundsElements vs. CompoundsCmpds can be broken down into simpler substances by chemical means….elements can’t

A “chemical change” is a change that produces matter with diff. composition than original matter

Chemical ChangeChemical Change1+ substances are converted into different substances.

Heat & light often indicate chem change.

Properties of CompoundsProperties of Compoundsdifferent from component elements.

cmpd has new props:•Table sugar – carbon, hydrogen, oxygen

•Table Salt – sodium, chlorine•Water – hydrogen, oxygen

Classification of MatterClassification of Matter

Symbols & FormulasSymbols & FormulasCurrently, 117 elements1 or 2 letter symbolcmpds have formulaElement’s 1st letter always CAP; if 2nd

letter, lowercase ◦B, Ba, C, Ca

Some names Latin ◦Table 2.2, page 52

Chemical ChangesChemical ChangesChemical property - ability of substance to undergo specific chem change •Fe + O forms rust•rusting is chem prop of Fe

During chem chge (also chemical rxn), comp of matter always changes.

Chemical Rxns are…Chemical Rxns are…When 1+ substances changed into new substances

Reactants- stuff u start w/Products- what u end w/Products have NEW PROPS diff from reactants

Arrow points from reactants to new products

Recognizing Chemical ChangesRecognizing Chemical Changes1) Energy absorbed/released (temp

changes hotter/colder)2) Color changes3) Gas production (bubbling, fizzing, or

odor change; smoke)4) formation of precipitate - solid

separates from solution (won’t dissolve)

5) Irreversibility - not easily reversedSome examples of these that are not

chemical – boiling water bubbles, choc syrup in milk, etc.

Conservation of Mass Conservation of Mass During any chem rxn, products mass always = reactants mass

All mass accounted for:◦Burning of wood results in products that appear to have less mass as ashes….

◦where is the rest?Law of conservation of mass

- Page 55

reactants = product

43.43 g Original mass = 43.43 g Final mass