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: H 2 O, CO 2 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 O 2, 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 - H 2, N 2, F 2, O 2, I 2, Cl 2, Br 2 “ have no fear of brutally interesting chemistry” – Allotrope- different molecular forms of the same element Ex: O 2, O 3 Pure Substance: Elements

Pure Substance: Compounds composed of more than 1 type of atoms in a definite proportion – Represented by formulas Ex: H 2 O – 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 mixed MixtureCompound Physically joined togetherChemically joined together Properties similar to substancesDifferent 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 H 2 O) – 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--