Chemistry Day 010 Major Topic: Classification of Matter Reading: Ch. 3.1 through 3.4 Focus: Students will be able to: 12PS#1, 12SWK#1,3 define, correctly use, and differentiate among the terms and concepts of mass, elements, compounds, mixtures (heterogeneous & homogeneous), substances differentiate between & give examples of physical & chemical properties, intensive & extensive properties differentiate between & give examples of physical & chemical changes Materials: Webquest to illustrate the different types of matter. Molecular models to demonstrate the difference between atoms, molecules, mixtures elements: Fe, Al, Si, Au, S compounds: sucrose, NaHCO3, water, sulfuric acid homogeneous mixtures: sucrose in water, brass weight, vinegar physical changes: candle wax, paper chemical changes: Lycopodium powder & Bunsen burner, Mg ribbon, Zn & I2, electrolysis setup ½ page in-class WS (Matter: Properties & Changes) Classification of Matter handout HW WS: Matter 2 Lab Procedures: % of Sn in Solder, Separation of a Mixture Procedure 1. Central questions: What is matter & how is it classified? Best done with a concept map. 2. Define matter - anything w/ mass & volume. a. Mass - how much stuff is in an object or sample. Already decided that mass is constant for a given object. Doesn’t change w/ gravity, temperature, etc. 3. Varieties of matter - What pigeonholes or classifications can we put different kinds of matter in? a. Elements - All the particles (atoms) in it are of the same type (use molecular models). i. All of the atoms behave the same way in the same situations (called physical and chemical properties). ii. All elements are on the periodic table - surefire method of knowing! iii. Pass around samples if S. want to see them. b. Compounds - The particles here are molecules, made up of 2 or more atoms, of different or same types. Use molecular models. i. All the molecules have the same set of physical & chemical properties, but they can be broken down into their elements by chemical or physical means. Demo electrolysis of water and/or dehydration of sugar by H2SO4 . ii. Further, the properties of a compound are different than the properties of the elements that make it up. e.g. sugar is C, H, O. iii. Have S. name some common compounds: NaCl, H2O, CO2, sugar, etc. iv. Elements & compounds are called substances. v. Law of Definite Proportions or Constant Composition - The elements in a compound are combined in fixed ratios. Different ratio = different compound! We can express these ratios as masses (100 g NaCl has 39.3 g of Na and 60.7 g of Cl), or in moles (the ratio of Na to Cl is 1:1). c. Mixtures - The particles here are of different types (Mix models together.) More than 1 type of element or compound in a mixture. Sugar water, brass, air ! i. The different particles (both elements & compounds) have different properties (they keep their own original properties.) ii. Because they have different properties, the components of a mixture can be separated by physical and chemical means. Let’s take two mixtures: Kool-Aid, and sand mixed in with salt. Who can think of a way of separating the different components of these two mixtures? Demo: sugar water. iii. Because a mixture just has different stuff mixed together, it’s composition isn’t fixed. You can mix Jell-O with different amounts of water: less and you get Jigglers, more = regular Jell-O d. Two basic types of mixtures i. Homogeneous - the mixture appears uniform throughout (brass, solutions of salt or sugar in water, etc.) a. Solutions – one substance dissolves into another substance. There is only one phase. b. Colloids – This is actually a suspension, but the particles are so small that they will not settle, even over long time periods. Milk is an example, as are fog, and cigarette smoke in air. Colloids disperse a beam of light that is passed through the colloid. This is called the Tyndall Effect. Demo with laser and chalk dust in air. http://en.wikipedia.org/wiki/Tyndall_effect http://www.agpix.com/catalog/AGPix_fundamental/AGPix_fundamental_0176.jpg ii. Heterogeneous - the mixture isn’t uniform, has pieces or discrete regions in it. (Piece of granite, cottage cheese, etc.) 4. Properties - How are you going to classify different stuffs, what criteria will you use? Anything about the material that you can detect and measure, how the stuff behaves in different situations. Pick a student - what properties does he or she have? a. Color, appearance, odor, taste, the phase of the substance (solid, liquid, gas), whether it’s flammable or explosive, density, mass, volume, reactivity to acids or bases, etc. b. Some of these properties depend only on how much of the stuff you’ve got. These are called extensive properties. Which of these are extensive? Mass, volume, weight. c. Some properties depend on the identity of the substance - these are intensive: all the other properties. Intensive properties are really useful, because they can be used to identify a substance. 5. Now we have a list of properties. There’s another way we can classify properties, so that we can classify substances: That’s by deciding whether a property is chemical or physical. a. Physical properties - any characteristic of a substance that you can observe in some way, without producing a new substance. What examples can you think of for physical properties? (Color, appearance, luster, odor, taste, feel, texture, surface area, hardness, ductility, malleability, density, melting point, and boiling point.) b. Chemical property - any characteristic of a substance that allows it to react with or be inert with another substance. What examples can you think of for chemical properties? (reactivity, explosivity (like TNT), and sensitivity to shock (like nitroglycerin). Non-reactivity is also a chemical property. Glass is non- reactive to most strong acids.) 