1. CHAPTER 2 PROPERTIES OF MATTER

2. BASED ON COMPOSITIONS, MATERIALS CAN BE DIVIDED INTO PURE SUBSTANCES OR MIXTURES.

3. PURE SUBSTANCE – matter that always has exactly the same composition – EVERY SAMPLE OF A GIVEN SUBSTANCE HAS THE SAME PROPERTIES BECAUSE A SUBSTANCE HAS A FIXED, UNIFORM COMPOSITION.

4. SUBSTANCES CAN BE CLASSIFIED INTO TWO CATEGORIES – ELEMENTS AND COMPOUNDS.

5. ELEMENT – an element is a substance that cannot be broken down into simpler substances AN ELEMENT HAS A FIXED COMPOSITION BECAUSE IT CONTAINS ONLY ONE TYPE OF ATOM. – NO TWO ELEMENTS CONTAIN THE SAME TYPE OF ATOM.

6. EXAMPLES OF ELEMENTS – AT ROOM TEMPERATURE MOST ELEMENTS ARE SOLIDS SUCH AS ALUMINUM AND CARBON. GOLD (Au) ALUMINUM (Al) CARBON (C) IODINE (I)

7. SYMBOLS FOR ELEMENTS – IN 1813 Jons Berzelius suggested that chemists use symbols to represent elements. – EACH SYMBOL HAS ONE OR TWO LETTERS THE FIRST LETTER IS ALWAYS CAPITALIZED THE SECOND LETTER IS ALWAYS LOWER CASE

8. COMPOUNDS – SUBSTANCE THAT IS MADE FROM TWO OR MORE SIMPLER SUBSTANCES AND CAN BE BROKEN DOWN INTO THOSE SIMPLER SUBSTANCES. – THE SIMPLER SUBSTANCES ARE EITHER ELEMENTS OR OTHER COMPOUNDS – THE PROPERTIES OF A COMPOUND DIFFER FROM THOSE OF THE SUBSTANCES FROM WHICH IT IS MADE EX. WATER (H2O)

9. A COMPOUND ALWAYS CONTAINS TWO OR MORE ELEMENTS JOINED IN A FIXED PROPORTION. – IF THE PROPORTION CHANGES THEN THE COMPOUND CHANGES.

10. MIXTURES – MIXTURES RETAIN SOME OF THE PROPERTIES OF THEIR INDIVIDUAL SUBSTANCES – THE PROPERTIES OF A MIXTURE ARE LESS CONSTANT THAN THE PROPERTIES OF A SUBSTANCE. – THE PROPERTIES OF A MIXTURE CAN VARY BECAUSE THE COMPOSITION OF A MIXTURE IS NOT FIXED

11. MIXTURES cont. – THERE ARE 2 TYPES OF MIXTURES HETEROGENEOUS MIXTURES HOMOGENEOUS MIXTURES

12. HETEROGENEOUS MIXTURE – THE PARTS OF THE MIXTURE ARE NOTICEABLY DIFFERENT FROM ONE ANOTHER EX. SAND

13. HOMOGENEOUS MIXTURES – THE SUBSTANCES ARE EVENLY DISTRIBUTED THAT IT IS DIFFICULT TO DISTINGUISH ONE SUBSTANCE IN THE MIXTURE FROM ANOTHER. HOMOGENEOUS MIXTURES APPEAR TO CONTAIN ONLY ONE SUBSTANCE. – EX. WATER IN SWIMMING POOL

14. SOLUTIONS, SUSPENSIONS, AND COLLOIDS – BASED ON THE SIZE OF ITS LARGEST PARTICLE, A MIXTURE CAN BE CLASSIFIED AS A SOLUTION, A SUSPENSION, OR A COLLOID.

