1. Elements Combine to Form Compounds

2. Compounds Compound: a pure substance made up of more than one kind of element in which the atoms of the elements are joined together. Compounds form through chemical bonds: these are links between two or more atoms that hold the atoms together Two types of compounds Ionic Compounds: typically formed between metals and non-metals. Ex. NaCl Molecular (covalent) compounds: formed between non- metals only. Ex CO 2

3. Compounds… Compounds are represented by a combination of element symbols known as a chemical formula Chemical formulas indicate the proportion in which the elements are present. Identify the elements and number of atoms for each element in the following Chemical Formulas CH 4Elements Present: Carbon and Hydrogen Proportion: (number of each element) 1 carbon atom and 4 hydrogen atoms

4. Complete the table below CompoundElements PresentProportion or Number of each element CO2 CaCO 3 C3H8C3H8 H2O

5. Ionic Compounds NameChemical Formula Sodium Chloride (table salt)NaCl Calcium Carbonate (chalk)CaCO3 Sodium Sulfate ???Na 2 SO4 Sodium HydroxideNaOH These are some common chemical ionic compounds that you should know

6. Chemical Names of Compounds When given a chemical formula, you can write the chemical name which indicates the elements present in the compound IUPAC (International Union of Pure and Applied Chemistry): a group that represent chemists around the world and is responsible for the rules when naming compounds.

7. Naming Ionic Compounds The first element is typically a metal and the name of the metal is left unchanged The second element is a non-metal and the name always end in “ide” Put the two names together What is the chemical name for the compound CaF? The first element is Ca: Calcium The second element is F: Fluorine but it needs to end in “ide” so it becomes fluoride The name for CaF is calcium fluoride.

8. Task Complete the Practice Problems at the bottom of page 82.

9. Molecular Compounds Compound NameChemical Formula Table sugar (sucrose)C12H22O11 Carbon DioxideCO2 MethaneCH4 WaterH2OH2O These are some common chemical molecular compounds that you should know

10. Naming molecular Compounds Name the first Element Name the second element and use the suffix “ide” Add prefixes to the names to indicate the number of each atom in the compound (see next slide for prefix names) Write the name of the compound Example: Name PF4 First element is Phosphorous The second element is fluorine but the ending changes to ide so it is fluoride There is only one P, so no prefix needed There are 4 F, so the prefix is tetra which gives tetrafluoride. The compound name is phosphorus tetrafluoride

11. Prefixes (table 3.4, page 83) Number of atomsPrefix 1Mono (used only for the second atom) 2di 3tri 4tetra 5penta 6hexa 7hepta 8octa 9nona 10deca

12. Task Practice problems on page 83

13. Physical and Chemical Changes Physical Change: the appearance of a substance may be changed but the bonds holding the atoms together have not been broken and new bonds have not been made. NO NEW SUBSTANCE IS PRODUCED. Examples of Physical Changes: Change of state Cutting Dissolving

14. Chemical Change: produces new substances with new properties. New bonds are formed while other bonds are broken Examples of Chemical Changes Corrosion (metals combining with oxygen) Combustion (burning) Fruit Ripening

15. Useful Websites http://videos.howstuffworks.com/hsw/8685-states-of- matter-chemical-changes-video.htm http://videos.howstuffworks.com/hsw/8685-states-of- matter-chemical-changes-video.htm http://www.quia.com/quiz/303980.html

16. Evidence that a chemical change may have occurred Heat is produced or absorbed A new color appears A precipitate is formed A gas is produced Difficult to reverse Note: these observations do not prove conclusively that a chemical change has occurred but it supports the possibility that it is a chemical change.

17. Brainstorm Are there examples of changes that are not easily identified as chemical or physical? It is not always a clear cut situation!

18. Core Lab Observing Changes in Matter

19. Chemical Change During a chemical change, elements are conserved but compounds are not Corrosion or the rusting of iron: In a piece of steel, iron atoms are bonded together. Overtime, oxygen will combine with the iron to form something new, rust. The number of iron atoms has not changed but they are now combined with oxygen to form a new compound

20. Task How many different structures has you make from 5 red leggos, 6 blue and 4 white. Will everyone's structure be the same? No, but the number of red, blue and white leggos in the structures will be the same. If the colored leggos represent 3 different elements, then the same number and types of elements can produce different compounds (or structures in this case)