Chemistry Unit 4 Section 4:Water and Aqueous Systems

Unit 4 Section 3: Water & Aqueous Systems

Fill in the Blank

1.43 kPa = ________ mm Hg Round to 1 Decimal Place!

(1 atm = 101.325 kPa and 1 atm = 760. mm Hg)

.

Multiple Choice

All changes in the state of matter of a substance requires

• vibration
• water
• permission
• energy

Multiple Choice

Change of a gas directly into a solid

• Sublimation

• Condensation

• Evaporation

• Deposition

Multiple Choice

this solid is formed from the attraction of ions

• molecular solid

• ionic solid

• network solid

• metallic solid

Multiple Choice

What is it called when a solid turns directly into a gas?

• Sublimation
• Condensation
• Liquid

Multiple Choice

These solids are typically poor conductors with low melting points

• metallic solids

• ionic solids

• molecular solids

• network solids

Fill in the Blank

The pressure inside a tire is 225 kPa. Express this value in atm. Round to 2 Decimal Places

.

Multiple Choice

Which type of Solids are typically easily malleable?

• ionic solid

• molecular solid

• network solid

• metallic solid

Dropdown

You can tell a chemical is an ionic compound because it contains a ​ ​

Select answer

bonded with a non-metal

Match

Match the point defect to its description

• Interstital

• Substitution

• Vacancy

Anxtra atom is in a spot it doesn't belong

An atom is in the wrong spot

An atom is missing

• Anxtra atom is in a spot it doesn't belong

• An atom is in the wrong spot

• An atom is missing

Lesson Objectives

• Describe the role polarity plays in hydrogen bonding between water molecules

  • Surface Tension

  • Boiling point

  • The formation of ice

The Structure of Water

• Water is made of three atoms in total

  • 2 hydrogen

  • 1 oxygen

• The bonds between the Hydrogen and oxygen are Polar covalent bonds

• The overall structure of the molecule is bent due to the unpaired electrons

  • Allows water molecules to arrange into a hexagonal pattern that holds them closer together

​

​Water and Hydrogen Bonding

• Water Molecules are highly polar and strongly attracted to each other

  • The force of Hydrogen Bonds pulls the hydrogen of one molecule towards the Unpaired electrons of another

• Affects many of the properties of water

  • Surface Tension

  • Boiling Point

  • Ice Properties

​

​Surface Tension

• Water naturally forms a spherical shape

  • Hydrogen Bonding pulls water molecules into a pattern where the oxygen on one molecule attracts the hydrogen on another

  • Molecules on the outer edge are only pulled inward

    • Creates a tension that acts like a membrane, holding water together

• Surface Tension: the tension of the surface film of a liquid caused by the attraction of the particles which tends to minimize surface area

​Altering Surface Tension

• Surface tension is affected by various things

  • The type of substrate​ (surface)

    • A non-polar substrate does not pull hard on water, so drops remain rounded

      • Round drops roll more easily

    • Polar substrates pull on water molecules and flatten them

​Surfactants

• Surfactant: A substance that decreases surface tension

  • Has a polar end and a non-polar end

    • Water bonds with the polar end, weakening the hydrogen bonding between water molecules and reducing surface tension

  • More surfactant = flatter drops

  • Used in Soaps and detergents

​Hydrogen Bonding and Boiling Point

• Most molecular compounds are gases at STP and have low boiling points

• Water has a relatively high boiling point of 100 °C

  • Multiple Hydrogen Bonds form between molecules

  • Each water molecule can form more hydrogen bonds because it has two electron pairs

​Structure of Water and Ice

• Ice is unique as a solid

  • Expands and becomes less dense as it freezes

    • Hydrogen bonding between water molecules pushes each molecule into a repeating pattern of hexagons

  • Ice on the surface can act as an insulator and stop freezing of water beneath the surface

​Hydrates

• Hydrates: a solid crystalline compound that contains water molecules as an integral part of its crystal structure

  • Water can be removed or gained through pressure changes

    • Efflorescence: the loss of water by a hydrate

  • Hydrates with a low vapor pressure can remove water from a substance

    • Desiccant: A substance that absorbs moisture from the air

Multiple Choice

The tension that forms on the outer surface of a liquid and acts like a membrane is known as

• Surfactants

• Surface Tension

• Hydrogen Filming

• Waxing

Dropdown

Water molecules are attracted to one another through hydrogen bonding because they are highly​

Select answer

Multiple Choice

The lone electron pairs on water lower the boiling point of water

• True

• False

Multiple Choice

Ice floats because the hexagon shape of ice crystals are less dense than water

• True

• False