1. Matter Flowchart MATTER Can it be physically separated? Homogeneous Mixture (solution) Heterogeneous MixtureCompoundElement MIXTUREPURE SUBSTANCE yesno Can it be chemically decomposed? noyes Is the composition uniform? noyes

2. A. Matter Flowchart  Examples:  graphite  pepper  sugar (sucrose)  paint  soda element hetero. mixture compound hetero. Mixture Solution (homogeneous mixture)

3. C. Johannesson Pure Substances  Element  composed of identical atoms  EX: copper wire, aluminum foil

4. Pure Substances  Compound  composed of 2 or more elements in a fixed ratio  properties differ from those of individual elements  Chemically combined and must be chemically separated  EX: table salt (NaCl)

5. Mixtures  Variable combination of 2 or more pure substances.  Physically combined and separated HeterogeneousHomogeneous

6. Mixtures  Solution  homogeneous  very small particles  no Tyndall effect Tyndall Effect  particles don’t settle  EX: rubbing alcohol

7.  What are the differences between an element, compound and mixture?

8. Matter has properties Two basic types of properties that we can associate with matter. Physical properties Chemical properties

9. Physical Properties Anything that can be observed without changing the identity of the substance. (Tends to be measurable.) melting point boiling point electrical conductivity color density thermal conductivity ductility malleability

10. Chemical Properties The way a substance may change or react to form other substances heat of combustion reactivity with water PH Oxidation Flammability Reactivity to other chemicals

11. Physical Changes Do NOT CHANGE THE TYPE OF MATTER Nothing new or different is formed Could be a change in: Mass Volume Density Change in state Color Shape Size

12. Examples of Physical Changes Boiling Freezing Dissolving Breaking Making a mixture 2 or more types of matter (substances) mixed together Not in specific amounts Can be separated physically

13. Chemical Changes The composition of the substance changes. The substances present at the beginning of the change are not present at the end; new substances are formed. The change cannot be “undone.” Picture from www.chem4kids.com www.chem4kids.com

14. Chemical Changes Evidence of a chemical reaction Formation of gas Formation of precipitate Change in color Change in energy Endothermic Absorbs heat energy (gets cold) Exothermic Releases heat energy (gets hot)

15. Chemical Changes Atoms are re-arranged, NOT created or destroyed

16. Law of Conservation of Matter Matter is conserved  type of atoms does not change Nothing is created or destroyed

17. Atoms and Ions An atom has a zero net charge How does an ion become an atom? Loses Electrons What element am I ? Protons=8 Electrons=8 Neutron=9 Are these the same element? Proton = 9 Electron =10 Neutron = 10 Proton = 9 Electron=9 Neutron = 11

18. Part 2 Notes: Compounds Noble gases-located… Right most column of the PT They are the only elements that tend to exist …as isolated atoms Molecule: the smallest electrically neutral unit of a substance that still has properties of that substance; two or more atoms that are covalently bonded and act as a single unit Diatomic molecule: molecule made of two atoms H 2 O 2 F 2 Br 2 I 2 N 2 Cl 2 (At 2 )

19. Molecular or covalent compounds: compounds composed of neutral molecules Relatively low MP and BP (below 300°C) Exits as gases or liquids because of low BP/MP Composed of generally 2 or more nonmetallic elements The smallest unit is a molecule

20. Ions: atoms or groups of atoms that have a positive or negative charge Ionic compounds: compounds composed of two or more ions that have opposite charges MP and BP: fairly to very high Exists as solid crystals Composed of a metallic ion with a nonmetallic ion in a ratio where there is a balance of opposite charges Smallest unit called formula unit (do not abbreviate)

21. Chemical formula: shows the kinds and numbers of atoms in the smallest representative unit of the substance Molecular formula: shows the kind and numbers of atoms present in one molecule of the substance Formula unit: smallest whole number ratio of positive and negative ions in the smallest electrically neutral portion of a compound which is ionically bonded

22. Pure Substances  Law of Definite Composition  A given compound always contains the same, fixed ratio of elements.  Law of Multiple Proportions  Elements can combine in different ratios to form different compounds.

23. Pure Substances  For example… Two different compounds, each has a definite composition.

24. Law of Definite proportions-does not depend on the amount of substance Example: Given the formulas CO and CO 2, what do you know about these compounds based on the Law of Definite proportions? The ratio of C to O within each compound will be constant-but it will be different from one compound to another

25. Example 1: Compound A: 2.41gC = 0.748 gC/gO 3.22g O Compound B: 6.71g C = 0.375 gC/gO 17.9g O A:B 0.748 gC/gO = _2_ 0.375 gC/gO 1 The mass ratio of C per gram of O in compound A to that of compound B is 2:1

26. Or… H 2 O and H 2 O 2 H:O 2:1 2:2 2g:16g 2g:32g

27. Example 2 N:O is 7:4 68g of N+O – 42g of N = 26g of O N:O is 42g/26g so 1.6gN per gram of O No, this is not nitrous oxide since it is not in a 7:4 mass ratio