Introduction to Water Flashcards
What are some uses of water?
1) Grow
2) Wash
3) process
4) dissolve
5) transport
6) digest
7) react
What are the two standard states chemistry and physics typically revolve around ?
Pure compounds and controlled reactions
What are colloids?
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)
What solvent is used most often?
Water
What is a water molecule composed of ?
A polar covalently bonded compound containing 2 hydrogen atoms bonded to oxygen by single covalent bonds
Sucrose + water =
Molecular state
Salt + water =
Ionic state
How is the solid structure of water characterized ?
1) Crystalline in nature
2) Even spacing
3) Repeating patterns
What are the 3 properties of water?
1) High melting and boiling point
2) High specific heat
3) High latent heat of fusion and vaporization
What is specific heat?
Heat required to change 1g by 1 degree Celsius
What is latent heat of fusion and vaporization?
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
What is a calorie?
A unit of heat, measured using a bomb calorimeter
What are the 3 forms of water?
1) solid
2) liquid
3) gas
True or false? Very dry foods still contain wate
True. (Beans, sugar, salt)
Scientific Utilizations of water
1) Enzymatic reactions
2) Digestion
3) microbial growth
What are some characteristics of oxygen?
1) very electronegative
2) electrical asymmetry
3) no overall net change
Explain the difference between polar and non- polar
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
Dipole-ion interactions use:
- solutes
- proteins
Dipole-dipole interactions use:
- proteins
- carbohydrates
What is the triple point on a phase diagram for water?
The specific temperature and pressure at which all three phases of water (solid, liquid, gas) can coexist in equilibrium
Why is the phase transition of water important to know?
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
Sublimation =
In a vacuum, water (ice) molecules “melt” but change into vapor instead of liquid
Density =
Mass per unit volume
Who discovered displacement of water by weight?
Archimedes
What are three considerations of water?
1) thermally dense water is a poor conductor
2) heat capacity and dielectric constant for water is high
3) promotes interactions, solubility, and change
Molar system-
The gram molecular weight of solute (1 mole) in a liter of solution
Molal system-
The gram molecular weight of solute in 1kg of solvent
Percent by weight-
The grams of solute present in 100g of solution
Percent by volume-
The grams of solute in 100ml of solution
According to bronsted-Lowry, acid =, base =
Acid = proton donor
Base = proton acceptor
Why is titration used?
Easy way to find the endpoint of a reaction
How is titration performed?
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
What is normality?
How many hydrogen are available for a reaction to take place
What happens to vapor pressure when solute is added?
The vapor pressure diagram for solutions shows that vapor pressure is lowered when a solute is added
What happens to vapor pressure when solute is added?
The vapor pressure diagram for solutions shows that vapor pressure is lowered when a solute is added
What is Raoult’s law?
Psoln = Xsolvent P^o solvent
What is the equation for water activity?
Vapor pressure of water in food (partial pressure) / vapor pressure of pure water
Hydration -
Combined with water to form a hydrate with the water molecule retained in its molecular states
Dehydration -
A process of removing water from a substance or compound
Solvent properties -
Capable of dissolving another substance without changing chemical form
Solution -
Physically and homogeneous mixture in which the solute is either in an ionic or molecular state of subdivision
Hydrolysis -
Decomposition of a chemical compound by reaction with water ; water does not maintain a chemical state such as with the hydrolysis of fats
Osmosis -
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