6. Physical and Chemical changes. a. Physical Changes - the outer form or condition of a material changes, but no chemical reaction has occurred and no new substance has been produced. i. Examples? Phase changes, eating & chewing food, a chunk of something being ground to a powder, condensation, crystallization, freezing, and the magnetization of certain metals. Demo: melt & recrystallize wax, on finger! b. Chemical Changes - the substance reacts in some way to produce a new substance. (Chemical bonds have been broken and different ones formed - atoms have re-arranged). i. Examples? digestion of food, combustion of wood, paper, gasoline, photosynthesis, clotting of blood, etc. a. Demo sugar & sulfuric acid (IN HOOD OR WINDOWSILL !!) b. Demo Lycopodium spores into a flame. c. Demo burning Mg ribbon d. Demo NaHCO3 + vinegar in big grad cyl. Put out candle flame. e. Demo Zn + I2 + water (small amount!) 7. The only math skill of the day: Determining the % of an element in a compound from the masses of the elements. Sugar contains the elements C, H, O. A 50.00 g sample of sugar contains 20.00 g C, 3.33 g H, and 26.67 g O. What is the % of each element in the sample? Show how. If the sample size were increased to 150.00 g, how much mass of each element would there be? What would the % of each element be in sugar imported from South America? The same. Remember Law of Definite Proportions. 8. Go over WS in class. 9. Hand out Infoquest. Due Friday (if assigned Monday). 10. EVALUATION - through responses on HW, Infoquest, and on tomorrow’s lab. Name: / ?? pts Chemistry Worksheet: Matter 1. Classify as (E)lement, (C)ompound, or (M)ixture: a) ____ water b) ____ milk c) ____ CO2 d) ____ vinegar e) ____ mercury f) ____ dilute HCl g) ____ sulfur h) ____ molasses I) ____ sugar j) ____ Na2CO3 k) ____ soil l) ____ sodium m) ____ tungsten n) ____ sea water o) ____ C6H6 2. Classify as either a (C)hemical or (P)hysical change: a) ____ wax melts b) ____ photosynthesis c) ____ water evaporates d) ____ water boils e) ____ milk turns sour f) ____ mercury expands in a thermometer g) ____ silver tarnishes h) ____ a wound heals i) ____ coal is converted into nylon j) ____ teeth get cavities k) ____ a candle burns l) ____ water freezes m) ____ sharpening a pencil n) ____ a He balloon floats o) ____ food is digested 3. The compound glycerol is composed of C, O, and H. When a 35.50 g sample of glycerol is analyzed, it is found to contain 13.89 g of C, 18.52 g of O, and the rest is H. (Show your math.) a) Determine the % of C, H, and O in glycerol. b) What is the % (not the mass) of C in a 200 kg sample of glycerol? c) Another sample of glycerol is tested. What will the % of O be in it? d) How many grams of C are there in a 250.0 g sample of glycerol? 4. Give an example of: a) a “substance”: __________________________ b) a homogeneous mixture _________________________ c) a heterogeneous mixture _____________________________ d) a chemical property __________________________________ 5. ______________ What is the mass of 2.0 kg of Au when the gold is taken to another planet having 3X the gravity of earth? Your name: _________________________ Your lab partner: / 50 pts Classification of Matter Chemistry Infoquest You will need both your book and access to the Internet for this exercise. The science of chemistry is the study of how matter behaves when it comes into contact with other forms of matter or with the various forms of energy (heat, light, electricity, etc.) The term “matter” is extremely broad, meaning anything that has both mass and volume. It’s tough to define “mass” without reference to matter, but we’ll try: mass is the ratio of the force applied to move an object divided by the acceleration that the applied force produces. Sound complicated? Not really; it’s just Sir Isaac Newton’s second law of motion: Force / acceleration = mass. Is mass the same thing as weight? No!! The weight of an object is really the downward force that is produced by the mass of an object being accelerated by gravity. If an object is taken into space, it no longer has weight, but its mass is still there! If you wanted to move a weightless astronaut, you’d still have to give him a pretty hefty push (force) to get him moving, even though he weighs nothing. For chemists, the most important way to classify matter is into elements, compounds, and mixtures. Use either your chemistry book, a dictionary, or search online to find a definition for each of the following terms. o element o compound o mixture o substance o atom o molecule Elements: Chemists have determined that all the atoms of a given element are similar in structure and behave the same way in any given situation. Not all atoms of an element are completely identical, however. For 2 atoms to be of the same element, they must have the same number of positively-charged protons. For an electrically neutral atom, the number of protons must equal the number of negatively-charged electrons. However, the number of neutrons, which have no electrical charge, is allowed to vary. Atoms of the same element which have different numbers of neutrons are called isotopes. Go to the website http://www.webelements.com/. Choose any element and record the following properties: o Element o Symbol o Number of protons (atomic number) o What isotopes exist for this element? o Where is the element found or how is it produced? o What chemical family is the