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Biology 1010 > Chapter 3 - Water and Life > Flashcards

Chapter 3 - Water and Life Flashcards

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0
Q

What is meant by water being a polar molecule?

A

It’s overall charge is unevenly distributed: oxygen has partial negative charge and each hydrogen has a partial positive charge.

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1
Q

What are the polar covalent bonds in water?

A

Electrons spending more time around O than H atoms.

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2
Q

What are the hydrogen bonds in water?

A

Slightly positive hydrogen is attracted to slightly negative oxygen of a nearby molecule.

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3
Q

What are the four emergent properties of water?

A

1) Cohesion of water molecules
2) Moderation of Temperature
3) Evaporative Cooling
4) Ice floats - expansion of water upon freezing

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4
Q

What are 3 characteristics of the cohesion of water molecules?

A

1) Cohesion
2) Surface Tension
3) Adhesion

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5
Q

Why do molecules stay close together?

A

Hydrogen bonding.

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6
Q

What is adhesion?

A

Clinging of one substance to another.

Ex. Water from roots of trees reaches leaves.

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7
Q

What is surface tension?

A

A measure of how difficult it is to stretch or break the surface of a liquid.
Ex. Water striders

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8
Q

What do cohesion, surface tension and adhesion all have in common?

A

Interactions between water molecules, hydrogen bonds.

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9
Q

How does water moderate temperature?

A

By absorbing heat from air that is warmer and releasing the stores heat to air that is cooler.

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10
Q

What is kinetic energy?

A

Anything that moves - energy of motion.

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11
Q

The total thermal energy of a body of matter depends on the matters _____.

A

Volume.

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12
Q

What is thermal energy?

A

Kinetic energy associated with the random movement of atoms or molecules.

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13
Q

What is temperature?

A

Measure of heat intensity that represents the average kinetic energy of the molecules in a system.

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14
Q

Does a swimming pool or pot of coffee contain more thermal energy?

A

The swimming pool because it has a greater volume.

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15
Q

When two objects of different temperatures are brought together, thermal energy passes from the _____ object to the ______ object.

A

Warmer/cooler

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16
Q

What is heat?

A

Thermal energy in transfer from one body of matter to a other.
Or measure of the total kinetic energy of material due to molecular motion.

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17
Q

What is the specific heat of a substance?

A

Amount of heat that must be absorbed or lost for 1g of the substance to change it’s temperate by 1 degree C.

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18
Q

Because of the high specific heat of water, water temperature will change _____ when it absorbs a given amount of heat.

A

Less.

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19
Q

What can waters high specific heat be attributed to?

A

Hydrogen bonding capacity.

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20
Q

What must be absorbed to break hydrogen bonds before the water molecules can move faster.

A

Heat.

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21
Q

What must be given off to make hydrogen bonds?

A

Heat.

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22
Q

What happens when water cools slightly?

A

Many additional hydrogen bonds form, thereby releasing a considerable amount of energy in the form of heat.

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23
Q

What is the relevance of waters high specific heat to life on earth?

A

A large body of water can absorb and store a huge amount of heat from the sun, warming up by a few degrees in the day and absorbing and storing large amounts of heat that is released at night. Gradual cooking can warm the air.

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24
Q

What does the specific high heat of water moderate?

A

Air temperatures, ocean water, and organism temperatures. (Most living things 79-95% water)

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25
Q

What is vaporization?

A

Phase change from liquid to gas.

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26
Q

What is condensation?

A

Phase change from gas to liquid.

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27
Q

If liquid is heated, the average kinetic energy of molecules _____ and the liquid evaporates more ______.

A

Increases/rapidly.

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28
Q

What is heat of vaporization?

A

Amount of heat required for 1g of a substance to go from liquid state to gaseous state.

29
Q

Why does water have a high heat vaporization? (25degrees = 580cal)

A

Because of the hydrogen bonds that must be broken before molecules can leave the liquid state.

30
Q

Why does evaporative cooling occur?

A

The “hottest” molecules, those with the greatest kinetic energy are most likely to leave as a gas.

31
Q

What happens when the most energetic molecules leave?

A

Decline or cooling in temperature.

32
Q

Water is _____ dense as a solid than as a liquid.

A

Less.

33
Q

Solid - liquid - gas the density decreases with the exception of…

A

Water.

