Table of Contents

1
Table of Contents

• Chapter Preview
• 6.1 Observing Chemical Change
• 6.2 Describing Chemical Reactions
• 6.3 Controlling Chemical Reactions
• 6.4 Fire and Fire Safety

2
Chapter Preview Questions

• 1. Which of the following is an example of a
  physical change?
• a. Wood burns and becomes ash.
• b. A silver fork tarnishes.
• c. Water boils and becomes water vapor.
• d. Leaves decay over time.

3
Chapter Preview Questions

• 1. Which of the following is an example of a
  physical change?
• a. Wood burns and becomes ash.
• b. A silver fork tarnishes.
• c. Water boils and becomes water vapor.
• d. Leaves decay over time.

4
Chapter Preview Questions

• 2. When a forest burns, it
• a. neither absorbs nor releases energy.
• b. loses matter and energy.
• c. absorbs energy.
• d. releases energy.

5
Chapter Preview Questions

• 2. When a forest burns, it
• a. neither absorbs nor releases energy.
• b. loses matter and energy.
• c. absorbs energy.
• d. releases energy.

6
Chapter Preview Questions

• 3. Fe, which stands for iron, is a
• a. chemical symbol.
• b. chemical equation.
• c. atomic number.
• d. name.

7
Chapter Preview Questions

• 3. Fe, which stands for iron, is a
• a. chemical symbol.
• b. chemical equation.
• c. atomic number.
• d. name.

8
Chapter Preview Questions

• 4. The ease and speed with which an element
  combines with other elements is called its
• a. atomic number.
• b. chemical property.
• c. physical property.
• d. reactivity.

9
Chapter Preview Questions

• 4. The ease and speed with which an element
  combines with other elements is called its
• a. atomic number.
• b. chemical property.
• c. physical property.
• d. reactivity.

10
What happens during a chemical reaction?

• Suppose you fill a sealable bag
• with ice cubes, and you allow the
• ice to melt. How would the mass
• of the bag and ice before
• melting compare to the mass of
• the water and the bag after
• melting? Explain your answer.

11
Section 1 Observing Chemical Change

• Standard 8.5.a Students know reactant atoms and
  molecules interact to form products with
  different chemical properties.
• Standard 8.5.c Students know chemical reactions
  usually liberate heat or absorb heat.

12
Matter and Change

• How can changes in matter be described?
• Physical Property
• Chemical Property

• Changes in matter can be described in terms of
  physical changes and chemical changes
• A characteristic of a substance that can be
  observed with out changing into another
  substance.
• A characteristic of a substance that describes
  its ability to change into other substances.

13
Matter and Change

• Physical Change

• Any change that alters the form or appearance of
  a substance but does not make the substance into
  another substance.

14
Matter and Change

• Chemical Property

• A characteristic of a substance that describes
  its ability to change into other substances.

15
Properties and Changes in Matter

• Chemical changes occur when bonds break and new
  bonds form.

16
Evidence for Chemical Reactions

• How can you tell when a chemical reaction occurs?
• Precipitate
• Endothermic Reaction
• Exothermic Reaction

• Chemical reactions involve changes in properties
  and changes in energy that you can observe.
• A solid that forms from solution during a
  chemical reaction.
• The making and breaking of bonds results in a net
  absorption of energy
• The making and breaking of bonds results in a net
  release of energy.

17
Evidence for Chemical Reactions

• How can you tell when a chemical reaction occurs?
• 4 Observations of Chemical Change

1. There is a formation of gas which can be seen by
   a fizzing or bubbling.
2. The reaction will cause heat, light, or odor to
   be emitted
3. A color change is produced.
4. A solid is formed during the change.

