1.
A _______ change occurs when a substance changes phase.
Correct Answer
A. pHysical
Explanation
When a substance changes phase, such as from solid to liquid or liquid to gas, it undergoes a physical change. This means that the substance's physical properties, such as shape, size, and state of matter, are altered, but its chemical composition remains the same. In contrast, a chemical change involves a transformation in the substance's chemical composition, resulting in the formation of new substances with different properties. Therefore, the correct answer is "physical" because a change in phase is a physical change.
2.
A change of phase from vapor to liquid is called ______.
Correct Answer
B. Condensation
Explanation
Condensation is the correct answer because it refers to the process in which a substance changes from a gaseous state to a liquid state. During condensation, the molecules lose energy and come closer together, forming liquid droplets. This change of phase commonly occurs when the temperature of a gas decreases, causing the gas molecules to slow down and bond together to form a liquid.
3.
When a substance dissolves, it undergoes a ______.
Correct Answer
B. pHysical change
Explanation
When a substance dissolves, it undergoes a physical change. Dissolving is a process in which solute particles separate and disperse in a solvent, forming a homogeneous mixture. This change does not involve the breaking or forming of chemical bonds, but rather the intermolecular forces between solute and solvent molecules. The chemical composition of the substance remains the same before and after dissolving, indicating that it is a physical change.
4.
As a change of state is occurring, the temperature of the system does not change.
Correct Answer
A. True
Explanation
When a change of state occurs, such as from solid to liquid or liquid to gas, the temperature of the system remains constant during the transition. This is because the energy being added or removed is used to break or form intermolecular forces, rather than increasing or decreasing the average kinetic energy of the particles. Therefore, the statement "the temperature of the system does not change" is true in the context of a change of state.
5.
The change of phase from a solid to a gas is called _____.
Correct Answer
C. Sublimation
Explanation
Sublimation is the correct answer because it refers to the process in which a solid directly changes into a gas without going through the liquid phase. This occurs when the temperature and pressure conditions are such that the solid particles have enough energy to overcome the attractive forces and enter the gas phase. Examples of substances that undergo sublimation include dry ice (solid carbon dioxide) and mothballs (solid naphthalene).
6.
Which of the following statements is true?
Correct Answer
B. For most substances, the solid state is more dense than the liquid state.
Explanation
The statement "For most substances, the solid state is more dense than the liquid state" is true because when a substance undergoes a phase change from a liquid to a solid, the particles become more closely packed together, resulting in a higher density. This is due to the decrease in thermal energy and the formation of stronger intermolecular forces in the solid state. However, there are a few exceptions to this general rule, such as water, where the solid state (ice) is less dense than the liquid state.
7.
Which of the following is the best name for a compound made from calcium and bromine (CaBr2)?
Correct Answer
A. Calcium bromide
Explanation
The compound made from calcium and bromine is called calcium bromide. The name is derived from the elements present in the compound, with "calcium" representing the metal and "bromide" representing the non-metal. The Roman numeral II is not necessary in this case since calcium only forms one type of cation.
8.
Which of the following is a properly written formula for a compound between copper and bromine?
Correct Answer
C. CuBr
Explanation
The correct formula for a compound between copper and bromine is CuBr. In chemical formulas, the elements are represented by their symbols, with the capital letter being the symbol for the element. The lowercase letter represents the second element in the compound. In this case, Cu represents copper, and Br represents bromine. The correct formula follows the convention of using a capital letter for the first element and a lowercase letter for the second element.
9.
Which of the following is the best name for a compound made from nitrogen and oxygen (N2O3)?
Correct Answer
D. Dinitrogen trioxide
Explanation
The compound N2O3 is composed of two nitrogen atoms and three oxygen atoms. The prefix "di-" indicates that there are two nitrogen atoms, and the prefix "tri-" indicates that there are three oxygen atoms. Therefore, the best name for this compound is "dinitrogen trioxide."
10.
Which part of an atom is actively exchanged or shared in a chemical bond?
Correct Answer
B. Electron
Explanation
In a chemical bond, electrons are actively exchanged or shared between atoms. This is because electrons are negatively charged particles that orbit around the nucleus of an atom and are involved in the formation of chemical bonds. Electrons are responsible for the interactions between atoms, allowing them to form stable compounds by gaining, losing, or sharing electrons. Protons and neutrons, on the other hand, are located in the nucleus of an atom and are not actively exchanged or shared in a chemical bond. Therefore, the correct answer is electron.