In a chemical change, bonds are broken and new bonds are formed between different atoms. This breaking and forming of bonds takes place when particles of the original materials collide with one another. An example of a chemical change is Photosynthesis - a process in which carbon dioxide and water are changed into sugars by plants. This is a chemical change because two different chemicals taken into the plant when combined with the sun give off the chemicals in a different form.
A physical change is a change in which original substances remain unchanged and no new substances are produced. An example of a physical change is pulling copper into a thin wire - a change of shape, but not a change of composition. No new substances are produced; the only thing that changes is the shape. The type of evidence that you could be looking for in a physical change is physical properties of the element being tested or changing.
The type of evidence you could be looking for in a chemical change the chemical bonds or chemical reaction to different elements have changed or have varied in different ways. When you are stuck in a scenario and you do not know whether a physical or chemical change is being taken place, a resource you can use is refer back to what you know about physical and chemical changes, you could see if heat/light is being absorbed or released or if a solid substance appears. The solution of sodium polyacrylate and water looks like pectin, and it could not be clear whether it is a chemical or physical change. This change would be a physical change because the reaction could be reversed and chemical changes cannot be reversed.
This is a physical change because it is a phase change.
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