Chemical Reactions and Equations

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Chemical Reactions and Equations
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How can you tell if a chemical reaction has
occurred?

• Color change
• Heat produced/gets warm (exothermic)
• Heat absorbed/gets cold (endothermic)
• Gas produced (fizz)
• Solid produced/turns cloudy (precipitate)
• These are indications of
• CHEMICAL CHANGES

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Physical Changes.

• DO NOT tell you a chemical reaction has
  occurred!
• Examples of physical changes
• Phase changes (solid-liquid-gas)
• Changes in shape

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Is a chemical reaction occurring?
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Is a chemical reaction occurring?
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Is a chemical reaction occurring?
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Is a chemical reaction occurring?
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Is a chemical reaction occurring?
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Is a chemical reaction occurring?
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Is a chemical reaction occurring?
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Is a chemical reaction occurring?
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Is a chemical reaction occurring?
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Chemical formulas

• are the words in the language of chemistry
• In the last unit you learned how to name
  compounds and write their formulas. You learned
  chemistry words like
• KNO3 and NaBr

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Chemical Equations

• are the sentences in the language of chemistry.
  
• You will put together the words (formulas) you
  learned in the last unit to make sentences
  (chemical equations)
• As in English, sentences are more interesting
  and give you more information than isolated
  words

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Punctuation and grammar

• In addition to needing words in your
  sentences, you will also need some punctuation
  and grammar to so your sentence makes sense and
  is easy to understand.
• Every chemical equation (sentence) has formulas
  (words) as well as special symbols (punctuation)

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Symbols used in Chemical Equations

and
yields
a gas forms
a precipitate forms
Heat needed (reaction is endothermic)
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More symbols
catalyst
a catalyst is needed
(s) Solid phase
(l) Liquid phase
(g) Gas phase
(aq) aqueous (dissolved
in water)
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Grammar

• Some basic rules for putting your chemical
  equations together correctly
• Like in English, always read from left to right
  across the page
• Start here end here

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Grammar

• Some basic rules for putting your chemical
  equations together correctly
• 2) Each equation has two halves. The half left of
  the arrow is the REACTANT side.
• The half right of the arrow is the PRODUCT side.
• REACTANTS PRODUCTS

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Chemical equations are easy!

• (compared to English!)
• You now know everything you need to know to write
  grammatically correct chemical equations

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Word Equations

• Translate the following word equation into an
  chemical equation
• Hydrogen chloride in the liquid phase and sodium
  hydroxide in the solid phase yields aqueous
  sodium chloride and water

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Word Equations

• Hydrogen chloride in the liquid phase and sodium
  hydroxide in the solid phase yields aqueous
  sodium chloride and water
• HCl (l) NaOH (s) NaCl (aq) H20