element in? (What is the name of the region or column of the periodic table that it lies in?) o What commercial or medical uses does the element have? Compounds: When 2 or more atoms (same kind or different kinds) chemically bond together, a chemical compound is produced. All the molecules of a chemical compound have the same set of physical and chemical properties, but these properties differ greatly from the properties of the atoms that make up the compound. For example, common sugar, sucrose – a white tasty crystalline solid, is made of carbon (a black powdery solid like soot), hydrogen (a colorless gas), and oxygen (another colorless, odorless gas). Compare the properties of table salt, NaCl or sodium chloride, with the properties of Na and Cl individually. state of matter o o 3 at room temp melting point, C boiling point, C density, g/cm o Sodium o Chlorine o NaCl Besides NaCl and sucrose, list 4 other chemical compounds, either by name or formula. ____________________ ____________________ ____________________ ____________________ More about compounds: We know that compounds can be broken down (decomposed) into their atoms by chemical reactions or by physical means (heating or electricity). It was just this ability to break down that an English chemist, John Dalton, used to find the formulas of a great many chemical compounds. Dalton and another chemist, Joseph Gay-Lussac, came up with the Law of Definite Proportions (sometimes called the Law of Constant Composition.) The law states that the elements in a compound are always combined in a fixed ratio of atoms. For example, a molecule of water always has 2 H’s and 1 O: H 2O. A molecule that has a different ratio of H to O is a different substance. For example: H 2O2 is hydrogen peroxide, not water. Below is a diagram of the decomposition of water into hydrogen and oxygen gases by an electric current. The process is called the electrolysis of water. Find out some information about John Dalton. o What is Dalton’s date of birth? o What city was he born in? o At what university did he teach? o Besides chemistry, Dalton was also interested in what other studies? Mixtures: When different kinds of elements and/or compounds are combined together without reacting with one another, a mixture is formed. The different substances (components) in the mixture each keep their own original properties, although the mixture as a whole may have a different set of properties from any of the separate substances. We can use the fact that the different substances in a mixture have different properties to separate the components of the mixture. Mixtures may also be made in varying proportions. You may choose to put a whole cup of sugar in Kool-Aid, or only ½ a cup. Use your book, a dictionary, or search online to define the following processes: o distillation o filtration There are other methods of separating mixtures besides the 2 you just defined. How might you go about separating: o iron particles from sand? o gold particles from sand? o water vapor from air? More about mixtures: Mixtures come in several varieties. Heterogeneous mixtures are mixtures with “chunks”. Cottage cheese, blood (cells + plasma), and gravel are heterogeneous mixtures. Give 1 more example of a heterogeneous mixture: There are also homogeneous mixtures. These appear as if they were composed of one material, even though there are really 2 or more components. Examples might be sugar water, air (nitrogen + oxygen + other gases), or brass. Yes, brass is a solid solution of copper and tin that have been melted together and allowed to cool. You can see that homogeneous mixtures can be solids, liquids, or gases. Use your book, a dictionary, or search online to define the following terms related to homogeneous mixtures: o solution o alloy o amalgam o tincture o colloid List 2 more examples of homogeneous mixtures. Physical and Chemical properties: We have been thinking about and using the properties of substances to classify them. Properties can be either physical or chemical. They can also be intensive or extensive. Physical properties are those properties of a substance that you can observe or measure, without producing a new substance: Color, odor, taste, etc. Chemical properties are those properties which describe how a substance reacts with other substances or with energy: reactivity and its opposite inertness, explosivity, sensitivity to shock (think nitroglycerin !!) Extensive properties are those which just describe the quantity of a substance: mass, weight, volume, etc. Intensive properties are those which help you identify a substance: density, atomic mass, etc. For example: boiling point is both an intensive and a physical property of a substance. Define the following terms related to physical and chemical properties: o luster o hardness o malleability o ductility Physical and Chemical Changes: Substances can also undergo changes in both form and in chemistry. Physical changes are when the outer form or condition of a material changes, but the material’s chemical composition doesn’t change. Examples are: water freezing or boiling, food being chewed, candle wax melting, paper being torn. Chemical changes occur whenever a new substance is being produced. This means that the chemical bonds in a substance have been broken and new bonds have been formed – atoms have rearranged themselves into new compounds. Examples: digestion of food, combustion of candle wax, photosynthesis, clotting of blood, etc. List 2 physical changes and 2 chemical changes that might be made to happen to an ordinary iron nail.
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