Lesson 2-3: CLASSIFYING MATTER Science 9: Unit B – Matter and Chemical Change Lesson 2-3: CLASSIFYING MATTER

The Study of matter and how it changes is Matter is anything having mass and volume. Mass- the amount of matter in an object CHEMISTRY Mass is measured with a balance, unit is grams mass is related to weight but isn’t the same thing. weight is dependent upon gravity. mass never changes Volume- anything that takes up space, unit L, cm3, mL

IS AIR MATTER? YES, to both, so air is matter Does air have volume? Have a balloon both empty and inflated, and an electronic scale. Weigh balloon. YES, to both, so air is matter Does air have volume? Does air have mass?

PROPERTIES OF MATTER Composition- what matter is made of. Water is made of hydrogen and oxygen (H2O), tea has caffeine Properties-what matter is like. For example, water can dissolve many substances and caffeine is a stimulant. What caffeine is made of… What caffeine is like…

THE BASIC UNIT OF MATTER IS AN ATOM There are over 118 varieties of atoms PERIODIC TABLE http://www.webelements.com/scandium/

ELEMENTS contain only one type of atom. Ex: hydrogen (H) is an element that contains only hydrogen atoms, carbon (C) contains only carbon atoms, oxygen (O) contains only oxygen atoms, etc. Atoms of elements can combine together to form compounds. COMPOUNDS are neutral groups of atoms held together by chemical bonds. Ex: CO2, H2O, H2, O2

HOW DO WE CLASSIFY MATTER? All matter is classified as either a pure substance or a mixture Alloy rims/ mixture of two metals Pure gold/Pure substance pure substance mixture 24 karat 18 karat End of introductory material. Return to index

CLASSIFYING MATTER Pure substance-a type of matter where all samples, no matter how big or small, have the same properties…they behave in exactly the same way. Elements Compounds Elements contain one type of atom, thus they CANNOT be broken down into simpler substances by chemical means. Elements consist of either: single atoms, such as Carbon (C), or Sodium (Na) groups of atoms of the same type (molecules), such as H2, O2, Br2, etc.

ELEMENTS MONATOMIC ELEMENTS DIATOMIC ELEMENTS ALLOTROPES Atomic nitrogen N Molecular nitrogen N2 Ozone O3 Atomic hydrogen H Molecular hydrogen H2 Graphite, buckyball Atomic oxygen O Molecular oxygen O2 Carbon C ALLOTROPE-different forms of an element in same physical state

COMPOUNDS Compounds are substances made up of 2 or more different elements that are chemically combined. CO2, H2O, HCl, Na2SO4 COMPOUNDS CAN BE BROKEN DOWN INTO SIMPLER SUBSTANCES BY CHEMICAL MEANS ONLY. COMPOUNDS HAVE DIFFERENT PROPERTIES THAN THE ELEMENTS THAT MAKE THEM UP. Example-dehydration of sugar: C12H11O22 12C(s) + 11 H2O(g) Sugar breaks down into carbon and water Wanna see? http://www.youtube.com/watch?v=pqi50sjJVc0

ELEMENTS TO COMPOUND Will Form… Sodium, Na, is a soft, shiny metal that can be cut with a butter knife. When in contact with moisture it will “explode”. COMBINED WITH… Chlorine gas, Cl2, which is a green, poisonous gas once used as a chemical weapon in military operations. Will Form…

TABLE SALT! 2 Na(s) + Cl2(g)  2 NaCl Sodium metal and chlorine gas, under the right conditions, undergo a chemical change and combine to become….. 2 Na(s) + Cl2(g)  2 NaCl The final compound has properties different from the elements that formed it.

REVIEW We are studying CHEMISTRY, the study of ________and how it ________. Matter is anything that has___ and takes up ___. ___ are the basic building blocks of matter. Matter can be classified as either a ___ or a ___. Substances are either ___ or ___. Answers: 1. matter, changes 2. mass, space 3. atoms 4. pure substance, mixture 5. elements, compounds

? THUS FAR WE HAVE REVIEWED MATTER AS PURE SUBSTANCES. NOW LETS DISCOVER MATTER AS MIXTURES MATTER PURE SUBSTANCE ELEMENT COMPOUND Carbon (C) H2O MIXTURE ?

