Structure of Water and Hydrogen Bonding

Anything that takes up space and has mass

Matter

A substance that cannot be broken down into other substances by chemical reactions

Element

How many elements occur in nature

92

A substance consisting of two or more different elements combined in a fixed ration

Compound

How many of the 92 naturally occuring elements are essential to survival and reproduction

20-25%

What are the 5 most essential elements

Carbon, Hydrogen, Oxygen, Phosphorous, Nitrogen

How much does CHOPN make up living matter

95%

What is an example of a trace element needed?

Iodine.

Number of protons plus neutrons averaged over all isotopes

Atomic mass.

Elements are always trying to be what_______

stable

How do elements become stable

By forming chemical bonds with other elements

Elements will gain, lose, or share electrons to complete their valence shell and become stable

Octet rule

What is the outermost layer of electrons in an atom

Valence shell

An attraction between two atoms resulting from the sharing or transferring of valence electrons

Chemical bond

Bond formed by the sharing of electrions

Ionic bond

Bond formed by the sharing of electrons

Covalent

The measure of an atoms ability to attract electrons to itself

Electronegativity.

What are covalent bonds usually between?

Two nonmetals

What are the two types of covalent bonds

Nonpolar and polar covalent

What is a nonpolar covalent bond

electrons are not shared equally between two atoms.

What does the unequal sharing of electrons result in, in h20

partial negatives on oxygen, and partial positive charges on the oxygens.

Bonds between the elements making up h2o are what?

Polar covalent

Bonds between hydrogen molecules are called what

Hydrogen bonds

What is the name of compounds formed by covalent bonds

Molecules

What are charged atoms

Ions

The attraction between oppositely charged atoms

Ionic bonds

What are ionic bonds usually between.

Metal and nonmetal

What does the metal transfer to the nonmetal

electrons

What is an example of a compound formed by ionic bonds?

Salt

Positively charged ion

Cation

Negatively charged ionb

Anion

The attraction of a partially positive hydrogen atom in one polar covalent molecule to an electronegative atom in one polar covalent molecule

Hydrogen bond

Bond that forms between molecules

Intermolecular

Why do hydrogen bonds happen

In polar covalent bonds with hydrogen, often electrons are not shared equally creating partial charges that can create bonds.

What is an example of a hydrogen bond

Water.

Why is water more structuredthan most liquids?

The hydrogen bonds that make it up.

What do hydrogen bonds do with great frequency?

Form, break, and reform.

What are the 8 properties of water.

Polarity, Cohesion, Adhesion, Capillary action, Temperature control, Density, Solvent, pH and buffering.

How is water polar?

Water molecules are made up of polar covalent bonds created by unequal sharing of electrons between oxygen and hydrogen within the molecule of water.

Attraction of molecules for other molecules of the same kind.

Cohesion.

What holds water together.

Hydrogen bonds that lead to large cohesive forces.

What are the water arteries of leaves known as

Xylem.

What is transpiration?

The release of water from inside plants as enacted by xylem.

What is cohesion responsible for

Surface tension.

What is surface tension

Tension created by cohesive surface molecules experiencing greater inward pull due to the absence of molecules above them to balance the force.

The attraction of different molecules to other molecules that are positive or have charge

Adhesion

What is adhesion due to

The polarity of water.

What does adhesion allow water to do in plant’s xylem?

Resist the downard pull of gravity.

The upward movement of water due to the forces of cohesion, adhesion, and surface tesnion

Capillary action

When does capillary action occur?

When adhesion is greater than cohesion.

What is the capillary action important for?

Transport of water and nutrients throughout plants.

What are the two temperature control characterisitics of water?

High specific heat, High Heat of vaporization.

H2O resists changes in temperature

High Specific Heat.

Why does hydrogen have a high specific heat?

Heat must be absorbed to break hydrogen bonds, but heat is released when hydrogen bonds form.

Where do temperature control properties stem from?

Hydrogen bonds.

What is the importance of high specifc heat?

Moderates air temperature, Stabilizes ocean temperature, Maintain internal temperature.

How does high specific heat moderate air temperature.

Large bodies of water can absorb heat in the daytime and release heat at night.

What is the benefit of stabilized ocean temperature

It benefits marine life

What does high specific heat help with in organisms

It helps them resist changes in their own internal temperature.

Water requires a large amount of energy to evaporate due to strong hydrogen bonds

High heat of vaporization.

What does evaporative cooling do, because of high heat of vaporization?

As water molecules evaporate, the surface they evaporate from gets cooler.

Why is evaporative cooling important?

Moderates Earth’s Climates, Stabilizes the lakes and ponds, Prevents organisms from overheating, Prevents leaves from becoming to warm in the sun..

As water solidifies it expands and becomes less dense

Water’s density property.

Why does water expand as it freezes?

Hydrogen bonds lock water into crystalline structures with more dispersed hydrogen bonds.

Why does water become solid?

When H2O molecules are cooled, they move to slowly to break bonds.

What does less dense floating water allow marine life to do?

Live under floating ice sheets.

Dissolving agent in a solution

Solvent

What is water in regards to solutions?

A universal solvent.

Why is water such a good solvent?

It’s polar molecules are attracted to ions and other polar molecules, so they pull compounds apart through bonding with them.

A homogenous mix of 2 substances

Solution

Dissolving agent in a solution

Solvent

Thing that is dissolved

Solute

What is one rule for dissolving?

Like dissolves like

What will hydrogen do to sugars or proteins to dissolve them?

Form hydrogen bonds with oxygens and hydrogens in molecules to pull them apart.

A measure of how acidic or basic a solution is.

pH

A substance that releases hydrogen ions (H+) when dissolved in water

Acid

A substance that accepts H+ or rleases hydroxide (OH-)

Base

What can water do that is unique among acids and bases?

Dissociate into hydrogen ions and hydroxide.

A solution that resists changes in pH when an acid or base is added.

Buffer

What do buffers help to do in biological systems

Maintain pH stability.

What is water in terms of pH

a buffer.

What is average human pH

7.35