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Chapter 3
Matter and Energy

03-05a,b
Title
Crystalline and amorphous solids
Caption
Crystalline solids are organized according to highly regular, repeating patterns. Amorphous solids do not follow a regular packing pattern.
Notes
Students might be encouraged to model, in two dimensions, crystalline and amorphous solids by packing coins in a flat tray: which arrangement—ordered or not ordered—yields the tightest packing? Properties such as density, melting point, and electrical conductivity are influenced by the crystalline state (or lack thereof), and can be explored here.
Keywords
crystal, amorphous, solid
03-07C
Title
Gases are compressible, but crystalline solids are not
Caption
Because crystalline solids are already packed as efficiently as possible, they cannot be compressed. Gases are very loosely packed, allowing much more compression when placed in a piston.
Notes
Gases are highly compressible: their volume depends on pressure applied (V = k/P). Solids experience a very slight degree of compressibility as pressure is applied; experiementally, the effect is on the order of 10-6 that experienced by gases. Students should be able to conclude that a gas can actually become solid if enough pressure is applied; this conclusion is reasonable, in that the pressure exerted by the piston forces the molecules close together.
Keywords
crystal, gas, solid, pressure
03-12-03un
Title
Solution map for converting Calories to joules
Caption
We can convert from Cal to joules by multiplying our original measurement, in Cal, by the factors shown, using the dimensional analysis approach.
Notes
The map is a flowchart designed to guide students in setting up a dimensional analysis calculation for Cal to joules, based on the known relationship between the units. Note that the Calorie (capital C) is the dietary unit; 1 Calorie = 1000 calories, where "calorie" (lowercase c) is the scientific calorie. Alternatively, we may think of the Calorie as equal to the kilocalorie.
Keywords
unit, conversion, dimensional analysis, English system, metric system, SI unit, calorie, joule, heat, energy
03-13
Title
Example of a perpetual motion machine
Caption
Inventors have avidly sought a working perpetual motion machine, despite well-established science which maintains that such machines are impossible.
Notes
For a perpetual motion machine to work, the machine must violate the Law of Conservation of Energy.
Keywords
perpetual motion machine, energy, thermodynamics
03-14
Title
Three common temperature scales
Caption
The Fahrenheit, Celsius, and Kelvin scales are all widely used temperature scales. Relationships between the scales have been worked out to allow conversion from one scale to another.
Notes
Students in the U.S. are probably most familiar with the Fahrenheit scale. It should be pointed out that the Celsius and Kelvin scales are related, in that their degrees are the same size. However, their zero-points differ.
Keywords
temperature, thermometer, Fahrenheit, Celsius, Kelvin, absolute zero
03-14-01un
Title
Solution map for K to oC conversion
Caption
We can convert from K to oC by applying the formula shown. We merely subtract 273 from our original measurement, in K.
Notes
Note that an algebraic rearrangement must be carried out on the equation shown, to solve for oC.
Keywords
temperature, Celsius, Kelvin
03-14-02un
Title
Solution map for oC to K conversion
Caption
We can convert from oC to K by applying the formula shown. We merely add 273 to our original measurement, in oC.
Notes
Unlike Kelvin, Celsius temperatures may be negative.
Keywords
temperature, Celsius, Kelvin
03-14-03un
Title
Solution map for oF to oC conversion
Caption
We can convert from oF to oC by applying the formula shown. We merely subtract 32 from our original measurement, in oF, then divide the result by 1.8.
Notes
The equation takes into account the difference in the size of Fahrenheit and Celsius degrees. A Fahrenheit degree is 5/9 as large as a Celsius degree.
Keywords
temperature, Celsius, Fahrenheit
03-14-04un
Title
Solution map for K to oF conversion
Caption
We can convert from K to oF by first applying the K-to-oC conversion formula, followed by application of the oC-to-oF formula.
Notes
This is a multistep solution map that uses two formulas in sequence.
Keywords
temperature, Celsius, Kelvin, Fahrenheit
03-14-06un
Title
Solution map for finding the heat associated with a temperature change
Caption
The property of heat capacity relates the amount of heat gained or lost by a sample to the temperature change experienced by the sample. We can solve for the heat, q, by applying the formula shown.
Notes
Note that DT is the change in temperature, m is the mass, and C is the heat capacity. For the equation to work, the heat capacity must contain the same units as the mass and DT.
Keywords
heat capacity, temperature, heat, energy, mass, Celsius, calorie, joule, gram
03-14-08un
Title
Solution map for finding the heat capacity
Caption
The property of heat capacity relates the amount of heat gained or lost by a sample to the temperature change experienced by the sample. We can solve for the heat capacity, C, by rearranging the formula shown: C = q/mDT.
Notes
Note that DT is the change in temperature, q is the heat, m is the mass, and C is the heat capacity. For the equation to work, the heat capacity must contain the same units as heat, mass, and DT.
Keywords
heat capacity, temperature, heat, energy, mass, Celsius, calorie, joule, gram
03-14-09un
Title
Multistep solution map for conversion of kilowatt-hours to calories
Caption
We can convert from kWh to cal by multiplying our original measurement, in kWh, by the factors shown, using the dimensional analysis approach.
Notes
The map is a flowchart designed to guide students in setting up a dimensional analysis calculation for kWh to cal, based on the known relationship between the units.
Keywords
kilowatt, heat, energy, calorie, joule
03-14-11un
Title
Solution map for oC to oF conversion
Caption
We can convert from oC to oF by applying the formula shown. We rearrange the equation shown to solve for oF: oF = 1.8(oC) + 32.
Notes
The equation takes into account the difference in the size of Fahrenheit and Celsius degrees. A Fahrenheit degree is 5/9 as large as a Celsius degree.