MATTER AS MIXTURES Mixtures are combinations of 2 or more substances where each substance retains its individual properties. HOW ARE MIXTURES LIKE COMPOUNDS? THEY ARE MADE FROM TWO OR MORE SUBSTANCES HOW ARE MIXTURES DIFFERENT FROM COMPOUNDS? MIXTURES DO NOT FORM CHEMICAL BONDS.

There are two types of mixtures: Classifying mixtures There are two types of mixtures: 1) HOMOGENEOUS 2) HETEROGENEOUS

is HOMOGENEOUS …a mixture that is the same throughout. A homogeneous mixture has a composition and properties that are identical regardless of the sample is Ways to identify a homogeneous mixture: HOMOGENEOUS one phase uniformly mixed won’t settle out small particles A SOLUTION is another name for a homogeneous mixture

HETEROGENEOUS is … a mixture that is visibly different throughout. Heterogenous mixtures have a composition and properties that differ in any given sample. not uniformly mixed more than one phase will settle out larger particles Ways to identify a homogeneous mixture: HETEROGENEOUS

HETEROGENEOUS MIXTURES There are special types of heterogeneous mixtures: Suspensions-appear uniform when mixed but settle out. Chocolate Quik Muddy water Pulpy oj Oil & Vinegar dressing Colloids-appear uniform but they do not settle out. However, their particles are too large to be classified as a homogeneous solution. Gelatin Milk Smoke Fog mayonnaise

TYNDALL EFFECT Colloids are evenly mixed, but their particles are too large to be considered homogeneous mixtures, which are also the same throughout. Colloids show the Tyndall Effect. The Tyndall effect is the scattering of light as a beam passes through a colloid. In each picture, the colloid on the left scatters the beam making it visible

Heterogeneous Mixture Mixtures Summary Heterogeneous Mixture Homogeneous Mixture Not evenly mixed Evenly mixed Individual components retain their own properties Properties of combined components are usually different than those of each component Individual components can be easily seen Individual components can not be easily seen Can be easily separated Not as easily separated Ex.: salt & pepper mix, rocks, cereal, bag of assorted candy Ex. salt-water solution, tea, Cool-Aid drink

Practice Problems Tossed salad Salt water Kool-aid Muddy water Determine whether each is a heterogeneous or homogeneous mixture: Tossed salad Salt water Kool-aid Muddy water OJ with pulp 6. Tea 7. Banana nut bread 8. Pizza 9. Blood 10. Brass Answers: 1. He 2. Ho 3. Ho 4. He 5. He 6. Ho 7. He 8. He 9. He 10. Ho

Now, lets put it all together and determine how to tell substances (compounds and elements) from mixtures. Pure Substances Made of either elements or compounds that are chemically bonded. Cannot be separated by physical means. When combined they take on new properties different from the original elements. Examples: Glucose: C6H12O6 Table Salt: NaCl Oxygen Gas: O2 Carbon Dioxide CO2 Mixtures: Two or more substances mixed together but not chemically combined. Tea = Crushed Leaf + H2O Rocks = minerals + sediments + organic matter Sugar Water = Sugar + H2O Each component retains its own identity; it does not change into something else. Can be separated by physical means Examples: Sweet tea Trail mix Air (O2, N2, CO2, Ar)

Elements, Compounds, and Mixtures Two types of atoms evenly mixed Two types of atoms chemically combined One type of atom Two types of atoms mixed An element A solution A compound A mixture Two of the descriptions to the right apply to each bottle below. Determine the appropriate descriptions. hydrogen atoms oxygen atoms hydrogen atoms d & h b & g c & e a & f 1_______ 2_______ 3_______ 4_______ Dorin, Demmin, Gabel, Chemistry The Study of Matter , 3rd Edition, 1990, page 68

Classifying Matter Matter Pure Substances Mixtures Tea, kool-aid He, O Review: How matter is classified Matter Pure Substances Mixtures Homogeneous Heterogeneous Elements Compounds Rocky Road ice cream, muddy water Tea, kool-aid He, O H2O, NaCl 25

More review Classify the following substances as: Pure substance, heterogeneous mixture, or homogeneous mixture Gatorade Homogenous mixture Fruit Loops Heterogeneous mixture Pure substance Gasoline Dirt Sugar Crystals Pure Substance Air Homogeneous mixture Granite Retur to index