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BIO122 > Chapter 3 > Flashcards

Chapter 3 Flashcards

1
Q

In what states do water exist in?

A

liquid, solid and gaseous state

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2
Q

How are water molecules polar molecules?

A

Oxygen is more electronegative than hydrogen and are able to attract shared electrons more strongly compared to hydrogen.
Therefore, water consists of a partially positive end (H) and a partially negative end (O).
This causes the formation of strong polar covalent bonds between oxygen and its two hydrogen.

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3
Q

What results from the polar covalent bonds in water molecules?

A

Hydrogen bonds

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4
Q

Why does water tend to form hydrogen bonds with other water molecules?

A

Polarity

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5
Q

What is the stronger bond, covalent bond or hydrogen bond?

A

Covalent bonds

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6
Q

What is the difference between a non-polar covalent bond and a polar covalent bond?

A

A non-polar covalent bond is the equal sharing of electrons while polar covalent bonds are the unequal sharing of electrons

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7
Q

What is the meaning of hydrogen bond?

A

The bonding between hydrogen atom to one of the highly electronegative atom such as oxygen

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8
Q

What are hydrophilic molecules?

A

Substances that dissolves in water that are composed of ions or polar molecules

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9
Q

What are hydrophobic molecules?

A

Substances that are insoluble or repels water, usually are non-polar molecules

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10
Q

What is the name of the phenomenon where the same molecules stick together?

A

Cohesion

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11
Q

What is adhesion?

A

The property in which different molecules stick together

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12
Q

Give two importance of cohesion and adhesion.

A
  1. Capillary action where plants pull water from the roots to their leaves from the ground.
  2. Transpiration where plants lose water through evaporation.
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13
Q

What is the meaning of surface tension?

A

An effect within the surface layer of a liquid that causes the layer to behave as an elastic sheet

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14
Q

Give two importance of surface tension.

A
  1. Walking on water
  2. Formation of dew drops
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15
Q

What is the meaning of high specific heat?

A

Specific heat is defined as the amount of heat that must be absorbed or lost by 1 gram of a substance to change its temperature by 1 degree Celsius

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16
Q

Due to water’s high specific heat…

A

It heats up more slowly than almost any other compound and holds its temperature longer

17
Q

What is the importance of high specific heat capacity of water?

A

To stabilise ocean temperature which creates a favourable environment for marine life

18
Q

What is the meaning of high heat of vaporisation of water?

A

Water must absorb a certain amount of additional heat to change from a liquid into a gas

19
Q

Why are high amounts of heat used to vaporise water?

A

Used to break the bonds between H molecules before it moves faster and transform into gas

20
Q

Give two importance of high heat of vaporisation of water.

A
  1. sweating - heat energy is transferred from the body to the water. as the water evaporates, the heat energy is removed from the body and prevents overheating
  2. keeps the tissues in the leaves from becoming too warm in the sunlight
21
Q

Why do water expand as it freezes?

A

Water molecules freeze in a hexagonal pattern and creates more space between them

22
Q

What is the meaning of solute?

A

A substance that is being dissolved by a solvent

23
Q

What is the meaning of solvent?

A

A substance that dissolves a solute

24
Q

What is the meaning of solution?

A

A homogenous mixture of dissolved substances

25
Q

What is the name of a water molecule that lost a proton?

A

hydroxide ion

26
Q

What is the name of a water molecule that gains the extra proton?

A

hydronium ion

27
Q

What is the concentration of H+ at equilibrium?

A

10^-7 (25 celsius)

28
Q

What is the meaning of an acid?

A

A substance that increases the hydrogen ion concentration in a solution. The addition of an acid makes a solution more acidic

29
Q

What is the meaning of base?

A

A substance that reduces the hydrogen ion concentration in a solution. Solutions with more OH- than H+ are basic solutions

30
Q

What is pH?

A

pH is the measure of the free hydrogen ion concentration

pH= -log10 [H+]

31
Q

What is the pH of pure water?

A

pH 7

32
Q

What is the pH of an acidic solution?

A

pH < 7

33
Q

What is the pH of a basic solution?

A

pH > 7

34
Q

What is the meaning of buffer?

A

Buffers resist changes to the pH of a solution when H+ or OH- is added to the solution.

Buffers accept hydrogen ions from the solution when they are in excess and donate hydrogen ions when they have been depleted

35
Q

What is the buffer in the human body?

A

Carbonic acid

BIO122 (13 decks)

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