Phases and Properties of Matter - Physical Chemistry
Card 0 of 124
Which of the following are responsible for the high boiling point of water, compared to molecules of similar size?
Which of the following are responsible for the high boiling point of water, compared to molecules of similar size?
Hydrogen bonding occurs between water molecules. While intermolecular forces between molecules exist for most molecules, these forces are much weaker than the bond formed between a hydrogen from one molecule and an oxygen, fluorine, and/or nitrogen atom of another molecule. Since the molecules are held more tightly together, more energy is required to break those bonds. This results in a higher temperature required to boil water (boiling breaks bonds between molecules, and this causes the molecules to escape into the gas phase).
Hydrogen bonding occurs between water molecules. While intermolecular forces between molecules exist for most molecules, these forces are much weaker than the bond formed between a hydrogen from one molecule and an oxygen, fluorine, and/or nitrogen atom of another molecule. Since the molecules are held more tightly together, more energy is required to break those bonds. This results in a higher temperature required to boil water (boiling breaks bonds between molecules, and this causes the molecules to escape into the gas phase).
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At constant temperature and moles, which of the following is true regarding pressure and volume of a gas?
At constant temperature and moles, which of the following is true regarding pressure and volume of a gas?
First, we need to figure out which gas law is applicable here. The question states that temperature and moles are constant. This means that we are dealing with Boyle’s law, which states that pressure is inversely proportional to volume. Inversely proportional means that the pressure decreases as volume increases and vice versa. Note that the relationship is still linear (change in one variable causes a proportional change in the other variable), but the two variables have a negative correlation. Positive correlation means increasing or decreasing a variable would also increase or decrease the other variable, respectively.
First, we need to figure out which gas law is applicable here. The question states that temperature and moles are constant. This means that we are dealing with Boyle’s law, which states that pressure is inversely proportional to volume. Inversely proportional means that the pressure decreases as volume increases and vice versa. Note that the relationship is still linear (change in one variable causes a proportional change in the other variable), but the two variables have a negative correlation. Positive correlation means increasing or decreasing a variable would also increase or decrease the other variable, respectively.
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According to __________ law, increasing temperature will __________ volume at constant pressure and constant moles.
According to __________ law, increasing temperature will __________ volume at constant pressure and constant moles.
Recall that Charles’ law defines the relationship between temperature and volume at constant pressure and constant moles. The law states that the two variables are directly proportional to each other. This means that increasing or decreasing temperature will have the same effect on volume. This makes sense because increasing the temperature increases the kinetic energy of the particles. This makes it easier for particles to move away from each other and expand, which results in an increase in volume.
Recall that Charles’ law defines the relationship between temperature and volume at constant pressure and constant moles. The law states that the two variables are directly proportional to each other. This means that increasing or decreasing temperature will have the same effect on volume. This makes sense because increasing the temperature increases the kinetic energy of the particles. This makes it easier for particles to move away from each other and expand, which results in an increase in volume.
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A researcher is analyzing two bases. He puts both bases in a solution of water and notices that base A precipitates at the bottom of the solution whereas base B doesn’t. What can you conclude from the given information?
A researcher is analyzing two bases. He puts both bases in a solution of water and notices that base A precipitates at the bottom of the solution whereas base B doesn’t. What can you conclude from the given information?
The question states that base A precipitates in a solution of water. We can conclude from this information that base A must be water insoluble. Recall that compounds that are hydrophobic tend to aggregate together when placed water, forming solid precipitates in the solution; therefore, base A must be a hydrophobic base. Base B, on the other hand, is soluble in water and doesn’t precipitate; therefore, base B must be a hydrophilic base.
Solubility rules state that all hydroxide compounds are insoluble in water, except sodium and potassium hydroxide. Calcium hydroxide is water insoluble and could possibly be the identity of base A.
The question states that base A precipitates in a solution of water. We can conclude from this information that base A must be water insoluble. Recall that compounds that are hydrophobic tend to aggregate together when placed water, forming solid precipitates in the solution; therefore, base A must be a hydrophobic base. Base B, on the other hand, is soluble in water and doesn’t precipitate; therefore, base B must be a hydrophilic base.