18
Section 1 Quick Quiz

• What happens when chemical bonds break and new
  bonds form?
• A physical change
• A chemical reaction
• Matter is destroyed
• Surface area increases
• Answer B A chemical reaction

19
Section 1 Quick Quiz

• A chemical reaction that absorbs energy in the
  form of heat is described as
• endothermic
• exothermic
• combustion
• unbalanced
• Answer A - endothermic

20
Section 1 Quick Quiz

• Every chemical reaction involves a change in
• mass
• energy
• concentration
• state
• Answer B - energy

21
Section 1 Quick Quiz

• One example of a chemical change is
• filtering
• burning wood
• boiling water
• crushing a can
• Answer B burning wood

22
Section 1 Quick Quiz

• Anything that has mass and takes up space is
  considered
• matter
• energy
• chemistry
• endothermic
• Answer A - matter

23
Energy in Chemical Changes

• A student places two substances in a flask and
  measures the temperature once per minute while
  the substances react. The student plots the time
  and temperature data and creates the graph at
  left.

24
Energy in Chemical Changes

• Reading Graphs
• What was the temperature in the flask at 3
  minutes? When was the first time the temperature
  was at 6ºC?

• At 3 minutes the temperature in the flask was
  about 30ºC. The first time the temperature was
  6ºC was at about 7 minutes.

25
Energy in Chemical Changes

• Calculating
• How many degrees did the temperature drop
  between2 minutes and 5 minutes?

• About 20ºC

26
Energy in Chemical Changes

• Interpreting Data
• Is the reaction endothermic or exothermic?
  Explain.

• The reaction was endothermic, because it absorbed
  thermal energy from the reaction mixture, causing
  the temperature to drop.

27
Energy in Chemical Changes

• Inferring
• At what temperature did the reaction stop? How
  can you tell?

• The reaction stopped at about 2ºC. You can tell
  because that is the lowest temperature reached.

28
Energy in Chemical Changes

• Drawing Conclusions
• Suppose the temperature in the flask increased
  instead of decreased as the reaction occurred. In
  terms of energy, what kind of reaction would it
  be? Explain.

• If the temperature increased instead, the
  reaction would be exothermic, because an
  exothermic reaction is one in which energy is
  released.

29
Section 2 Describing Chemical Reactions

• Standard 8.5.b Students know the idea of atoms
  explains the conservation of matter. In chemical
  reactions the number of atoms stays the same no
  matter how they are arranged, so their total mass
  stays the same.

30
What Are Chemical Equations?

• What information does a chemical equation contain?

• Chemical equations use chemical formulas and
  other symbols instead of words to summarize a
  reaction.

31
Conservation of Matter

• The principle of conservation of matter states
  that in a chemical reaction, the total mass of
  the reactants must equal the total mass of the
  products.

32
Balancing Chemical Equations

• To describe a reaction accurately, a chemical
  equation must show the same number of each type
  of atom on both sides of the equation.

33
Balancing Chemical Equations

• Magnesium (Mg) reacts with oxygen gas (O2),
  forming magnesium oxide (MgO). To write a
  balanced equation for this reaction, first write
  the equation using the formulas of the reactants
  and products, then count the number of atoms of
  each element.

34
Balancing Chemical Equations

• Balancing Chemical Equations
• Balance the equation for the reaction of sodium
  metal (Na) with oxygen gas (O2), forming sodium
  oxide (Na2O).

35
Balancing Chemical Equations

• Balancing Chemical Equations
• Balance the equation for the reaction of tin (Sn)
  with chlorine gas (Cl2), forming tin chloride
  (SnCl2).

36
Balancing Chemical Equations
http//education.jlab.org/elementbalancing/index.h
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37
Classifying Chemical Reactions

• Many chemical reactions can be classified in one
  of three categories synthesis, decomposition, or
  replacement.

