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Chemical Reactions

Chemical Reactions. Midway Middle School. How do we know that matter is composed of atoms?. Atoms are the building blocks of all matter. Atoms are the smallest particle that cannot be broken down. Atoms join with others atoms to make everything. Chemical Changes.

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Chemical Reactions

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  1. Chemical Reactions Midway Middle School

  2. How do we know that matter is composed of atoms? Atoms are the building blocks of all matter. Atoms are the smallest particle that cannot be broken down. Atoms join with others atoms to make everything.

  3. Chemical Changes Chemical Reactions often cause observable changes

  4. Observable Changes in Chemical Reactions Color Odor Release or Absorption of Heat Release or Absorption of Light Release of Gas

  5. Physical Changes in matter Examples of Physical Changes *Melting ice *Dissolving salt *Cutting paper

  6. What happens when there is a Physical Changes *No new product is formed *Substance just physically appears different

  7. Chemical Changes in matter Examples of Chemical Changes *Color change *Heat absorbed or released *Formation of gas

  8. What elements are found in organic compounds Hint: CHOPS Carbon Hydrogen Oxygen Phosphorus Nitrogen Sulfur

  9. How do you differentiate between elements and compounds? *Elements are made of only one kind of atom *Elements are all listed on the periodic table Examples of elements: Oxygen – O Iron – Fe Sodium - Na

  10. How do you differentiate between elements and compounds? *Compounds are made of two or more elements chemically combined Examples of compounds: Water – H2O Baking soda – NaHCO3 Carbon dioxide – CO2

  11. Chemical compounds NaHCO3 This is the chemical formula for baking soda. *How many elements are there? 4 Sodium(Na) Hydrogen(H) Carbon(C) Oxygen(O)

  12. Chemical compounds NaHCO3 This is the chemical formula for baking soda. *How many total atoms are there? 6 1 - Sodium(Na) 1 - Hydrogen(H) 1 - Carbon(C) 3 - Oxygen(O)

  13. Law of Conservation of Mass Matter can NOT be created Nor can it be destroyed Chemical Equations MUST balance

  14. How do balanced equation relate to the Law of Conservation of Matter? Product Reactants The same number of atoms of each element must be in the products that were in the reactants of a chemical equation. Example:

  15. Chemical Equations • Chemical reactions are represented on paper by chemical equations. • Example: • 2hydrogen gas (2H2)can react (burn) with oxygen gas (O2)to form 2water molecules(H20).

  16. Written Chemical Equations subscript yields

  17. Because atoms are neither created nor destroyed in a reaction, a chemical equation must have an equal number of atoms of each element on each side of the arrow(i.e. the equation is said to be 'balanced'). Why do Chemical Equations have to balance?

  18. Steps to Balancing the Equation Is this a balanced equation? Yes atoms in = atoms out

  19. Working Together Balance the following equation:

  20. Step 1count up the atoms in the reactants and products

  21. Think about it: We seem to be o.k. with our number of (C)carbon atoms in both the reactants and products But, we have only half the (H)hydrogen in our products as in our reactants.

  22. Step 2  We can fix this by doubling the number of water molecules in the list of products 2

  23. *This has balanced our (C)carbon and (H)hydrogen atoms *But, we now have 4 (O)oxygen atoms in our products, and only have 2 in our reactants.

  24. Step 3 We can balance our (O)oxygen atoms by doubling the number of (O)oxygen atoms in our reactants: 2

  25. We have a balanced chemical equationfor the reaction of methane with oxygen.

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