Text A Chemistry 2.4 Water

Question 1

What percentage of a watermelon is water by mass?

Answer 1

About 92 percent

This highlights the high water content of many fruits.

Question 2

What percentage of the human body is water by mass?

Answer 2

About 67 percent

This indicates the significance of water in human physiology.

Question 3

How long can a person live without water?

Answer 3

About two days

This emphasizes the critical need for water compared to food.

Question 4

What is one unique property of water regarding its solid state?

Answer 4

Ice is less dense than liquid water

This property allows ice to float on water.

Question 5

What would happen if ice were denser than water?

Answer 5

Ice would sink, causing lakes to freeze solid

This would be detrimental to aquatic life.

Question 6

What are the three states in which water exists on Earth?

Answer 6

Solid, liquid, gas

Water is unique for existing in all three states in large quantities.

Question 7

What is the molecular mass of water?

Answer 7

18 u

This is a key measure in comparing water to other substances.

Question 8

What is the boiling point of water?

Answer 8

100 degrees Celsius

This is a characteristic temperature for water.

Question 9

Fill in the blank: The molecular formula for methane is _______.

Answer 9

CH4

Methane has a similar molecular mass to water but different properties.

Question 10

What is the state of water at room temperature?

Answer 10

Liquid

This distinguishes it from many other substances.

Question 11

What is the melting point of water?

Answer 11

0 degrees Celsius

This is the temperature at which water transitions from solid to liquid.

Question 12

True or False: Hydrogen sulfide is a liquid at room temperature.

Answer 12

False

Hydrogen sulfide is a gas at room temperature.

Question 13

What is the boiling point of hydrogen selenide?

Answer 13

42 degrees Celsius

This is one of the comparative properties of hydrogen selenide.

Question 14

What are the properties compared in Inquiry Investigation 2-D?

Answer 14

Properties of water, oil, and an aqueous solution

This investigation allows for practical understanding of water’s properties.

Question 15

What is the melting point of methane?

Answer 15

-183 degrees Celsius

This is significantly lower than that of water.

Question 16

What is the boiling point of methane?

Answer 16

-161 degrees Celsius

This highlights the gaseous state of methane at room temperature.

Question 17

What is the shape of a water molecule?

Answer 17

Bent shape

The bent shape is due to the arrangement of electrons within the molecule.

Question 18

How many O-H bonds are present in a water molecule?

Answer 18

Two O-H bonds

Each bond consists of two shared electrons.

Question 19

Which atom in a water molecule attracts electrons more strongly?

Answer 19

Oxygen atom

This results in the electrons spending more time near the oxygen atom than near the hydrogen atom.

Question 20

What type of charge does the oxygen atom have in a water molecule?

Answer 20

Partial negative charge

Represented by the symbol δ-.

Question 21

What type of charge does the hydrogen atom have in a water molecule?

Answer 21

Partial positive charge

Represented by the symbol δ+.

Question 22

What term describes the overall charge distribution in a water molecule?

Answer 22

Polar molecule

A polar molecule is also referred to as a dipole.

Question 23

What is the angle between the O-H bonds in a water molecule?

Answer 23

105°

This angle contributes to the bent structure of the molecule.

Question 24

What type of bond forms between the hydrogen end of one water molecule and the oxygen end of another?

Answer 24

Hydrogen bond

Hydrogen bonds are a type of intermolecular force.

Question 25

What distinguishes intermolecular forces from intramolecular forces?

Answer 25

Intermolecular forces act between molecules, while intramolecular forces act within molecules ## Footnote A covalent bond is an example of an intramolecular force.

Question 26

Which type of intermolecular force is the strongest?

Answer 26

Hydrogen bonds ## Footnote Hydrogen bonds are stronger than other intermolecular forces but weaker than covalent bonds.

Question 27

What type of bonds occur in substances that contain hydrogen bonded to oxygen?

Answer 27

Hydrogen bonds ## Footnote Examples include water and methanol.

Question 28

In addition to oxygen, which other atoms can hydrogen form bonds with to create hydrogen bonds?

Answer 28

Fluorine and nitrogen ## Footnote Example includes hydrogen fluoride (HF).

Question 29

Why do water's boiling and melting points exceed those of similar substances without hydrogen bonds?

Answer 29

Hydrogen bonds require a great deal of energy to break ## Footnote This is why ice melts and water boils at higher temperatures.

Question 30

What is the significance of perspiration in relation to water's properties?

Answer 30

It cools the body by evaporating ## Footnote Significant energy is needed to evaporate water, thus cooling the body.

Question 31

What happens to the average speed of particles in water when its temperature increases?

Answer 31

The average speed of the particles increases ## Footnote Particles must overcome attractive forces among them.

Question 32

What occurs when water cools?

Answer 32

A great deal of energy is released ## Footnote This is a significant property of water.

Question 33

What is capillary action?

Answer 33

The force that draws water up from roots to leaves ## Footnote It is due to the attraction between polar water molecules and container sides.

Question 34

What shape does water form in a container, and what causes this shape?

Answer 34

Concave meniscus due to attraction between water molecules and container sides ## Footnote This phenomenon is part of capillary action.

Question 35

How does water regulate Earth's temperature?

Answer 35

It absorbs energy from the Sun and releases it at night ## Footnote This moderation allows Earth to support life.

Question 36

What temperature variation can occur in deserts due to lack of water?

Answer 36

Up to 40°C between day and night ## Footnote This is in contrast to more moderated environments.

Question 37

What is the temperature range on the Moon due to the absence of liquid water?

Answer 37

Between 100°C and -150°C ## Footnote This extreme variation occurs on the same day.

Question 38

What happens to water as it freezes?

Answer 38

Water expands as it freezes because polar molecules arrange in an open pattern held by hydrogen bonds.

Question 39

Why does ice float on liquid water?

Answer 39

Ice is less dense than liquid water.

Question 40

What is the effect of hydrogen bonding on the density of freezing substances?

Answer 40

Substances without hydrogen bonding pack more tightly and their denser solid material sinks.

Question 41

What contributes to water's high surface tension?

Answer 41

Hydrogen bonds between surface molecules pull them together into the smallest possible area.

Question 42

What shape does a small volume of water form when falling through the air?

Answer 42

A circular drop.

Question 43

How do liquids without hydrogen bonds behave under gravity?

Answer 43

They spread out over a larger area.

Question 44

How do small water insects utilize water's surface tension?

Answer 44

They move across the surface of the water.

Question 45

What is the structure of ice when it forms?

Answer 45

Ice has a six-pointed crystal structure held in place by hydrogen bonds.

Question 46

What happens to the volume of water when it freezes?

Answer 46

Its volume increases.

Question 47

What is the attractive force experienced by molecules at the surface of a water drop?

Answer 47

Molecules on the surface are not attracted equally on all sides, resulting in a net inward force.

Question 48

Fill in the blank: The six-sided shape of a snowflake reflects the _______ of ice.

Answer 48

[six-sided crystal structure]

Question 49

True or False: Molecules of water in the center of a drop are attracted equally by hydrogen bonds.

Answer 49

True.

Question 50

What allows water's surface tension to counteract the pressure exerted by the water strider's legs?

Answer 50

The net inward force due to hydrogen bonding.