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Transcript of Chapter Menu Lesson 1:Chemical Properties and ChangesChemical Properties and Changes Lesson...
Chapter Menu
Lesson 1:Chemical Properties and Changes
Lesson 2: Chemical Equations
Lesson 3: Energy and Chemical Change
Click on a hyperlink to view the corresponding lesson.
chemical property
chemical change
dissolving
8.1 Chemical Properties and Changes
Ability to Change
• In a chemical change, the properties that give a substance its identity change.
8.1 Chemical Properties and Changes
• Properties of matter help identify objects.
• Properties are either physical or chemical.
What properties do elements have?
Ability to Change (cont.)
• A chemical property is the ability or inability of a substance to combine with or change into one or more new substances.
8.1 Chemical Properties and Changes
Chemical Properties
• Examples of chemical properties include burning or rusting.
• Some substances do not react.
8.1 Chemical Properties and Changes
Physical Properties• Physical properties can be observed without
changing the substance.
8.1 Chemical Properties and Changes
Chemical and Physical Changes• Chemical changes change one substance into
another substance.
• Usually chemical changes cannot be easily reversed.
8.1 Chemical Properties and Changes
Property Changes
Forming New Substances• All chemical changes produce substances that are different
from the starting substances.
– A compound is decomposed into its elements.
– Two elements join to form a compound.
8.1 Chemical Properties and Changes
Physical Changes• A physical change is a change in which the properties of a substance
change but the identity of the substance remains the same.
• Dissolving is a process in which substances mix evenly with one another.
8.1 Chemical Properties and Changes
Lesson 1 Review
Which is a chemical change?
A boiling
B burning
C dissolving
D melting
8.1 Chemical Properties and Changes
A B C D
0% 0%0%0%
1. A
2. B
3. C
4. D
Lesson 1 Review
Which is NOT a chemical change?
A sodium metal and chlorine gas react to form salt
B salt dissolving in water
C paper burning
D iron rusting
8.1 Chemical Properties and Changes
A B C D
0% 0%0%0%
1. A
2. B
3. C
4. D
Lesson 1 Review
Which is NOT a physical change?
A melting
B boiling
C dissolving
D burning
8.1 Chemical Properties and Changes
A B C D
0% 0%0%0%
1. A
2. B
3. C
4. D
End of Lesson 1
law of conservation of mass
reactants
products
diatomic molecule
coefficient
8.2 Chemical Equations
Is matter conserved in chemical reactions?
• Chemical equations show that in chemical reactions, atoms rearrange, but no atoms are gained or lost.
8.2 Chemical Equations
Antoine Lavoisier• Lavoisier invented a balance to make more precise
measurements.
• He also determined that the mass before and after a chemical reaction was the same.
8.2 Chemical Equations
Conservation of Mass• The law of conservation of mass states that the total mass before a
chemical reaction is equal to the total mass after the reaction.
8.2 Chemical Equations
Writing a Chemical Equation• Reactants are the starting materials in a chemical reaction and are placed on the
left side.
• Products are the ending materials in a chemical reaction and are placed on the right side.
8.2 Chemical Equations
Word Equations• “Tin + oxygen → tin oxide” reads as “tin plus oxygen
produces tin oxide.”
• Word equations can be long and do not show that mass is conserved.
8.2 Chemical Equations
Elements, Compounds, and Molecules
• Instead of writing long word equations, scientists use symbols and formulas.
– Symbols represent atoms.
– Formulas represent molecules.
– Molecules may be elements or compounds.
8.2 Chemical Equations
Elements, Compounds, and Molecules (cont.)
• Some elements are diatomic, that is, they contain two atoms.
8.2 Chemical Equations
• Molecules may also contain two different elements, such as hydrogen and oxygen in a water molecule.
Elements, Compounds, and Molecules (cont.)
8.2 Chemical Equations
Chemical Equations• Use the symbols and formulas instead
of words.
8.2 Chemical Equations
Balancing a Chemical Equation• Atoms are neither gained nor lost in a reaction, so both
sides of the equation must have the same number of atoms.
8.2 Chemical Equations
Counting Atoms• A subscript tells how many atoms of
an element are in one molecule.
8.2 Chemical Equations
• A coefficient tells how many atoms, molecules, or formula units are in a reaction.
8.2 Chemical Equations
Comparison of Coefficients and Subscripts
Writing Balanced Equations
Step 1 Determine the correct symbols and formulas for reactants and products.
Step 2 Write reactant symbols and formulas to the left of an arrow and product symbols and formulas to the right.
Step 3 Count the number of each kind of atom on both sides.
Step 4 Use coefficients to make the number of each kind of atom the same on both sides of the arrow.
Step 5 Check to see that each kind of atom balances.
8.2 Chemical Equations
Equations for Common Chemical Reactions
Reaction of methane:
CH4 + O2 → CO2 + H2O balance hydrogen
CH4 + O2 → CO2 + 2H2O balance oxygen
CH4 + 2O2 → CO2 + 2H2O
8.2 Chemical Equations
Equations for Common Chemical Reactions (cont.)
Baking soda and vinegar:
NaHCO3 + HC2H3O2 → CO2 + H2O + NaC2H3O2
8.2 Chemical Equations
Using Parentheses with Formulas• When counting atoms inside parentheses, the
subscript multiplies all atoms inside.
Ca + H2O → Ca(OH)2 + H2
Ca + 2H2O → Ca(OH)2 + H2
8.2 Chemical Equations
Lesson 2 Review
Which is a diatomic molecule?
