10th Grade Chemistry Quiz

Rusting of iron is a chemical change because it results in the formation of a new substance, iron oxide, which has different properties from the original iron.

Sodium chloride is composed of one sodium (Na) atom and one chlorine (Cl) atom, giving it the chemical formula NaCl.

Oxygen has 8 electrons. The correct electron configuration fills the first energy level (1s²) with 2 electrons, the second energy level's s orbital (2s²) with 2 electrons, and the p orbital (2p⁴) with the remaining 4 electrons.

A covalent bond is formed when two atoms share one or more pairs of electrons to achieve a full outer electron shell, typical in molecules like H₂O or CO₂.

A pH of 7 is considered neutral, meaning the concentration of hydrogen ions (H⁺) is equal to the concentration of hydroxide ions (OH⁻) in the solution, typical of pure water at 25°C.

Sodium (Na) tends to lose one electron to achieve a stable electron configuration, forming a positively charged ion (cation), Na⁺.

The molar mass of CO₂ is calculated by adding the atomic masses of one carbon atom (12 g/mol) and two oxygen atoms (16 g/mol each), giving a total of 44 g/mol.

Evaporation is the process where a liquid changes into a gas at temperatures below its boiling point, such as when water evaporates from a puddle on a warm day.

An exothermic reaction releases energy, often in the form of heat. The combustion of gasoline releases a significant amount of energy, making it exothermic.

The Law of Conservation of Mass states that the mass of the reactants in a chemical reaction equals the mass of the products, meaning matter is neither created nor destroyed.