Chemistry II F13 Final Exam

Food coloring mixes easily with water because it is hydrophilic. Hydrophilic substances have an affinity for water, meaning they are attracted to and can easily dissolve in water. Food coloring molecules are polar, which allows them to form hydrogen bonds with water molecules, facilitating their dispersion and even distribution throughout the water. This property makes food coloring an ideal additive for coloring water-based solutions, such as beverages or icing.

Tanning beds emit concentrated levels of ultraviolet (UV) radiation, specifically UVA and UVB rays, which can be more intense than natural sunlight. Prolonged exposure to these rays can increase the risk of skin damage, premature aging, and skin cancer. Sunlight, on the other hand, contains a mix of UVA and UVB rays, but its intensity can vary depending on factors like time of day and geographical location. While both tanning beds and sunlight can be harmful, tanning beds are considered more dangerous due to their higher levels of UV radiation.

The balanced equation for the reaction is 4Fe + 3O2 --> 2Fe2O3. This means that for every 4 iron (Fe) atoms and 3 oxygen (O2) molecules, 2 iron oxide (Fe2O3) molecules are formed. The coefficients in the answer choice 4, 3, 2 match the balanced equation, indicating that 4 moles of Fe, 3 moles of O2, and 2 moles of Fe2O3 are needed to balance the reaction.

Cooking an egg in a frying pan involves direct contact between the egg and the pan. This allows heat to transfer from the pan to the egg through conduction. Conduction is the process of heat transfer through direct contact between two objects or substances. In this case, the heat from the pan is conducted to the egg, causing it to cook.

SPF stands for sun protection factor. This term is used to measure the effectiveness of sunscreen in protecting the skin from harmful UV rays. The higher the SPF number, the greater the level of protection it provides. SPF is a widely recognized term in the skincare industry and is commonly seen on sunscreen products.

Smaller wavelengths of light have a higher energy level. This is because the energy of a photon is directly proportional to its frequency, and inversely proportional to its wavelength. Since smaller wavelengths correspond to higher frequencies, they also have higher energy levels.

The correct answer is "move in constant rapid random motion." This statement is a fundamental principle of the Kinetic Molecular Theory, which describes the behavior of gases. According to this theory, gas particles are in constant motion, moving rapidly and randomly in all directions. This motion is what gives gases their ability to fill a container and diffuse throughout a space.

When proteins are denatured, they lose their shape and structure, causing them to unravel. This is typically due to factors such as heat, pH changes, or exposure to certain chemicals. Denaturation disrupts the weak bonds that hold the protein's structure together, leading to the unfolding and loss of its biological function.

For a solution to be conductive, it must have ions that can move. In a conductive solution, the ions are able to freely move and carry an electric charge. This movement of ions allows for the flow of electric current through the solution. Therefore, the ability of ions to move is a crucial characteristic for a solution to exhibit conductivity.

A combustion reaction occurs when fuel and oxygen are present. Fuel provides the necessary energy source, while oxygen acts as the oxidizing agent. Without fuel, there would be no source of energy to initiate the reaction, and without oxygen, there would be no oxidizing agent to support the reaction. Therefore, both fuel and oxygen are required for a combustion reaction to occur.

When a metal skewer is stuck into a potato, it allows heat to be conducted directly into the center of the potato. This means that the heat can reach the center of the potato more quickly and efficiently, reducing the overall cooking time required. Therefore, the cooking time will decrease.

UVB rays are the most likely to cause sunburn because they have shorter wavelengths and higher energy levels compared to UVA and UVC rays. UVB rays penetrate the outer layer of the skin and cause damage to the DNA, leading to sunburn and an increased risk of skin cancer. UVA rays, on the other hand, have longer wavelengths and can penetrate deeper into the skin, causing premature aging and wrinkling. UVC rays are mostly absorbed by the Earth's atmosphere and do not reach the surface.

In the water cycle, water undergoes a process called evaporation, where it changes from a liquid state to a gas state. This occurs when heat energy from the sun causes the water molecules to gain enough energy to escape from the surface of oceans, lakes, and streams. The water vapor then rises into the atmosphere and forms condensation in the clouds, leading to the formation of rain or other forms of precipitation.

Proteins can be denatured through various methods, including heat, acid, and salt. Heat disrupts the hydrogen bonds and weakens the protein's structure. Acidic conditions alter the protein's charge distribution, causing it to unfold. Salt disrupts the electrostatic interactions within the protein. Therefore, when heat, acid, and salt are combined, they collectively denature the protein by breaking its bonds and altering its structure.

Calibration refers to the process of adjusting and verifying the accuracy of an instrument or device by comparing its measurements to a known standard. In this case, ensuring that an instrument makes exact and accurate measurements is an example of performing calibration. Calibration helps to ensure the reliability and precision of measurements, making it the correct answer for this question.

The dissolved salt in the ocean is an example of a solute because it is the substance that is being dissolved in the solvent, which in this case is water. The solute particles are dispersed throughout the solvent, forming a solution. In the case of the ocean, the salt particles are spread out in the water, making it a saline solution.

Heat is defined as the amount of kinetic energy. Kinetic energy is the energy possessed by an object due to its motion. When the particles of a substance move faster, they have higher kinetic energy, which results in an increase in temperature. Therefore, heat can be understood as the measure of the total kinetic energy of the particles in a substance.

