unit 1- the science of chemistry allotrope atom chemical chemical change chemical properties...

Unit 1- The Science of Chemistry• Allotrope• Atom• Chemical • Chemical change• Chemical properties• Chemical reaction• Compound• Conversion factor• Density• Element• Extrinsic properties• Heterogeneous• Homogeneous

• Intrinsic properties• Mass • Matter• Mixture• Molecule• Physical change• Physical properties• Pure substance• Reactant • States of matter• Volume

Why study chemistry?• It plays a vital role in your

everyday life• EVERYTHING is made up of

chemical elements• Clothes, food, make up, sports

equipment, computers, --- all chemistry!– Even the things you can’t see

chemistry• Air, gases, atoms, cells

An example of everyday chemistry…

…..and why you don’t want to swallow it

What is chemistry?• Chemistry is concerned with the properties of

chemicals and the changes they can undergo.• A chemical is:

– a substance that has a definite composition– Ex: H2O, CO2

• Some are natural, some are man-made and some are natural but manipulated by man– Carbon monoxide?– Polyethylene?– Aluminum?

Chemical Reactions are happening ALL the time!!

– Chemical Reaction- the process by which one or more substances change to produce one or more different substances

• Cooking/baking, taking photos, digesting food, turning on a light, starting an engine, lighting fireworks

• Chem rx’s are necessary for living things to grow and dead things to decay

Matter Matters!– anything that has mass or volume = matter

• Mass- quantity of matter contained in an object– Measured with a balance or scale

• It’s related to weight but NOT THE SAME• Weight- force produced by gravity acting on mass

(expressed in newton)– In lab “weigh” usually means to find mass

• Volume- the space an object occupies– A block l x w x h– A liquid graduated cylinder– A gas same vol as the container it fills

Using density to identify a substance

• Density- ratio of mass to volume

- density is the same regardless of sample size (**it can identify a substance)

- it can also be found by the slope of a graph

• 1- weigh the substance (to find mass)• 2- use water displacement in graduated cylinder (to find

volume)• 3- divide mass by volume

Units of Measurement

King Henry Died Unexpectedly Drinking Chocolate Milk

Converting one unit to another:

• Use a conversion factor• **unit you want to find goes on top of factor**

How many kg in 2345g? 2345g x 1kg/1000g = 2.345kg (g’s are crossed out)

Convert these practice problems:• 7.359m = ________ cm• 8.0km = ________ Decameters• 2.43mm = ________ m• 51mL = __________ hL• 1.43cm = ________m

*K H D U D C M

• Physical property- can be determined without changing the nature of the substance– Ex- color, texture, melting point, boiling point (physical changes)

**matter can’t be described by physical property only• Chemical property- describes a substance’s ability to

participate in a chemical rx– Ex: reacts with O2, reacts with light, forms a precipitate, combustion,

solubility

Properties of Matter

Extrinsic vs. Intrinsic Properties • Extrinsic- doesn’t depend on the amount of

matter– Color, odor, luster, malleability, ductility,

conductivity, hardness, melting/freezing point, boiling point, density

• **can be used to identify a substance

• Intrinsic- depends on the amount of matter– Mass, weight, volume, length

• **CAN’T be use to identify a substance

States of Matter• Solid- Fixed volume and shape

– due to particle arrangement, tight in rigid structure, only vibrate slightly

• Liquid-Fixed volume, no fixed shape, particles not held together as strongly as solids (particles move past one another…takes shape of container)

• Gas-No fixed volume or shape– particles weakly attracted to one another,

move at high speed, fill container they occupy

Classifying matter• All matter is composed of atoms• Atoms can be mixed physically or chemically to make

up different types of matter• If they are mixed chemically:

– Pure substances- have properties (phys or chem) that identify it

– 2 types: elements and compounds• If they are mixed physically:

– Mixtures-– 2 types: Homogeneous

and heterogeneous

• contain 1 type of atom– Has a unique set of phys. and chem. properties, is

represented by a chemical symbol– Ex:

– Can be a single atom or molecule• Helium gas is individual atoms- monotomic gas (He)• Molecules- 2 or more atoms that can exist as a single unit-

diatomic molecules - H2, N2, F2, O2, I2, Cl2, Br2

• “ have no fear of brutally interesting chemistry” – Allotrope- different molecular forms of the same element

Ex: O2, O3

Pure Substance: Elements

Pure Substance: Compounds• composed of more than 1 type of atoms in a definite

proportion– Represented by formulas Ex: H2O– Subscripts represent #of atoms of each element

– Compounds are classified by their properties, bonds or the elements they are made of

Atoms Compound

Different representations of aspirin:

Mixtures• Contain 2 or more pure substances

– ex: air, blood

• Vary in composition and properties– More or less sweet iced tea, diff karat gold, metal alloys

• Homogeneous- substances distributed uniformly throughout

• Heterogeneous- substances not easily mixedMixture Compound

Physically joined together Chemically joined together

Properties similar to substances Different properties from substances

Various proportions of substances

Definite composition

Separating Mixtures

• Filtration- to separate precipitate from solution• Distillation- separate by boiling point• Evaporation- remove water from a mixture• Chromatography- separate by solubility

Changes of Matter• Physical- a change of state

– Doesn’t change identity– Ex: ice water steam (all H2O)– Ex: dissolving salt in water

• Chemical- substance changes and new one forms– Set up as an equation with reactants (used by rx)

and products (made by rx)

• In chemical reactions atoms in reactants are rearranged– Atoms aren’t created or destroyed so mass

doesn’t change neither does energy or charge• Evidence of chemical change:

– Production of a gas (bubbling,odor)– Precipitate (2 clear solns cloudy)– Release/absorb E (temp change, light emitted)– Color change (phenolphthalein in ammonia)

--Classification of Matter--