Solubility rules state that all hydroxide compounds are insoluble in water, except sodium and potassium hydroxide. Calcium hydroxide is water insoluble and could possibly be the identity of base A.
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Which of the following is a property of an atom that always makes a hydrophilic molecule?
Which of the following is a property of an atom that always makes a hydrophilic molecule?
Hydrophilic molecules, by definition, are soluble in water. A compound’s solubility in water can be determined qualitatively using the solubility rules. If we look at the solubility rules, we will notice that there are three main cations that are always soluble in water. This means that a compound containing one of these three cations will always be soluble in water. The three cations are sodium, potassium and ammonium ions. Recall that sodium and potassium are alkali metals (column I of periodic table); therefore, these elements have one electron in its outermost shell (valence electron).
Alkali earth metals are on the second column of periodic table and have two valence electrons. Not all alkali earth metal containing compounds are water soluble (for example, calcium hydroxide).
Hydrophilic molecules, by definition, are soluble in water. A compound’s solubility in water can be determined qualitatively using the solubility rules. If we look at the solubility rules, we will notice that there are three main cations that are always soluble in water. This means that a compound containing one of these three cations will always be soluble in water. The three cations are sodium, potassium and ammonium ions. Recall that sodium and potassium are alkali metals (column I of periodic table); therefore, these elements have one electron in its outermost shell (valence electron).
Alkali earth metals are on the second column of periodic table and have two valence electrons. Not all alkali earth metal containing compounds are water soluble (for example, calcium hydroxide).
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Which of the following is true regarding the liquid phase?
I. Liquids have lower entropy than gases
II. Compared to solids, more energy is required to separate liquid molecules
III. Liquids have higher intermolecular forces than gases
Which of the following is true regarding the liquid phase?
I. Liquids have lower entropy than gases
II. Compared to solids, more energy is required to separate liquid molecules
III. Liquids have higher intermolecular forces than gases
Liquid is an intermediate phase, between solid and gas. Solids are characterized by tightly packed molecules in an organized manner whereas gases are characterized by greatly spread out molecules that are highly disordered; liquids lie somewhere in the middle. This means that they are more disordered than solids (more entropy) and less disordered than gases (less entropy).
The boiling point of a substance is always higher than the melting point; therefore, you always need higher energy to break the interactions between liquid molecules.
The key difference between a liquid and a gas is the distance between the molecules. Liquid molecules are closer together whereas gas molecules are spread apart. Intermolecular forces are the forces between adjacent molecules. Since they are highly spread apart, the gas molecules have lower intermolecular forces.
Liquid is an intermediate phase, between solid and gas. Solids are characterized by tightly packed molecules in an organized manner whereas gases are characterized by greatly spread out molecules that are highly disordered; liquids lie somewhere in the middle. This means that they are more disordered than solids (more entropy) and less disordered than gases (less entropy).
The boiling point of a substance is always higher than the melting point; therefore, you always need higher energy to break the interactions between liquid molecules.
The key difference between a liquid and a gas is the distance between the molecules. Liquid molecules are closer together whereas gas molecules are spread apart. Intermolecular forces are the forces between adjacent molecules. Since they are highly spread apart, the gas molecules have lower intermolecular forces.
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An unknown molecule (molecule A), in its solid phase, is found to have a density of 
. Eight grams of this molecule is added to a cubic container with length of 
. The container is then heated until all of the solid has melted. What can you conclude from the given information?
An unknown molecule (molecule A), in its solid phase, is found to have a density of
The dimensions of the cubic container are 
by 
by 
(cube has same length, height, and width); therefore, the volume of the cubic container is
Recall that 
is the same as 
; therefore, the container can contain 
of volume. This means that all of the solid will fit into the container. Upon melting, the solid will expand and the volume will increase (as it becomes liquid). This means that the volume of the container will not be sufficient for the liquid and, consequently, lead to an overflow of the liquid.
The dimensions of the cubic container are
Recall that
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Which of the following is true regarding solids?
Which of the following is true regarding solids?
