Amazing Milk - ANSWERS
Question/Problem:
Why do milk and food coloring react the way they do when there is soap present?
Background Information:
Milk is the most “perfect food”. Why? Think about what kinds of nutrients our bodies
need: ____water_________, _____vitamins_________, _____minerals_______, _____proteins_____,
____carbohydrates_____ and ____fats_________. Milk contains ___ALL______ of them!
Milk is ____87%______% water that holds
___dissolved__________ carbohydrates and proteins.
Milk also contains ____fats_________, but how is that
possible, since fats/oils and water don’t mix???
Milk is considered a Colloid, which is a
___suspension________ of droplets of one liquid in
another. In milk’s case, it is a mixture of two
immiscible (___’unmixable’_____) substances: droplets
of __fats_______ suspended in the water, (which is also
called milk ___serum________). Because it is two
immiscible substances suspended together, it’s a
special type of colloid called an
____EMULSION________________________
The fat droplets are ____small_________ enough to be suspended in the water so we don’t see
them separate from the milk. This type of solution, where particles are distributed evenly
throughout, is called a _____homogeneous_________ solution. Milk fat is a mixture of different
fatty acids, which make up about __90____% of milk fat. What makes different types of milk
different? ___the amount of fat__________________
Skim milk = <_0.5________%
Lowfat milk = ___0.5-2_______%
Whole milk = at least ___3.25_______%
Half & Half = __10.5-18_______%
Vitamins & Minerals? Milk has ___calcium______________, ____magnesium_______,
_____phosphate_________, ____potassium_______ and ______sodium__________. It contains
vitamins ____A____, ___B6_____, __B12_____, __C______, ___D___, ___E_____, ____K____ -- and many
more!
Proteins are dissolved in the milk serum (water) and have 2 main types:
__casein___________ and ___whey_________ proteins. The casein proteins are the
____solid__________ kind, and is what makes __cheese_________ when it is separated from the
whey proteins, which are found in the milk serum. Weak chemical bonds hold the proteins
in the solution.
Soap: How does it work?
Soap is an excellent cleanser because of its ability to act as an
emulsifying agent. An ___emulsifier_______ is capable of
_____dispersing______________ or distributing one liquid into another
immiscible liquid. (Immiscible means that they
_____aren’t meant to be ______ mixed together, like oil and water).
Nearly all compounds fall into one of two categories: Hydrophilic (_____waterloving____________) or hydrophobic (_________water-hating____________). Water and
anything that will mix with water are ____hydrophilic___________________. Oil and anything
that will mix with oil are ______hydrophobic__________. When water and oil are mixed they
______separate_______________, which is why hydrophilic and hydrophobic compounds just
____do___________ ______not_________ mix.
Water is a most amazing substance.
It is a ____POLAR ____molecule which means it has a definite
positive (+) and definite negative(-) end to it. This allows it to have a special quality which creates
something call __________surface tension__________. Water molecules produce
____attractive forces_ which cause the particles to pull themselves ___together___ and
___resist____ being pushed ____apart____. When the particles on the surface resist being
pushed apart they create surface tension which causes the liquid to act as if a thin film
were stretched across its surface. As a result of these attractive forces, belly flops in a
pool really hurt, rain drops are round, you can fit many drops of water on a penny and bugs
can walk on water!
Soap is a molecule that has ____2_______ different ends. One end (“the head”) has a
negatively-charged, __polar_________ molecule that is _____attracted________________ to water.
It is ______hydrophilic__________ (water-loving).
The other end of a soap molecule “the tail” is hydrophobic (water-
___fearing_________). Its long, nonpolar hydrocarbon chain ___does___________
______not______ interact with water molecules. The hydrophobic ends of soap are attracted
to each other and cluster together, forming structures called micelles. (see the picture
below)
Grease and oil are ____nonpolar____________ and insoluble (_do____ ____not____ dissolve) in
water. When grease or oil is mixed with a soap-water solution, the soap molecules work as
a bridge between __polar________ water molecules and non-polar oil molecules. This means
that while oil (which attracts dirt) doesn't naturally mix with water, soap can suspend
oil/dirt in such a way that it can be removed.
When soap and soiling oils are mixed, the nonpolar (hydrophobic-water __hating_________)
ends of the micelles break up the oil molecules. A different type of micelle then forms, with
the dirt or oil molecules _in_____ _____the_____ _____center_______. Thus, grease and oil and the
'dirt' attached to them are caught inside the micelle and can be rinsed away.
A soap micelle has a hydrophilic head that is in contact with the water and a
center of hydrophobic tails, which can be used to isolate grime
After the soap molecules surround the dirt and grime, water molecules can then come
through and simply rinse the dirt away!!!