Mixtures and solutions 3 2


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Mixtures and solutions 3 2

  1. 1. Focus Question: What happens during a chemical reaction? Fizz Quiz 3-2 Chemical Reactions Mixtures and Solutions
  2. 2. Precipitate <ul><li>A precipitate is an insoluble substance that forms as a product in a reaction. </li></ul><ul><li>What is the substance that precipitated in the calcium chloride/baking soda reaction? </li></ul>
  3. 3. Chalk <ul><li>The precipitate formed from the reaction of calcium chloride and baking soda is chalk - Calcium carbonate </li></ul><ul><li>One of the properties of calcium carbonate is that it reacts with vinegar. </li></ul><ul><li>How could we test our precipitate to find out for sure if it calcium carbonate? </li></ul><ul><li>How can we separate the precipitate from the rest of the mixture? </li></ul>
  4. 4. Procedure <ul><li>Label paper filter with group and room # </li></ul><ul><li>Use paper filter and funnel to separate the precipitate from the liquid </li></ul><ul><li>Set the paper filter on the paper towel to dry - stack on the back counter when asked to </li></ul>
  5. 5. Filtered Liquid <ul><li>Do you think the liquid that came through the filter is a solution? </li></ul><ul><li>How could we find out? </li></ul><ul><li>Label scrap paper and place in evaporating tray with evaporating dishes </li></ul><ul><li>Add a small amount of liquid to each dish </li></ul><ul><li>Rinse and replace cups in bins - clean up </li></ul>
  6. 6. Focus Question: How do the products of a chemical reaction form? Investigation 3-2 Part 2 Mixtures and Solutions
  7. 7. When Substances Change <ul><li>What is a molecule? </li></ul><ul><li>What is an atom? </li></ul><ul><li>What happens during chemical reactions? </li></ul><ul><li>Explain how there can be so many different kinds of substances in the world. </li></ul>
  8. 8. Evaporation Results <ul><li>Observe the contents of the evaporation dishes. </li></ul><ul><li>Do you recognize the crystal? Have you seen similar crystals before? </li></ul><ul><li>Where did the salt come from? How did the salt get into the cups? </li></ul>
  9. 9. Testing Chalk <ul><li>One property of chalk (Calcium Carbonate) is that it reacts with vinegar. </li></ul><ul><li>Test your precipitate to see if it also reacts with vinegar. </li></ul><ul><li>Complete Reaction Analysis worksheet </li></ul>
  10. 10. Chemical Formulas <ul><li>Scientists use a code, called a Chemical Formula, to represent substances. </li></ul><ul><li>Constructed with atom symbols and numbers. </li></ul><ul><li>Chemical formulas tell the kind and number of atoms in the molecule of a substance. </li></ul>
  11. 11. CaCl 2 NaHCO 3 Calcium chloride Baking Soda Ca = Calcium, Cl = Chlorine, Na = Sodium, H = Hydrogen, C = Carbon, O = Oxygen Chemists use models and equations to help them understand the chemical reactions they observe. Look at what happens during a reaction:
  12. 12. Chemical Reactions <ul><li>During chemical reactions, atoms rearrange. </li></ul><ul><ul><li>Reactant substances no longer exist because their atoms form new molecules. </li></ul></ul><ul><li>During reactions, molecules are destroyed and other molecules are created. </li></ul><ul><ul><li>HOWEVER………… </li></ul></ul>
  13. 13. Chemical Reactions <ul><li>Atoms are NEVER destroyed OR created. </li></ul><ul><ul><li>All the atoms in the reactants are used to make the products </li></ul></ul><ul><ul><li>No atoms are left behind </li></ul></ul><ul><ul><li>No atoms come from some other place </li></ul></ul><ul><li>The number and kind of atoms on the reactant side is exactly the same as the number and kind of atoms on the product side. </li></ul>Reactant Atoms = Product Atoms
  14. 14. Vocabulary <ul><li>Atom - the basic particles from which all matter is made. There are 90 naturally occurring atoms on Earth. </li></ul>
  15. 15. <ul><li>Chemical Formulas - can represent atoms and molecules. Chemical formulas use symbols and numbers to describe the kinds and numbers of atoms in a molecule. </li></ul><ul><ul><li>H 2 O CO 2 NaCHO 3 NaCl CaCl 2 </li></ul></ul><ul><li>Chemical Equations - used by scientists, along with atom models, to represent chemical reactions. </li></ul><ul><li>6CO 2 + 6H 2 O  C 6 H 12 O 6 + 6O 2 </li></ul>
  16. 16. Content <ul><li>What forms can chemical reactions take? </li></ul><ul><li>Products of reactions can be a new solid (precipitate), liquid, gas (bubbles), or dissolved. </li></ul>
  17. 17. Content <ul><li>How can you identify the products of a reaction? </li></ul><ul><li>The physical properties (crystal shape), and chemical properties (reacting with acid), of substances help identify them. </li></ul><ul><li>Your questions? </li></ul>
  18. 18. Homework <ul><li>Read “Chemical Formulas” </li></ul><ul><ul><li>Pages 32 - </li></ul></ul>