Water And Ions

Question 1

Characteristics of water? (3 points)

Answer 1

• a polar molecule
• very good general purpose solvent for anything with a charge or partial charge
• the water molecule can align so that either the positive or negative charges are facing inwards

Question 2

What is a solvent?

Answer 2

A liquid that dissolves a substance ie water or ethanol

Question 3

What is a solute?

Answer 3

A substance which dissolves in a solvent ie salt, water

Question 4

What is a solution?

Answer 4

The mixture of a solvent and a solute ie the solution saline is a mixture of water (solvent) and salt (solute)

Question 5

A water based solution is called?

Answer 5

Aqueous

Question 6

A non-water based solution is called?

Answer 6

Non-aqueous

Question 7

What is the concentration?

Answer 7

Any measure of the amount of a given substance that is dissolved in a liquid

Question 8

What is solubility?

Answer 8

A measure of the maximum amount of the substance that will dissolve

Question 9

What are the characteristics of a solution?

Answer 9

• they are homogenous
• they are stable (solute won’t settle out, nor can you filter it out)
• may reach saturation (solute will precipitate out as a solid eg. Gallstones, kidney stones)

Question 10

Concentration can be specified in terms of?

Answer 10

• the weight of a substance dissolved in a given volume eg. Mg/L or %
• the number of atoms or molecules dissolved in a given volume eg. Moles/L

Question 11

How are medicines administered?

Answer 11

On a dose basis, an amount given per kilogram of body weight

Question 12

What depends on the concentration?

Answer 12

The amount of a medicine required for a given dose

Question 13

What is toxicity?

Answer 13

The toxicity of a drug is directly related to dose

Question 14

What are suspensions?

Answer 14

Liquids containing particles that are large enough to settle out (by gravity) if you leave them for long enough. Particles don’t dissolve.

Question 15

Characteristics of a suspension? (7 points)

Answer 15

• particles are ‘suspended’ in the solvent
• heterogeneous (not evenly mixed)
• are cloudy (also called turbid)
• have particles that settle
• contain particles that reflect light
• can’t be given intravenously
• particles over 100nm
  Eg. Whole blood, calamine lotion, barium meal

Question 16

What are colloids?

Answer 16

A type of homogenous mixture in which the dispersed particles won’t settle out

Question 17

Characteristics of colloids?

Answer 17

• can look clear or coloured
• contains particles small enough to never settle
• particles can be removed by filtering, if the pore size is small enough
• particles range from 1-100nm

Question 18

What does homogenous mean?

Answer 18

Homogenous means ‘same kind’, homogenous mixtures look the same throughout

Question 19

What does heterogenous mean?.

Answer 19

Heterogeneous means ‘different in kind’, a heterogeneous mixture is non-uniform in composition

Question 20

What is the Tyndall effect?

Answer 20

The visible path of light produced by the scattering action of the particles in a colloidal solution when a beam of light passes through it

Question 21

What is blood made up of? (3 points)

Answer 21

• suspension - various blood cells
• colloid - proteins in plasma
• solution - electrolytes, gases, glucose in the plasma

Question 22

What is an emulsion?

Answer 22

A mixture of two immiscible (unmixable) liquids eg. Oil and water

Question 23

Characteristics of emulsions? (2 points)

Answer 23

• can be either stable or unstable

- a unstable emulsion will naturally separate

Question 24

What is an emulsifier?

Answer 24

A chemical that stabilises an emulsion allowing them to mix

Question 25

Characteristics of emulsifiers?

Answer 25

• have a polar and non-polar end
• bile salts are important emulsifiers in fat digestion
• detergents are emulsifiers, they are designed to pull oils into water

Question 26

What does body water consist of?

Answer 26

• intracellular fluid (ICF) 2/3

- extracellular fluid (ECF) 1/3

Question 27

Extracellular fluid is broken down into?

Answer 27

• interstitial fluid (IF) in the spaces between cells, 80%

- plasma (liquid portion of blood) 20%

Question 28

What percentage of the body is water?

Answer 28

About 60%

Question 29

What can make body water vary?

Answer 29

• age (decreases with age)
• gender
• body fat % (more fat less water)
• muscle mass (more muscle more water)

Question 30

What is plasma?

Answer 30

It is 92% water and makes up 55% of blood

Question 31

Plasma contains a wide range of….?

Answer 31

Solutes both:

• electrolytes - Na+, K+, Cl-, Ca2+
• non-electrolytes - glucose, lipids, urea

Question 32

What does the body need to balance?

Answer 32

Water gain with water loss

Question 33

Where do most water gains come from?

Answer 33

Food and drink

Question 34

How much water a day do we gain though metabolism?

Answer 34

300mL

Question 35

How is water lost in the body?

Answer 35

Through urine, faeces, skin and lungs

Question 36

What is the main source of water loss?

Answer 36

Urine

Question 37

What are the insensible losses?

Answer 37

Losses through skin and lungs around 900ml a day

Question 38

What is the obligatory urine output?

Answer 38

Around 4 to 500 ml per day in order to excrete solutes