Read the passage about Mr. Ellis.
Mr. Ellis is showing his science class how salt dissolves in water. He pours 500 mL of water into a saucepan. He turns on the burner to a medium heat for 5 minutes. He adds 30 grams of salt to the water, starts a timer, and stirs gently for 2 minutes. He records how long it takes for the salt to dissolve.
Mr. Ellis wants to slow the speed of the salt dissolving. Which change to his method would most likely help him to do this?
A.
He should stir vigorously for 2 minutes.
B.
He should turn down the heat on the burner.
C.
He should add 20 grams of salt instead of 30.
B. He should turn down the heat on the burner.
To slow the speed of the salt dissolving, Mr. Ellis should change his method by selecting option B: He should turn down the heat on the burner.
To answer this question, let's consider the process of dissolving salt in water. When salt is added to water, the water molecules surround the salt particles and break them apart, causing the salt to dissolve. The speed at which this occurs can be influenced by various factors.
In Mr. Ellis's experiment, he wants to slow down the speed of the salt dissolving. Let's analyze each proposed change to his method and determine which one would most likely help him achieve this goal:
A. Stirring vigorously for 2 minutes:
Stirring vigorously increases the contact between water and salt, allowing the particles to mix more effectively. This would likely speed up the dissolving process, which is the opposite of what Mr. Ellis wants to achieve. Therefore, this change would not help him slow down the salt dissolving.
B. Turning down the heat on the burner:
Heat can increase the kinetic energy of the water molecules, which in turn can speed up the dissolving process. By reducing the heat, Mr. Ellis can lower the energy of the water molecules, thus slowing down the dissolving. This change would likely help him achieve his goal of slowing down the salt dissolving.
C. Adding 20 grams of salt instead of 30:
The amount of salt used can also affect the speed of dissolving. Generally, a greater amount of salt would dissolve more slowly than a smaller amount. Therefore, reducing the amount of salt from 30 grams to 20 grams would likely slow down the dissolving process, aligning with Mr. Ellis's goal.
Considering the options, both turning down the heat on the burner and using less salt would likely slow down the speed of the salt dissolving. However, reducing the heat on the burner is the most relevant change and directly affects the energy of the water molecules involved in the dissolving process. Therefore, Option B - "He should turn down the heat on the burner" - would most likely help Mr. Ellis slow down the speed of the salt dissolving.