There are three main phases: solids, liquids, and gases. Solids molecules are closely packed in an organized, lattice structure, liquid molecules are more spread apart and more disorganized, and gas molecules are spread even farther apart from each other and are extremely disorganized. Each type of solid is made up of unique type of atoms. For example, magnesium metal is made up of magnesium atoms whereas copper metal is made up of copper atoms. Since they are made up of unique atoms, different types of solids have different interactions between atoms. Some have strong interactions whereas others have very weak interactions; therefore, the energy required to break these interaction and separate the atoms/molecules (melt) is different for each solid.
Recall that entropy is the level of disorder in a system. As mentioned, solids are highly organized structures; therefore, they will have the lowest entropy.
There are three main phases: solids, liquids, and gases. Solids molecules are closely packed in an organized, lattice structure, liquid molecules are more spread apart and more disorganized, and gas molecules are spread even farther apart from each other and are extremely disorganized. Each type of solid is made up of unique type of atoms. For example, magnesium metal is made up of magnesium atoms whereas copper metal is made up of copper atoms. Since they are made up of unique atoms, different types of solids have different interactions between atoms. Some have strong interactions whereas others have very weak interactions; therefore, the energy required to break these interaction and separate the atoms/molecules (melt) is different for each solid.
Recall that entropy is the level of disorder in a system. As mentioned, solids are highly organized structures; therefore, they will have the lowest entropy.
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You freeze a sample of nitrogen. Compared to the reactant, the end product has __________ density and __________ mass.
You freeze a sample of nitrogen. Compared to the reactant, the end product has __________ density and __________ mass.
Freezing the is process of converting a liquid to a solid. This question is asking about the freezing process of liquid nitrogen to solid nitrogen; therefore, the end product of the reaction is solid nitrogen. Recall that solids are more tightly packed. This means that the volume taken up by the molecules in solid is lower than in liquid; therefore, solids generally have a lower volume. Mass, on the other hand, depends on the number of molecules present. Phase changes do not alter the amount of molecules present. For example, the end product in this question (solid nitrogen) will have the same amount of molecules as its liquid counterpart; therefore, the mass doesn’t change when the phase changes.
Density is defined as follows.
Since its volume decreases and the mass stays the same, a solid will have a lower density than liquid. Note that water is an exception to this general rule, as solid ice has a lower density (higher volume) than the same mass of liquid water. This is due to the arrangement of its hydrogen bonds throughout its crystalline structure.
Freezing the is process of converting a liquid to a solid. This question is asking about the freezing process of liquid nitrogen to solid nitrogen; therefore, the end product of the reaction is solid nitrogen. Recall that solids are more tightly packed. This means that the volume taken up by the molecules in solid is lower than in liquid; therefore, solids generally have a lower volume. Mass, on the other hand, depends on the number of molecules present. Phase changes do not alter the amount of molecules present. For example, the end product in this question (solid nitrogen) will have the same amount of molecules as its liquid counterpart; therefore, the mass doesn’t change when the phase changes.
Density is defined as follows.
Since its volume decreases and the mass stays the same, a solid will have a lower density than liquid. Note that water is an exception to this general rule, as solid ice has a lower density (higher volume) than the same mass of liquid water. This is due to the arrangement of its hydrogen bonds throughout its crystalline structure.
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An object is floating on water. Which of the following is true?
I. The object has a lower density than water
II. The buoyancy force would be higher if the object sank
III. The volume of fluid displaced would be higher if the object sank
An object is floating on water. Which of the following is true?
I. The object has a lower density than water
II. The buoyancy force would be higher if the object sank
III. The volume of fluid displaced would be higher if the object sank
Recall than an object floats on water if it has a lower density than water. A floating or submerged object in a liquid has a gravitational pull (downward force) equal to the buoyancy force (upward force). The force due to gravity (gravitational pull) depends only on the mass of the object. In this case, the object can never be submerged because the density of the solid cannot be changed (unless the phase of the object is changed). To submerge, the object has to be placed in a liquid with LOWER density.
The volume of fluid displaced depends on the volume occupied by the object in the liquid. When an object floats, only part of the object is inside the liquid. This means that only part of the object’s volume is occupied inside the liquid (lower volume of fluid displaced). If the object were to be submerged (in a different liquid), the entire volume of the object would be inside the liquid and there would be an increase in the volume of fluid displaced.
