Chapter 17 Classification of Matter •Everything in life can be put into some form of a classification. Think of your room (ok, not the messy ones!) There is a place for books, clothes, sports, •Stuff, music stuff, etc. Classifying objects into broad groups makes things easier to find, identify, look at, and to learn about. • Classification of matter is based on the makeup of matter • According to makeup, matter exists as elements, compounds, mixtures or solutions. •A mixture is a combination of two or more substances that are not chemically combined. •Each substance has its own specific properties and is the same throughout the entire mixture. Ex. Pg 88- granite rock is made up of quartz, mica and •Feldspar. Sand has dark specks and light specks when you pick up a handful of sand. Properties of Mixtures • Substances in a mixture are not chemically combined. They keep their separate identities and most of their own • properties. Ex. You can easily taste the difference be/w a sugar-water mixture and plain water even though they will look exactly the same be/c sugar keeps the identity of sweetness. •Substances in a mixture may change physical appearance when they dissolve • (89) Subs. in a mixture can be present in any amount • Ex. Cereal in morning is not in equal amts in the bowl. •Subs. in a mixture can be separated by physical means. Ex. Salt and water. (pg 89 in book ex-iron and sulpher) • (90)Mixtures are classified by how well they are mixed. Ex. Compare stainless steel and concrete. Which is •Types of Mixtures: • A heterogeneous mixture (91)is a mix that does not appear the same throughout. •It is easy to see because the particles are large enough. Ex. Sand, dirt, pizza •They are considered to be the “least mixed” of all. The particles are easy to separate from the mixture. Ex. Concrete. • The particles usually settle out easily. Ex. Shake a jar of water and pebbles together and quickly the pebbles will fall to the bottom. Oil and water separate in dressings. • Colloid- a heterogeneous mix with larger particles that never settle out(91). • Warning: you will see colloids listed as homogenous mixtures also-visually they look like homogenous mixtures but microscopically they are heterogeneous mixtures. • They (the particles) scatter light in the Tyndall effect, which is the scattering of light by minute particles in its path, such as dust in the air. Hence, the mixture appears cloudy. • Ex. Of colloids: • Milk, whipped cream, toothpaste, suntan lotion, fog, smoke, foam. Suspension - a heterogeneous mixture containing a liquid in which the visible particles settle. Example •Italian Dressing or muddy water •A homogeneous mixture is a mixture that appears to be the same throughout. •The particles that make up this type of mixture are small and not easy to see. It is “well-mixed”. Ex. Stainless stell, you can’t see the chromium verses the iron in it. • The particles do not settle out when allowed to stand. • Solutions- (92) a type of homogenous mixture of two or more substances in a single physical state. • It is considered the “best- mixed” of all mixtures and is formed when one •Substance dissolves in another. Ex. Ocean water, lemonade, and iced tea from a powdered mix as long as they are all totally dissolved. The air in the room is a solution of oxygen and other gases dissolved in nitrogen. A solution always has • Solvent-the subs that does the dissolving; its the greater amount. Ex. The water in the lemonade. • A solution always has a solute -the substance that gets dissolved; the lesser amount. Ex. The lemonade mix itself. • solutions look the same throughout b/c the particles are evenly spread. Most liquid solutions can be easily separated by simple physical •Means like evaporation but solid solutions like alloys are much harder to separate. •Types of solutions: • (93-4) • There are seven types of solutions that are possible. Solute Solvent Example Gas Gas Air Gas Liquid Soda Water Gas Solid Charcoal gas mask Liquid Liquid Antifreeze Liquid Solid Dental filling Solid Liquid Ocean Water Solid Solid Gold jewelry •A subs that dissolves in another is said to be soluble •A substhat does not dissolve is said to be insoluble • Water is known as the universal solvent. • As temperature increases so does solubility • Metal solutions are called alloys. Ex. Brass Pure Substances (96) they Can either be an element or a compound (2 pure substances together. ) • --A sample taken from any pure substance is identical to any other sample of the same type of pure sample. A sample of iron is the same no matter where you get it from. • Ex. Iron, aluminum, pure water, sugar, and table salt will be the same throughout no matter where you find it in the world! Elements—a pure substance that is made up of only one kind of material and has definite properties • Elements are the simplest pure substances. • An element can not be changed into a simpler substance. • The smallest part of an element is an atom. • An atom is a