ELEMENTS, COMPOUNDS

AND MIXTURES

Food Chemistry

OBJECTIVES Distinguish between pure substances and

mixtures. Compare homogeneous and heterogeneous

mixtures. Define solutions. Distinguish between a solute and solvent. Recognize water as a universal solvent. Understand the processes of solubility and

saturation.

OVERVIEWMatter Anything that has mass and takes up space.

Physical Properties A characteristic that can be observed or

measured without changing the substance Solid Liquid Gas

Chemical Properties The ability of a substance to react with other

substances

PHYSICAL PROPERTIES

CLASSIFICATIONS OF MATTER

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PURE SUBSTANCES Made of only one kind of material and

has definite properties

Elements Sodium, Carbon, Iron

Compounds Table salt, water, sugar

MIXTURES A combination of two or more

substances in which each substance keeps at least some of its original properties.

Physically blended, not chemically.

Homogeneous Mixtures

Heterogeneous Mixtures

Solutions Colloids

HOMOGENEOUS MIXTURES The same in every part of a given

sample.Examples: salt water, milk, air, cola

Another name for a homogeneous mixture:

Solution – one substance is dissolved in another

Solution

Solute Solvent

SOLUTE VS. SOLVENT

SOLUTE SOLVENT

The substance that is dissolved Sugar Salt

The substance that dissolves another substance Water

Water is recognized as a universal solvent.

This can be a problem with vitamins and minerals dissolving in cooking water.

HETEROGENEOUS MIXTURES Individual substances are dissimilar and

can be recognized by sight.This is also known as “Immiscible”Examples: salad, potato soup, Italian

dressing

SATURATED VS. UNSATURATED SOLUTIONSUnsaturated Solution: A solution that contains less solute than

can be dissolved in it at a given temperature.

Saturated Solution: A solution that contains all the solute

that can be dissolved at a given temperature.

SOLUBILITY The maximum amount of solute that can

dissolve in a given quantity of solvent at a specific temperature.

The solubility of most solids dissolved in a liquid increases as the temperature increases.

Example: Sugar dissolves faster in boiling water.

The solubility of gas decreases as the temperature increases.

Example: A warm can of soda will go flat faster than a cold can of soda.

SOLUTE & PHASE CHANGES The amount of solute in a solution

affects the temperature at which the solution boils or freezes.

The more solute present in a solution, the higher the boiling point and the lower the freezing point.

Example: Ice cream is still soft in the freezer because of the sugar dissolved in the water.

IDENTIFY THE MIXTURESYour table now has 4 glasses. Add 4 different

solutions to the glasses and identify the type of mixture as homogeneous or heterogeneous.

Glass # 1 – Place 1 drop of food coloring in your glass of water and stir.

Glass # 2 – Add ¼ cup oil to the water.Glass # 3 – Add ¼ cup vinegar the water.Glass # 4 – Add ¼ cup vinegar to the oil.

SOLUBILITY LAB Make Iced Tea using both cold and hot

water. Compare the flavors and answer the

questions to review the scientific theme of the week.