Water & the Fitness of the Environment Name_________________________
Date
__________________________
Student Objectives:
1.
Explain the difference between hydrophobic and hydrophilic substances
2.
Define and calculate molarity
3.
Explain how the dissociation of water affects acid concentration and base concentration in solution
4.
Use the pH scale to indicate whether a substance is acidic or basic
5.
Describe what a buffer does
Notes:
A ________________________________ substance does not have an affinity for water.
A_________________________________ substance has an affinity for water.
Most biochemical reactions occur in water. Therefore, it is important to understand the calculation of concentration of solutes in an aqueous solution.
A mole represents an exact number of molecules of a substance
_______________________________.
M =
Molarity is the number of moles of solute per 1 liter of solution.
: What is the M (molarity) of an aqueous solution of 4 moles of solute in 8 liters of solvent?
: How many moles of solute are needed to prepare 3 liters of a 2 M solution?

Water & the Fitness of the Environment Name_________________________
Date
__________________________
Dissociation is the __________________________ of ions/ molecules that occurs when a compound dissolves.
Dissociation of ___________________ molecules leads to ______________ and _______________ conditions that affect living organisms.
Water can dissociate into __________________________________ ions and _______________________________ ions.
Changes in the _______________________________ of these ions can have a great effect on living organisms.
Concentration of H+ and OH are equal in pure water
Adding certain solutes – acids or bases modifies the concentration of _______ and ________.
The _________________ is used to describe how acid or basic
(alkaline) a solution is.
The letters pH are an abbreviation for
“___________________________”
An acid is any substance that ______________________ the hydrogen ion (H+) concentration of a solution.
A base is any substance that _______________________ the hydrogen ion (H+) concentration of a solution
The pH of a solution is determined by the relative
_____________________ of ___________________________.
The pH scale ranges is from 1 to 14
The pH of acids are below ___________
The pH of bases are above _______ up to 14
A pH of __________ is neutral.

Water & the Fitness of the Environment Name_________________________
Date
__________________________
The internal pH of most living cells must remain close to pH __________.
Buffers are substances that _______________ changes in the ______________________ of hydrogen and hydroxide ions in a solution.
Buffers consist of and acid-base pair that reversibly combines with hydrogen ions.
Skill Building & Application of concepts:
1) Calculate the molarity of a solution when there are 5 moles of solute and 7 liters of solution.
2) Calculate the molarity of a solution when 650 grams of sucrose (C
12
H
22
O
11
) in 1 liter of solution.
(hint use the molar mass calculation to convert grams to moles)
3) Which contains the greatest number of moles of solute? a.
0.5L of 0.5M solution b.
0.5L of 2M solution c.
2.0L of 0.5M solution d.
2.0L of 2M solution
4) Explain the difference between hydrophobic and hydrophilic substances
5) Define molarity.
6) Explain how the dissociation of water affects acid concentration and base concentration in solution
7) Use the pH scale to indicate whether the following substance are acidic or basic: a.
Coffee_______________ b.
Blood_______________ c.
Hand Soap__________ d.
Cola (soda)__________
8) Describe what a buffer does.