building block of matter. • Atoms of diff. elements are different. • An element of iron is different than aluminum. Compounds (99) A pure substance that is made up of more than one element and the elements are chemically combined in a fixed ratio. • Ex’s: sugar is a compound made up of the elements carbon, hydrogen, and oxygen. Other compounds are carbon dioxide, ammonia, and baking soda. • (100) Compounds can be broken down into simpler substances sometimes by a physical means, but sometimes it may take electrical energy. •The properties of the elements that make up a compound are different from the properties of the compound. •Would you really sprinkle a poisonous gas and a highly active metal on your french fries? NO WAY- but basically you do with table salt! • Ex. Na (soduim) is a silvery metal that explodes if placed in water and Cl (cholrine) is a yellow-green gas that is poisonous. But when chemically combined they produce a new sub that’s safe to eat called salt • (101)Most comps are made up of molecules, which is made up of two or more atoms chemically bonded together. •A molecule is the smallest part of a compound that has the properties of that compound. •Water is a compound. A molecule of water is made up of 2 atoms of hydrogen chemically bonded to 1 atom of oxygen. • Just like all the atoms of a certain element are alike, all molecules of a •Diatomic elements: (not in book) In nature some elements exists as a molecule. For ex. O (oxygen) really is only found with two atoms bonded together so it’s •formula is O2 •The diatomic elements are Oxygen (O2), hydrogen (H2), Iodine (I2), Bromine (Br2), Fluorine (Fl2), chlorine (Cl2), nitrogen (N2) •Chemical symbols (98) are a shorthand way of representing the elements •(See list of symbols and elements) pgs. 142-143 • If the symbol has two letters, capitalize the first letter of the symbol. • If the symbol has one letter, capitalize it •They are representative of the element’s name, the person who discovered the element or its Latin name. •Chemical formulas: (101) Chemical symbols are like the letters of the chemical alphabet. Just as you put letters together to make words, chemical symbols can •be put together to make chemical “words”. •1. combinations of chem sym are called chemical formulas. Chemical formulas are a shorthand way of •representing chemical substances. Ex. NaCl or H2O •2. (102) Subscripts are a numerical representation that represents how many •atoms of that element are present. Subscripts are written to the lower right of the chemical symbol. Ex. Ammonia is a compound made of the elements nitrogen (N) and • Hydrogen (H). The chemical formula for ammonia is NH3. • A molecule of ammonia contains 1 atom of nitogen and 3 atoms of hydrogen. • The (3) behind the NH is the subscript! •3. No subscript is used when there is only 1 atom of an element. In the example above there was only 1 nitrogen atom so you do not see 1 as a subscript. •4. A coefficient (104) is written to tell you how many whole units of that substance are present. •2 NaCl -means there are two molecules Each containing 1 atom of Na and 1 atom of Cl •Ex.s- (not on handout) PO2Mg3 • # of units= 1 • Elements & # of atoms: potassium has 1 atom, oxygen has 2 atoms, magnesium has 3 atoms. •3Ag2N3O2= •3 units total •6 silver atoms total •9 nitrogen atoms total •6 oxygen atoms total •Now work the ones on your handout. •Chemical equations: (102-3) If chem sym’s are letters and chemical formulas are the words, then we must be able to write chemical sentences. •A chem sentence is a way to describe a chemical equation. •It describes how atoms of one substance are chemically changed into atoms of a whole new •Substance with totally different properties. (remember how Na Cl combine to make something you can ingest?) •Ex. •C + O2 CO2 reactants products • Carbon + Oxygen yields (produces) carbon dioxide •The right side of the chemical equation are the products and the left side are the reactants. The arrow means yields are produces. •Balanced equations: (104) •The Law of Conservation of Mass/Matter and the The Law of Conservation of Energy •states that neither of these (mass nor energy) can ever be created or destroyed. They can only be conserved. •The chemical equation is basically explaining to you what things went into the reaction and how did they combine, or the opposite, what went into the reaction •and how did it chemically break apart. •The key to an equation being written correctly is that the formulas on each side must always show that they are equal •Amounts of mass on both sides of the yield sign because of the law of conservation of mass! •To balance an equation remember this: YOU MAY NEVER CHANGE •A SUBSCRIPT, YOU CAN ONLY CHANGE A COEFFICIENT!!!!! •The total amount of atoms present on the reactant side of equation must match •the total number of atoms on the product side of the equation. •Now let’s try some basic balancing!!
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