DE CHEMISTRY: King William High School
Pure substances (elements &
compounds) have definite composition
 Mixture is two or more different
substances physically combined
 Homogeneous mixtures – uniform
throughout (solution)
 Heterogeneous mixtures – NOT uniform
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 Solid – definite shape and
volume
 Liquid – definite volume; NOT
shape
 Gas – neither definite shape nor
volume
 Physical properties – shape, color,
MP, BP, FP
 Chemical properties – describe a
substance changing into something
new (metal rusting)
 Physical change – changes in
state (melting, freezing, etc.)
 Chemical change – changes
into a new substance
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Kinetic v. potential
Heat- energy associated with the motion of
molecules
Units (Joule and calorie)
1 cal = 4.184 J
1Cal = 1 kcal = 1000 cal
Convert 6.2 x 102 J to cal and Cal.
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Carbohydrate = 4kcal/g
Fat = 9 kcal/g
Protein = 4 kcal/g
EX: You eat a meal that has 37 g of carbs, 19 g
of fat and 23 g of protein. How many Calories
did you intake?
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Q = cmDT
Table 3.11 on page 74
How much heat is released when 7 g of
copper is cooled from 20oC to 10oC?
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Melting and freezing points
Heat of fusion – energy needed to melt a
substance
Heat = mass x heat of fusion
How much heat will be absorbed from 26.0 g
of ice in a soft drink at 0oC if the heat of
fusion = 334 j/g?
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Heat of vaporization – energy required to
turn a liquid to a gas at its BP
Heat = mass x heat of vap.
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Page 81
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Opposite of heating curves
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How much energy is needed to heat 100 g of
diethyl ether from 5oC to its boiling point and
boil it? The specific heat is 2.33 J/goC. The
heat of vaporization is 357 j/g.