Matter
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Matter
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A 2.01 -- Matter
A pure substance or a mixture
Composed of one or more elements that are
displayed on the periodic table
The periodic table; a tabular way to display
all known chemical elements
To provide a framework to classify and
compare chemical elements
Food is matter
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A 2.01 -- Matter
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Physical properties
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Physical Changes
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Food is matter-A pure substance
or mixture
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Thermodynamics -- effect of change in
temperature, pressure, and volume (canning)
Heat transfer -- the passage of thermal energy
from a hot to a cold body (cooking and cooling)
Microwave -- passing microwave radiation
through food and water, fat, and sugar so they
absorb energy (cooking)
Texture
Appearance
A 2.01 -- Matter
Physical changes to matter
Why study physical changes?
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Physical changes are crucial in:
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Product development
Process design
Shelf life
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Physical changes to matter involve:
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Changing shape/size – crushing ice
Changing temperature – boiling ice
Changing phase – melting ice
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Changing its Shape or Size
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Changing the Temperature
Change the temperature
of matter without
changing its chemical
identity – heating and
cooling.
Chopping
Slicing
Mashing
Grinding
Examples include
pasteurization and rapid
cooling.
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Changing Phase:
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 Phase is a physical
change in state of
matter that does not
change the molecular
structure.
 The three states of
matter – solid, liquid,
and gas.
Solid -- ice
Liquid -- water
Gas – steam
Physical change in the state of matter
that does not change the molecular
structure.
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Changing Its Phase
Three states of matter are:
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What Is Energy?
Energy and Heat Transfer
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Types of energy
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Mechanical
Chemical
Electrical
Radiant
Nuclear
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Mechanical Energy
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Chemical Energy
What makes a
machine to perform
work.
Examples include:
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Hand mixers
Water wheel
Flour mill
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Examples include:
Energy transmitted
in the form of waves
through space or
some medium.
Examples:
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Electrical home appliances – stove,
refrigerator, dishwasher
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Nuclear Energy
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Microwave oven
Sun
Charcoal grills
Gas flames
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What Is Heat?
Splitting or combining
atoms of certain
elements which give off
radiation.
Examples:
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Radiant Energy
Movement of electrons
Transported through wires
to where needed.
Easily changed to heat or
mechanical energy.
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Using ice and salt to
make ice cream.
Digestion of foods.
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Electrical Energy
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As bonds break or
form between
atoms, chemical
energy is generated.
Examples include:
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Definition – An energy transfer from
one body to another caused by a
temperature difference between the
two bodies.
X-rays in medicine
Nuclear power
Irradiation – food
preservation
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Conduction
Three Ways Heat is Transferred
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Conduction
Convection
Radiation
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Heat (or energy) is
transferred by
molecular collisions.
Example:
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Convection
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Heat (energy) is
transferred through
molecular collisions and
and currents.
Heat (energy) is more
rapid than conduction.
Example:
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Heat (energy) is
transferred by
light waves
through space.
Examples:
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Food cooked in boiling water.
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Radiation
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Cooking foods in an
oven.
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Sunlight
Microwave
Acids and Bases
(Acidity and Alkalinity)
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Acidity
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Have more hydrogen ions
(H+)
Make foods acid
Examples include:
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Bases /Alkalinity
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Lemon juice
Vinegar
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Other characteristics of
acidic foods:
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Have more hydroxide ions
(OH)
Makes foods more alkaline
Examples include:
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Sour taste
Sting when touched
React strongly when
combined with metals
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BASES
 Taste bitter
 Turn blue when teted
 pH between 7.1 and 14
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pH is a measure of acidity or alkalinity of food.
Changes in pH effect quality.
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Color
Texture
Stability
Changes in pH effect safety
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Effects of pH on food
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Bitter taste
Feel slippery to touch
Do not react when combined
with metals
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Acids and Bases identified by:
ACIDS
 Taste sour
 Turn red when
tested
 pH between 0 and
6.9
Other characteristics of a
alkaline:
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A 2.01 -- Matter
Soap
Egg whites
Foods are generally acidic (pH less than 7.0)
Low acid foods have a pH between 4.6 and 7.0 (potentially
hazardous food)
High acid foods have a pH of 4.6 or less. (non-potentially
hazardous food)
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pH Measurement
Methods for Reliable and
Accurate Measures of pH
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Measurement Method–
Litmus Paper
Definition of pH
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1. Used by dipping litmus
paper into solution
2. Turns yellow to red in
acidic solution (acid)
3. Turns green or blue in
alkaline solution (base)
4. Easy method
5. Not completely accurate
A way to measure acids (acidic) and
bases (alkalinity) in food.
Expression of the concentration of
hydrogen (H+) and hydroxide ions
(OH-) in an aqueous solution (waterbased).
Uses a scale between 0 and 14
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Measurement Method –
Indicator Strips
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Measurement Method –
Indicator Dye
Dip the strip into the
aqueous (liquid) food being
tested for a few seconds.
Remove strip from test
solution and compare color
segments to center color
printed on the strip.
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1. Add base with know
pH to an acid.
2. Use burette.
3. More difficult to
calculate.
4. Use if have
chemistry
knowledge.
Digital reading
Accurate
Some units are
expensive
Easy and sanitary
A 2.01 -- Matter
Organic dyes
Done with dropper
Acidic (acid) -- pink or red
Alkaline (base) -- green or blue
Neutral solution may turn lilac
Not totally accurate
Measure Method – Titratable
Acidity
Measurement Method – pH
Meter
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Chemical Properties Of Food
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Chemical Properties
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Chemical Changes
pH – measure of acidity and alkalinity
Total solids -- total content of suspended
and dissolved solids in water
Ash -- mineral content of the food
Titratable acidity -- approximation of a
solution's total acidity
Total sugars – approximation of all
carbohydrates
Total fatty acids
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Occurs whenever new substances with
different chemical and physical properties are
formed.
Chemical changes result in:
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Changes in color – enzymatic browning,
carmelization of sugar
Changes in odor – cooked cabbage smell
Flavor changes – cooked onions, fermented
foods.
Release of gas – mixing baking soda and
vinegar, alcoholic beverages
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