1. The Chemical Nature of Food
Unit 4 Notes
The Chemical Nature of Food

2. Key Terms
Matter Molecule Dispersed Phase Nucleus Mixture Tyndall Effect Proton Solution Colloid Neutron Ionic Bond Emulsion Electron Covalent Bond Foam Atomic Number Pure Substance Suspension Atomic Mass Organic Substance Distillation Compound Inorganic Substance Evaporation

3. Basic Nature of matter
Although atoms are the smallest unit of any element, they are not the smallest particles known. Each atom is composed of smaller parts called subatomic particles which include:
Protons: positively charged subatomic particles
Neutrons: subatomic particles with no charge
Electrons: negatively charged subatomic particles

4. Basic Nature of matter

5. Elements
An element is a substance that contains only one kind of atom. There are about 90 naturally occurring elements known on earth. All matter in the universe is composed of one or more of these elements. The number of electrons and neutrons can vary to create different forms of an element, but protons do not vary therefor an element can be determined by the number of protons.

6. Periodic Table
During the 19th century, researchers became aware of links between the physical and chemical characteristics of elements. The properties seemed to repeat in a regular fashion.
So in an effort to classify the elements a Russian chemist, named Dmitry Mendeleev, developed the Periodic Table!
Fun Fact: Mendeleev rejected the notion of subatomic particles, because he was afraid that they would disprove his life’s work!

7. Periodic Table

8. Periodic Table
How is the Periodic Table Organized? Groups: Elements share similar chemical properties Periods: Elements share the same energy level Metals vs Non-Metals: Elements are grouped by physical properties

9. Compounds vs molecules
A molecule is formed when two or more atoms are chemically combined. A compound is formed when two or more elements are chemically combined.

10. Chemical Bonding
A chemical bond is the force that holds two atoms together. These bonds are formed through the transfer or sharing of electrons.
There are two types of chemical bonds:
Ionic Bonds: Bond formed by the transfer of electrons
Covalent Bonds: Bond formed by the sharing of electrons

11. Chemical Bonding
Why do you think atoms bond?

12. Chemical Bonding
Ionic Bonds are created when an electron is transferred between atoms. A positive and negative charge is created from the transfer, called ions, and the two atoms are held together by attractive forces.

13. Chemical Bonding
Covalent Bonds are formed when atoms share one or more pairs of electrons. Covalent bonds are formed only between non-metals.

14. Physical & Chemical Changes
The Law of Conservation of Matter states that matter cannot be created or destroyed, but it can be changed.

15. Physical & Chemical Changes
A physical change involve changing the shape, physical state, size, or temperature without changing the chemical identity of a substance. Example: If you freeze water, crush ice, melt ice to water, or boil water into water vapor, then you are changing the shape, size, temperature and physical state, but you do not change the substance into something new. It is still H20!

16. Physical & Chemical Changes
A phase change is a physical change in the visible structure of matter without changing the molecular or unit structure.

17. Physical & Chemical Changes
A chemical change occurs whenever new substances with different chemical and physical properties are formed.
Chemical changes can produce…
Color changes
Flavor changes
Emission of a gas
Energy Changes

18. States of Matter
Matter can be classified into two general categories, each with a few subcategories:
Pure substance
Organic & Inorganic Compounds
Elements
Mixtures
Homogeneous Mixtures
Heterogeneous Mixtures
Inorganic
Organic

19. States of Matter
A pure substance is matter in which all the basic units are the same.
A pure substance can be categorized as a….
Element: a substance that only contains one kind of atom
Compound: two or more elements chemically bonded
Organic Compound: contains rings of carbon
Inorganic Compound: contains no carbon or only a single carbon atom

20. States of Matter
A mixture is a substance that consist of two or more substances that are not chemically bonded. A mixture can be categorized as a ... Homogeneous Mixture: uniformed distribution of particles Heterogeneous Mixture: non-uniformed distribution of particles

21. Mixtures
A solution is a homogeneous mixture of two or more substances. Solutions are composed of two parts: Solute: the dispersed phase or substances that breaks up and dissolves Solvent: the continuous phase or substances that stays together Example: Think of sweet tea! The sugar is dispersed into the tea, therefore the sugar is the solute and the tea is the solvent.

