During digestion, the energy in food is converted to energy the body can use. Scientists use calorimetry experiments to measure the calories, or energy, provided by food when it is digested or burned. 

The relationship used to find the heat transferred energy  is given by , where  is the mass of the material,  is the given specific heat capacity, and  is the change in temperature of the material. 

In this experiment, food was burned over a Bunsen burner under a can of 200 ml of water. The temperature change of the water and mass change of the food can be used to determine the calories in four different food items.

Table 1 shows the values of the change of mass of the food items, the change in temperature of the water and the energy. Table 2 shows the energy to mass ratio of three of those food items.

                                                    Table 1

                                  Roasted Peanut  Peanut    Cracker    Cheese Puff

Water Temp. Initial         23.9 °C           33.2 °C     40.3 °C      53.9 °C

Water Temp. Final           30.0 °C           40.9 °C     55.9 °C      62.8 °C

Food Mass Initial             0.69 g             0.61 g       3.21 g        1.22 g

Food Mass Final               0.38 g             0.21 g       0.91 g        0.48 g

Energy                            1.22 Cal          1.54 Cal     3.12 Cal     1.78 Cal

                           Table 2

Sample         Energy to Mass Ratio (Cal/g)

     1                                 1.36

     2                                 3.93

     3                                 2.40

Based on the results shown in Table 1 from the experiment, what is the relationship between the mass change of the food sample and the calories in the food?

Two students are studying hydrocarbon combustion, or the burning of compounds containing carbon and hydrogen in the presence of oxygen gas. Both students express their views on this phenomenon. 

Student 1: Hydrocarbons are high in energy and therefore naturally burn in order to release that energy. That energy is released in the form of light and heat. If water is thrown onto a fire, it will extinguish it because it cuts the combustion from the oxygen gas required for it to burn.

Student 2: Hydrocarbons are compounds at a greater energy state than the compounds produced when they burn. This excess energy changes to heat when hydrocarbons burn. Lastly, hydrocarbons require a spark to initiate the combustion. 

Which of the following statements would both students be most likely to agree?

Two students are studying hydrocarbon combustion, or the burning of compounds containing carbon and hydrogen in the presence of oxygen gas. Both scientists express their views on this phenomenon.

Student 1: Hydrocarbons are high in energy and therefore naturally burn in order to release that energy. That energy is released in the form of light and heat. If water is thrown onto a fire, it will extinguish it because it cuts the combustion from the oxygen gas required for it to burn. 

Student 2: Hydrocarbons are compounds at a greater energy state than the compounds produced when they burn. This excess energy changes to heat when hydrocarbons burn. Lastly, hydrocarbons require a spark to initiate the combustion. 

Which of the following statements would Student 2 be most likely to agree with and not Student 1?

There are two types of forces that occur with all substances on Earth. Intramolecular forces occur between atoms in a molecule, while intermolecular forces occur between neighboring molecules. Intermolecular forces can be dipole-dipole forces, hydrogen bonding, or London dispersion forces.

Professor 1:

Water molecules represent an example of hydrogen bonding due to the attraction between the hydrogen atoms and the oxygen atoms in the molecule. This strong dipole-dipole occurs due to lone pairs present on such atoms as Fluorine, Nitrogen, and Oxygen, which are able to pair more closely to the hydrogen atom in another nearby molecule. Water can be present in a solid, liquid, or gaseous state on Earth depending on the competition between the strength of intermolecular bonds and the thermal energy of the system. In 1873, a Dutch scientist, Van der Waals derived an equation that included both the force of attraction between the particles of a gas and the volume of the particles at high pressures. This equation led to a better fit for experimental data than the Ideal Gas Law.

Professor 2: 

Water is the only substance on Earth that we routinely encounter as a solid, liquid, and gas. At low temperatures, the water molecules lock into a rigid structure, but as the temperature increases, the average kinetic energy of the water molecules increases and the molecules are able to move more creating its other natural states of matter. The higher the temperature, the more likely water is to be a gas. Water is proof of the kinetic theory, which assumes that there is no force of attraction between the particles of the gas state. The best fit for experimental data involving water in a gaseous form is found by using the Ideal Gas Law, since there is no interaction between the gaseous molecules. This law accounts for all of the forces that occur with gases on Earth.

Which of the following statements is professor 1 most likely to agree with?

There are two types of forces that occur with all substances on Earth. Intramolecular forces occur between atoms in a molecule, while intermolecular forces occur between neighboring molecules. Intermolecular forces can be dipole-dipole forces, hydrogen bonding, or London dispersion forces.

Professor 1:

Water molecules represent an example of hydrogen bonding due to the attraction between the hydrogen atoms and the oxygen atoms in the molecule. This strong dipole-dipole occurs due to lone pairs present on such atoms as Fluorine, Nitrogen, and Oxygen, which are able to pair more closely to the hydrogen atom in another nearby molecule. Water can be present in a solid, liquid, or gaseous state on Earth depending on the competition between the strength of intermolecular bonds and the thermal energy of the system. In 1873, a Dutch scientist, Van der Waals derived an equation that included both the force of attraction between the particles of a gas and the volume of the particles at high pressures. This equation led to a better fit for experimental data than the Ideal Gas Law.