15. SOLUTIONS – SUBSTANCES THAT DISSOLVE AND FORM A HOMOGENEOUS MIXTURE – SOLUTIONS DO NOT SEPARATE INTO LAYERS OVER TIME. – EX. WIPER FLUID TAP WATER

16. SUSPENSIONS – HETEROGENEOUS MIXTURE THAT SEPARATES INTO LAYERS OVER TIME. – SUSPENDED PARTICLES SETTLE OUT OF A MIXTURE OR ARE TRAPPED BY A FILTER BECAUSE THEY ARE LARGER THAN THE PARTICLES IN A SOLUTION. – EX. MUDDY WATER

17. COLLOID – CONTAINS SOME PARTICLES THAT ARE INTERMEDIATE IN SIZE BETWEEN THE SMALL PARTICLES IN A SOLUTION AND THE LARGER PARTICLES IN A SUSPENSION. – THEY DO NOT SEPARATE INTO LAYERS – CANNOT USE A FILTER TO SEPARATE THE PARTS OF A COLLOID – EX. FOG IN THE AIR

18. VISCOSITY, CONDUCTIVITY, MALLEABILITY, HARDNESS, MELTING POINT, BOILING POINT, AND DENSITY ARE EXAMPLES OF PHYSICAL PROPERTIES.

19. VISCOSITY – THE TENDENCY OF A LIQUID TO KEEP FROM FLOWING, ITS RESISTANCE TO FLOWING. – THE GREATER THE VISCOSITY THE SLOWER IT MOVES. – VISCOSITY DECREASES WHEN HEATED – VISCOSITY INCREASES WHEN COOLED

20. CONDUCTIVITY – MATERIALS ABILITY TO ALLOW HEAT TO FLOW – MATERIALS THAT HAVE A HIGH CONDUCTIVITY SUCH AS METALS ARE CALLED CONDUCTORS. – GOOD CONDUCTOR OF HEAT = GOOD CONDUCTOR OF ELECTRICITY

21. MALLEABILITY – ABILITY OF A SOLID TO BE HAMMERED WITHOUT SHATTERING. – MOST METALS ARE MALLEABLE EX. GOLDSMITHS, BLACKSMITHS – BY CONTRAST, ICE WILL SHATTER WHEN HIT WITH HAMMER.

22. HARDNESS – THE ABILITY OF ONE MATERIAL TO SCRATCH ANOTHER – STAINLESS STEEL IS HARDER THAN COPPER – DIAMOND IS THE HARDEST KNOWN MATERIAL

23. MELTING POINT – THE TEMPERATURE AT WHICH A SUBSTANCE CHANGES FROM A SOLID TO LIQUID – EX. ICE MELTING TO WATER

24. BOILING POINT – THE TEMPERATURE AT WHICH A SUBSTANCE BOILS. – SOME SUBSTANCES CHANGE FROM A LIQUID TO A GAS AT THIS POINT

25. DENSITY – MASS OF AN OBJECT DIVIDED BY ITS VOLUME – D=M/V – DENSITY CAN BE USED TO TEST THE PURITY OF A SUBSTANCE.

26. PHYSICAL PROPERTIES ARE USED TO IDENTIFY A MATERIAL,TO CHOOSE A MATERIAL FOR A SPECIFIC PURPOSE, OR TO SEPARATE THE SUBSTANCE IN A MIXTURE.

27. USING PROPERTIES TO IDENTIFY MATERIALS – STEP 1: DECIDE WHICH PROPERTIES TO TEST EX. DENSITY, MASS, MELTING POINT, BOILING POINT, ETC. – STEP 2: TEST THE UNKOWN SAMPLE – FINAL STEP: COMPARE THE RESULTS WITH THE DATA REPORTED FOR KNOWN MATERIALS

28. USING PROPERTIES TO CHOOSE MATERIALS – PROPERTIES DETERMINE WHICH MATERIALS ARE CHOSEN FOR WHICH USES. WOODEN SHOELACES METAL TIRES PAPER CHAINS

29. USING PROPERTIES TO SEPARATE MATERIALS – FILTRATION AND DISTILLATION ARE TWO COMMON SEPARATION METHODS.

30. FILTRATION – PROCESS THAT SEPARATES MATERIALS BASED ON THE SIZE OF THEIR PARTICLES. – EX. COFFEE FILTERS FILTER COFFEE GRAINS BUT ALLOW CAFFIENE AND SMALLER COFFEE GRAINS TO PASS THROUGH

