Water activity in food preservation
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Water Activity in Food Preservation. -solutions -ions -properties of water. Salts are IONIC COMPOUNDS. -Ions form between metals and nonmetals. -All atoms will react until the atoms have 8 electrons in their valence (outer) shells.

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Water Activity in Food Preservation

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Water activity in food preservation

Water Activity in Food Preservation

-solutions

-ions

-properties of water


Salts are ionic compounds

Salts are IONIC COMPOUNDS

-Ions form between metals and nonmetals.

-All atoms will react until the atoms have 8 electrons in their valence (outer) shells.

-Watch the animation of sodium reacting with chlorine to form table salt, sodium chloride (NaCl):

http://www.visionlearning.com/library/module_viewer.php?mid=55

-Other examples of ionic bonding:

http://www.teachmetuition.co.uk/Chemistry/Chemicalstructureandbonding/ionic_bonding.htm


Properties of water

Properties of Water

http://www.northland.cc.mn.us/biology/Biology1111/animations/hydrogenbonds.html

Water molecule


Water as a solvent

Water as a Solvent

http://www.northland.cc.mn.us/biology/Biology1111/animations/dissolve.html

Dissolving animation

Water Activity (Aw) and Free Water in

Food Preservation

http://physioweb.med.uvm.edu/bodyfluids/osmosis.htm

Water activity osmosis (follow links to sample problems)

http://www.stolaf.edu/people/giannini/flashanimat/transport/osmosis.swf

Salt and free water


Review questions

REVIEW QUESTIONS

  • What holds ionic compounds together (example: salts?)

  • Water is a molecule with polar covalent bonds. What does polar mean?

  • Why is water such a good solvent for salts?

  • What does Aw stand for?

  • How can the water activity be decreased?

  • Water moves or diffuses from an area of high water activity to an area of low water activity.

    -At the beginning of the meat experiment, where was the water activity the highest: inside of the meat or outside in the bag?

    -Would water move from inside meat to outside bag, or from bag into meat? WHY?????


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