34
Q

What is the cause of water expanding and becoming less dense as a solid?

A

As substances cool they contract. As molecules lose energy they move closer together. (Warmer-they expand) contraction of molecules allows hydrogen bonds to form.

35
Q

What happens to water molecules at 0 degrees?

A

Water freezes- molecules are not moving enough to break hydrogen bonds and molecules become locked in a crystal lattice with the formation of 4 hydrogen bonds.

36
Q

Ice is ___ less dense than liquid water at 4 degrees Celsius.

A

10%

37
Q

At what temperature are the hydrogen bonds in water molecules broken?

A

Above 0 degrees

38
Q

What is a solution?

A

A liquid that is a homogenous mixture of two or more substances.

39
Q

What is a solvent?

A

Dissolving agent.

40
Q

What is solute?

A

Substance that is dissolved.

41
Q

What is an aqueous solution?

A

Solution in which water is the solvent.

42
Q

What makes water a versatile solvent?

A

Polarity of water molecules.

43
Q

Why does water make an excellent solvent for polar and ionic substances?

A

Because it has charged regions.

44
Q

Water is a poor solvent for what kind of substances?

A

Non polar and non ionic substances. (Hydrophobic)

45
Q

Water is a good solvent for what types of substances?

A

Polar and ionic. (Hydrophilic)

46
Q

How does water dissolve materials?

A

By forming a hydration shell around that material and overcoming the charge (electrostatic) interactions within the material.

47
Q

What is a hydrophilic substance?

A

“Water loving” attraction to water. But can be hydrophilic and not dissolve. Ex cellulose in cotton.

48
Q

What allows water transport to occur in plants?

A

Adhesion of water to hydrophilic walls.

49
Q

What is a hydrophobic substance?

A

Repels water. Ex. Oil. Cell membranes.

50
Q

What is a mole?

A

Convenient chemical mass unit. 1=avogadros number.

51
Q

What is molecular mass?

A

Sum of all masses of all atoms in a molecule.

52
Q

How many Dalton’s are in 1 gram?

A

6.02 x 10^23 Dalton’s.

53
Q

How would you make a L o solution consisting of 1 mil of sucrose dissolved in water?

A

Measure out 342 (molecular mass) grams of sucrose then gradually add water + stirring until dissolved.

54
Q

What is molarity?

A

Measure of concentration - the number of moles of solute/L of solution.

55
Q

What is the mass of one mole of NaOH?

A

40.00g/mole

56
Q

How many grams of NaOH are in 1L of a 2.0M solution of NaOH?

A

8 grams of NaOH?

57
Q

What are the products of water molecule dissociation?

A

2H20 = OH- and H3O+

Water dissociates to a hydroxide ion and a hydronium ion?

58
Q

An acid is a substance that ____ the hydrogen ion concentration in a solution.

A base is a substance that _____ the hydrogen ion concentration in a solution.

A

Increases/decreases.

59
Q

An acidic solution has higher ____ than ____.

A

H+ than OH-

60
Q

A basic solution has higher ____ than ___.

A

OH- than H+

61
Q

A solution I’m which H+ and OH- concentrations are equal are said to be…

A

Neutral.

62
Q

How can you tell what are strong acids and strong bases?

A

Dissociate completely. ➡️

63
Q

How can you tell what are weak acids and weak bases?

A

Undergo incomplete or reversible dissociation. ➡️⬅️

64
Q

In any aqueous solution at 25 degrees Celsius, the product of H+ and OH- is _____.

A

Constant. [H+][OH-] = 10^14

65
Q

If a solution has a pH of 3, what are the concentrations of H+ and OH-?

A

Solution.

66
Q

What is a buffer?

A

Substances that minimize changes in the concentrations of H+ and OH- in a solution. Can either accept or donate H+.

67
Q

Buffers are usually ____ acids or bases that combine reversible with hydrogen ions.

A

Weak.

68
Q

When the pH increases there is a shift in the equilibrium to the _____.

When the pH decreases there is a shift in the equilibrium to the _____.

A

Right/left.

69
Q

Why does water takes a lot more heat energy to change the temperature of water or make it vaporize?

A

Because individual water molecules are polar, and they stick together by means of hydrogen bonds.

Biology 1010 (5 decks)

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