A1.1 Water

Question 1

State that the first cells originated in water

Answer 1

Cells first originated in water

Question 2

List reasons why water is a substance on which life depends

Answer 2

The first cells originated in water

Water is the solvent

Water is a metabolite

Water is a temperature buffer

Water maintains biological structures

Question 3

Describe the structure of an atom.

Answer 3

An atom is composed of a nucleus with protons and neutrons and is surrounded by electron orbits

Question 4

Outline the formation of ionic and covalent bonds between atoms.

Answer 4

Covalent Bond : Two atoms held together that share one or more pair of electrons

Ionic Bond : Attraction between a positively charged ion (cation) and an negatively charge ion (anion)

Question 5

Explain the sharing of electrons between atoms in a polar covalent bond.

Answer 5

In a polar covalent bond since one side has more protons it has a stronger pull on the electrons resulting in a slightly negative charge on the side with a bigger pull and a slightly positive charge on the side with a weaker pull

Question 6

State the location of the polar covalent bond within a water molecule.

Answer 6

Polar Covalent bonds are between the two hydrogen molecules and oxygen molecule

Question 7

Explain the partial charges of the oxygen and hydrogen atoms within a water molecule.

Answer 7

The hydrogen’s are slightly positive and the oxygen is slightly negative. This is due to oxygen’s nucleus which has a stronger pull

Question 8

Outline the cause of the formation of hydrogen bonds between water molecules.

Answer 8

Hydrogen bonds are formed because of the attraction between the slightly negative side of hydrogen and the slightly positive side of oxygen. And vice versa

Question 9

Outline the consequences of the collective strength of hydrogen bonds between water molecules.

Answer 9

Hydrogen bonds are weak individually however collectively contribute to the stability and retainment of water on Earth.

Question 10

Define cohesion.

Answer 10

Cohesion is the property of water in which it makes hydrogen bonds with itself, causing water molecules to stick together

Question 11

Describe how water moves through the xylem of a vascular plant.

Answer 11

Transpiration (evaporation) occurs through stomata of a leaf and creates negative pressure

The tension created by transpiration “pulls” water in the plant xylem drawing it upwards

Cohesion pulls up water molecules in a chain from the top-most water molecule

Question 12

Outline the cause of surface tension.

Answer 12

Surface tension is caused by the cohesion of water molecules on the surface of the water which forms a barrier of hydrogen bonds. These hydrogen bonds are also stronger as there is no water molecule in the air meaning it creates an inward force and stronger bonds with other water molecules on the surface

Question 13

State a benefit to living things that results from surface tension.

Answer 13

Surface tension allows organisms such as water striders to live on. As they are not strong enough to break the water tension.

Question 14

Define adhesion.

Answer 14

Adhesion is the property of water in which it bonds with other substances that are polar

Question 15

Define polar.

Answer 15

Polar means there is an unequal sharing of electrons within atoms

Question 16

Define ion.

Answer 16

An ion is an atom that has lost or gained an electron and has an unequal number of electrons to protons

Question 17

Compare cation and anion.

Answer 17

Cation, is an ion that is positive

Anion, is an ion that is negative

Question 18

Explain why water is attracted to molecules that are polar or charged.

Answer 18

The slightly negative side of a water molecule is attracted to the positive charge of molecules that are polar or charged

The slightly positive side of a water molecule is attracted to the negative side of a polar or charged molecule

Question 19

Outline the cause of capillary action.

Answer 19

Capillary action is the movement of water through a narrow space, often in opposition to external forces like gravity. Adhesion of water to the walls of the vessel will cause an upward force on the liquid and cohesion will drag the chain of water behind it

Question 20

Describe capillary action in plant tissue.

Answer 20

Capillary action helps bring water from the roots all the way up to the branches and leaves. Adhesion allows water to stick to the xylem walls which will cause an upward force on the water.

Question 21

Outline the cause and effect of capillary action in soil.

Answer 21

Capillary action in soil means moving though soil pores on spaces between soil particles the same way it moves through a tube

Question 22

Identify solvent and solutes of a solution.

Answer 22

Solvent : the liquid in which a solute dissolves

Solutes : the substance that dissolves in a solvent

Question 23

Define solvation.

Answer 23

Solvation is the interaction of a solvent and a dissolved solute

Question 24

Explain why water is able to dissolve charged and polar molecules.

Answer 24

Because water is a polar solvent attracted to polar and charged molecules which are solutes.

Question 25

Outline the solvation of hydrophilic and hydrophobic substances.

Answer 25

Hydrophobic means water fearing, because they aren’t polar or charged they do not dissolve within water

Hydrophilic means water loving, because they are charged or polar they dissolve within water

Question 26

State an example of the function of a molecule depending on it being hydrophobic and insoluble.

Answer 26

Cholesterol - component of membrane structure

Question 27

State an example of the function of a molecule depending on it being hydrophilic and soluble.

Answer 27

Salt dissolving in water

Question 28

Outline the role of water as a medium for metabolism.

