UNIT 4.1 INTRODUCTION FOR REACTIONS
Chemistry is the study of matter and interactions. Chemistry overlaps with many other sciences.
Below is the contents for this sub unit.
INTRODUCTION FOR REACTIONS
Physical change is not a reaction. Physical change can be when a substance changes states from solid, liquid, or gas but is still the same molecule. Water as ice, liquid water, or steam are all H2O and are not a reaction when they change state.
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Separation techniques are designed to separate a substance without changing it and therefore are physical changes (think about distillation).
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Chemical changes occur when substances change into a new substance. This is a new chemical composition. A reaction can be identified by a change in the following:
change in heat
emission of light
formation of gas
formation of precipitate (solid)
color change