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Chemical Reactions

Chemical Reactions. Chapter 14 Section 1 Forming New Substances. Chemical reaction – process by which one or more substances undergo change to produce one or more different substances. The new substances have different chemical and physical properties from the original substances.

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Chemical Reactions

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  1. Chemical Reactions Chapter 14 Section 1 Forming New Substances

  2. Chemical reaction – process by which one or more substances undergo change to produce one or more different substances. The new substances have different chemical and physical properties from the original substances. An example is when chlorophyll in leaves breaks down into simpler substances. The green that covered the colors is gone and the red, orange, and yellow colors show through.

  3. What happens during a chemical reaction? - chemical bonds break - atoms rearrange - new bonds form Some clues to a chemical reaction: Gas formation (bubbling, fizzing) Solid formation (precipitate forms) Color change Energy change

  4. Chemical formula – a shorthand notation for a compound or a diatomic element using chemical symbols and numbers. The chemical formula shows how many of each kind of atom is present in a molecule. The chemical formula for water H2O shows that the water molecule has 2 atoms of hydrogen and 1 atom of oxygen. The formula for carbon dioxide CO2 has 1 atom of carbon and 2 atoms of oxygen.

  5. The formula for glucose (sugar made by plants during photosynthesis) is C6H12O6. Every molecule of glucose has 6 _____ atoms of carbon 12 _____ atoms of hydrogen 6 _____ atoms of oxygen

  6. Prefixes Used in Chemical Names mono 1 penta 5 octa 8 di 2 hexa 6 nona 9 tri 3 hepta 7 deca 10 tetra 4 The formulas of covalent compounds (between nonmetals) are written using prefixes. carbon dioxide – CO2 carbon monoxide – CO carbon tetrahydride – CH4

  7. Formulas for ionic compounds (between a metal & nonmetal) must be written to make sure the overall charge is zero or neutral. NaCl sodium has a 1+ charge & chlorine has a 1- charge The overall charge is (1+) + (1-) = 0 MgCl2 magnesium has 2+ & chlorine has 1- charge 2 chlorine atoms are needed for 1 magnesium atom The overall charge is (2+) + (1-) + (1-) = 0

  8. Write the formula for sodium nitride. 1+ Sodium has a ____ charge. 3- Nitrogen has a ____ charge. The formula is Na__N __. 3 Write the formula for potassium oxide. 1+ Potassium has a ____ charge 2- Oxygen has a ____ charge The formula is K__O __. 2

  9. Ionic or Covalent? (check the elements) Write the formula. • sulfur trioxide _________ ______ • calcium fluoride _________ ______ • phosphorus pentachloride _______ ______ • dinitrogen trioxide _________ ______ • lithium oxide _________ ______ covalent SO3 ionic CaF2 covalent PCl5 covalent N2O3 ionic Li2O

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