Question

Which of the following is a reliable way to observe that a chemical change has occurred when two substances come in contact with one another?(1 point) Responses conduct a test to determine the chemical makeup of the molecules conduct a test to determine the chemical makeup of the molecules monitor for the release of a gas monitor for the release of a gas test for the release of heat test for the release of heat observe a color change

Answer 1

To observe a chemical change when two substances come in contact with one another, the most reliable options from your list would be:

• Monitor for the release of a gas
• Test for the release of heat
• Observe a color change

All of these are indicators that a chemical reaction may have occurred. However, if you must choose just one reliable approach, "observe a color change" is often a clear visual indication that a chemical change has taken place.

Answer 2

Which of the following example demonstrates the reversibility of a chemical change?(1 point) Responses the rotting of eggs the rotting of eggs refreezing carbon dioxide gas into dry ice refreezing carbon dioxide gas into dry ice recharging batteries recharging batteries dehydrating sugar water

Answer 3

The example that demonstrates the reversibility of a chemical change is recharging batteries.

Recharging batteries involves a chemical reaction that can be reversed when the battery is charged again, restoring the original reactants and allowing the battery to be used repeatedly.

The other examples either involve irreversible changes (like the rotting of eggs) or physical changes (like refreezing carbon dioxide gas into dry ice and dehydrating sugar water).