Properties of Water Part 2

​2.2 Why is water vital to Life?

Solutions and Suspensions​

​

Explain how water's polarity affects the way it interacts with other substances​

• define the terms mixture, solution, solute, solvent, and suspensions

• describe how the polarity of water allows it to dissolve certain molecules

• compare and contrast between solutions, mixtures, and suspensions​

S

2.2​

​2.2 Why is water vital to Life?

definitions:​

• Mixture: two or more elements or compounds physically mixed together but not chemically combined

• Solution: mixture with the components evenly distributed throughout the solution.

• Solute: substance dissolved in a solution

• Solvent: dissolving substance in a solution

• Suspension: mixture of water and nondissolved material​

S

2.2​

​2.2 Why is water vital to Life?

Explain how water's polarity affects the way it interacts with other substances​

• Water's polarity gives it the ability to dissolve both ionic compounds and other polar molecules.

  • Water is life's most important solvent​

  • When a given amount of water has dissolved all of the solute that it can, the solution is said to be saturated. ​

S

2.2​

​2.2 Why is water vital to Life?

Explain how water's polarity affects the way it interacts with other substances​

Suspensions

• mixture of water and undissolved materials

• undissolved materials are suspended in the water.

• Example:

  • Blood: mostly water (92%) but also contains undissolved materials- RBCs, WBCs, platelets

S

2.2​

​2.2 Why is water vital to Life?

Acids, Bases, and pH​

Explain why buffers are important to the survival of an organism

• define pH scale, acid, base, and buffer

• explain the formation of ions by water

• explain the pH scale

• differentiate acids and bases

• explain how pH is critical to humans

• explain the important role of buffers​

​

S

2.2​

​2.2 Why is water vital to Life?

definitions:​

• pH scale: scale with values from 0 to 14, used to measure the concentration of H+ ions in a solution

• acid: a compound that forms hydrogen ions (H+) in a solution with a pH less than 7

• base: compound that forms hydroxide ions (OH-) in a solution with a pH more than 7

• buffer: compound that prevents sharp, sudden changes in pH

S

2.2​

​2.2 Why is water vital to Life?

Formation of ions by water​

• water molecules sometimes separate into ions in water

• Result:

  • H+ ions and OH- ions

  • H+ and OH- ions are equal in number

    • why? H2O​ = H+ and OH-

  • Therefore pure water has a neutral pH of ________.

S

2.2​

​2.2 Why is water vital to Life?

Explain the pH scale​

• scale used to measure the concentration of H+ ions and OH- ions in a solution.

• ranges from 0-14

• pH of 7 = concentration of H+ ions and OH- equal

  • remember - pure water is neutral- pH 7

• solutions with a pH less than 7 are acids​

  • more H+ ions than OH- ions​

• solutions with a pH more than 7 are bases

  • more OH- ions than H+ ions​

S

2.2​

​2.2 Why is water vital to Life?

Explain the pH scale​

• Each step on the pH scale represents a 10 fold increase or decrease of acidity or alkalinity.

  • Example a pH of 3 is _________X more acidic than a pH of 6.​

  • Problem:

    • How many times more basic is a solution with a pH of 13 to a solution with a pH of 8?

S

2.2​

​Acids: 0-6.99

Bases: 7.01 - 14

Neutral: 7​

​pH Scale

​2.2 Why is water vital to Life?

​Differentiate acids and bases

​

Acids​

• A compound that releases H+ into solution

• Contain more H+ ions than pure water

• ​pH values less than 7

• Example:

  • Hydrochloric Acid​ - HCl

    • stomach acid- pH of 1.5 to 3

S

2.2​

Bases​

​Some text here about the topic of discussion.

​Acids

​

​2.2 Why is water vital to Life?

​Differentiate acids and bases

​

Bases​

​

• ​A compound that releases OH- ions in solution

• Contain​ more OH- ions than water

• ​pH value more than 7

• Example:

  • Sodium hydoroxide (NaOH)

    • lye- used in soapmaking- p​H 11 to 14

S

2.2​

Bases​

​Some text here about the topic of discussion.

​Acids

​

​2.2 Why is water vital to Life?

​Explain how pH is critical to humans.

​

• ​pH of cells in the human body need to be maintained between 6.5 and 7.5

• reactions of the body work only in this range

• must have homeostatic mechanisms to maintain this pH range

  • Example:

    • Blood pH: 7.4 - Slightly basic

      • Buffers like Bicarbonate and phosphate ions are necessary to prevent sharp changes in pH

      • Other measures?​

S

2.2​

​2.2 Why is water vital to Life?

​Explain the important role of buffers

​

• Buffers are weak acids or bases that can prevent sharp changes in pH

  • Example:

    • Blood pH: 7.4 - Slightly basic

    • Buffers like Bicarbonate and phosphate ions are necessary to prevent sharp changes in pH

• Buffers dissolved in life's fluids play an important role in maintaining homeostasis​

S

2.2​

Multiple Choice

When Amanda added table salt to the first test tube and shook it, she noted that the

liquid had dissolved the __________.

• solute

• solvent

• solution

• water

Multiple Choice

When Pol filled another test tube to the top, the liquid formed a low dome, which is

evidence of __________.

• adhesion

• cohesion

• solution

• compound

Multiple Choice

When Amanda poured some of the liquid in a test tube, she noticed that the edges of

the water curved upward, which is an example of __________.

• adhesion

• cohesion

• solution

• compound

Multiple Choice

All of these indicated the presence of _____________ bonds.

• covalent

• ionic

• hydrogen

• peptide

Multiple Choice

Which of the following observations BEST demonstrates water’s special property

of cohesion?

• a spoon held near a stream of water from a tap deflects the water towards

  itself

• a drop of water behaves like glue to stick a slip of paper to a window

• water can dissolve other substances, such as sugar and salt

• water forms droplets of dew on a spider web in the morning

Multiple Choice

Blood is a mixture of a variety of materials. Some of the materials are dissolved

in the fluid portion of blood. Other materials, such as blood cells, do not dissolve

but move along with the blood.

For these reasons, blood is an example of which type of mixture?

• a solvent

• a solution

• a suspension

• a buffer

Multiple Choice

Buffers are

• strong acids or weak bases

• strong acids and weak bases

• strong bases and weak acids

• weak acids or weak bases

Multiple Choice

Buffers react with strong acids and bases to

• prevent sudden changes in pH

• keep solutions neutral

• increase the effect of the base

• increase the effect of the acid

Multiple Choice

Carrie is conducting an experiment on a solution. The solution’s initial pH is 3.2.

Then, as Carrie gradually adds Compound X into the solution, the pH increases

to 9.8.

Which is the most likely identity of Compound X?

• a strong acid, such as hydrochloric acid (HCl)

• a strong base, such as sodium hydroxide (NaOH)

• a salt, such as sodium chloride (NaCl)

• a solvent, such as water (H 2 O)

Multiple Choice

A solution has a pH of 5. It is a(n)

• acid

• base

• buffer

• neutral

Multiple Choice

Buffers are critical in living things to

• maintain homeostasis

• increase adhesion

• decrease bond formation

• insure solutions are neutral