Both gases and liquids are considered to be fluids that have individual molecules that move around with kinetic and potential energy. Kinetic energy, defined as the energy related to motion, takes three forms: translational energy that occurs as a molecule moves from position A to position B, rotational energy that occurs as a molecule spins around an imaginary axis at its center of mass, and vibrational energy that occurs as individual atoms in a molecular bond move towards and away from each other. Usually, molecules possess varying combinations of kinetic energy forms. In contrast, potential energy is defined as stored energy that could be released to become kinetic energy. The total energy of a molecule is fixed, meaning that a molecule has some combination of kinetic and potential energies.

Varying amount of kinetic and potential energies define how molecules in a fluid interact with each other. For example, when the kinetic energy of a molecule is high (greater than 1000J), it can no longer interact with neighboring molecules strongly enough to remain a liquid. However, if the potential energies are too high (greater than 1000 J), molecules cannot escape a liquid to become a gas. If the kinetic energy is high and the potential energy is low, molecules tend to become a gas and can be modeled by an equation known as the Ideal Gas Law:

Where P is the pressure of a gas, V is the volume, n is the number of moles of a gas, R is a constant, and T is temperature in degrees Kelvin.

The Ideal Gas Law perfectly applies to particles with no mass, no intermolecular interactions, and no true volume. However, real molecules do not adhere perfectly to the Ideal Gas Law.

As the kinetic energy of a molecule increases, one would expect the potential energy to:

Both gases and liquids are considered to be fluids that have individual molecules that move around with kinetic and potential energy. Kinetic energy, defined as the energy related to motion, takes three forms: translational energy that occurs as a molecule moves from position A to position B, rotational energy that occurs as a molecule spins around an imaginary axis at its center of mass, and vibrational energy that occurs as individual atoms in a molecular bond move towards and away from each other. Usually, molecules possess varying combinations of kinetic energy forms. In contrast, potential energy is defined as stored energy that could be released to become kinetic energy. The total energy of a molecule is fixed, meaning that a molecule has some combination of kinetic and potential energies.

Varying amount of kinetic and potential energies define how molecules in a fluid interact with each other. For example, when the kinetic energy of a molecule is high (greater than 1000J), it can no longer interact with neighboring molecules strongly enough to remain a liquid. However, if the potential energies are too high (greater than 1000 J), molecules cannot escape a liquid to become a gas. If the kinetic energy is high and the potential energy is low, molecules tend to become a gas and can be modeled by an equation known as the Ideal Gas Law:

Where P is the pressure of a gas, V is the volume, n is the number of moles of a gas, R is a constant, and T is temperature in degrees Kelvin.

The Ideal Gas Law perfectly applies to particles with no mass, no intermolecular interactions, and no true volume. However, real molecules do not adhere perfectly to the Ideal Gas Law.

As the potential energy of a molecule decreases, one would expect the kinetic energy to:

Both gases and liquids are considered to be fluids that have individual molecules that move around with kinetic and potential energy. Kinetic energy, defined as the energy related to motion, takes three forms: translational energy that occurs as a molecule moves from position A to position B, rotational energy that occurs as a molecule spins around an imaginary axis at its center of mass, and vibrational energy that occurs as individual atoms in a molecular bond move towards and away from each other. Usually, molecules possess varying combinations of kinetic energy forms. In contrast, potential energy is defined as stored energy that could be released to become kinetic energy. The total energy of a molecule is fixed, meaning that a molecule has some combination of kinetic and potential energies.

Varying amount of kinetic and potential energies define how molecules in a fluid interact with each other. For example, when the kinetic energy of a molecule is high (greater than 1000J), it can no longer interact with neighboring molecules strongly enough to remain a liquid. However, if the potential energies are too high (greater than 1000 J), molecules cannot escape a liquid to become a gas. If the kinetic energy is high and the potential energy is low, molecules tend to become a gas and can be modeled by an equation known as the Ideal Gas Law:

Where P is the pressure of a gas, V is the volume, n is the number of moles of a gas, R is a constant, and T is temperature in degrees Kelvin.

