2. NOTES: Introduction to Chemistry

3. CHEMISTRY! ● CHEMISTRY = the study of the composition of matter, its chemical and physical changes, and the energy changes that accompany these changes.

4. The Nature of Science ● Scientific law versus theory: -Scientific law: a summary of an observed natural event -Scientific theory: a well-tested explanation of a natural event; supported by EVIDENCE

5. The Way Science Works… ● Science involves critical thinking, or applying logic and reason to observations and conclusions. ● Observation vs. Inference -Observation: description of what you see, hear, taste, feel, smell -Inference: the conclusion you draw as a result of an observation (not always correct!!)

6. Variables and Controls ● A variable is anything that can change in an experiment. -Independent variable: The variable being changed or controlled by the scientist. -Dependent variable: The variable being measured or observed by the scientist. ● A controlled experiment tests only one variable at a time.

7. The Scientific Method: A series of logical steps to follow in order to solve problems. OBSERVE FORMULATE A QUESTION FORM A HYPOTHESIS DESIGN AND CONDUCT AN EXPERIMENT MAKE OBSERVATIONS RECORD AND ANALYZE DATA DRAW CONCLUSIONS FORMULATE NEW QUESTIONS and CONTINUE CYCLE

8. Making Measurements ● Measurements are made in this class using SI units. ● LENGTH (m): distance between 2 points ● VOLUME (L): space occupied ● MASS (g): the amount of matter in an object ● WEIGHT (N): the force with which gravity pulls on a quantity of matter

10. Graph - visual representation of data 1) title 2) x and y axis labeled 3) units for both the x and y axis 4) scale is evenly and correctly spaced for data 5) legend when appropriate Organizing Data Data is organized and presented in tables, charts, and graphs.

11. LINE GRAPH: best for displaying data that change. **a.k.a. a SCATTER PLOT!! –Independent Variable: x-axis –Dependent variable: y-axis

12. BAR GRAPH: useful when you want to compare data for several individual items

13. PIE CHART: ideal for displaying data that are parts of a whole.

14. MATTER = ANYTHING WITH MASS AND VOLUME (CHAPTER 2, sections 2.1 & 2.4)

15. Matter Pure Substances Mixtures Elements Compounds Homogeneous Heterogeneous

16. Everything that is, is made up of matter.

17. From the very large...

18. To the very small...

19. Properties of Matter can be… ● Extensive properties: depend on the AMOUNT of matter -Example: Mass, Volume ● Intensive properties: depend on the TYPE of matter -Example: Absorbancy, Density

20. STATES OF MATTER: ● SOLID ● LIQUID ● GAS

21. SOLIDS: ● Definite shape? ● YES ● Definite volume? ● YES ● Molecules in a solid are tightly packed and constantly vibrating.

22. LIQUIDS: ● Definite shape? ● NO ● Definite volume? ● YES ● Some liquids flow more easily than others. The resistance of a liquid to flow is called viscosity. –Honey has a high viscosity compared to water.

23. GASES: ● Definite shape? ● NO ● Definite volume? ● NO ● The particles in a gas are spread very far apart, but can be compressed by pumping them into a restricted volume.

24. Physical Properties: ● Physical properties: characteristics that can be observed without changing the identity of the substance. ● Examples: -mass-melting pt. -volume-boiling pt. -color -magnetism -shape -texture -density

25. Physical Changes: ● Physical change: a change in the physical form or properties of a substance that occurs without a change in composition. ● Examples: -melting-bending -freezing-tearing -grinding-crushing -dissolving-boiling

26. Phase Changes: ● Changes in phase are examples of physical changes. ● Melting: solid  liquid ● Freezing: liquid  solid ● Vaporization: liquid  gas ● Condensation: gas  liquid ● Sublimation: solid  gas

27. Chemical Properties: ● Chemical property: describes a substance’s ability to change into a different substance. ● Examples: -flammability -reactivity

28. Chemical Changes: ● Chemical change: occurs when a substance changes composition by forming one or more new substances. (bonds are broken and bonds are formed)

29. What is a Chemical Reaction? ● Chemical Reaction – one or more substances change into new substances ● Process involves reactants and products ● Reactant – a starting substance in a chemical reaction ● Product – a substance formed in a chemical reaction

30. What is a Chemical Reaction? ● Example: Nitrogen and hydrogen gas can react to form ammonia under certain conditions. Reactants Yield Products N 2 (g) + H 2 (g)  NH 3 (g)

31. How Can You Tell Whether or Not a Chemical Reaction Has Taken Place? ● Chemical Change – alters a given material by changing its chemical composition ● Examples: burn, rust, decompose, corrode, explode

32. Other Indicators of a CHEMICAL CHANGE: -c hange in heat -change in color -change in odor -light is given off -formation of a gas -formation of a solid -irreversibility

33. Evaporation is a physical change

34. Breaking is a physical change.

35. Boiling is a change of state, and therefore a physical change!

36. Rusting is a Chemical Change

37. Burning is a Chemical Change

38. CONSERVATION: ● Law of Conservation of Matter (Mass): in a physical change or a chemical reaction, matter is neither created nor destroyed; it is conserved

39. Matter MUST be conserved; it’s the LAW!