Chapter 6- Chemical Reactions
CUE WORDS or QUESTIONS
MatterX
NOTES WRITTEN
Matter- anything that has mass and takes up space
Chemistry- study of matter and how matter changes (physical or chemical)
Physical properties-
Physical properties- characteristics of a substance that can be observed
without changing it into another substance
Ex- melting point, boiling point, color, texture, density, flexibility…
Physical change-
Physical change- a change that alters the form or appearance of a
substance but does not change it into another substance
Chemical properties-
Chemical property- characteristics of a substance that describes its ability
change into other substances
Chemical changeReactantsProducts-
Chemical change- change in matter that produces one or more substances
Reactants- the substances that go into a reaction
Products- the substances that come out of a reaction
reactants → products
2Mg + O2 → 2 MgO
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Chemical changes occur when bonds break and new bonds form
Conservation of matter-
Conservation of matter- no matter is created or destroyed in chemical
reactions, it is just rearranged
The total mass always remains the same in a closed system
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Closed system- matter is not allowed to enter or leave
Open system- matter can enter or escape from its surroundings
Evidence for chemical reactions Chemical reactions involve changes in properties and changes in energy
Things to look for when detecting a chemical reaction:
1- energy change
2345SUMMARY
X
color change
bubbles (gas)
change in odor
precipitate (solid)
CUE WORDS or QUESTIONS
Energy as heatX
Endothermic reactions-
NOTES WRITTEN
Reactions absorb or give off heat
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Breaking bonds requires energy
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Making bonds releases energy
Endothermic reactions- energy is absorbed by matter, which lowers temp.
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Exothermic reactions-
Exothermic reactions- energy is released from matter, which raises temp.
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Chemical equations-
More bonds are broken than created
More bonds are created than broken
Chemical equations are short easy ways to show a chemical reaction with
chemical symbols instead of words
Coefficient- number in front of a chemical formula (use distributive property)
Subscript- number within or after a chemical formula
Balancing equations-
X
Balanced chemical equations- the total number of atoms for each element
is the same on both sides of the equation (there are the same number of
reactants as products)
1- count the number of atoms
2- use coefficients to balance the number of atoms
3- count the number of atoms again to verify the conservation of matter
Activation energy-
Activation energy- amount of energy needed to start a chemical reaction
(all chemical reactions need activation energy, some require less while
some require more)
Rates of chemical reactions-
Factors that affect rates of a chemical reaction
1- surface area (increased surface area, increased rate of reaction)
2- temperature (increased temperature, increased rate of reaction)
3- concentration (increased amount of reactants, increased rate of reaction)
4- catalysts (increased catalysts, increased rate of reaction)
5- inhibitors (increased inhibitors, decreased rate of reaction)
SUMMARY
Practice!!
SnO2 + H2  Sn + H2O
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NaOH + HCl  NaCl + H2O
H2 +O2  H2O