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Describing MatterDescribing Matter Properties used to describe matter Properties used to describe matter

can be classified as:can be classified as:

1)1) ExtensiveExtensive – depends on the – depends on the amountamount of matter in the sample of matter in the sample

- Mass, volume, calories are examples- Mass, volume, calories are examples

2)2) IntensiveIntensive – depends on the – depends on the typetype of matter, not the amount presentof matter, not the amount present

- Hardness, Boiling Point, density- Hardness, Boiling Point, density

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Physical vs. Chemical ChangePhysical vs. Chemical Change Physical changePhysical change will change the visible will change the visible

appearance, without changing the appearance, without changing the composition of the material.composition of the material.– Boil, melt, cut, bend, split, crackBoil, melt, cut, bend, split, crack– Is boiled water still water?Is boiled water still water?

Can be Can be reversiblereversible, or , or irreversibleirreversible

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Physical vs. Chemical ChangePhysical vs. Chemical Change

Chemical changeChemical change - a change where a - a change where a new form of matter is formed.new form of matter is formed.– Rust, burn, decompose, fermentRust, burn, decompose, ferment

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Chemical ChangeChemical ChangeA change in which one or more substances are converted into different substances.

Heat and

light are often evidence of a chemical change.

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Chemical ChangesChemical Changes The ability of a substance to undergo The ability of a substance to undergo

a specific chemical change is called a a specific chemical change is called a chemical propertychemical property..

• iron plus oxygen forms rust, so the iron plus oxygen forms rust, so the ability to rust is a chemical property ability to rust is a chemical property of ironof iron

During a chemical change (also called During a chemical change (also called chemical reaction), the composition of chemical reaction), the composition of matter always changes. matter always changes.

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Chemical Reactions are…Chemical Reactions are… When one or more substances are When one or more substances are

changed into new substances.changed into new substances. ReactantsReactants- the stuff you start with- the stuff you start with ProductsProducts- what you make- what you make The products will have NEW The products will have NEW

PROPERTIES different from the PROPERTIES different from the reactants you started withreactants you started with

Arrow points from the reactants Arrow points from the reactants toto the the new productsnew products

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Properties of CompoundsProperties of Compounds Products have different properties than Products have different properties than

their component elements.their component elements. Due to a CHEMICAL CHANGE, the Due to a CHEMICAL CHANGE, the

resulting compound has new and resulting compound has new and different properties:different properties:• Table sugar – carbon, hydrogen, Table sugar – carbon, hydrogen,

oxygenoxygen• Sodium chloride – sodium, chlorineSodium chloride – sodium, chlorine• Water – hydrogen, oxygenWater – hydrogen, oxygen

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Recognizing Chemical ChangesRecognizing Chemical Changes1)1) EnergyEnergy is absorbed or released is absorbed or released

(temperature changes hotter or colder)(temperature changes hotter or colder)

2)2) ColorColor changes changes

3)3) GasGas production (bubbling, fizzing, or odor production (bubbling, fizzing, or odor change; smoke)change; smoke)

4)4) formation of aformation of a precipitateprecipitate - a solid that - a solid that separates from solution (won’t dissolve)separates from solution (won’t dissolve)

5)5) IrreversibilityIrreversibility - not easily reversed- not easily reversed

But, there are examples of these that are not But, there are examples of these that are not chemical – boiling water bubbles, etc.chemical – boiling water bubbles, etc.

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Conservation of Mass Conservation of Mass During any chemical reaction, the During any chemical reaction, the

mass of the products is always equal mass of the products is always equal to the mass of the reactants.to the mass of the reactants.

All the massAll the mass can be accounted for: can be accounted for:

–Burning of wood results in products Burning of wood results in products that appear to have less mass as that appear to have less mass as ashes; where is the rest?ashes; where is the rest?

Law of conservation of massLaw of conservation of mass

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reactants = product

43.43 g Original mass = 43.43 g Final mass