The Ideal Gas Law perfectly applies to particles with no mass, no intermolecular interactions, and no true volume. However, real molecules do not adhere perfectly to the Ideal Gas Law.

The relationship between kinetic and potential energy may best be illustrated by: 

Chemists can model how solids, liquids, and gases behave at different temperatures and pressures with a graph called a phase diagram. When the pressure and temperature are simultaneously known, a scientist can predict whether the material will be in a specific state. The diagram is divided into sections depending on the phase and the lines between sections represent phase transitions occurring between two or more separate phases.

In general, solids of neatly stacked molecules exist when temperatures are low and pressures are intermediate. These values decrease the kinetic energy of the molecules enough to allow for attractive forces to begin the stacking process. Liquids, by contrast, are found at intermediate pressures and temperatures. The temperature is high enough to impart enough kinetic energy to prevent solid formation and the pressure is high enough to prevent the liquid from becoming a gas. Finally, a gas forms at low pressures and high temperatures. The high level of kinetic energy prevents molecules from associating with one another.

Materials can undergo processes called phase transitions, meaning they can transition from one phase to another. The transition from a solid to a liquid is called melting, while the reverse transition is called freezing. Vaporization occurs when a liquid becomes a gas, while condensation occurs when a gas becomes a liquid. Finally, in a process called sublimation, a solid can directly become a gas without passing through a liquid phase. Additionally, when a gas directly becomes a solid, this is known as deposition.

In order to predict the state of a material, the scientist must know __________.

The Millikin oil drop experiment is among the most important experiments in the history of science.  It was used to determine one of the fundamental constants of the universe, the charge on the electron. For his work, Robert Millikin won the Nobel Prize in Physics in 1923.

Millikin used an experimental setup as follows in Figure 1. He opened a chamber of oil into an adjacent uniform electric field.  The oil droplets sank into the electric field once the trap door opened, but were then immediately suspended by the forces of electricity present in the field.

Figure 1:

By determining how much force was needed to exactly counteract the gravity pulling the oil droplet down, Millikin was able to determine the force of electricity.  This is depicted in Figure 2.

Using this information, he was able to calculate the exact charge on an electron.  By changing some conditions, such as creating a vacuum in the apparatus, the experiment can be modified. 

Figure 2:

When the drop is suspended perfectly, the total forces up equal the total forces down.  Because Millikin knew the electric field in the apparatus, the force of air resistance, the mass of the drop, and the acceleration due to gravity, he was able to solve the following equation: 

Table 1 summarizes the electric charge found on oil drops in suspension.  Millikin correctly concluded that the calculated charges must all be multiples of the fundamental charge of the electron.  A hypothetical oil drop contains some net charge due to lost electrons, and this net charge cannot be smaller than the charge on a single electron.

Table 1: 

Which of the following statements is most consistent with the findings of this experiment?

Current high levels of fossil fuel use, including coal-burning power plants and gasoline-powered automobiles, have helped contribute to the high concentrations of sulfur trioxide, SO₃, found in the atmosphere. When sulfur trioxide and water interact, they can undergo the following chemical reaction to produce sulfuric acid, which is the main contributor to acid rain worldwide: 

Acid rain showers are particularly common near coal-burning power plants and large cities. These showers are responsible for significant economic damage to sidewalks, roads, and buildings. Scientists interested in studying the effects of acid rain often use basic substances like calcium carbonate, the main component of limestone buildings, and expose them to varying volumes of acid rain to determine what volume of acid rain is necessary to begin to erode a building. A sample graph of one scientist’s experiment is replicated below:

Measuring acid and base levels is commonly done with a scale called pH, which uses the concentration of hydrogen ions to determine the acidity. Hydrogen ions are in a balance with hydroxide ions to give a scale with a range from 0 to 14. Values equal to or between 0 and 6.9 represent the acidic range where hydrogen ions predominate and values equal to or ranging from 7.1 and 14 represent the basic range where hydroxide ions predominate. Thus, the more hydrogen ions present, the more acidic the solution.