Professor 2: 

Water is the only substance on Earth that we routinely encounter as a solid, liquid, and gas. At low temperatures, the water molecules lock into a rigid structure, but as the temperature increases, the average kinetic energy of the water molecules increases and the molecules are able to move more creating its other natural states of matter. The higher the temperature, the more likely water is to be a gas. Water is proof of the kinetic theory, which assumes that there is no force of attraction between the particles of the gas state. The best fit for experimental data involving water in a gaseous form is found by using the Ideal Gas Law, since there is no interaction between the gaseous molecules. This law accounts for all of the forces that occur with gases on Earth.

Which of the following statements would professor 2 agree with?

There are two types of forces that occur with all substances on Earth. Intramolecular forces occur between atoms in a molecule, while intermolecular forces occur between neighboring molecules. Intermolecular forces can be dipole-dipole forces, hydrogen bonding, or London dispersion forces.

Professor 1:

Water molecules represent an example of hydrogen bonding due to the attraction between the hydrogen atoms and the oxygen atoms in the molecule. This strong dipole-dipole occurs due to lone pairs present on such atoms as Fluorine, Nitrogen, and Oxygen, which are able to pair more closely to the hydrogen atom in another nearby molecule. Water can be present in a solid, liquid, or gaseous state on Earth depending on the competition between the strength of intermolecular bonds and the thermal energy of the system. In 1873, a Dutch scientist, Van der Waals derived an equation that included both the force of attraction between the particles of a gas and the volume of the particles at high pressures. This equation led to a better fit for experimental data than the Ideal Gas Law.

Professor 2: 

Water is the only substance on Earth that we routinely encounter as a solid, liquid, and gas. At low temperatures, the water molecules lock into a rigid structure, but as the temperature increases, the average kinetic energy of the water molecules increases and the molecules are able to move more creating its other natural states of matter. The higher the temperature, the more likely water is to be a gas. Water is proof of the kinetic theory, which assumes that there is no force of attraction between the particles of the gas state. The best fit for experimental data involving water in a gaseous form is found by using the Ideal Gas Law, since there is no interaction between the gaseous molecules. This law accounts for all of the forces that occur with gases on Earth.

With which of the following statements would both professors agree?

There are two types of forces that occur with all substances on Earth. Intramolecular forces occur between atoms in a molecule, while intermolecular forces occur between neighboring molecules. Intermolecular forces can be dipole-dipole forces, hydrogen bonding, or London dispersion forces.

Professor 1:

Water molecules represent an example of hydrogen bonding due to the attraction between the hydrogen atoms and the oxygen atoms in the molecule. This strong dipole-dipole occurs due to lone pairs present on such atoms as Fluorine, Nitrogen, and Oxygen, which are able to pair more closely to the hydrogen atom in another nearby molecule. Water can be present in a solid, liquid, or gaseous state on Earth depending on the competition between the strength of intermolecular bonds and the thermal energy of the system. In 1873, a Dutch scientist, Van der Waals derived an equation that included both the force of attraction between the particles of a gas and the volume of the particles at high pressures. This equation led to a better fit for experimental data than the Ideal Gas Law.

Professor 2: 

Water is the only substance on Earth that we routinely encounter as a solid, liquid, and gas. At low temperatures, the water molecules lock into a rigid structure, but as the temperature increases, the average kinetic energy of the water molecules increases and the molecules are able to move more creating its other natural states of matter. The higher the temperature, the more likely water is to be a gas. Water is proof of the kinetic theory, which assumes that there is no force of attraction between the particles of the gas state. The best fit for experimental data involving water in a gaseous form is found by using the Ideal Gas Law, since there is no interaction between the gaseous molecules. This law accounts for all of the forces that occur with gases on Earth.

Which statement would both professors agree with?

There are two types of forces that occur with all substances on Earth. Intramolecular forces occur between atoms in a molecule, while intermolecular forces occur between neighboring molecules. Intermolecular forces can be dipole-dipole forces, hydrogen bonding, or London dispersion forces.

Professor 1:

Water molecules represent an example of hydrogen bonding due to the attraction between the hydrogen atoms and the oxygen atoms in the molecule. This strong dipole-dipole occurs due to lone pairs present on such atoms as Fluorine, Nitrogen, and Oxygen, which are able to pair more closely to the hydrogen atom in another nearby molecule. Water can be present in a solid, liquid, or gaseous state on Earth depending on the competition between the strength of intermolecular bonds and the thermal energy of the system. In 1873, a Dutch scientist, Van der Waals derived an equation that included both the force of attraction between the particles of a gas and the volume of the particles at high pressures. This equation led to a better fit for experimental data than the Ideal Gas Law.

