Unit 6: Chemistry (Part 2)

Bonding

electrons are exchanged or shared to fill outer energy levels

What are the types of bonds (Hint 4 types)

1. ionic bonds

2. covalent bonds

3. hydrogen bonds

4. Van Der Waals forces

Which bonds are associated with bonding between elements (Hint 2 types)

1. ionic bonds

2. covalent bonds

Which bonds are associated with bonding between molecules (Hint 2 types)

1. hydrogen bonds

2. Van Der Waals forces

What is the difference between ionic + covalent bonding

ionic --> electrons transferred

covalent --> electrons shared

Ionic Bonding

bonding where elements transfer their electrons

Ions

form when atoms gain or lose electrons (charged electrons)

What are the 2 types of ions

1. cation --> positive

2. anion --> negative

Cation

loses electrons = positive ion

Anion

gains electron = negative ion

Which types of elements usually bond through ionic bonding (Hint 2 pairs)

1. metals + nonmetals

2. metaloids + nonmetals

Covalent Bonding

bonding where elements share electrons

Which types of elements usually bond through covalent bonding (Hint 1 pair)

1. nonmetals + nonmetals

What are the 2 types of covalent bonds

1. polar covalent

2. nonpolar covalent

Polar Covalent Bond

unequal sharing of electrons

True or False: Water is an example of polar covalent

True --> bc has a slightly negative charge on oxygen + slightly positive charge on hydrogens

Nonpolar Covalent Bond

equal sharing of electrons

True or False: Oxygen is an example of nonpolar charge

True --> oxygen is shared evenly

Van Der Waals forces

intermolecular attractions between 1 molecule + another molecule

Hydrogen Bonding

bonding between 2 water molecules

Explain the structure and bonding of a water molecule (Hint 2 things)

1. between 1 oxygen + 2 hydrogens

2. bonding = polar covalent

Electronegativity

measure of tendency of atom to attract shared pair of electrons in chemical bond

Which way does electronegativity travel

lower-left --> upper-right

Explain why water is polar covalent (Hint 2 main things)

1. hydrogens = more postivie bc have less electronegativity (don't hold on to electrons as long --> more positive)

2. oxygen = more negative bc has more electronegativity (holds on to electrons longer --> more negative)

What type of bonding does water have with other molecules

hydrogen bond

Properties of water (Hint 6 things)

1. universal solvent

2. specific heat capacity

3. adhesion

4. cohesion

5. surface tension

6. capillary action

Universal Solvent

Water's ability to dissolve more substances than any other liquid

Why is water a universal solvent

1. water = polar + has charge

2. able to dissolve like bases (dissolve other polar/charged substances)

Explain "like" dissolves "like"

polar dissolves polar

nonpolar dissolves nonpolar

(Like in math when you combine lile terms)

Is water able to dissolve sugar, explain (Hint 1 thing)

1. both substances are polar solvents

Is water able to dissolve salt (NaCl), explain (Hint 4 things)

both substances are polar solvents

1. sodium = positive + chloine = negative

2. oxygen = negative + hydrogens = positive

3. opposites attract + breaks bond between sodium + chlorine

Is water able to dissovle oil, explain (Hint 2 things)

1. water = polar + oil = nonpolar

2. not like bases --> can't combine

Specific Heat Capacity

amount of heat energy needed to raise temp of one gram of a substance by one degree Celsius

What does it mean if something has a low specific heat capacity

substance needs less energy to change its temperature (heats up faster)

What does it mean if something has a high specific heat capacity

substance needs more energy to change its temp (heats up slower)

Why does water have a high specific heat capacity

it needs more heat to break apart strong hydrogen bonds

Adhesion

attraction between molecules of different substances (water attracted to something else)

Give 2 examples of adhesion with water

1. water + paper towels

2. water + glass

Cohesion

Attraction between molecules of the same substance (water attacted to water)

Give an example of cohesion with water

1. water + water

Surface Tension

property of water that allows its surface to resist external forces

(stretchy "skin" on surface of liquid)

How does cohesion relate to surface tension

1. water molecules at surface don't have any molecules above them

2. experience greater downward pull + make surface tension

How is a paper clip able to float in water

surface tension --> cohesion makes bonds between water stronger + helps support paper clip's weight

What happens to paper clip when surface tension is disrupted

paper clip sinks --> surface tension = disrupted + strong cohesive bonds break/weakens + no longer support objects

What happens to surface tension when soap is added to water

soap = distrupts cohesive bonds --> bonds become weak + break

Capillary Action (Hint 3 things)

1. water sticks to narrow tube

2. sticks to itself

3. moves upward

How does capillary action relate to adhesion and cohesion

Ahesion --> water sticks to sides of glass

Cohesion --> water sticks to itself

(then can slowly move upwards)

Meniscus

curved surface of water you see in container

How does structure of water influence its functions

1. universal solvent = allows to dissolve like vs like substances

2. hydrogen bond = strong bonds --> high specific heat capacity + surface tension + capillary action

pH

degree of acidity in solution

True or False: pH is a ratio between hydrogens (H+) + hydoroxides (OH-)

True --> ratio determines whether substance is acidic, nuetral, or basic

Describe the pH scale

ranges from 0 - 14

0 --> acidic

7 --> neutral

14 --> basic

What does it mean to be acidic

OH- less than H+ (range between 0-6)

What does it mean to be nuetral

OH - equal to H+ (range = 7)

What does it mean to be basic

OH - greater than H+ (ranger between 8-14)

Describe when pH is acidic

1. H+ > OH-

2. pH < 7

Describe when pH is neutral

1. H+ = OH- ions

2. pH = 7

Describe when pH is basic

1. H+ < OH-

2. pH > 7

Give 2 examples of acidic

1. lemon juice

2. vinegar

Give 2 examples of neutral

1. water

2. distilled water

Give 2 examples of basic

1. baking soda

2. soap

What are pH indicators (Hint 2 types)

1. pH meter

2. litmus paper

pH Meter

uses probe + measures voltage to determine pH

Litmus Paper

changes color depending on pH

How to maintain pH using buffers

cancel out any other reactivity to make it around regular pH level

What is an example of maintaining pH levels using buffers

sugar on apple --> doesn't make it brown

1. stops enzymes (blocks H+) from working + combining w/ oxygen (keeps it from browning)