Unit 2 Part 3: Ph and Water

Boiling point

The temperature at which the liquid's vapor pressure equals the air pressure above the liquid (basically when liquid turns to gas)

Heat of Fusion

The amount of heat needed to change 1.0 g of a substance from a solid to liquid phase. When the situation is reversed, and the liquid phase becomes a solid, the heat is released.

Latent Heat

The heat is required to create a phase change without a change in temperature.

Heat of Vaporization

The amount of heat needed to change 1.0 g of a substance from the liquid phase to the gas phase

Acidic

pH of less than 7 is...

Neutral

pH of 7 is...

Basic

pH of greater than 7 (to 14) is...

Sublimation

The change from the solid phase directly to the gas phase (bypasses the liquid stage)

Solvent

The substance in which the solute dissolves

Free Water

Water that readily separates from foods that are sliced, diced, or dried

Freezing Point

The temperature at which a liquid changes into a solid

Melting Point

The temperature at which a substance changes from solid to liquid

Polar Compound

A molecule that has a clear division of opposite electrical charges. One side has (a) negative charge(s) and the other side (a) positive charge(s).

Hydrogen Bond

An attractive force between any molecules in which hydrogen is covalently bound to a highly electronegative element

Molarity

The number of moles of solute per liter of solution

Vaporization

Can only occur when molecules gain enough energy to exert a force equal to the force of the air pressure over the liquid

Surface tension

An inward or pull that tends to minimize the surface area of liquid

Solute

A substance that is dissolved in a solution.

Bound water

Water that cannot be easily separated in food, it freezes at very low temperatures and doesn't evaporate

A physical change is an alteration of a substance that does not change it's chemical composition. Alters phase changes, shape changes, or size changes. A chemical change is the change of substances into other substances.

Compare and contrast chemical and physical changes.

Physical changes are not reversible. Not all chemical changes can be reversed.

Are physical change reversible? Are chemical changes reversible?

Since 50-65% of your body weight is water it helps maintain a constant temperature and redistributes heat. (They barely had anything on the PowerPoint about this)

How does water help regulate your body? (3 main points)

Extra hydrogen bonds between molecules are formed when water freezes which increases the space between molecules, causing a decrease in overall density.

What about water molecules help explain why ice is less dense than water? (2 main points)

A hydrogen ion is a positively charged molecule (written as H+)

What is the charge of a hydrogen ion?

A hydroxide ion is a negatively charger molecule (written as OH-)

What is the charge of a hydroxide ion?

hydroxide ion (OH-)

Out of the hydrogen and the hydroxide ions, which of the two ions would a base solution produce?

Number of moles of solute/volume of solution in liters = molarity

What is the formula for calculating molarity?

As ice melts, it absorbs heat energy without a rise in temperature. Instead, water molecules use energy to break out of the solid ice structure. That's why we put foods on ice instead of cold water.

Why do we store foods on ice to keep them cold? (2 main points)

When water (steam) condenses back into a liquid, heat is released. When steam contacts your skin it condenses because your body temp is well below the boiling point of water (you know when you put your hand in steam and it gets wet). As the water cools on your skin, you absorb more heat which intensifies the burn.

Why does steam burn your skin? (3 main points)

Water is a medium for heat to flow through. When cooking heat is transferred from the bottom of the pan to the water. Then the water transfers the heat to the food. This allows the food to not get burned.

Why is water necessary for cooking? What would happen without it? (3 main points)

Ionization is the process of forming ions in water. When water ionizes both hydrogen and hydroxide molecules are produced. It happens because hydrogen loses its election (positive charge) and hydroxide gains that election (negative charge).

What is ionization? What molecules are involved? How does it happen? (4 main points)

When equal numbers of hydrogen and hydroxide ions are present to react with each other, neutralization occurs and the acidic and and basic properties of the solutions disappear.

What happens in a neutralization reaction with a strong acid and a strong base? (2 main points)

sour taste, can change color of some foods, turns blue litmus paper red

What are 3 properties of acids?

bitter taste, feels slippery, turns red litmus paper blue

What are 3 properties of bases?

Concentration

The measure of the amount of substance in a given unit of volume (is expressed through moles of a material dissolved in it)

Titration

A common method used in a laboratory to determine the concentration of an acid or a base

Freezing and Melting, Boiling and Condensing, Sublimation, Surface Tension

What are the 4 properties of water?

its polarity

What allows water to have many of its unique properties?