22. Mixtures
A Colloidal Dispersion is a mixture where microscopic particles of one substance are evenly distributed in another substance. The nature of the particles is what gives the colloidal dispersion their unique characteristics. Colloids are a common type of solution. When the dispersed particles are large enough, they can scatter visible light and create the tyndall effect.

23. Mixtures Colloids remain dispersed due to two factors:
The lower mass of the smaller molecules of the continuous phase allow them to move faster than the molecules of the dispersed phase. This will increase collisions between molecules which keeps the dispersed molecules dispersed.
Colloids are usually molecules of the same substance, therefore they all have the same electrical charge. The like charges will repel each other and create space between the molecules when in a continuous phase.

24. Mixtures
An emulsion is a mixture of two immiscible liquids, where one is dispersed in droplet form in the other. Immiscible liquids are liquids that will separate when combined. Example: Oil and Water Why don’t they mix?

25. Mixtures Types of emulsions: Water-In-Oil Oil-In-Water
Examples: Butter and margarine
Oil-In-Water
Examples: Mayonnaise, salad dressing, ice cream, cake batters

26. Mixtures Factors that affect the stability of an emulsion:
Temperature: Because fats and water have different thermal conductivity levels.
Electrical Charges: because water based liquids are electrically attracted to the polar end of the emulsifier.
Example: Ice-cream is stable when cold, but separates when warm.

27. Mixtures
A foam is a colloidal dispersion of gas or air bubbles that are dispersed in a liquid.
Examples:
Root Beer Fizz
Whipped Cream
Meringue
Which are stable?

28. Mixtures Four necessary conditions for a foam:
1. Liquid needs to be viscous enough to hold air.
2. Dispersion needs to contain a stabilizer that will stretch to form thin film around air bubbles.
3. Surface tension of the film should be less than that of the water. (This keeps air from being squeezed out of the bubble)
4. Liquid with a low vapor pressure.

29. Mixtures
Factors affecting the stability of a foam: 1. Temperature: because normally the viscosity of liquids tend to decrease as the temperature rises. 2. Acidity: because when there is a drop in the acidity there is a disruption in the ability of the casein in cream to form.

30. Mixtures
A suspension is a mixture of undissolved particles in a liquid. This is the most unstable form of a mixture due to its particle size. The mass of the particles cause them to either sink to the bottom of the mixture if they have a higher density, or float to the top of the mixture if they have a lesser density.

31. Mixtures
Aren't solutions, colloids and suspensions the same? No, the difference is in there particle size. Solutions have small solute particles that actually break up and dissolve. Colloids have medium sized particles the do not break up, but remain dispersed. Suspensions have larger particle sizes and tend to separate quickly due to particle density.

32. Separation Techniques
Many processes in the food industry involve sorting and separating food. Some types of separation processes are simple as spotting fruit by size and others are more involved, such as the process of isolating gluten from wheat.
There are two basic methods of separation:
Mechanical
Chemical

33. Separation Techniques
Mechanical Separation does not rely on chemical changes to separate substances. Types of mechanical separation are: 1. Separation by physical properties - Color - Size 2. Separation by density - Cranberries 3. Separation by force - Centrifuge - Pressure - Magnetic

34. Separation Techniques
Chemical Separation requires a grasp of the physical and chemical properties of foods. Chemical separation methods include the use of:
Solvents
Crystallization
Precipitation
Evaporation
Distillation

35. Separation Techniques
What is a natural separation process that we do every day?

36. Separation Techniques
Digestion is the process of breaking food into substances that that are usable by the body cells.