Advanced Chemistry
Notes 1.3
Changes in Matter
1.3a Physical and Chemical Changes
Physical Change – a change in matter which alters a substance without changing its composition
Ex: change in state, change in size, dissolving
Chemical Change – a change in matter in which the composition of the substance is changed
Ex: burning, cooking, decaying, fermenting
1.3b Indications of a Chemical Change
 Change in color
 Production of light
 Change in temp
 Production of a gas
 Change in smell
 Production of a precipitate
Ex NaCl (aq) + AgNO3  NaNO3 (aq) + AgCl (s)
Precipitate – a solid formed during a chemical reaction
Law of Conservation of Mass – (also known as Conservation of Matter)
Matter can be neither created nor destroyed, though it can be rearranged.
Mass always remains constant in an ordinary chemical change.
Precipitate
Carbon + Oxygen → Carbon dioxide
Reactants
Products
1st Law of Thermodynamics (Conservation of energy) - the energy of the universe is constant; it can be neither
created nor destroyed but can transform from form one change to another.
• A change in matter in which energy is released is an exothermic process (heat exits).
 Examples: freezing water & condensation, Burning of paper gives off heat to the surroundings.
 All combustion reactions are exothermic
•
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A change in matter in which energy is absorbed from the surroundings is an endothermic process (heat
enters).
 Examples: melting ice & boiling water
 When barium hydroxide reacts ammonium nitrate are mixed the test-tube feels cold to touch
because energy has been absorbed
Energy – is the ability to do work
 Potential energy – energy that is stored (in BONDS)
 Kinetic Energy – energy of motion
 Kinetic energy in atoms and molecules
o Kinetic energy in atoms and molecules increases as temp. goes up
o Kinetic energy decreases as temp goes down
Advanced Chemistry
Notes 1.3
Questions
1. What are the indicators of chemical change? What is a chemical change? Examples?
2.
What is a physical change? Examples?
3.
Ice melting is a physical or chemical change? What is exothermic?
4.
What is endothermic?
5.
Water freezing is exothermic or endothermic?
6.
A reaction gives off light. Is that exothermic or endothermic?
7.
A reaction feels cold after the reaction is complete. Is that exothermic or endothermic?
8.
Which of these is a homogeneous mixture?
a. Tree
b. NaOH
c.
d.
Cl2
Milk
Which of these is a compound
a. Tree
b. NaOH
c.
d.
Cl2
Milk
9.
10. Which of the following is not an indicator of chemical change?
a. Color change
d. Perspiration
b. Gain or loss of heat
e. Evolution of gas
c. Gain or loss of energy
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12. Which of the following are exothermic?
a. A reaction absorbs heat
b. A reaction gives off heat
c. A reaction gives off energy
d. A reaction gives off light
e. All of the above
f. a, b & c
g. b, c & d
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11. What is a chemical change?
a. Change resulting in a change in the appearance of a substance
b. Change that requires energy
c. Change that results in a change in the chemical make-up of a substance
d. Change the does not result in a change in the appearance of a substance
Advanced Chemistry
Notes 1.3
h. None of these
13. What is exothermic?
a. Gain of heat
b. Gain of energy
c. Loss of heat
d. Loss of energy
14. Water boiling is exothermic or endothermic?
15. Steam condensing to water is a physical or chemical change?
16. Which is an example of a physical change?
a. Dissolving a solid in a liquid to make a solution, and the solution becomes cold
b. Dissolving a green solid in a liquid to make a cloudy blue solution
c. Heating solid iodine results in a purple gas
d. All of these
e. a & b
f. None of these
Match the following with the correct term:
Solid to liquid
Liquid to gas
Gas to solid
Solid to Gas
Gas to Liquid
Liquid to Solid
A.
B.
C.
D.
E.
F.
Deposition
Sublimation
Freezing
Melting
Condensation
Boiling
Physical or Chemical change? Indicate with a P of a C
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23. glass breaking
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24. hammering wood together
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25. a rusting bicycle
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26. separate sand from gravel
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27. melting butter
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28. bleaching your hair
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29. frying an egg
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30. squeeze oranges for juice
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31. melting ice
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31.
32.
33.
34.
35.
36.
37.
38.
39.
mixing salt and water
mixing oil and water
water evaporating
cutting grass
burning leaves
fireworks exploding
crushing a can
cutting your hair
boiling water
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17.
18.
19.
20.
21.
22.
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