Recall than an object floats on water if it has a lower density than water. A floating or submerged object in a liquid has a gravitational pull (downward force) equal to the buoyancy force (upward force). The force due to gravity (gravitational pull) depends only on the mass of the object. In this case, the object can never be submerged because the density of the solid cannot be changed (unless the phase of the object is changed). To submerge, the object has to be placed in a liquid with LOWER density.
The volume of fluid displaced depends on the volume occupied by the object in the liquid. When an object floats, only part of the object is inside the liquid. This means that only part of the object’s volume is occupied inside the liquid (lower volume of fluid displaced). If the object were to be submerged (in a different liquid), the entire volume of the object would be inside the liquid and there would be an increase in the volume of fluid displaced.
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Fluid A and Fluid B flow through the same pipe. However, it is found that fluid A flows much slower than fluid B. What can you conclude about fluid A and fluid B?
Fluid A and Fluid B flow through the same pipe. However, it is found that fluid A flows much slower than fluid B. What can you conclude about fluid A and fluid B?
Viscosity is a measure of resistance to flow. A liquid with high viscosity is said to have strong forces between its layers, making it harder to flow whereas a liquid with low viscosity has weak forces between its layers, making it easier to flow. Viscosity is quantified by the coefficient of viscosity (higher the coefficient, higher the viscosity and higher the resistance to flow). The question states that fluid A has more trouble flowing; therefore, fluid A has higher coefficient of viscosity and stronger forces between layers.
Viscosity is a measure of resistance to flow. A liquid with high viscosity is said to have strong forces between its layers, making it harder to flow whereas a liquid with low viscosity has weak forces between its layers, making it easier to flow. Viscosity is quantified by the coefficient of viscosity (higher the coefficient, higher the viscosity and higher the resistance to flow). The question states that fluid A has more trouble flowing; therefore, fluid A has higher coefficient of viscosity and stronger forces between layers.
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According to Poiseuille’s principle, the flow rate __________ as viscosity increases and the flow rate __________ as length of pipe increases.
According to Poiseuille’s principle, the flow rate __________ as viscosity increases and the flow rate __________ as length of pipe increases.
Poiseuille’s principle quantifies the flow rate of a fluid through a pipe to numerous variables as follows.
where 
is the flow rate, 
is change in pressure, 
is radius, 
is viscosity, and 
is length. We can see that viscosity and length terms are in the denominator; therefore, flow rate and these two terms are inversely related. This means that increasing viscosity and/or length of pipe will decrease the flow rate (and vice versa). Note that the radius has the biggest exponential factor; therefore, altering radius of the pipe will contribute to the biggest change in flow rate.
Poiseuille’s principle quantifies the flow rate of a fluid through a pipe to numerous variables as follows.
where
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One end of a pipe (End A) has twice the radius as the second end (End B). What can you conclude about the flow of fluid through this pipe?
One end of a pipe (End A) has twice the radius as the second end (End B). What can you conclude about the flow of fluid through this pipe?
To solve this question, we need to use the continuity equation and Bernoulli’s equation. The continuity equation is as follows:
where 
is flow rate, 
is velocity, and 
is the area. This equation states that that the flow rate of a fluid is the same, regardless of changes in velocity and area. The equation implies that as the area is increased (for example, 
) the velocity (
) decreases to maintain a constant flow rate and vice versa. The question states that End A has the larger radius; therefore, the velocity is lower at End A.
Bernoulli’s equation is as follows
where 
is pressure, 
is density, 
is velocity, 
is acceleration due to gravity, and 
is the height from ground. This equation implies that as velocity is increased on one side, the pressure decreases to compensate. Since we already determined that End B has the higher velocity, it will also have the lower pressure.
To solve this question, we need to use the continuity equation and Bernoulli’s equation. The continuity equation is as follows:
where
Bernoulli’s equation is as follows
where
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A sample of argon gas at a pressure of 0.959atm and a temperature of 
, occupies a volume of 563mL. If the gas is compressed at constant temperature until its pressure is 1.40atm, what will be the final volume of the sample of gas?
A sample of argon gas at a pressure of 0.959atm and a temperature of
The argon gas, as the problem states, is under constant temperature with varying volume and pressure, so we need to use Boyle's Law:
We are given the initial pressure, the initial volume, and the final pressure, and need to solve for the final volume. Therefore, we can rearrange Boyle's law to be as follows:
Plug in known values and solve.
