1. Physical and chemical change

2. Dissolving salt in water does not change the chemical composition of salt.
PHOTOSYNTHESIS IS A CHEMICAL CHANGE BECAUSE PLANTS USE LIGHT TO MAKE chemical ENERGY.
Freezing water is a physical change (There is no change in chemical composition).
B. New substances were formed.
B. law of conservation of mass.

3. Chemical change
A chemical change is a also called a chemical REACTION.
MATTER CHANGES INTO AN ENTIRELY NEW SUBSTANCE WITH POTENTIALLY DIFFERENT PROPERTIES .

4. Chemical change Fireworks are complex chemical changes.
Fire is a simpler chemical change.
another example of a chemical reaction is the rusting of a steel garbage can. That rusting happens because the iron (Fe) in the metal combines with oxygen (O2) in the atmosphere. Chemical bonds are created and destroyed to finally make iron oxide (Fe2O3). 

5. Physical changes
Physical changes involve states of matter and energy. No new substance is created during a physical change, although the matter takes a different form. The size, shape, and color of matter may change. Also, physical changes occur when substances are mixed, but don't chemically react.

6. One way to identify a physical change is that such a changes may be reversible, especially phase changes. For example, if you freeze an ice cube, you can melt it into water again.

7. Ask yourself:
Is the change reversible? (note not all physical changes are easy to reverse)
Was there a color change (with exceptions), bubble formation, or formation of a precipitate? (all signs of a chemical change, not a physical change)
Is the chemical identity of the end product the same as it was before the change? If the answer is yes, it's a physical change. If the answer is no, it's a chemical change.

8. Can you think of 5 examples of chemical change?

9. rusting of iron
combustion (burning) of wood
metabolism of food in the body
mixing an acid and a base, such as hydrochloric acid (HCl) and sodium hydroxide (NaOH)
cooking an egg
digesting sugar with the amylase in saliva
mixing baking soda and vinegar to produce carbon dioxide gas
baking a cake
electroplating a metal
using a chemical battery
explosion of fireworks
rotting bananas
grilling a hamburger
milk going sour

10. Can you think of 5 examples of physical changes?

11. crushing a can
melting an ice cube
boiling water
mixing sand and water
breaking a glass
dissolving sugar and water
shredding paper
chopping wood
mixing red and green marbles
sublimating dry ice

12. summary
Chemical changes involve chemical reactions and the creation of new products. Typically, a chemical change is irreversible. In contrast, physical changes do not form new products and are reversible.
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