Chapter 2: Properties of Matter

1. Chapter 2: Properties of Matter • Matter – has mass takes up space • Can be classified as a substance or mixture

2. Substance vs. Mixtures Substance Mixture • A substance always has the same composition • Every sample has the same properties • Two types are Elements and Compounds • Properties can vary because the composition in not fixed • Classified by how well the parts are distributed • Two types are heterogeneous and homogeneous

3. Substances Element Compound • A substance that cannot be broken down • An atom is the smallest particle • Fixed composition because it contains only one type of atom • Made from two or more simpler substances • Can be broken down • Properties are different than those it is made of • Contains elements in a fixed proportion

4. Mixtures Heterogeneous Homogeneous • The parts are different • Evenly distributed so difficult to distinguis • Appears to contain only one substance

5. Now it is your turn… you tell me: Homogeneous or Heterogeneous Flat soda pop Cherry vanilla ice cream Sugar (C2H3O2) Salt (NaCl) City Air Iron (Fe) Beach Sand Spaghetti Sauce

6. Mixtures can also be classified by their largest particle • Solutions • When dissolves and forms a homogeneous mixture • Cannot be filtered • Suspension • A heterogeneous mixture that separate into layers over time • Settle out or filtered out • Are cloudy • Colloids • Particles of intermediate size • Do not separate • Cannot filter

8. Physical Properties • A physical property is any characteristic that can be observed or measured without changing the composition • Examples: • Viscosity • Conductivity • Malleability • Hardness • Melting/Boiling • Density

9. Physical Properties • Viscosity • Resistance to flowing • The greater the viscosity the slower the liquid moves • Usually decreases when heated

10. Conductivity • Ability to allow heat to flow • Materials with high conductivity are conductors

11. Malleability • Can be hammered • Most metal are malleable • Solids that shatter when struck are brittle

12. Hardness • One way to compare is to see which can scratch the other • Diamond is the hardest known material

13. Melting/Boiling • Melting: changes from a solid to a liquid • Boiling: temperature a which it boils

14. Density • Can be used to test the purity • Ratio of mass to its volume • D = Mass/Volume

15. Physical Properties • Are used to identify a material, to choose a material for a specific purpose, or to separate the substance • Separating Mixtures (2 Ways) • Filtration – process that separates based on the size of their particles • Distillation – process the separates bases on boiling points

16. Filtration vs. Distillation

17. Physical Changes • Occurs when some of the properties of a material change but the substance in the material remains the same. • Ex. Melting Butter, Crumpling Paper, Slicing • Some can be reversed ( melting, boiling)

18. Chemical Properties • Is any ability to produce a change in the composition of matter • Can be observed only when the substances are changing into different substances • 2 Examples • Flammability • Is a materials ability to burn in the presence of oxygen • Sometimes is not a desirable property

19. Reactivity – Example of Chemical Property • Describes how readily a substance combines chemically with other substance.

20. Recognizing Chemical Changes • A chemical change occurs when a substance reacts and forms one or more new substances. • Ex. • Change in Color • Production of a gas • Formation of a precipitate

21. Evidences of Chemical Change • 1. Change in Color • Is a clue that a chemical change has produced at least one new substance • Production of a Gas • Bubbles can show a chemical change (ex. Cake) • Formation of a Precipitate • Any solid that forms and separates from a liquid

22. Chemical or Physical? • Even if you observe a color change, a gas, or a precipitate you cannot be sure • Ask yourself??? • Are different substances being formed???-If yes then is chemical!