2The Properties of Matter Matter: The “stuff” that makes up the universeHas mass and volumeAll matter is made up of tiny particles called atoms
3Elements and Compounds There are over 100 different kinds of atomsWe call these different types of atoms different elementsAll matter is made up of different combinations of elements
4Molecules A molecule is made of atoms that are “stuck” together Smallest part of a compound that has properties of that compoundCan be the same atoms
5CompoundsCompounds: substances made by bonding atoms together in specific ways.Two or more different types of atoms bonded togetherA compound has the same particles throughout
6Pure Substances Pure substances always have a definite composition ElementsSpecific CompoundsThey are not generic (Orange Juice)
7Physical vs. Chemical Properties Chemical Properties: examples are:Rusting, not reacting, fermentation, combustionYou must perform a chemical reaction to test chemical properties (and then you change the substance!)
8Physical vs. Chemical Properties Physical properties: examples are:Odor, color, volume, solid, liquid, or gas, density, melting point, boiling pointYou can test physical properties without changing the substance
9Intensive vs Extensive Properties Depend on how much substanceMass, length, volumeIntensiveInherent quality of substanceDensity, odor, color
10Chemical and physical changes Physical changes – don’t affect the composition of the substanceInvolves physical propertiesSolid liquid gasChemical changes – a given substance is changed to another substanceSilver tarnishingLeaves growing from soil, water, and air
11Which is which? Iron is melted Iron combines with oxygen to form rust Wood burns in airA rock is broken in to small piecesMilk turns sourWax is meltedWax catches on fireA bee stings you and you swell up
12Mixtures and Pure Substances A mixture is something that has variable compositionWood – varies depending on the tree it is cut fromSoda – contains lots of dissolved substances (CO2, sugar)Air – contains lots of different substances in different amounts, depending on where you are.
13Substances in the air N2 = 78.08% O2 = 20.95% H2O = depends on humidityAr = 0.93%CO2 = 0.033%Ne = %He = %
14Compounds vs. Mixtures The air is not the same everywhere Florida’s air is probably not the same as Death Valley’s air!
15GoldPure gold is too soft and “bendy” (the scientific word is malleable) to be usefulWe mix it with silver and copper to strengthen itMixtures of metals are called Alloys
16Compounds vs. mixturesRemember – a compound has particles that are ALL THE SAMEA mixture has different compounds/elements in different proportionsIs this an example of a mixture or a compound?
17Pure substances A pure substance always has the same composition Pure substances can be elements or compoundsMixtures can be separated in to pure substances:Two or more pure substancesMixtures
18Types of mixturesHomogeneous mixtures: the mixture is the same throughoutGatoradeSalt waterThese are also called solutionsHeterogeneous mixtures: some regions have different properties than others (not uniformly mixed)Sand in waterDirt
19Which is which? Gasoline A stream with gravel at the bottom Maple syrupOxygen and helium in a scuba tankAirBrassCopper metalSodium chloride (salt)
20Law of Definite Proportions Compounds are always composed of the same elements.Table salt is always sodium chloride, otherwise it is something elseExample: A 58.5 gram sample of Table Salt is composed of 23.0g of Sodium.What mass % is sodium & chlorine?
21Law of Multiple Proportions When different compounds are formed by the combination of the same elements the mass ratio of the two elements of the different compounds is a whole number.Hydrogen and Oxygen – 2 compoundsH2O H2O2
22Mass % of element in one compound compared to % mass of same element in a different compound is always a whole number ratio.
23Law of Multiple Proportions Example: Iron combines with oxygen in different ratios FeO & Fe2O3In a 100g sample of eachIn compound 1 Fe is 77.7g of the compoundIn compound 2 Fe is 69.9g of the compoundFind the whole number ratio of the mass %’s?Which compound is which? (Hint: definite prop)