Introduction to Water

Question 1

What are some uses of water?

Answer 1

1) Grow
2) Wash
3) process
4) dissolve
5) transport
6) digest
7) react

Question 2

What are the two standard states chemistry and physics typically revolve around ?

Answer 2

Pure compounds and controlled reactions

Question 3

What are colloids?

Answer 3

a mixture where tiny particles of one substance are dispersed throughout another, creating a complex system that contributes significantly to the texture, stability, and appearance of many food products
(ex. Milk, cream, egg yolk)

Question 4

What solvent is used most often?

Answer 4

Water

Question 5

What is a water molecule composed of ?

Answer 5

A polar covalently bonded compound containing 2 hydrogen atoms bonded to oxygen by single covalent bonds

Question 6

Sucrose + water =

Answer 6

Molecular state

Question 7

Salt + water =

Answer 7

Ionic state

Question 8

How is the solid structure of water characterized ?

Answer 8

1) Crystalline in nature

2) Even spacing

3) Repeating patterns

Question 9

What are the 3 properties of water?

Answer 9

1) High melting and boiling point

2) High specific heat

3) High latent heat of fusion and vaporization

Question 10

What is specific heat?

Answer 10

Heat required to change 1g by 1 degree Celsius

Question 11

What is latent heat of fusion and vaporization?

Answer 11

The # of calories to convert 1g of ice at 1degree Celsius into liquid at the same temperature or 1g of liquid to vapor at the boiling point

Question 12

What is a calorie?

Answer 12

A unit of heat, measured using a bomb calorimeter

Question 13

What are the 3 forms of water?

Answer 13

1) solid

2) liquid

3) gas

Question 14

True or false? Very dry foods still contain wate

Answer 14

True. (Beans, sugar, salt)

Question 15

Scientific Utilizations of water

Answer 15

1) Enzymatic reactions

2) Digestion

3) microbial growth

Question 16

What are some characteristics of oxygen?

Answer 16

1) very electronegative

2) electrical asymmetry

3) no overall net change

Question 17

Explain the difference between polar and non- polar

Answer 17

Non-polar has less attraction, is electronically equal, has a equal number of positive and negative chargers, and has equally shared electron pairs while polar has an uneven distribution of charges

Question 18

Dipole-ion interactions use:

Answer 18

• solutes
• proteins

Question 19

Dipole-dipole interactions use:

Answer 19

• proteins
• carbohydrates

Question 20

What is the triple point on a phase diagram for water?

Answer 20

The specific temperature and pressure at which all three phases of water (solid, liquid, gas) can coexist in equilibrium

Question 21

Why is the phase transition of water important to know?

Answer 21

the state of water (solid, liquid, gas) significantly influences the physical properties of food during storage, preparation, and consumption; essentially, knowing how water changes phases allows food scientists to optimize food processing techniques and predict how a food product will behave under different temperature conditions

Question 22

Sublimation =

Answer 22

In a vacuum, water (ice) molecules “melt” but change into vapor instead of liquid

Question 23

Density =

Answer 23

Mass per unit volume

Question 24

Who discovered displacement of water by weight?

Answer 24

Archimedes

Question 25

What are three considerations of water?

Answer 25

1) thermally dense water is a poor conductor

2) heat capacity and dielectric constant for water is high

3) promotes interactions, solubility, and change

Question 26

Molar system-

Answer 26

The gram molecular weight of solute (1 mole) in a liter of solution

Question 27

Molal system-

Answer 27

The gram molecular weight of solute in 1kg of solvent

Question 28

Percent by weight-

Answer 28

The grams of solute present in 100g of solution

Question 29

Percent by volume-

Answer 29

The grams of solute in 100ml of solution

Question 30

According to bronsted-Lowry, acid =, base =

Answer 30

Acid = proton donor

Base = proton acceptor

Question 31

Why is titration used?

Answer 31

Easy way to find the endpoint of a reaction

Question 32

How is titration performed?

Answer 32

In titration, a burette is used to deliver a precise amount of an acid or base of KNOWN concentration to a KNOWN volume of a solution with an UNKNOWN concentration

Question 33

What is normality?

Answer 33

How many hydrogen are available for a reaction to take place

Question 34

What happens to vapor pressure when solute is added?

Answer 34

The vapor pressure diagram for solutions shows that vapor pressure is lowered when a solute is added

Question 35

What happens to vapor pressure when solute is added?

Answer 35

The vapor pressure diagram for solutions shows that vapor pressure is lowered when a solute is added

Question 36

What is Raoult’s law?

Answer 36

Psoln = Xsolvent P^o solvent

Question 37

What is the equation for water activity?

Answer 37

Vapor pressure of water in food (partial pressure) / vapor pressure of pure water

Question 38

Hydration -

Answer 38

Combined with water to form a hydrate with the water molecule retained in its molecular states

Question 39

Dehydration -

Answer 39

A process of removing water from a substance or compound

Question 40

Solvent properties -

Answer 40

Capable of dissolving another substance without changing chemical form

Question 41

Solution -

Answer 41

Physically and homogeneous mixture in which the solute is either in an ionic or molecular state of subdivision

Question 42

Hydrolysis -

Answer 42

Decomposition of a chemical compound by reaction with water ; water does not maintain a chemical state such as with the hydrolysis of fats

Question 43

Osmosis -

Answer 43

If separated from pure water by semi-permeable membrane, water molecules will pass through the membrane to equalize the concentration

To stop osmosis, apply osmotic pressure

Two solutions with equal osmotic pressure - isotonic solutions