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Biology > Water (Unit 1) > Flashcards

Water (Unit 1) Flashcards

1
Q

Water

A

A molecule where the structure allows it to interact with other molecules

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2
Q

What type of bond is water?

A

Water has polar covalent bonds, that are more attracted to oxygen than hydrogen

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3
Q

What are the 4 abilities of water that allow it to facilitate life?

A

Cohesive behavior

Ability to moderate temperature

Expansion upon freezing

Versatility as a solvent

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4
Q

Cohesion

A

hydrogen bonds hold water molecules
together; helps the transport of water against gravity
in plants

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5
Q

Adhesion

A

an attraction between different
substances, for example, between water and plant
cell walls

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6
Q

Water Names .

A

H20, hydroxide, hydrogen dihydrogen monoxide

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7
Q

Surface Tension

A

a measure of how difficult it is to
break the surface of a liquid

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8
Q

Surface Tension of water?

A

Water has an unusually high surface tension due to hydrogen bonding between the molecules at the air-water interface and to the water below.

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9
Q

Explain the moderation of temperature by water

A

Water absorbs heat from warmer air and releases
stored heat to cooler air

Water can absorb or release a large amount of heat
with only a slight change in its own temperature

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10
Q

Thermal energy

A

kinetic energy associated with random motion of
atoms or molecules

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10
Q

Kinetic energy

A

the energy of motion

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11
Q

Temperature

A

represents the average kinetic energy
of the molecules in a body of matter

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11
Q

Heat

A

Thermal energy in transfer from one body of matter to another

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11
Q

Calorie (cal)

A

the amount of heat required to
raise the temperature of 1 g of water by 1ºC

It is also the amount of heat released when 1 g of water cools by 1ºC

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12
Q

Kilocalories

A

1 kcal = 1,000 cal

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13
Q

Joule

A

1 cal = 4.184 J

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14
Q

Specific Heat

A

The specific heat of a substance is the amount of heat that must be absorbed or lost for 1 g of that substance to change its temperature by 1ºC

Water resists changing its temperature because of its high specific heat

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15
Q

Why does water have a high specific heat?

A

This can be traced to hydrogen bonding

Heat is absorbed when hydrogen bonds break

Heat is released when hydrogen bonds form

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16
Q

Evaporation (or vaporization)

A

transformation of a
substance from liquid to gas

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17
Q

Heat of vaporization

A

the heat a liquid must
absorb for 1 g to be converted to gas

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18
Q

evaporative cooling

A

As a liquid evaporates, its remaining surface cools

19
Q

Function of Evaporative Cooling

A

helps stabilize
temperatures in organisms and bodies of water

20
Q

Why does ice float in water?

A

Ice floats in liquid water because hydrogen bonds in ice are more “ordered,” making ice less dense than
water

21
Q

When does water reach its greatest density?

A

Water reaches its greatest density at 4ºC

22
Q

Solution

A

a liquid that is a completely homogeneous mixture of substances

23
Q

Solvent

A

the dissolving agent of a solution

24
Q

Solute

A

the substance that is dissolved

25
Q

Aqueous solution

A

solution in which water is the solvent

26
Q

Why is water a versatile solvent?

A

This is because of polarity.

27
Q

Hydration Shell

A

When an ionic compound is dissolved in water, each
ion is surrounded by a sphere of water molecules
called a hydration shell

28
Q

What is the condition for a substance to dissolve in water?

A

Large polar molecules such as proteins
can dissolve in water if they have ionic and polar regions

29
Q

Hydrophilic

A

A hydrophilic substance is one that has an
affinity for water

30
Q

Hydrophobic

A

A hydrophobic substance is one that does not have
an affinity for water

31
Q

Hydrophobic Substance example?

A

Oil molecules are hydrophobic because they have relatively nonpolar bonds

32
Q

Molecular Mass

A

the sum of all masses of all
atoms in a molecule

33
Q

Mole

A

Numbers of molecules are usually measured in
moles

34
Q

Avogadro’s Number

A

6.02 × 1023 daltons = 1 g

35
Q

Molarity

A

the number of moles of solute
per liter of solution

36
Q

How do the bonds in water act?

A

A hydrogen atom in a hydrogen bond between two water molecules can shift from one to the other

37
Q

Hydrogen Ion

A

A hydrogen atom in a hydrogen bond between two water molecules can shift from one to the other

38
Q

Hydroxide
ion (OH–)

A

The molecule that lost the proton

39
Q

Hydronium ion (H3O+)

A

The molecule with the extra proton is now a
hydronium ion (H3O+), though it is often represented as H+

40
Q

What is water’s dynamic state?

A

Water is in a state of dynamic equilibrium in which water molecules dissociate at the same rate at which they are being reformed

41
Q

Concentrations of H+ and OH–

A

Concentrations of H+ and OH– are equal in
pure water

42
Q

Ph

A

Biologists use the pH scale to describe whether a
solution is acidic or basic (the opposite of acidic)

Concentration of hydrogen ions

43
Q

Acid

A

An acid is a substance that increases the H+
concentration of a solution

44
Q

Bases

A

A base is a substance that reduces the H+
concentration of a solution

45
Q

Behavior of acids and bases in water

A

Strong acids and bases dissociate completely
in water

46
Q

How do you tell the ph of a solution?

A

The pH of a solution is defined by the negative
logarithm of H+ concentration, written as

pH = –log [H+]

47
Q

How many hydrogen ions increase/decrease when you change ph

A

Every time you change the ph by 1 it is different by a factor of 10

48
Q

Buffer

A
  • don’t like to change PH

Buffers are substances that minimize changes in
concentrations of H+ and OH– in a solution

49
Q
A

Biology (20 decks)

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