The argon gas, as the problem states, is under constant temperature with varying volume and pressure, so we need to use Boyle's Law:
We are given the initial pressure, the initial volume, and the final pressure, and need to solve for the final volume. Therefore, we can rearrange Boyle's law to be as follows:
Plug in known values and solve.
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A sample of methane gas at a pressure of 0.723atm and a temperature of 
, occupies a volume of 16.0L. If the gas is allowed to expand at constant temperature to a volume of 24.2L, what will the pressure of the gas sample be?
A sample of methane gas at a pressure of 0.723atm and a temperature of
The methane gas, as the problem states, is under constant temperature with varying volume and pressure, so we need to use Boyle's Law:
We are given the initial pressure, the initial volume, and the final volume and need to solve for the final pressure. Therefore, we can rearrange Boyle's law to be as follows:
Plug in known values and solve.
The methane gas, as the problem states, is under constant temperature with varying volume and pressure, so we need to use Boyle's Law:
We are given the initial pressure, the initial volume, and the final volume and need to solve for the final pressure. Therefore, we can rearrange Boyle's law to be as follows:
Plug in known values and solve.
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A researcher places a closed piston container at room temperature. He places a Bunsen burner at the bottom of the container and observes that the piston moves up. What can best explain this phenomenon?
A researcher places a closed piston container at room temperature. He places a Bunsen burner at the bottom of the container and observes that the piston moves up. What can best explain this phenomenon?
There are three main gas laws. Avogadro’s law states that the moles of a gas is directly proportional to the volume (under constant pressure and temperature). Boyle’s law states that the pressure of the gas is inversely proportional to the volume (under constant moles and temperature). This means that the pressure decreases proportionally when the volume increases. Charles’ law states that the temperature is directly proportional to the volume (under constant moles and pressure). The question states that the piston moves up. This means that the volume of the gas is expanding inside and pushing the piston up to make room for the expanding gas. The gas expansion occurs due to increased temperature (Charles’ law).
There are three main gas laws. Avogadro’s law states that the moles of a gas is directly proportional to the volume (under constant pressure and temperature). Boyle’s law states that the pressure of the gas is inversely proportional to the volume (under constant moles and temperature). This means that the pressure decreases proportionally when the volume increases. Charles’ law states that the temperature is directly proportional to the volume (under constant moles and pressure). The question states that the piston moves up. This means that the volume of the gas is expanding inside and pushing the piston up to make room for the expanding gas. The gas expansion occurs due to increased temperature (Charles’ law).
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An unknown gas is being analyzed in lab. You place 
of this gas in a container at 
. You observe that the pressure and volume of the gas is 
and 
, respectively. What is the identity of the gas? Assume the gas behaves ideally.
An unknown gas is being analyzed in lab. You place
To solve this question we need to use the ideal gas law equation:
Above, 
is pressure in 
, 
is volume in liters, 
is moles, 
is 
, and 
is temperature in Kelvins. The question gives us pressure, volume, and temperature; therefore, we can solve for 
. First, we need to convert temperature from Celsius to Kelvins.
Rearrange the ideal gas law and solve for 
:
The question states that you place one gram of gas in the container. Since we know the moles, we can solve for the molecular weight of the gas and figure out its identity from the molecular weight.
The molecular weight of oxygen gas, 
is 
; therefore, the unknown gas must be oxygen.
To solve this question we need to use the ideal gas law equation:
Above,
Rearrange the ideal gas law and solve for
The question states that you place one gram of gas in the container. Since we know the moles, we can solve for the molecular weight of the gas and figure out its identity from the molecular weight.
The molecular weight of oxygen gas,
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Given the ideal gas law:
Where 
is density, 
is pressure, 
is the gas constant, 
is molar mass, and 
is temperature.
Based on the Ideal gas law, which of the following are true?
I. Pressure and volume are inversely proportional
II. Pressure and density are inversely proportional
III. Pressure and temperature are directly proportional
IV. Density and temperature are inversely proportional
V. R and M are inversely proportional
Given the ideal gas law:
Where
Based on the Ideal gas law, which of the following are true?