Answer 28

Cytosol the liquid part of the cytoplasm, is a structure that contains dissolved salts, fatty acids, sugar, amino acids and proteins such as enzymes. These dissolved substances are needed to carry out the metabolic processes required to keep the cell alive.

Question 29

Describe the role of water as a medium for transport in vascular plants.

Answer 29

Water is used to transport dissolved ions and sugars through the body of vascular plants.

Question 30

Describe the role of water as a medium for transport in animal blood.

Answer 30

Water is used to transport molecules through the body within the blood of animals. Blood plasma transports salt ions, amino acids, proteins, glucose and waste products of metabolism.

Question 31

Define physical property.

Answer 31

A physical property is a measurable characteristic of a matter that exists without the matter reacting or interacting with other things

Question 32

List physical properties of water that are consequential for animals in aquatic habitats.

Answer 32

Buoyancy

Viscosity

Thermal Conductivity

Specific Heat capacity

Question 33

Outline the cause and effect of buoyancy.

Answer 33

Cause : The upward force on an object when submerged in water

Effect : If the buoyant force is stronger than the object’s weight, the object will float.

Question 34

Outline the cause and effect of viscosity.

Answer 34

Cause : due to the amount of friction the molecules experience as they flow over each other

Effect : A thick fluid is more viscous than a thin fluid

Question 35

Compare viscosity of air to water to blood.

Answer 35

Air has very minimal friction between molecules and is therefore less thick and less viscous than water which has more friction between molecules. However blood has more friction between molecules and is more thick and viscous

Question 36

Define thermal conductivity.

Answer 36

Thermal conductivity is a measure of a material’s ability to move heat across a temperature gradient.

Question 37

Compare less conductive to more conductive materials.

Answer 37

Less conductive : Heat slowly moves through material. Better for insulating and conserving heat

More conductive : Heat rapidly moves through the material. Better for absorbing and transferring heat

Question 38

Outline a consequence to life of the thermal conductivity of air and water.

Answer 38

Marine mammals are exposed to both air and water. The marine mammal will lose more heat within water than within air because water is able to rapidly absorb heat whereas air isn’t. This would mean that within colder regions, marine mammals would need an insulating layer of some sort in order to submerge themselves in water.

Question 39

Define specific heat capacity.

Answer 39

Specific heat capacity is the amount of energy required to lift the temperature of a chemical per unit mass

Question 40

Describe why water has a high specific heat capacity.

Answer 40

Water has a high specific heat capacity because of the amount of energy required to collectively break all hydrogen bonds. The amoumt of heat energy absorbed when trying to break thses bonds increases the temperature

Question 41

State two benefits to life of the high specific heat capacity of water.

Answer 41

The high specific heat capacity allows the water to maintain a consistent temperature, which provides a stable environment and habitat of living things

Question 42

Outline a benefit to life of water’s high specific heat capacity.

Answer 42

Because living bodies contain a lot of water our body temperature is slow to to change when our environmental temperature changes.

Question 43

Compare the physical properties of water to those of air.

Answer 43

Water

Greater buoyant force

Greater viscosity

Greater thermal conductivity

Greater specific heat capacity

Air

Lower buoyant force

Lower viscosity

Lower thermal conductivity

Lower specific heat capacity

Question 44

Describe how the black-throated loon (Gavia arctica) and/or the ringed seal (Pusa hispida) interact with the physical properties of water in their habitat.

Answer 44

The black throated loon is able to float on water without expending too much energy due to the buoyancy of water. However in the air it requires a lot of energy to stay aloft. The water is viscous, so the loon takes advantage of it’s streamline shape to move through the water and in the air can easily move through it when flying. The loon doesn’t lose as much body heat to the air because air has low thermal conductivity. However because the air has a low specific heat, it’s temperature changes rapidly

Buoyancy in water allows the seal to stay afloat without expending a lot of energy. However the water is viscous, so the seal has adaptations to streamline as it swims. Water has a greater thermal conductivity than air, so the seal needs to insulate itself with blubber to maintain body temperature. However, because of the water’s high specific heat capacity, the water maintains a stable water temperature

Question 45

Explain the hypothesis that asteroids are responsible for the origin of water on Earth.

Answer 45

Asteroids and comets up to a few 100 kilometers away seem like the most likely sources of most of Earth’s water. Studies of rocks that date to soon after the formation of Earth suggest that water may have begun to exist on Earth as early as 4.4 Billion years ago.

Question 46

State two reasons why water was retained on early Earth

Answer 46

Water was retained because of the gravitational pull and the distance from the sun

Question 47

Explain why the presence of water is considered fundamental to the search for extraterrestrial life.

Answer 47

Water is essential for all life because it functions as a solvent allowing the key chemical reactions to take place.

Question 48

Define “Goldilocks zone” in relation to the search for extraterrestrial life.

Answer 48

The goldilocks zone is when a planet is nor too far or too close to the sun so that the water remains liquid.