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Changes in Matter

Changes in Matter. Physical Changes Altering a substance without changing its composition Cutting up paper Breaking a pencil Crushing rocks Changing states of matter Ice –melting  liquid Water –melting water. Changes in Matter. Chemical Changes 

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Changes in Matter

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  1. Changes in Matter • Physical Changes • Altering a substance without changing its composition • Cutting up paper • Breaking a pencil • Crushing rocks • Changing states of matter • Ice –melting liquid • Water –melting water

  2. Changes in Matter • Chemical Changes  • Process where one or more substance changes into a new substance • Rusting • Fire • Reactants- substances that we begin with • Products-substances that we end with • Reactant  Products

  3. Changes in Matter • Evidence of chemical reaction: • Gas is produced • Color Change • Change in smell • Formation of solid—precipitate • Light is produced • Temperature change -exothermic -endothermic

  4. Law of Conservation of Mass • Mass is neither created nor destroyed • Mass reactants = Mass products Reactants  Products H2 + O2 H2O 18 g + 22 g  ?g H2O

  5. Steps to solve Law of Conservation of Mass problems • Write what you know • chemical reaction • reactants and their masses • products and their masses • What are you solving for? • Solve for your unknown

  6. From a laboratory experiment designed to separate water into hydrogen and oxygen gas, a student collected 10.0 g of hydrogen and 79.4 g of oxygen. How much water was initially involved in the process? Law of Conservation of Mass says… Mass reactants = Mass of Products H2Omass = H2 mass + O2 mass H2Omass = 10.0 g + 79.4 g H2O mass = 89.4 g Chemical Reaction H2O  H2 + O2 Reactants  Products What do we know? H2 = 10.0 g O2 = 79.4 g What is our unknown? H2O = ??? g

  7. A student carefully placed 15.6 g of sodium in a reactor supplied with an excess quantity of chlorine gas. When the reaction was complete, the student obtained 39.7 g of sodium chloride. How many grams of chlorine gas reacted? Chemical Reaction Reactants  Products Sodium + Chlorine  Sodium Chloride Law of Conservation of Mass says… Mass reactants = Mass of Products Sodium mass + Chlorine mass = Sodium Chloride mass 15.6 grams + ? grams = 39.7 grams ? grams = 24.1 grams of Chlorine What do we know? Sodium = 15.6 g Sodium Chloride = 39.7 g What is our unknown? Chlorine = ??? g

  8. In a flask, 10.3 g of aluminum reacted with 100 g of liquid bromine to form aluminum bromide. After the reaction, no aluminum remained, and 8.5 grams of bromine remained unreacted. How many grams of compound were formed? Chemical Reaction Reactants  Products Aluminum + Bromine  Aluminum Bromide What do we know? Aluminum = 10.3 g Bromine = 100 g Bromine left over = 8.5 g Bromine used = ?? = 100 – 8.5 g = 91.5 g Law of Conservation of Mass says… Mass reactants = Mass of Products Aluminum used+ Bromine used = Aluminum Bromide made 10.3 grams + 91.5 grams = ??? grams 101. 8 grams = ? Grams of Aluminum Bromide What is our unknown? Aluminum Bromide = ??? g

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