Hannah heats a beaker of water using a burner, as shown in the diagram.
Which statement best describes the movement of water molecules in Hannah's beaker, represented by the arrows in the diagram?
a
Water molecules move slower near the bottom of the beaker where they are hotter, but then move faster as they cool and rise due to convection.
b
Water molecules move faster near the bottom of the beaker where they are hotter, but then move slower as they cool and rise due to convection.
c
Water molecules move slower near the bottom of the beaker where they are hotter, but then move faster as they cool and rise due to conduction.
d
Water molecules move faster near the bottom of the water where they are hotter, but then move slower as they cool and rise due to radiation.
b) Water molecules move faster near the bottom of the beaker where they are hotter, but then move slower as they cool and rise due to convection.
The correct answer is option a: Water molecules move slower near the bottom of the beaker where they are hotter, but then move faster as they cool and rise due to convection.
To answer this question, we need to understand how heat affects the movement of water molecules.
When a beaker of water is heated using a burner, the heat energy is transferred to the water molecules. As the water molecules absorb this heat energy, they gain kinetic energy, causing them to move faster.
In the given diagram, the beaker is heated from the bottom. As a result, the water molecules near the bottom of the beaker, where they are directly in contact with the heat source, will gain the most heat energy and move faster. This is because heat is being conducted from the burner to the water molecules in direct contact.
As the water molecules near the bottom move faster, they collide with neighboring molecules, transferring some of their kinetic energy. This leads to an increase in the kinetic energy and speed of the surrounding molecules. This transfer of energy in the form of movement is called conduction.
Due to the increased kinetic energy and faster movement, the water molecules near the bottom will rise towards the surface of the beaker. This upward movement is known as convection. As the heated water molecules rise, they gradually lose their heat energy to the surrounding water molecules and the atmosphere. Consequently, their movement and speed start to decrease.
Therefore, the correct statement regarding the movement of water molecules in Hannah's beaker, as represented by the arrows in the diagram, is:
b) Water molecules move faster near the bottom of the beaker where they are hotter, but then move slower as they cool and rise due to convection.