The example of a physical change from the options provided is dry ice becoming vapor. This process, known as sublimation, involves the transition of dry ice (solid carbon dioxide) directly into gas without changing its chemical composition. The other options involve chemical changes or are indicators of chemical processes.
Which of the following is an example of only a physical change?
Responses:
the green color of the Statue of Liberty
dry ice becoming vapor
the smell of rotten eggs
the creation of table salt
9 answers
Which of the following demonstrates a chemical change?(1 point)
Responses
dry ice vaporizing
iron (Fe) reacting to water(H2O) and oxygen(O) to form iron oxide(Fe2O3
sugar and water mixing to create sugar water
steam condensing on a mirror
Responses
dry ice vaporizing
iron (Fe) reacting to water(H2O) and oxygen(O) to form iron oxide(Fe2O3
sugar and water mixing to create sugar water
steam condensing on a mirror
The response that demonstrates a chemical change is iron (Fe) reacting to water (H2O) and oxygen (O) to form iron oxide (Fe2O3). This reaction involves the formation of a new substance (iron oxide) and is an example of oxidation.
The other options are physical changes: dry ice vaporizing is sublimation, mixing sugar and water creates a solution, and steam condensing on a mirror is a change of state from gas to liquid.
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
Responses:
monitor for the release of a gas
conduct a test to determine the chemical makeup of the molecules
test for the release of heat
observe a color change
Responses:
monitor for the release of a gas
conduct a test to determine the chemical makeup of the molecules
test for the release of heat
observe a color change
All of the responses you provided can indicate that a chemical change has occurred when two substances come in contact with one another; however, the most reliable ways to observe a chemical change directly during the interaction are often considered to be:
- Monitor for the release of a gas - This can indicate a new chemical being formed.
- Test for the release of heat - This can indicate an exothermic reaction.
- Observe a color change - A change in color can indicate new substances have formed.
Since you're looking for a reliable indication of a chemical change, monitor for the release of a gas and observe a color change are particularly strong indicators. However, if you are looking for one option that is generally recognized as a reliable observation of chemical change, observe a color change is often cited as a clear indicator of chemical reactions.
In experimental contexts, conducting tests to determine the chemical makeup would also confirm a chemical change but is a more indirect method compared to observing immediate physical signs like gas release or color change.
Which of the following happens during a chemical change but does not happen during a physical change
Responses
The state of the substance changes.
The mass of the substance changes.
The appearance of a substance changes, but it is still the same substance.
Atoms of one or more substances rearrange into a new substance.
Responses
The state of the substance changes.
The mass of the substance changes.
The appearance of a substance changes, but it is still the same substance.
Atoms of one or more substances rearrange into a new substance.
The statement that happens during a chemical change but does not happen during a physical change is:
Atoms of one or more substances rearrange into a new substance.
In a chemical change, the original substances (reactants) undergo a transformation to form new substances (products), which involves the rearrangement of atoms.
The other options pertain to physical changes or do not necessarily distinguish a chemical change from a physical one. For instance, the state of a substance can change in both physical and chemical changes, and changes in appearance can occur without a chemical change. The mass of the substance remains constant in a closed system during both physical and chemical changes (according to the law of conservation of mass).
Which of the following example demonstrates the reversibility of a chemical change?(1 point)
Responses
the rotting of eggs
refreezing carbon dioxide gas into dry ice
dehydrating sugar water
recharging batteries
Responses
the rotting of eggs
refreezing carbon dioxide gas into dry ice
dehydrating sugar water
recharging batteries
The example that demonstrates the reversibility of a chemical change is recharging batteries.
When batteries are recharged, the chemical reactions that occur during discharging (when the battery is used) can be reversed, allowing the battery to return to its original state and store energy again.
The other options involve changes that are either not reversible or are primarily physical changes (e.g., refreezing carbon dioxide gas into dry ice is a physical change, and while dehydration can be somewhat reversible, it often involves chemical processes that do not return to their original state). The rotting of eggs is a chemical change that is not reversible.