Keywords
temperature, Celsius, Fahrenheit
03-14-12un
Title
Solution map for finding the temperature change associated with addition or removal of heat
Caption
The property of heat capacity relates the amount of heat gained or lost by a sample to the temperature change experienced by the sample. We can solve for the temperature change, DT, by rearranging the formula shown: DT = q/mC.
Notes
Note that DT is the change in temperature, m is the mass, and C is the heat capacity. For the equation to work, the heat capacity must contain the same units as the heat and mass.
Keywords
heat capacity, temperature, heat, energy, mass, Celsius, calorie, joule, gram
03-14-13h
Title
Helium atoms in the gaseous state
Caption
Helium atoms in the gaseous state are separated by large distances, relative to the atoms' size.
Notes
Students could explore the boiling point of He, noting that it is extremely low. Why is this? The atoms must not interact strongly with one another, in order for them to separate readily.
Keywords
helium, gas, physical state
03-14-14i
Title
Carbon dioxide molecules in the gaseous state
Caption
Carbon dioxide molecules in the gaseous state are separated by large distances, relative to the molecules' size.
Notes
Students should learn that chemists have agreed on some color conventions for the elements represented in various model systems, including spacefilling models: Here, carbon is black, and oxygen is red.
Keywords
carbon dioxide, gas, physical state
03-14-15j
Title
Spacefilling models of pentane molecules in the liquid state
Caption
Molecules of pentane, C5H12, in the liquid state, show no long-range order. However, the distance between the molecules is much smaller than in the gaseous state.
Notes
The models represent n-pentane. Students might explore how physical properties (density, boiling point, etc.) would differ if the liquid were another isomer of pentane, say, isopentane.
Keywords
pentane, hydrocarbon, liquid, physical state
03-14-16k
Title
Sugar water: sugar and water molecules combined in solution
Caption
Sugar molecules and water molecules are thoroughly mixed together in solution, as shown by these spacefilling models. Note the lack of long-range order among the molecules.
Notes
Sugar dissolves well in water despite the difference in size, because the sugar molecule possesses many -OH groups. The -OH groups interact readily with their counterparts in the water molecules.
Keywords
water, sugar, carbohydrate, solution, liquid
03-14-17l
Title
Spacefilling models of ethanol molecules in the liquid state
Caption
Molecules of ethanol, C2H5OH, in the liquid state, show no long-range order. However, the distance between the molecules is much smaller than in the gaseous state.
Notes
The models represent ethanol. Students might explore how physical properties (density, boiling point, etc.) would differ if the liquid were another alcohol, say isopropyl alcohol, or methanol.
Keywords
ethanol, alcohol, liquid, physical state
03-14-18m
Title
Ethanol solution in water: ethanol and water molecules combined in solution
Caption
Ethanol molecules and water molecules are thoroughly mixed together in solution, as shown by these spacefilling models. Note the lack of long-range order among the molecules.
Notes
Ethanol dissolves well in water because the ethanol molecule possesses an -OH group. The -OH groups make the ethanol molecule polar, allowing it to interact readily with their counterparts in the water molecules.
Keywords
water, ethanol, alcohol, solution, liquid
03-14-19n
Title
Oil and water don't mix
Caption
The nonpolar hydrocarbon molecules (the long C/H structures) and the polar water molecules fail to interact with one another; as liquids, they remain separated in distinct layers.
Notes
Students might work out why water is polar and C18H38 is nonpolar, based on electronegativity and molecular geometry. The positive and negative regions in water molecules cause the molecules to attract one another, but water finds no charged regions in the hydrocarbon with which to form an attraction.
Keywords
water, hydrocarbon, liquid, physical state, immiscible
03-14-20o
Title
Copper atoms in the solid state
Caption
As a solid, copper exhibits long-range atomic order. The atoms are organized in a way that leaves minimal open space between them.
Notes
Students could model this structure for themselves by arranging pennies on a tabletop.
Keywords
copper, solid, physical state
03-14-21p
Title
Liquid acetone vaporizes when the distance between molecules becomes large
Caption
By providing energy to liquid acetone molecules, such as one might do through heating, the molecules move apart from one another.
Notes
Students could do a brief lab experiment: spray a little acetone on a thermometer and measure the temperature change. The observed drop in temperature can be related to the acetone molecules gaining energy (heat) from their surroundings as they vaporize.
Keywords
acetone, liquid, physical state, gas
03-14-22q
Title
Acetone molecules in the gaseous state
Caption
Acetone molecules in the gaseous state are separated by large distances, relative to the molecules' size.
Notes
Students should learn that chemists have agreed on some color conventions for the elements represented in various model systems, including spacefilling models: Here, carbon is black, oxygen is red, and hydrogen is white.
Keywords
acetone, gas, physical state
03-14-23r
Title
Combustion of methane in oxygen
Caption
When methane burns in oxygen, the atoms originally belonging to the methane and oxygen molecules rearrange themselves to form carbon dioxide and water molecules.
Notes
Combustion is accompanied by the release of heat; this heat is energy given up by the carbon, hydrogen, and oxygen atoms, because they have found a lower-energy arrangement when they formed carbon dioxide and water.
Keywords
carbon dioxide, water, oxygen, methane, combustion, carbon, hydrogen, chemical reaction, gas
03-14-24s
Title
Molecular water and carbon dioxide mixture in the gaseous state.
Caption
As is the case with pure gas samples, the molecules in gaseous mixtures are far apart, relative to the molecules' sizes.
Notes
This image represents the oucome of the combustion of a hydrocarbon in excess oxygen.
Keywords
carbon dioxide, water, oxygen, carbon, hydrogen, gas

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