Transcript No Slide Title

A recipe calls for 3.0 Tablespoons of salt
to make a loaf of bread. You want to
make 3 loaves of bread. If a Tablespoon
is 3.3 cm3, how many cm3 of salt will
you need?
A.
B.
C.
D.
solution
9.9 cm3
9.0 cm3
30 cm3
29.7 cm3
3 loaves
1
3.0 Tablespoons 3.3 cm3
1 loaf
Tablespoon
= 29.7 cm3
2 significant figures 30 cm3
A trip from LAX to Hawaii is 2650
miles. How far is that in km?
1 mile = 1600 meters
A.
B.
C.
D.
4240 km
1.63 km
4.24 X 106 km
4,000 km
solution
2650 miles
1
1600 m
1 mile
1 km
= 4,240 km
1000 m
A cube is 220.0 mm X 220.0 mm X 410 mm.
What is its volume in cm3?
A.
B.
C.
D.
solution
198 cm3
19844 cm3
2.0 X 104 cm3
440 cm3
220 mm
1m
100 cm = 22 cm
1
1000 mm 1 m
Similarly:
410 mm
= 41 cm
Volume = length x width x height
V = 22 cm(22 cm)(41 cm) = 19844 cm3
2 significant figures = 2.0 X 104 cm3
There are 1.008 grams of hydrogen in one mole.
One mole of a gas has a volume of 22.4 L.
If you have 33 L of hydrogen, how many grams
does it weigh?
A.
B.
C.
D.
solution
1.5 grams
745 grams
1.49 grams
63 grams
1.008 grams = 1.485 grams
33 Litres
1 mole
1 mole
1
22.4 Litres
2 significant figures, 1.5 grams
You’ve probably all seen the demonstration where
a card is put over the mouth of a glass of water and
when the glass is flipped over and the card is
released, the water doesn’t fall out. This is caused
by the air pressure pushing up being stronger than
the weight of the water pushing down. The cup
that was used for this demo holds 110 mL of water.
One mL of water weighs one gram.
Air pressure is 13.5 pounds per square inch
(lbs/sq. in.). How many square inches must the cup
be for this trick to work? (1 pound = 453 grams)
solution
A.
B.
C.
D.
18 in2
.20 in2
.018 in2
12 in2
110 ml 1 gram 1 pound 1 sq. inch = .01799. . . sq. in.
1
1 mL 453 grams 13.5 pounds
2 significant figures, .018 sq. in.
1
2
33
4
55
1
2
3
4
5