An exothermic reaction is a reaction that releases heat. Therefore, if you were to touch an object or substance undergoing an exothermic reaction, it would feel hot to the touch.

Mg is above Zn in the metal activity series, indicating that Mg is more reactive than Zn. This means that Mg has a higher tendency to lose electrons and form positive ions compared to Zn. In order for a reaction to occur between Mg and Zn, Mg needs to be in the solid state because it is more reactive. Therefore, the solid in the reaction would have to be Mg.

Phosphorescence refers to the emission of light after being exposed to and then removed from a source of radiation. Glow-in-dark stars exhibit phosphorescence because they absorb light energy from their surroundings and then release it slowly over time, causing them to glow in the dark. This is different from LED lights, overhead lights, and flashlights, which produce light through other mechanisms such as electrical currents or incandescence. Therefore, the correct answer is glow-in-dark stars.

A redox reaction involves the transfer of electrons between species. In these reactions, one species loses electrons (oxidation) while another species gains electrons (reduction). The flow of electrons is what drives the chemical changes in the reaction. Protons and neutrons are not involved in the transfer of electrons during a redox reaction. Antimatter, although it can participate in reactions, is not specifically associated with redox reactions. Therefore, the correct answer is electrons.

When water freezes, the molecules slow down and arrange themselves into a rigid, ordered structure. This decrease in molecular motion and randomness leads to a decrease in entropy. Entropy is a measure of the disorder or randomness in a system, so as the water transitions from a liquid to a solid state, the level of disorder decreases, resulting in a decrease in entropy.

When atoms absorb energy, the electrons gain enough energy to move to a higher energy level or orbital. This higher energy level is known as the excited state. In this state, the electrons are not in their usual stable configuration and can eventually release the excess energy by emitting light or heat and returning to their ground state. The ground state refers to the lowest energy level that an electron can occupy in an atom. The middle state is not a term used to describe the electron's energy levels.

During World War II, soldiers were exposed to intense sunlight for long periods of time, leading to sunburn and other skin issues. As a result, sunscreen was developed to protect them from the harmful effects of the sun. This development was crucial in ensuring the well-being and health of the soldiers during the war.

Reduction is a chemical process in which electrons are gained. This means that during reduction, a species accepts or gains electrons, resulting in a decrease in its oxidation state. In other words, reduction involves the addition of negatively charged electrons to a species, leading to a more negative charge or a lower oxidation state.

The formula 4 C3H5(NO3)3 indicates that there are four molecules of C3H5(NO3)3. Each molecule contains three nitrogen atoms (N), so to find the total number of N's, we multiply the number of molecules (4) by the number of N's per molecule (3), which gives us a total of 12 N's.

When the amount of gas and pressure are constant, according to Charles's Law, the volume of a gas is directly proportional to its temperature. Therefore, when the temperature decreases, the volume of the balloon decreases as well. This can be explained by the fact that as the temperature decreases, the gas molecules have less kinetic energy and move slower, causing them to occupy less space and resulting in a decrease in volume.

Metals readily lose electrons to form positively charged particles. This is because metals have a tendency to have fewer electrons in their outermost energy level, making it easier for them to lose those electrons and achieve a stable electron configuration. The loss of electrons results in the formation of positively charged ions, also known as cations. These cations are attracted to negatively charged particles or anions, creating an overall neutral charge in a compound or molecule.

When vinegar and baking soda are reacted, a chemical reaction takes place, resulting in the formation of new products. However, the law of conservation of mass states that matter cannot be created or destroyed in a chemical reaction. Therefore, the mass of the products should be the same as the mass of the starting materials.

When a material boils, it undergoes a phase change from a liquid to a gas. During this phase change, the temperature of the material remains constant. This is because the heat energy being supplied to the material is being used to break the intermolecular bonds holding the molecules together, rather than increasing the temperature. Once all the molecules have enough energy to overcome these bonds, the material can transition into a gas state, and only then will the temperature start to increase again.

Uranium has a higher atomic mass compared to helium and lead. Therefore, a mole of uranium will have a greater mass than a mole of helium or lead.

The question asks which of the given options contains more atoms. The correct answer states that all the options contain the same number of atoms. This means that helium, lead, and uranium all have an equal number of atoms. The answer suggests that there is no variation in the number of atoms among these elements.

Glass has the highest specific heat among the given materials. Specific heat is the amount of heat required to raise the temperature of a substance by a certain amount. Since glass has a higher specific heat, it can absorb more heat energy compared to the other materials for the same mass. Therefore, when removed from a burner, glass would retain more heat and remain hotter after 5 minutes compared to copper, iron, and aluminum.

The coefficients in a balanced chemical equation represent the mole to mole ratio. This means that they indicate the ratio in which the reactants and products combine or are produced in the reaction. The coefficients show the relative number of moles of each substance involved, allowing for the calculation of stoichiometry and determining the amount of each substance needed or produced in a reaction.

The difference in charges on the atoms in a water molecule causes other water molecules to bond through a hydrogen bond. In a water molecule, the oxygen atom is slightly negative due to its higher electronegativity, while the hydrogen atoms are slightly positive. This creates a polarity in the molecule, with the oxygen atom having a partial negative charge and the hydrogen atoms having partial positive charges. These opposite charges allow the oxygen atom of one water molecule to attract the hydrogen atoms of neighboring water molecules, forming a hydrogen bond. This bond is weaker than a covalent bond but still strong enough to give water its unique properties such as high boiling point and surface tension.