Professor 2: 

Water is the only substance on Earth that we routinely encounter as a solid, liquid, and gas. At low temperatures, the water molecules lock into a rigid structure, but as the temperature increases, the average kinetic energy of the water molecules increases and the molecules are able to move more creating its other natural states of matter. The higher the temperature, the more likely water is to be a gas. Water is proof of the kinetic theory, which assumes that there is no force of attraction between the particles of the gas state. The best fit for experimental data involving water in a gaseous form is found by using the Ideal Gas Law, since there is no interaction between the gaseous molecules. This law accounts for all of the forces that occur with gases on Earth.

Which of these statements made by professor 2 is not contradicted by professor 1?

There are two types of forces that occur with all substances on Earth. Intramolecular forces occur between atoms in a molecule, while intermolecular forces occur between neighboring molecules. Intermolecular forces can be dipole-dipole forces, hydrogen bonding, or London dispersion forces.

Professor 1:

Water molecules represent an example of hydrogen bonding due to the attraction between the hydrogen atoms and the oxygen atoms in the molecule. This strong dipole-dipole occurs due to lone pairs present on such atoms as Fluorine, Nitrogen, and Oxygen, which are able to pair more closely to the hydrogen atom in another nearby molecule. Water can be present in a solid, liquid, or gaseous state on Earth depending on the competition between the strength of intermolecular bonds and the thermal energy of the system. In 1873, a Dutch scientist, Van der Waals derived an equation that included both the force of attraction between the particles of a gas and the volume of the particles at high pressures. This equation led to a better fit for experimental data than the Ideal Gas Law.

Professor 2: 

Water is the only substance on Earth that we routinely encounter as a solid, liquid, and gas. At low temperatures, the water molecules lock into a rigid structure, but as the temperature increases, the average kinetic energy of the water molecules increases and the molecules are able to move more creating its other natural states of matter. The higher the temperature, the more likely water is to be a gas. Water is proof of the kinetic theory, which assumes that there is no force of attraction between the particles of the gas state. The best fit for experimental data involving water in a gaseous form is found by using the Ideal Gas Law, since there is no interaction between the gaseous molecules. This law accounts for all of the forces that occur with gases on Earth.

A 3rd professor mentions that he has he has seen Hydrogen Bonding have an effect on his experimental results. What would each professor say about his statement?

In its refined form, iron is a shiny, silver-gray metal; however, when refined iron is exposed to atmospheric conditions for an extended period of time, its surface becomes flaky, pitted, and red- or orange-colored. This process is known as "rusting," and the new flaky, orange or red substance is called "rust."

Below, two scientists discuss how rust forms and the composition of rust.

Scientist 1:

Both water and oxygen are needed for rust to form. Water is an electrolyte, meaning that it allows ions to move within it. When iron comes into contact with water, some iron naturally dissociates into iron ions (Fe²⁺) and free electrons. Additionally, when atmospheric oxygen (O₂) dissolves in water, some oxygen reacts with water to form hydroxide ions (OH^-). Because water allows ions to move freely, iron ions and hydroxide ions combine to form a new compound: iron hydroxide. However, iron hydroxide is not a stable compound. Over time, as water evaporates, it changes into a hydrated form of iron oxide. This is rust.

Salts can act as catalysts for rust formation, meaning that they speed up the rate at which rust forms. However, rust can form in pure water, in the absence of added salts.

Increasing the ambient temperature increases the rate of rust formation. Additionally, increasing the amount of iron's surface area that is exposed to water also increases the rate at which rust forms. However, because a layer of rust is porous to water and oxygen, water and oxygen will continue to cause the interior of a piece of iron to rust even after the iron's surface has been rusted.

Scientist 2:

Attack by acids causes rust to form. In water, acids ionize to create positively-charged hydronium (H⁺) ions and negatively-charged anions. Hydronium ions are electron-deficient; because of this, they attract electrons from iron. This creates iron ions (Fe²⁺), which are soluble in water. Once dissolved in water, iron ions react with dissolved atmospheric oxygen (O₂) to create iron oxide, or rust.

Acids can come from a variety of sources. For example, when carbon dioxide in the atmosphere dissolves in water, carbonic acid (H₂CO₃) is created. Carbonic acid is the most common cause of rusting. However, other environmental sources of acids exist. Rainwater is normally slightly acidic because it has come into contact with molecules in the atmosphere, like sulfur dioxide and nitrogen oxides. These molecules also dissolve in water to form acids. Additionally, iron itself may contain impurities such as phosphorous and sulfur, which react with water to produce acids. Both acidic environments and impurities within iron itself create the conditions under which iron rusts.

Rusting can be prevented by painting the surface of iron, thus preventing it from coming into contact with water, oxygen, and acids. Iron can also be protected in a process called "galvanizing," which involves coating iron in a thin layer of zinc. Because zinc is more reactive than iron, it is corroded while the iron is protected.

Boiling water does not contain dissolved oxygen. Suppose that a new piece of iron is immersed in boiling water for an extended period of time. Afterwards, scientists observe that the iron has rusted. How would this affect the arguments of Scientist 1 and Scientist 2?