Chemistry Review and Properties of Water

What is matter?

Anything that takes up space and has mass

What is an element?

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

What is a compound?

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

What is the atomic number?

Number of protons

What is the atomic mass?

Number of protons plus neutrons averaged over all isotopes

What is a group?

Elements in the same vertical column have the same number of valence electrons

What is a period?

Elements in the same horizontal row have the same total number of electron shells

Where is the proton located, charge, and size (atomic mass unit)

Nucleus, positive, 1

Where is the neutron located, charge, and size (atomic mass unit)

Nucleus, neutral, 1

Where is the electron located, charge, and size (atomic mass unit)

Outside nucleus, negative, 0

What happens if you add or remove a proton?

Creates New Element

What happens if you add or remove a neutron?

Creates an isotope

What happens if you add or remove an electron?

Creates an ion

What do elements want to be at the end of everything?

They want to be stable (back to ground state)

What is the octet rule?

Elements will gain, lose, or share electrons to complete their valence shell and become stable (like noble gases)

What is the valence shell?

Outermost layer of electrons in an atom

Up to how many electrons are in each level?

2 - first level

8 - second level

18 - those beyond

Octet rule

Outer level can only have 8, outer level always wants 8 valence electrons

If electrons gain energy

They move to a higher level

If electrons release energy

They fall back down

What is ground state

Where they started

What is excited state

Where they are when energized

What is a chemical bond?

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

What is electronegativity?

The measure of an atom’s ability to attract electrons to itself determines willingness to bond

What is a covalent bond?

When two or more atoms share electrons (usually between two nonmetals)

What are the two types of covalent bonds?

Nonpolar covalent and polar covalent

What is a nonpolar covalent bond?

Electrons are shared equally between two atoms (atoms don’t differ much in their electronegativity)

What are polar covalent bonds?

Electrons are not shared equally between two atoms (H2O)

one pulls or attracts the electrons more strongly than the other atom

What is an ionic bond?

The attraction between oppositely charged atoms (ions) , usually between a metal and nonmetal

Occurs when there is a transfer of electrons from one atom to another atom forming ions

What is a cation?

Positively charged ion

What is an anion?

Negatively charged ion

What is a hydrogen bond?

The partially positive hydrogen atom in one polar covalent molecule will be attracted to an electronegative atom in another polar covalent molecule

What is an intermolecular bond?

Bond that forms between molecules

What is a polar covalent bond?

When a hydrogen atom is bonded to an electronegative atom (usually O, N, or F) the electrons are not being shared equally between atoms

This causes the hydrogen to have a partial positive charge and the electronegative atom to have a partial negative charge

pH of an environment / solution is important

organisms are acclimated to that pH and changes can lead to serous consequences, even death

What are buffers?

Buffers are solutions that can neutralize acids and bases

What can strong buffers do?

They can neutralize lots of acid/base, weak buffers only a little

Will addition of acid or base to buffer change the pH?

The pH will not change the pH or change it very little

Do buffer’s have a capacity?

Yes

What is polarity?

Polar covalent bonds created by unequal sharing of electrons between oxygen and hydrogen within the molecule of water

What is cohesion?

Attraction of molecules for other molecules of the same kind

What is adhesion?

The attraction to other molecules that are polar or have charge that are difference substances

What is capillary action?

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

Occurs when adhesion is greater than cohesion

What is temperature control in water?

High specific heat which is where H2O resists changes in temperature

Why is high specific heat important?

-Moderates air temperature, large bodies of water can absorb heat in the daytime and release heat at night

-Stabilizes ocean temp, benefits marine life

-Organisms can resist changes in their own internal temp

What is high heat of vaporization?

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

What is evaporative cooling?

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

What is the importance of evaporative cooling?

• Moderates Earth’s climate

• Stabilizes temp in lakes and ponds

• Prevents terrestrial organisms from overheating

• Prevents leaves from becoming too warm in the sun

What is density (floating ice)?

As water solidifies it expands and becomes less dense

(due to hydrogen bonds, when cooled H2O molecules move too slowly to break the bonds, allows marine life to survive under floating ice sheets)

What do hydrogen bonds do to water molecules?

They form a crystalline structure

What is a solvent?

Dissolving agent in a solution

Hydrophilic?

Attracted to water / polar

Hydrophobic?

Scared of water / nonpolar

Ionic compounds

• The partially negative oxygen in water will interact with a positive atom

• The partially positive hydrogen in water will interact with a negative atom

• Dissolves ions

What is pH?

A measure of how acidic or basic (alkaline) a solution is

What is acid?

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

What is base?

Substances that accepts H+ OR releases hydroxide ions (OH-) when dissolved in water

What can water dissociate into?

Hydrogen (H+) and hydroxide ions (OH-)

Buffer in biological systems?

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

• Buffers help maintain pH stability in biological systems