I. Pressure and volume are inversely proportional
II. Pressure and density are inversely proportional
III. Pressure and temperature are directly proportional
IV. Density and temperature are inversely proportional
V. R and M are inversely proportional
Condition I is true. Pressure and volume are inversely proportional. The ideal gas law with volume can be rederived to show this:
We introduce an expression for moles:
Where 
is moles, 
is mass, and 
is molar mass in 
Rearranging (1) to solve for 
and plugging into the following:
We get:
(2)
Finally, we use the following for density, where 
is volume, and plug into (2)
The masses cancel out and we have the ideal gas law expressed with volume and moles.
Condition II is false. It is clear from the equation that pressure and density are directly proportional.
Condition III is true because it is clear from the equation that temperature and pressure are directly proportional.
Condition IV is true because density and temperature are on the same side of the equation in the numerator, so the must be inversely proportional.
Condition V is false because the ideal gas constant and molar mass can be rearranged to be on opposite sides of the equation and in the numerator.
Condition I is true. Pressure and volume are inversely proportional. The ideal gas law with volume can be rederived to show this:
We introduce an expression for moles:
Where
Rearranging (1) to solve for
We get:
Finally, we use the following for density, where
The masses cancel out and we have the ideal gas law expressed with volume and moles.
Condition II is false. It is clear from the equation that pressure and density are directly proportional.
Condition III is true because it is clear from the equation that temperature and pressure are directly proportional.
Condition IV is true because density and temperature are on the same side of the equation in the numerator, so the must be inversely proportional.
Condition V is false because the ideal gas constant and molar mass can be rearranged to be on opposite sides of the equation and in the numerator.
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Under which conditions do gases deviate from ideality?
I. Low temperature
II. High temperature
III. Low pressure
IV. High pressure
V. Gases always behave ideally
Under which conditions do gases deviate from ideality?
I. Low temperature
II. High temperature
III. Low pressure
IV. High pressure
V. Gases always behave ideally
Gases deviate from ideal conditions at low temperature and high pressure. This because the postulates of the kinetic molecular theory of gasses ignore the volume of the molecules and all interactions between gas molecules. However, neither are true for real gasses. As the temperature increases, the kinetic energy of the particles can overcome the intermolecular forces of attraction or repulsion between the molecules. At high pressures, and subsequently low volume, the distance between molecules becomes shorter, and therefore intermolecular forces become significant. So, ideal conditions are when the distance between molecules is great, and the energy each molecule has is much greater in relative magnitude to the intermolecular forces. This occurs when the pressure is low, and the temperature is high.
Gases deviate from ideal conditions at low temperature and high pressure. This because the postulates of the kinetic molecular theory of gasses ignore the volume of the molecules and all interactions between gas molecules. However, neither are true for real gasses. As the temperature increases, the kinetic energy of the particles can overcome the intermolecular forces of attraction or repulsion between the molecules. At high pressures, and subsequently low volume, the distance between molecules becomes shorter, and therefore intermolecular forces become significant. So, ideal conditions are when the distance between molecules is great, and the energy each molecule has is much greater in relative magnitude to the intermolecular forces. This occurs when the pressure is low, and the temperature is high.
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Given the van der Waals Equation:
Which statement accurately identifies and explains the corrections that van der Waals made to the ideal gas law, where the first correction is the 
term and the second correction is the 
term?
Given the van der Waals Equation:
Which statement accurately identifies and explains the corrections that van der Waals made to the ideal gas law, where the first correction is the
All the statements say similar things, but only one correctly identifies the resulting change to volume and pressure. Let's break things down by the correction.
Correction 1:
The correction decreases the volume, since it is subtracting 
from the overall volume. As n (or the number of molecules) goes up, volume will go down.
Correction 2:
Since we are subtracting 
from the overall pressure, we are correcting for molecular attraction by decreasing pressure. We are doing this with a term 
that gets largerwhen 
increases and and gets larger as 
decreases.
All the statements say similar things, but only one correctly identifies the resulting change to volume and pressure. Let's break things down by the correction.
Correction 1:
The correction decreases the volume, since it is subtracting
Correction 2:
Since we are subtracting
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