Which observation most likely indicates that only a chemical change has taken place won the shape changes to states of matter changes three the change to not be reversed for a reaction occurs
You need to rephrase the question as well as the answers. It makes no sense as posted.
The observation that most likely indicates that only a chemical change has taken place is when the change cannot be reversed and a reaction occurs. Physical changes, such as changes in shape or changes in states of matter (solid, liquid, gas), can usually be reversed without any chemical reactions occurring. However, if a change cannot be reversed and a reaction occurs, it suggests that a chemical change has taken place.
The observation that most likely indicates that only a chemical change has taken place is when the change cannot be reversed and a reaction occurs. Additionally, changes in shape and states of matter can also be indicators.
To determine whether a chemical change has occurred, you can look for several key signs:
1. Irreversibility: Chemical changes are often irreversible, meaning that it is difficult or impossible to reverse the reaction and return to the original substances.
2. Formation of new substances: During a chemical reaction, new substances are formed. This can be observed by changes in color, formation of a precipitate (solid), release or absorption of heat or light, production of gas bubbles, etc.
3. Energy changes: Chemical reactions often involve the absorption or release of energy. For example, a chemical reaction might produce heat or a change in temperature.
In contrast, physical changes, such as changes in shape or states of matter, can typically be reversed, and they do not involve the formation of new substances. Physical changes may include melting, freezing, vaporization, condensation, dissolving, etc.
It is important to note that sometimes it can be challenging to distinguish between physical and chemical changes, as some changes may exhibit characteristics of both. However, the key indicators mentioned above can help in making the determination.