Exam Review
Before you study this review sheet, make sure you are familiar with all the experiments we did in this chapter, and the possible errors that might have occurred in each one. You can refer to the book, handouts, and/or the web review sheets for this.
A characteristic property is a property of a substance that is:
1. independent of the
quantity of the substance, and
2. helps identify the substance.
2. helps identify the substance.
We studied 3 characteristic properties in this chapter.
a. density.
b. melting/freezing point.
c. boiling point.
b. melting/freezing point.
c. boiling point.
Density is computed by dividing mass by volume. We measure density in units of grams per cubic centimeter.
If you measure the mass and
volume of a substance, you can calculate its density.
Density = Mass/Volume
If you know the density of a substance and its mass, you can find its volume.
Volume = Mass/Density
If you know the density of a substance and its volume, you can find its mass.
Mass = Volume x Density
For example, pure gold has a denisty of 19.32 g/cc.
If you have 100 cc's of gold (about the size of a tangerine), then you have 100 x 19.32 grams of gold (about 4 pounds).
If you have 100 grams of gold, then you have 100/19.32 cc's of gold.
If you weigh your grandma's gold ring and it is 3.0 grams, and you use a graduated cylinder to find its volume as .2 cc, then the density of the ring is 3.0/.2 = 15. Is you grandmas ring pure gold? (No, it is not as dense as pure gold - it might be only 14 karat gold.)
The density of water is 1 gram per cubic centimeter.
Adding salt to water increases its density. That's why everyone floats in the Dead Sea. That's how our color wars experiment worked. The more salt in the solution the lower that color would sink.
The freezing/melting point of a subtsance is the temperature when it changes from a solid to a liquid
The boiling point of a subtsance is the temperature when it changes from a liquid to a gas.
The freezing/melting point of water is 0 degrees Celsius (32 F).
The boiling point of water is 100 degrees Celsius (212 F).
Adding salt to water increases its boiling point.
Melting means to change from solid to liquid.
Freezing means to change from liquid to solid.
Boiling (and evaporating) means to change from liquid to gas.
Condensing means to change from gas to liquid.
Sublimating means to change from solid to gas, skipping the liquid state.
Density = Mass/Volume
If you know the density of a substance and its mass, you can find its volume.
Volume = Mass/Density
If you know the density of a substance and its volume, you can find its mass.
Mass = Volume x Density
For example, pure gold has a denisty of 19.32 g/cc.
If you have 100 cc's of gold (about the size of a tangerine), then you have 100 x 19.32 grams of gold (about 4 pounds).
If you have 100 grams of gold, then you have 100/19.32 cc's of gold.
If you weigh your grandma's gold ring and it is 3.0 grams, and you use a graduated cylinder to find its volume as .2 cc, then the density of the ring is 3.0/.2 = 15. Is you grandmas ring pure gold? (No, it is not as dense as pure gold - it might be only 14 karat gold.)
The density of water is 1 gram per cubic centimeter.
Adding salt to water increases its density. That's why everyone floats in the Dead Sea. That's how our color wars experiment worked. The more salt in the solution the lower that color would sink.
The freezing/melting point of a subtsance is the temperature when it changes from a solid to a liquid
The boiling point of a subtsance is the temperature when it changes from a liquid to a gas.
The freezing/melting point of water is 0 degrees Celsius (32 F).
The boiling point of water is 100 degrees Celsius (212 F).
Adding salt to water increases its boiling point.
One reason we add salt to
water when we cook is to cook at a hotter temperature. With no
salt, the
water will boil at 212 F, but with salt it will not boil until the
water is hotter than 212. (Of course, the main reason we use salt
in water is for
taste! )
Adding
salt to water lowers
its freezing point.That's why we put salt on
the ice on Minnesota streets. The salt makes the ice melt because
water with lots of salt will freeze only when the temperature gets much
colder than 32 F.
Melting means to change from solid to liquid.
Freezing means to change from liquid to solid.
Boiling (and evaporating) means to change from liquid to gas.
Condensing means to change from gas to liquid.
Sublimating means to change from solid to gas, skipping the liquid state.
At both the freezing/melting point and the boiling point, the graph of temperature versus time goes flat. This means that energy is absorbed in order to make the change of state from solid to liquid and liquid to gas, but the temperature does not increase. See graph below for water.
1
is solid (ice)
2 is melting (0 Celsius - water and ice)
3 is liquid (water)
4 is boiling (100 Celsius - water and gas)
5 is gas (water vapor)
2 is melting (0 Celsius - water and ice)
3 is liquid (water)
4 is boiling (100 Celsius - water and gas)
5 is gas (water vapor)
When you multiply or divide numbers you answer should be written with the correct number of significant figures. See the review sheet for practice.