38
Section 2 Quick Quiz

• CaCO represents a chemical
• symbol.
• subscript.
• formula.
• reaction.
• Answer C - formula

39
Section 2 Quick Quiz

• A chemical equation that shows the same number of
  each kind of atom on both sides of the equation
  is said to be
• balanced.
• unbalanced.
• an incomplete reaction.
• a replacement reaction.
• Answer A - balanced

40
Section 2 Quick Quiz

• A bottle of hydrogen peroxide that eventually
  turns into a bottle of water and oxygen gas is an
  example of a
• replacement reaction.
• precipitate reaction.
• decomposition reaction.
• synthesis reaction.
• Answer C - decomposition

41
Section 2 Quick Quiz

• The substances listed on the left side of a
  chemical equation are the
• coefficients.
• products.
• reactants.
• precipitates.
• Answer C - reactants

42
Section 2 Quick Quiz

• In a chemical equation, numbers often appear in
  front of a chemical formula. These numbers tell
  you the
• number of molecules in each atom in the reaction.
• number of molecules or atoms of each substance in
  the reaction.
• number of elements in the reaction.
• number of atoms in each molecule in the reaction.
• Answer B number of molecules or atoms of each
  substance in the reaction

43
Section 3 Controlling Chemical Reactions

• Standard 8.5.a Students know reactant atoms and
  molecules interact to form products with
  different chemical properties.
• Standard 8.5.c Students know chemical reactions
  usually liberate heat or absorb heat.

44
Energy and Reactions

• How is activation energy related to chemical
  reactions?
• Activation Energy
• Potential Energy
• Kinetic Energy

• All chemical reactions require a certain amount
  of activation energy to get started.
• The minimum amount of energy needed to start a
  chemical reaction.
• Stored energy that results from the position or
  shape of an object.
• Energy that an object has due to its motion.

45
Energy and Reactions

• All chemical reactions require a certain amount
  of activation energy to get things started.

46
Energy and Reactions

• Exothermic Reaction
• Endothermic Reaction

• A reaction that releases energy in the form of
  heat.
• A reaction that absorbs energy in the form of
  heat.

47
Energy and Reactions

• Both exothermic and endothermic reactions need
  energy to get started.

48
Rates of Chemical Reactions

• Factors that affect rates of reaction include
• surface area
• temperature
• concentration and
• the presence of catalysts and inhibitors.
• A material that increases the rate of reaction by
  lowering the activation energy.
• A material used to decrease the rate of reaction.
• Biological catalysts found in the
• cells of the body.

• What factors affect the rate of a chemical
  reaction?
• Catalyst
• Inhibitor
• Enzyme

49
Rates of Chemical Reactions

• The cells in your body (as in all living things)
  contain biological catalysts called enzymes.
  After a reaction, an enzyme molecule is unchanged.

50
Section 3 Quick Quiz

• The minimum amount of energy that has to be added
  to start a reaction is the
• exothermic energy.
• endothermic energy.
• activation energy.
• chemical energy.
• Answer C activation energy

51
Section 3 Quick Quiz

• Chemicals that act as biological catalysts by
  speeding up reactions in living things are
• enzymes.
• inhibitors.
• reactants.
• fuels.
• Answer A - enzymes

52
Section 3 Quick Quiz

• A material used to decrease the rate of a
  chemical reaction is a(n)
• catalyst.
• enzyme.
• fuel.
• inhibitor.
• Answer D - inhibitor

53
Section 4 Fire and Fire Safety

• Standard 8.5.c Students know chemical reactions
  usually liberate heat or absorb heat.

54
Understanding Fire

• What are the three things necessary to maintain a
  fire?

• Three things necessary to start and maintain a
  fire are
• fuel
• oxygen
• heat

55
Understanding Fire

• The fire triangle can be controlled in the grill.
  If any part of the fire triangle is missing, a
  fire will not continue.

56
Home Fire Safety

• If you know how to prevent fires in your home and
  what to do if a fire starts, you are better
  prepared to take action.
• The best form of fire safety is prevention.

57
Section 3 Quick Quiz

• In what way can a fire be brought under control?
• Add fuel.
• Add oxygen.
• Remove oxygen.
• Remove carbon dioxide.
• Answer C Remove oxygen

58
Section 3 Quick Quiz

• What is the best form of fire safety?
• a water hose
• an extinguisher
• the fire department
• fire prevention
• Answer D fire prevention

59
Section 3 Quick Quiz

• The best way to put out a small kitchen fire is
  to
• blow it out
• use a garden hose
• turn off the appliances
• cover it or use a home fire extinguisher
• Answer D cover it or use a home fire
  extinguisher