Physical and Chemical Change help understand?

First, I'm not trying to get an easy answer for my homework, I'm just trying to understand the concept. I get that a chemical change changes the makeup of the substance while a physical change can change color, odor, shape etc of a substance. I'm having trouble distinguishing the difference between the two. The examples I have been given are

1)a banana peel turning a dark color after being peeled (I'm saying it's chemical because it's eventually going to rot)

2) The development of a polaroid picture (physical? But it could never go back to an undeveloped picture)

3) making tea from a tea bag and hot water (chemical because your adding herbs?)

4) The souring of milk (physical because it's still milk but it's all lumpy and smells bad)

5) Bleaching of hair (Physical because it's still hair, just a different color)

2 Answers

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  • 1 decade ago
    Favorite Answer

    You can answer these questions easily once you've corrected your concepts of chemical change and physical change:

    Chemical change: yes, a change in makeup - the chemical contents - of a substance.

    Physical change: any other change not caused by the above. But odor and colour changes ARE chemical changes because they are caused by chemical reactions changing the chemicals and hence what you smell or how the light is reflected from the substance.

    I would suggest only one of the examples is a physical change. Can you identify it? Think about whether each process involves a chemical being turned into another chemical, and you have your answer.

  • ?
    Lv 4
    4 years ago

    A actual replace is a replace in length, structure, state or answer. you nonetheless have an similar cloth. A chemical replace produces a clean cloth. you could tell this because there'll be a colour replace, a precipitate or gasoline formed, a great deal of warm temperature given off. Salt dissolving is actual because you nonetheless have the salt and the water. similar in soup. Helium leaking out of a balloon and blending with the air is actual. the vehicle battery includes a chemical reaction of sulfuric acid and lead. it truly is a chemical replace. oftentimes warmth and hydrogen gasoline are given off by utilising batteries.

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