which observation most likely indicates that only a chemical change has taken place?
a.) states of matter changes
b.) the shape changes
c.) the reaction occurs
d.) The change cannot be reversed
c.) the reaction occurs
Why is it a physical change to freeze water?
a. Only a phase change occurs
b. A temperature change occurs
c. He is released during the process
d. The new and original substances are different
a. Only a phase change occurs
Which option is an example of a chemical change?
a. Chopping vegetables
b. Stretching a rubber band
c. Folding paper
d. Burning wood
d. Burning wood
The observation that most likely indicates that only a chemical change has taken place is option c) the reaction occurs.
To understand why, let's go over the differences between physical and chemical changes.
A physical change is a change that occurs in the physical properties of a substance, such as its shape, size, or state of matter (like from a solid to a liquid or a gas). These changes are usually reversible, meaning you can revert the substance back to its original state without chemically altering it. For example, if you melt an ice cube to form liquid water, you can freeze the water again to form an ice cube.
On the other hand, a chemical change is a change that occurs at the molecular level, resulting in the formation of new substances with different properties. Chemical changes are usually accompanied by the release or absorption of energy. They are often not easily reversible. For example, if you burn a piece of paper, it turns into ashes, and you cannot easily reverse this change to reform the original paper.
Considering this, if you observe that a reaction occurs, it suggests a chemical change has taken place. Reactions involve the rearrangement of atoms and molecules to form new substances, indicating a chemical transformation. The formation of new substances and the irreversibility of the change are key indicators of a chemical change.
Therefore, option c) the reaction occurs is the observation that best indicates that only a chemical change has taken place.