At room temperature, 20° C, water (H2O) is a liquid and oxygen (O2) is a gas. Based on kinetic molecular theory, which answer best explains the states of the two fluids?
aThe particles in the liquid have greater kinetic energy than the particles in the gas.
bThe particles in both substances are able to flow because of weak intermolecular forces.
cThe particles in both substances are able to fill any container because both have indefinite shape and indefinite volume
dWater molecules have a lower boiling temperature than oxygen molecules, so at room temperature they exist as a liquid rather than a gas.
To determine the best explanation based on the kinetic molecular theory for the states of water and oxygen at room temperature, let's analyze the given answer choices:
a) "The particles in the liquid have greater kinetic energy than the particles in the gas."
This answer is inaccurate. According to the kinetic molecular theory, the state of matter (solid, liquid, or gas) is determined by the average kinetic energy of its particles. In a gas, the particles have the highest kinetic energy because they move rapidly and have more freedom of motion than particles in a liquid. Thus, option a) is incorrect.
b) "The particles in both substances are able to flow because of weak intermolecular forces."
This answer is partially correct. According to the kinetic molecular theory, intermolecular forces are weaker in gases compared to liquids. The weak forces allow the particles in both water and oxygen to flow or move around more freely. However, it doesn't fully explain why water is a liquid and oxygen is a gas at room temperature. Therefore, option b) is not the best answer.
c) "The particles in both substances are able to fill any container because both have indefinite shape and indefinite volume."
This answer is also partially correct. According to the kinetic molecular theory, both gases and liquids have indefinite shape and can fill the container they are in. However, this explanation does not address why water remains a liquid while oxygen exists as a gas at room temperature. Hence, option c) is not the best answer either.
d) "Water molecules have a lower boiling temperature than oxygen molecules, so at room temperature, they exist as a liquid rather than a gas."
This answer is the most accurate explanation based on the kinetic molecular theory. The boiling temperature of a substance is determined by the strength of the intermolecular forces within it. Water molecules have stronger intermolecular forces compared to oxygen molecules, which leads to a higher boiling temperature for water. Consequently, at room temperature (20°C), the kinetic energy of water molecules is not sufficient to overcome these intermolecular forces completely. Thus, water exists as a liquid, whereas oxygen molecules have weaker intermolecular forces and a lower boiling temperature, causing them to exist as a gas at room temperature.
Therefore, the correct answer would be d) "Water molecules have a lower boiling temperature than oxygen molecules, so at room temperature, they exist as a liquid rather than a gas."