Unit 1- The Science of Chemistry

1. 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 Unit 1- The Science of Chemistry

2. 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

3. An example of everyday chemistry… …..and why you don’t want to swallow it

4. 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?

5. 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

6. 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

7. 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

8. Units of Measurement King Henry Died Unexpectedly Drinking Chocolate Milk

9. 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)

10. 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

11. Properties of Matter • 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

12. 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 What's heavier a ton of bricks or a ton of feathers?

13. 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

14. 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

16. Pure Substance: Elements • 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

18. Pure Substance: Compounds Atoms   Compound • 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

19. Different representations of aspirin:

20. 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

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

22. 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)

23. 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)

25. --Classification of Matter--