Chapter 2.2 Water and mixtures Flashcards
Two important aspects of water’s structure
- It’s Atoms are joined polar covalent bonds
- The molecule is V-shaped with a 105° bond angle
This makes the whole molecule polar, because there’s a slight negative charge on the oxygen at the apex of the V and a slight positive charge on each hydrogen. So water molecules are attracted to one another by hydrogen bonds
Waters properties that account for its ability to support life are:
Solvency, cohesion, adhesion, chemical reactivity, thermal stability
Solvency
The ability to dissolve other chemicals. Water is the universal solvent
Adhesion
The tendency of one substance to cling to another
Cohesion
The tendency of molecules of the same substance to cling to each other
Chemical reactivity of water
Its ability to participate in chemical reactions.
Water ionizes acids and salts, and also Ionizes its self into H+ and H-
Thermal stability of water
Helps to stabilize the internal temperature of the body.
Hydrogen bonds of water molecules inhibit their movement so water can absorb a given amount of heat without changing temperature
High heat capacity of water
The amount of heat required to raise the temperature of one gram of a substance by 1°C
Calorie
1 cal is the amount of heat that raises the temperature of 1 g of water 1°C
What is the difference between a mixture and a compound?
Compounds are formed by chemically combining two or more elements. Mixtures are formed by physically mixing two or more substances
Kinds of mixtures
Solutions, colloids, and suspensions
Solution
Particles of matter called the solute mixed with a more abundant substance usually water call the solvent. The solute can be gas (O), solid(NaCl), or liquid (Alcohol)
Ex: copper sulfate
Solution properties
- Can’t see particles (under 1nm)
- Transparent
- Solute can pass through most selectively permeable membranes
- Doesn’t separate when allowed to stand
Colloids
Mixtures of protein and water
Can change from liquid to gel states
Ex: milk, gelatin, agar culture media, Fluids within and between ourselves

Physical properties of colloids
- 1-100 nm in size
- Usually cloudy because the particles scatter light
- Particles too large to pass through most selectively permeable membranes
- Remains permanently mixed when mixture stands
Suspension Properties
- Greater than 100 nm in size
- Cloudy or opaque
- Do not penetrate selectively permeable membranes
- Suspension separate on standing
Ex: blood cells in blood plasma
Emulation
Suspension of one liquid in another
Ex: oil and vinegar salad dressing, The fat in breastmilk.
Hydrophilic
Dissolves in water
Hydrophobic
Does not dissolve in water.
Ex: fats
Amphipathic
Has both hydrophobic and hydrophilic groups on the same molecule
Concentration
Amount of solute present in volume of solution
Mole
Amount of substance: molecular weight and Avogrado’s number.
grams—>mole
Molarity
Number of solute molecules in a solution.
g/L
An acid does what in water?
Give up hydrogen ions: so
>H+= >acidic
A base does what in water?
Accepts protons:
basic/alkaline
>OH- = >basic
Normal blood pH is:
7.35-7.45
Buffers are what
Chemical substances that resist change to pH EX: strong acid, strong base
Physiological importance of pH
Slight disturbance can disrupt drug actions and physiological functions: can cause proteins to unfold which causes problems
PH scale
-1-14
-7: neutral (pure water)
-Lower than seven: more H+ less OH-: acidic
-Higher than seven: less H+ more OH-: basic
What does it mean that the pH scale is logarithmic?
There is a tenfold change between pH numbers
