1. Properties Physical property: Can be observed without changing the identity (formula) of a substance Chemical Property: Can ONLY be observed when the identity (formula) of a substance is changed

2. Changes Physical Change: Can be observed without changing the identity (formula) of a substance Chemical Change: Can ONLY be observed when the identity (formula) of a substance is changed Involves a chemical reaction

3. Examples of Properties Physical Chemical

4. Chemical change is a chemical reaction Reactants:Starting substances Products:Final (new) substances Reactants →Products

6. Physical or Chemical Property? Iron Rusts Iron Melts (at high temperature) Sugar dissolves in water Alka-Seltzer fizzes when you add it to water

7. Physical Separation Methods Distillation: –Separates substances by differences in their boiling points (usually liquids) Filtration: –Separates solid from liquid Chromatography: –Separates substances by differences in how they are absorbed by a stationary phase and a mobile phase. (Ex: liquid mobile phase and paper stationary phase)

8. Physical Separation Techniques Each method separates on the basis of a physical property Distillation Sorting Filtration Evaporation

9. Separation of a Mixture How would you separate a mixture of Salt and Sand into its separate components?

10. What do you need to know? Properties of salt White solid Does not melt (until it reaches HIGH temp) Dissolves in water Properties of sand Solid (color varies) Does not melt Does not dissolve in water

11. Difference in properties Salt dissolves in water Sand does not

12. Possible Method Add mixture to water Dissolve salt Filter out sand Salt left in water Evaporate off water

14. Mixture 2: Salt, sand and iron filings How would you separate this mixture into its separate components?

15. Physical Properties— Changes of State Heat must be added MeltingSolid to Liquid Evaporation or Vaporization Liquid to Gas SublimationSolid to Gas directly— Skip Liquid state

16. Physical Properties— Changes of State Heat must be removed Freezing or Fusion Liquid to Solid CondensationGas to Liquid DepositionGas to Solid directly— Skip Liquid state

17. Energy Energy is ability to do work (cause change) Potential energy—stored energy (Boulder on top of hill) Kinetic energy—energy in use (motion) (Boulder rolling down hill)

18. Forms of energy Electrical Mechanical Chemical Heat Light

19. Intensive Properties: Independent of amount of substance boiling point, density, color Extensive properties: Depend on amount of substance mass, volume

20. Can We Explain and Predict Physical and Chemical Properties of Matter? Properties are related to the structure of matter Need to examine pure substances in order to determine what the properties of a substance are

21. Element Cannot be broken down into simpler substances by chemical means. Contains only one kind of atom Smallest unit is atom Represented by atomic symbol (one or two letters) http://www.privatehand.com/flash/elements.html

22. Approximately 116 elements known Most are solids. Some are gases. Only two (Br and Hg) are liquids. Most elements are metals (are shiny, conduct electricity) A few elements are nonmetals (including the gaseous elements)

23. Seven gaseous elements exist as diatomic molecules (two atoms) H 2 O 2 N 2 F 2 Cl 2 Br 2 I 2 The subscript “2” indicates that there are two atoms of the element

24. Compounds Can be broken down into simpler substances (elements) by chemical means Contains two or more kinds of atoms (elements) combined in definite ratio Atoms are held together by bonds between atoms Smallest unit is molecule Represented by formula

25. Chemical Formula Chemical formula uses atomic symbols to show what elements and how many atoms of each element are in the compound The number of each type of atom is shown by using a subscript after the symbol If there is no subscript, we assume it is “1”

26. Examples H 2 O2 H atoms1 O atom CO1 C atom1 O atom CO 2 1 C atom2 O atoms Extra O makes a big difference CO kills quickly. CO 2 made by body.

27. Types of formulas Molecular Formula gives the number and type of atoms in molecule Structural Formula gives number and type of atoms in molecule AND shows how they are connected

28. MolecularNH 3 Structural H ─ N ─H ׀ H Lines show “bonds” between atoms

29. Language of Chemistry Alphabet:Atomic Symbols Words:Formulas Sentences:Chemical Equations

30. Chemical Equations Reactants → Products CO + O 2 →CO 2

31. Law of Conservation of Mass (Matter) Cannot create or destroy matter by chemical means

32. Must “balance” equation so that there are the same number of atoms of each kind on both sides of the equation 2 CO + O 2 →2 CO 2 RULE: Cannot change the formula of substance---can only change the number of molecules

33. Coefficients The numbers in front of a formula show the number of molecules of the substance 2 CO + O 2 →2 CO 2 2 CO = 2 molecules of CO

34. Practice Balancing Equations AgNO 3 + HCl AgCl + HNO 3 HCl + O 2 H 2 O + Cl 2 Ba(OH) 2 + HCl BaCl 2 + H 2 O

35. Practice Balancing Equations AgNO 3 + HCl AgCl + HNO 3 HCl + O 2 H 2 O + Cl 2 Ba(OH) 2 + HCl BaCl 2 + H 2 O