Which observation most likely indicates that only a chemical change has taken place?(1 point)ResponsesThe change cannot be reversed.The change cannot be reversed.The shape changes.The shape changes.A reaction occurs.A reaction occurs.States of matter changes.
A reaction occurs.
Which changes shown in the table are physical changes?
(1 point)
Responses
2 and 4
2 and 4
1 and 4
1 and 4
1 and 2
1 and 2
2 and 3
2 and 4
Why is it a physical change to freeze water?(1 point)
Responses
A temperature change occurs.
A temperature change occurs.
Heat is released during the process.
Heat is released during the process.
Only a phase change occurs.
Only a phase change occurs.
The new and original substances are different.
The new and original substances are different.
Only a phase change occurs.
The observation "A reaction occurs" most likely indicates that only a chemical change has taken place.
The observation that most likely indicates that only a chemical change has taken place is when a reaction occurs.
To understand why, let's break down the options provided:
1. "The change cannot be reversed." - This statement does not specifically indicate a chemical change, as both physical and chemical changes can sometimes be irreversible.
2. "The shape changes." - Change in shape typically indicates a physical change, such as bending or molding, rather than a chemical change.
3. "A reaction occurs." - This observation is the most definitive indication of a chemical change. A chemical reaction involves the rearrangement of atoms and molecules to form new substances with different properties.
4. "States of matter change." - Changes in states of matter, such as the transformation from a solid to a liquid or a gas, can occur in both physical and chemical changes. So, while it may indicate a change is happening, it cannot definitively indicate that only a chemical change has occurred.
Therefore, option 3 - "A reaction occurs" - is the observation that best indicates that only a chemical change has taken place.