Matter: Grainy Evidence of Particles

1. Unit II : Matter Matter is Grainy

2. Evidence of Particles 2000 B C 1805 1990s Sand on Atomic Tunneling a beach Theory electron microscope

3. Hierarchy of Matter Matter MixturesPure Substances heterogeneous homogeneous element compound

4. New Term Mixture • Loose combination of materials • Variable composition • Components retain their properties • Can be separated by using differences in properties of components • Heterogeneous or homogeneous

5. New Term Heterogeneous • Non-uniform mixture • Two or more components or phases clearly visible • Mud and water, chunky peanut butter, Italian dressing are examples • Heterogeneous mixtures are called suspensions

6. New Term Homogeneous • Uniform mixture • Appears to contain only one phase or component • saltwater, creamy peanut butter, non-carbonated beverages are examples • Homogeneous mixtures are called solutions

7. New Term Pure Substance • Definite, non-variable composition • Homogeneous • Characteristic set of properties • Elements or Compounds

8. New Term Element • Cannot be broken down chemically into simpler substances • Homogeneous • Characteristic set of properties • Contains only one type of atom

9. New Term Compound • Can be broken down chemically into simpler substances • Homogeneous • Characteristic set of properties which radically differ from the pure elements in it • Contains two or more types of atoms chemically combined • Binary-two elements, tertiary-three elements, quaternary –four elements

10. New Term Alloy • An alloy is a solid solution • A homogeneous mixture of metals • 18 carat gold, sterling silver, steel, dental amalgums are all examples • They are usually mixed while molten, then solidified

11. New Term Solution is a homogeneous mixture of • a solute and a solvent • Solute is the dissolvee • Solvent is the dissolver • In aqueous solutions, the solvent is water

12. More About Mixtures • To make a mixture, just mix the components together • They keep their characteristic properties • How do you separate a mixture? • Use differences in the properties of the components

13. More About Mixtures Separating Mixtures • Distillation- separate solutions • Filtration- separate suspensions • Chromatography- separate solutions • Decanting- separate suspensions

14. New Term Distillation • Uses differences in boiling point to separate the components of a solution( non-volatile solute) • Heat the solution in a flask • Condense the vapor and collect the liquid in a new container • Solid solute remains in the boiling flask • Used to make distilled water

15. New Term Fractional Distillation • Uses differences in boiling point to separate the components of a solution of liquids • Heat the solution in a flask • Force the vapor up a tall column • Higher boiling liquids recondense and don’t reach the condensor • Lowest boiling liquid’s vapor gets condensed and collected • Then the next lowest boiling liquid can reach the condensor and be collected. • This continues until all the liquids have boiled off and been collected • Use to refine petroleum into gas , gasoline, kerosene, diesel, etc.

16. New Term Decanting • Pour off the liquid from a suspension leaving the solid on the bottom of the container • Used in the salt sand separation lab • Wine sits in a decanter before it is poured at the table into glasses.

17. New Term Filtration • Pour off the liquid from a suspension through a filter in a funnel and collect the liquid in a container • Solid stays on the filter paper • Sediment free liquid(filtrate) collects in container under funnel

18. New Term Chromatography • Put a dot of ink on a long strip of filter paper • Hang the paper on a rod on top of a beaker with some water(or other solvent) • The bottom of the paper should hang in the water • Water travels up the paper and carries the dyes in the ink with it. • Lighter (Mass)dyes travel farther up the paper, faster than heavier dyes, and they are separated by mass on the strip • Modern gas chromatographs are used in forensics to analyze liquids for different solutes contained in solution

19. New Term Colloid • Size of particles in solvent are between those in a suspension and those in a solution • As a result, they don’t settle(Mud settles) and are hard to filter(cannot filter solutions) • Tyndall Effect- colloidal particles are big enough to scatter light and the beam of light can be tracked through the solution. Solutions don’t reflect light.

20. Making a Compound • To make a compound, a chemical reaction must occur which bonds the atoms of the two elements together • How do we know a reaction has occurred? • Hydrogen gas + oxygen gas are sparked • Flames shoot out of balloon and water vapor is formed • In a chemical change, the product has new properties(unlike the original materials) and a noticeable energy change is observed

21. Energy and Chemical Change • In the formation of water, energy is released to the surroundings. • Heat comes out of the reaction- exothermic process • Reactions like these are called exothermic • Do all reactions release energy when they occur? • Some(photosynthesis) use up energy when the react • Heat goes into the reaction- endothermic

22. Energy and Chemical Change • In exothermic reactions, the temperature goes up • Burning a log in a fireplace gives off heat to the room, room temperature goes up • In endothermic reactions, energy is taken from the surroundings and stored in products • An endothermic reaction lowers the temperature as it runs

23. Energy and Physical Change • Physical changes also involve energy changes, both endo and exothermic • Melting water requires an input of energy(endo) with no change in temperature of the ice- water mixture, but it is very small by comparison to the chemical change which formed the water • Likewise boiling water requires an input of energy(endo ) with no change in the boiling water’s temperature. It is larger than for melting, but still very small compared to the chemical change. • Freezing water and condensing steam release(exo) exactly the same amount of energy put in to melt and boil them

24. Decomposing a Compound • Roasting can be used to break up compounds of fairly stable elements • Iron, copper, mercury are made in this fashion by roasting ores(oxides) of these metals • Electrolysis is used to break up compounds of unstable elements • Electrolysis is passing an electric current through the material • Water can only be broken up into hydrogen and oxygen by electrolysis

25. Recognizing Chemical Change • There are four indicators that a chemical change has occurred • Only one of them needs to be present for the change to be chemical • A noticeable energy change • A change in the color • Formation of a precipitate(ppt) • Formation of a gas