31. DISTILLATION – PROCESS THAT SEPARATES SUBSTANCES IN A SOLUTION BASED ON THEIR BOILING POINTS. – EX. BOILING SEA WATER, CAPTURING THE WATER VAPORS, COOLING THE VAPORS AND COLLECTING THEM IN A SEPARATE CONTAINER…THIS PROVIDES FRESH WATER WITHOUT THE SALT.

32. RECOGNIZING PHYSICAL CHANGES – A PHYSICAL CHANGE OCCURS WHEN SOME OF THE PROPERTIES OF A MATERIAL CHANGE, BUT THE SUBSTANCES IN THE MATERIAL REMAIN THE SAME. EX. METLING BUTTER IN A PAN CAUSES THE BUTTER TO CHANGE FROM A SOLID TO A LIQUID BUT THE SUBSTANCES IN THE BUTTER DO NOT CHANGE. – SOME PHYSICAL CHANGES CAN BE REVERSED AND SOME CANNOT. EX. MELTING ICE AND REFREEZING IT (REVERSED) EX. REPLACING THE PEELING ON AN ORANGE AFTER YOU PEELED IT. (IRREVERSIBLE)

33. CHEMICAL PROPERTY – THE ABILITY TO PRODUCE A CHANGE IN THE COMPOSITION OF MATTER. – EX. THE ABILITY TO BURN. CHEMICAL PROPERTIES CAN BE OBSERVED ONLY WHEN THE SUBSTANCE IN A SAMPLE OF MATTER ARE CHANGING INTO DIFFERENT SUBSTANCES.

34. FLAMABILITY – MATERIAL ABILITY TO BURN IN THE PRESENCE OF OXYGEN REACTIVITY – THE PROPERTY THAT DESCRIBES HOW READILY A SUBSTANCE COMBINES CHEMICALLY WITH OTHER SUBSTANCES

35. RECOGNIZING CHEMICAL CHANGES – A CHEMICAL CHANGE OCCURS WHEN A SUBSTANCE REACTS AND FORMS ONE OR MORE NEW SUBSTANCES. EX. CAKE BAKING IN THE OVEN, LEAVES ON A TREE CHANGING COLORS

36. RECOGNIZING CHEMICAL CHANGE – THREE COMMON TYPES OF EVIDENCE FOR A CHEMICAL CHANGE ARE A CHANGE IN COLOR, THE PRODUCTION OF A GAS, AND THE FORMATION OF A PRECIPITATE.

37. A CHANGE IN COLOR – SILVER WILL DARKEN WHEN EXPOSED TO AIR – COPPER WILL CHANGE COLORS (COPPER TO GREEN) A CHANGE IN COLOR IS A CLUE THAT A CHEMICAL CHANGE HAS PRODUCED AT LEAST ONE NEW SUBSTANCE.

38. PRODUCTION OF GAS – IF THE COMBINATION OF TWO OR MORE SUBSTANCES PRODUCES A GAS A CHEMICAL CHANGE IS HAPPENING. EX. CARBONATION FIZZING IN SOFT DRINKS, BAKING SODA AND VINEGAR

39. FORMATION OF A PRECIPITATE – HAPPENS WHEN A SOLID FORMS AND SEPARATES OUT OF A LIQUID. EX. ADDING ACID TO MILK WILL CAUSE THE PROTEIN IN MILK TO CLUMP TOGETHER.

40. HOW TO DETERMINE IF A CHANGE IS CHEMICAL OR PHYSICAL: – WHEN MATTER UNDERGOES A CHEMICAL CHANGE, THE COMPOSITION OF HE MATTER CHANGES; WHEN MATTER UNDERGOES A PHYSICAL CHANGE, THE COMPOSITION OF THE MATTER REMAINS THE SAME.