A O2
B H2O
C CH4
D N
8.2 Chemical Equations
A B C D
0% 0%0%0%
1. A
2. B
3. C
4. D
Lesson 2 Review
What is potassium bromide (KBr)?
A an element
B a mixture
C a compound
D a diatomic molecule
8.2 Chemical Equations
A B C D
0% 0%0%0%
1. A
2. B
3. C
4. D
Lesson 2 Review
In the following equation, which is a reactant?
Ca +2H2O → Ca(OH)2 + H2
A H2
B (OH)2
C Ca
D none of the above
8.2 Chemical Equations
A B C D
0% 0%0%0%
1. A
2. B
3. C
4. D
End of Lesson 2
8.3 Energy and Chemical Change
law of conservation of energy
exothermic process
endothermic process
Energy and Chemical Reactions• In chemical reactions, energy is either absorbed or
released.
• In chemical reactions, atoms rearrange.
• Rearrangement involves some form of energy, usually thermal energy.
8.3 Energy and Chemical Change
Light From Chemical Reactions• Some reactions give off light with almost
no thermal energy.
• Cold light occurs at room temperature.
8.3 Energy and Chemical Change
Conservation of Energy
• Energy is stored in reacting molecules.
• The law of conservation of energy states that energy cannot be created or destroyed, simply changed from one form to another.
8.3 Energy and Chemical Change
Chemical Bonds• Molecules have chemical energy stored in their bonds.
• Energy is stored in the food that you eat and transferred to your cells.
8.3 Energy and Chemical Change
Net Release of Energy• When atoms rearrange, bonds are broken and new
bonds form.
– Breaking bonds requires energy.
– Forming bonds releases energy.
8.3 Energy and Chemical Change
Net Release of Energy (cont.)
• An exothermic process releases energy.
• The products in an exothermic reaction have less energy than the reactants.
8.3 Energy and Chemical Change
Net Release of Energy (cont.)
• An endothermic process absorbs energy.
• The products in an endothermic reaction have a higher energy than the reactants.
8.3 Energy and Chemical Change
Lesson 3 Review
Products have a higher energy level than the reactants in an endothermic reaction.
A False
B True
8.3 Energy and Chemical Change
1. A
2. B
Lesson 3 Review
____ bonds ____ energy.
A Breaking; releases
B Breaking; requires
C Forming; requires
D Ionic; release
8.3 Energy and Chemical Change
A B C D
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1. A
2. B
3. C
4. D
Lesson 3 Review
The law of ____ states that energy is neither created nor destroyed in a chemical reaction.
A conservation of mass
B definite proportions
C conservation of matter
D conservation of energy
8.3 Energy and Chemical Change
A B C D
0% 0%0%0%
1. A
2. B
3. C
4. D
End of Lesson 3
Chapter Resources Menu
Click on a hyperlink to view the corresponding feature.
Chapter Assessment
California Standards Practice
Image Bank
Science Online
Interactive Table
Virtual Lab
BrainPOP
Which is a chemical change?
A copper turning green from exposure to air
B drying clothes
C ice melting
D none of the above
Chapter Assessment 1
A B C D
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1. A
2. B
3. C
4. D
Which is a chemical property?
A boils at 100°C
B has a volume of 500 ml
C does not rust
D has a luster
Chapter Assessment 2
A B C D
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1. A
2. B
3. C
4. D
Which does NOT describe an exothermic reaction?A There is a net release
of energy.B The reactants have a
higher energy than the products .
C The reactants are lower in energy than the products.
D The products are less stable than the reactants.
Chapter Assessment 3
A B C D
0% 0%0%0%
1. A
2. B
3. C
4. D
What is the coefficient of H2O?
Ca + 2H2O → Ca(OH)2 + H2
A 1
B 0
C 4
D 2
Chapter Assessment 4
A B C D
0% 0%0%0%
1. A
2. B
3. C
4. D
How many (OH) molecules are in the products?
Ca + 2H2O → Ca(OH)2 + H2
A 1
B 2
C 3
D 4
Chapter Assessment 5
A B C D
0% 0%0%0%
1. A
2. B
3. C
4. D
In a chemical reaction, which law states the products have the same mass as the reactants?A Law of Conservation
of WaterB Law of Conservation
of EnergyC Law of Conservation
of MassD Law of Conservation
of Particles
CA Standards Practice 1
SCI 5.b
A B C D
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1. A
2. B
3. C
4. D
Energy is ____ in exothermic reactions.
A absorbed
B created
C released
D stored
CA Standards Practice 2
SCI 5.c
A B C D
0% 0%0%0%
1. A
2. B
3. C
4. D
If an equation is balanced, the number of atoms in the products is ____ the number of atoms in the reactants.
A greater than
B less than
C equal to
D none of the above
CA Standards Practice 3
SCI 3.b
A B C D
0% 0%0%0%
1. A
2. B
3. C
4. D
Which of the following is a physical change?
A hydrogen burning
B iron rusting
C copper turning green when exposed to air
D none of the above
CA Standards Practice 4
SCI X.X
A B C D
0% 0%0%0%
1. A
2. B
3. C
4. D
Symbols represent ____ and ____ represent molecules.
A elements; formulas
B formulas; equations
C molecules; formulas
D elements; equations
CA Standards Practice 5
SCI 3.f
A B C D
0% 0%0%0%
1. A
2. B
3. C
4. D
Image Bank
Interactive Table
Comparison of Coefficients and Subscripts
End of Resources