Chemical Bonds
Chemical Bonds - The force that holds two
atoms together.
The subatomic particle that forms the bond is the
electron.
Whether two elements will combine, and in what
ratio, depends on their electrons.
Two types of chemical bonds
Chemical Bonds Cont.
Electrons move in orbitals about the nucleus of
atoms in predictable patterns of space
Shells – An area of space surrounding the nucleus
that has one or more orbitals.
Atoms can have up to 7 shells
The number of shells in the atoms of a element
determines the element’s period, or row in the
periodic table.
Shells
Chemical Bonds Cont.
Ionic Bonds - The electrons are transferred
from one atom to another
Causes both atoms to have a charge.
Atom that receiving an electron are negatively charged.
Atoms that loose an electron become positively
charged.
Ionic bonds are results of the attraction between
positive and negative charges.
Chemical Bonds Cont.
Ion – an atom or group of atoms that has a positive or
negative charge.
Like charges repel each other
Opposite charges attract
Substances with ionic bonds will tend to dissolve in water.
One end of the water molecule is slightly positive, whereas the
other end is slightly negative.
Chemical Bonds Cont.
Covalent Bonds- are formed when atoms
share one or more pairs of electrons.
Example: Water molecules are formed by covalent
bonds between 2 hydrogen atoms and 1 oxygen
atom.
Double Bond – More than one pair of electrons
can be shared when two atoms share two pairs
of electrons.
Organic vs. Inorganic
Compounds
o Scientist group compounds in two main categories,
Organic VS Inorganic
o Organic Compounds contain chains or rings
of carbon.
• Most also contain hydrogen and oxygen
• All the sources of energy in your diet are organic
Compounds. (carbohydrates, fats, vitamins &
protein)
• All of these are the main components of your diet.
Organic vs. Inorganic
Compounds
Inorganic compounds either contain
no carbon or have only single carbon
atoms.
Examples of inorganic compounds in
your diet…
Table Salt, Water, minerals and potassium
chloride (no salt)
Classes of Organic
Compounds Important in Food
Mixtures
Mixtures - substances that are put together but
not chemically combined.
Ex: Calcium an element, Salt is a compound.
Both are pure substances. Milk contains both
calcium and salt.
Milk is a mixture of these two substances plus
many others.
Categorizing Mixtures
Two categories: Homogeneous and
Heterogeneous.
Homogeneous – has a uniform distribution
of particles throughout the sample.
Visually you can’t tell one from another.
Examples: Tea and soft drinks.
Categorizing Mixtures
Heterogeneous – has a non-uniform
distribution of particles.
Example: A bowl of vegetable soup. Because when
you look at the soup you see the corn, okra,
potatoes etc.
If you puree the soup in the blender it would then
be a homogeneous mixture.
Determining Mixtures
Sometime what you see isn’t what it seems when
classifying a mixture.
Example: Hot Cocoa looks homogeneous but when
it sits a while the heavier cocoa molecules will
settle to the bottom and the smaller ones will stay at
the top.
This makes it a heterogeneous mixture.
Understanding Mixtures
Most homogeneous mixture are solutions.
Solution – homogeneous mixture of one material
dissolved in another.
The material that dissolves is a called the Solute.
The material that doesn’t dissolve is the Solvent.
Ex: Sweetened drinks, water is the solvent & sugar
is the solute.
Understanding Mixtures
The substances in heterogeneous mixtures can be
separated by mechanical means
Ex: you can strain vegetable soup and then hand sort the vegetables.
Separating homogeneous heterogeneous is more
difficult but not impossible.
Ex: Salt water is a homogeneous mixture. You cannot separate the salt
from water by hand. You can heat saltwater and the water will turn to
steam and evaporate, Leaving salt crystals behind.
Resources
Ward, Janet. Principles of Food Science. Third
ed. Goodheart-WIllcox.