Scientists can tell when a titration (pH) experiment passes a certain pH using compounds called indicators. Indicators are usually colorless at pH levels below that of their specified color change. A table of indicators used by the above scientists and the pH at which they change colors is presented below. 

The relationship between the concentrations of hydrogen and hydroxide ions in an acid-base solution may best be illustrated as which of the following?

A student wants to perform an experiment that tests the relationship between the pressure of a gas and the volume it occupies. To perform this experiment, the student places a specific type of gas in a sealed chamber that can change pressure and that can adapt its volume to the gas within it. The chamber also adjusts to the changing pressure such that the temperature (which also has an effect on gas volume) does not change. The following data was obtained:

In Trial 4, the chamber used in the experiment malfunctioned and there was a slight decrease in temperature, leading to a faulty reading of volume for Trial 4. Given this information, what can we say about the relationship between the temperature of a gas and its volume?

A student wants to perform an experiment which tests the relationship between the pressure of a gas and the volume it occupies. To perform this experiment, the student places a specific type of gas in a sealed chamber that can change pressure and which can adapt its volume to the gas within it. The chamber also adjusts to the changing pressure such that the temperature (which also has an effect on gas volume) does not change. The following data was obtained: 

In a second experiment, the student tries the same experiment described in the pre-question text and uses a different gas for each trial. If the readings for volume yielded the same results, what could be said about the relationship between type of gas and volume?

Two scientists wanted to test the solubility of different substances. Solubility is a measure of how many moles of a given substance (known as the solute) can dissolve in a given volume of another substance (known as the solvent). The solvent can also be thought of as the substance present in greater amount, while the solute can be seen as the substance present in lesser amount. The scientists performed the following experiments to investigate this property.

Experiment 1

The scientists tested the number of moles of several substances that could be completely dissolved in  of water at various temperatures. They made their solutions by slowly adding amounts of each substance to beakers sitting on a hot plate containing water and a stirring rod until no more of the substance dissolved in the solution. The beakers were weighed before and after the additions and the difference in mass was calculated to be the added mass of the substance. The researchers then calculated the number of moles that dissolved for each trial using the molecular mass and the recorded mass for each trial. Results are recorded in Table 1.

Table 1

Experiment 2

In this experiment, the scientists wanted to test the solubility of  in a variety of liquids at several temperatures. Their procedure was similar to that of Experiment 1, but with a range of liquids and only one solid. The results are compiled in Table 2.

Table 2

Which of the following correctly ranks the solutes from Experiment 1 in decreasing order of solubility in water at ?

Two scientists wanted to test the solubility of different substances. Solubility is a measure of how many moles of a given substance (known as the solute) can dissolve in a given volume of another substance (known as the solvent). The solvent can also be thought of as the substance present in greater amount, while the solute can be seen as the substance present in lesser amount. The scientists performed the following experiments to investigate this property.

Experiment 1

The scientists tested the number of moles of several substances that could be completely dissolved in  of water at various temperatures. They made their solutions by slowly adding amounts of each substance to beakers sitting on a hot plate containing water and a stirring rod until no more of the substance dissolved in the solution. The beakers were weighed before and after the additions and the difference in mass was calculated to be the added mass of the substance. The researchers then calculated the number of moles that dissolved for each trial using the molecular mass and the recorded mass for each trial. Results are recorded in Table 1.

Table 1

Experiment 2

In this experiment, the scientists wanted to test the solubility of  in a variety of liquids at several temperatures. Their procedure was similar to that of Experiment 1, but with a range of liquids and only one solid. The results are compiled in Table 2.

Table 2

Which of the following best explains the relationship between temperature and solubility of ?