what are the characteristics of a physical change?
The substance may change state but it does not change composition.
To determine the characteristics of a physical change, you need to observe how substances behave during the change. Here are the key characteristics:
1. Change in state: During a physical change, a substance may change its state from solid to liquid, liquid to gas, or vice versa. For example, when ice melts to form water or when water evaporates to form water vapor, it is a physical change.
2. No change in composition: In a physical change, the substance's molecules remain the same, and there is no change in the chemical composition. The atoms or molecules simply rearrange to form a different structure. An example of this is when you dissolve salt in water - the salt particles disperse into the water molecules, but the composition of salt remains the same.
3. Reversible: Physical changes can be reversed by applying certain conditions, such as changing temperature or pressure. For instance, freezing water can turn it back into ice, and condensing water vapor can convert it back to liquid water.
4. No energy transfer: Physical changes generally do not involve the transfer of energy to or from the system. Energy may be absorbed or released during the change, for example, in the form of heat, but it does not result in any chemical reactions.
By observing these characteristics, you can identify whether a change is physical or not. If the substance undergoes a change in state without any alteration in its composition and can be reversed by appropriate conditions, it is most likely a physical change.