DIGESTION

PHYSICAL CHANGES vs. CHEMICAL CHANGES

What is the Goal of Digestion? The goal of digestion is to break down food through physical and chemical changes into forms that the body's cells can use.  Digestion can be intracellular (it takes place INSIDE the vacuoles of cells) or extracellular (it takes place OUTSIDE the cells).

What is a Physical (Mechanical) Change? A physical change occurs when an objects physical properties (size, shape, weight, color, density etc) are changed without changing the chemical make up of the object.  In the case of digestion, a physical change occurs when food is broken down into smaller pieces by chewing, tearing, grinding, or moistening. Physical changes are REVERSIBLE!

                Examples of Physical Changes:

                        1) Chewing food

                        2) Freezing or Boiling Water

                        3) Cutting a piece of paper into strips

What is a Chemical Change? A chemical change occurs when a substance is changed or converted to another substance.  A chemical change is IRREVERSIBLE!

                Examples of Chemical Changes:

                        1) Carbohydrates being broken down into simple sugars (glucose)

                        2) Burning Leaves

                        3) A car rusting

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