Thermochemical Cycle things. ΔHf, ΔHc

Hess' Law states that the enthalpy change for a chemical reaction is the same, whatever ther route taken for the reactants to products. This means they can be made into cycles.

When in enthalpy of formation, (the enthalpy it takes to form one mole of compund from its constituent elements, under standard conditions, all reactants/products in standrad states), you write the balanced equation of your reactions on top, and the constiuent elements on the bottom. The arrows point up. Then, to follow the path of it, fill in the values, and flip the first arrow, and the negative/positive charges round. Add it up and you'll get the ΔH, from the ΔHf.

When it's the enthalpy of combustion, (the enthalpy it takes to burn one mole of compound in oxygen under standard conditions, with all products and reactants in their standard states), the balanced equation is on the top, and the arrows point downards. You'd the flip the second arrow and charges when you add all stuffs upppp.

So,

• Write an equation for the reaction
• Write down the constituent elements or CO2 and H2O at the bottom, balanced.
  
• Put in all the ΔHf/ΔHc values you have.
  
• Turn the correct arrows around
  
• Follow the path round, adding up.
  

Chem bits. Kinetics and that (:

Endothermic, heat going in. Exothermic, heat given out. (In reaction.)

So, endothermic, as in, takes heat/energy in to make the reaction actually go anywhere. In exothermic, it gives out energy as heat.

Enthalpy change is when we measure heat change at a constant pressure.

Enthalpy is shown by the letter H, and change is shown by Δ/delta. So, a change in is enthalpy is ΔH.

Enthalpy level diagrams show the relative enthalpy levels of the reactants, and products, which, in turn, shows the ethalpy change.

Enthalpy of formation is the enthalpy change when one mole of compund is formed from it's constituent elements, under standard conditions, all reactants and products in standard states.

Enthalpy of combustion is the enthalpy change when one mole of compound is burned in oxygen under standard conditions, all products and reactants in standard states.

Enthalpy change = mass of substance X specific heat capacity X change in temperature.

OR

q=mcΔT

(Q = enthalpy change)

In a calorimeter, fuel is burnt to heat a known mass of water (m), and then measure the temperature at the beginning and throughout, to get the change in temperature (ΔT) and the standard heat capacity can be used, or one is given, and then q=mcΔT can be used.

The calorimeter, and measurement of enthalpy change can be made more accurate by preventing heat loss. This can be as simple as adding a lid, draught screen, and insulation around the beaker.

To measure enthalpy changes in solution it is normally in a polythene cup. These are insulators, so heat loss will be reduced, and the heat capapcity is low, and this means they don't absorb much heat, and it all stays in the solution.

Chlorine and all that jazz (:

What is chlorine used for?

• properties
• oxidisng abilities.
  

Chlorine is used in water to kill off unwanted bacteria.

Cl2(g) + H2O(l) => HClO(aq) + HCl(aq)

This ONLY happens in the sun/UV

Chlorine = swimming pool outdoors = pH change.

reaction w/ alkali ...
Cl2 + 2NaOH => NaClO + NaCl + H2O

Sodium chloride = bleach.

The agents, oxidisng and reducing, are the opposite of what happens.

Group Seven :D

Trends:

1. Electronegativity. This increases as you go up the group.
   
2. Atomic Radius, increases as you go down the group.
   
3. Melting point, increases as you go down the group.
4. Boiling point, increases as you go down the group.
   
5. The oxidisng agent ability increases and you go up the group (so, Astetine to Fluorine.)

Their colours, in solution... Fluorine is clear, Cl is yellowy, Br is red/brown, and Iodene is purple.

The Sodium Hallides + Sulphuric Acid:

Eqn1 ...
NaCl (solid) + H2SO4 (liquid) => NaHSO4 (solid) + HCl (gas)
This produces steamy fumes of HCl

Eqn2 ...
- NaBr(s) + H2SO4(l) => NaSO4(s) + HBr(g) [Steamy fumes]
-- 2H+ + 2Br- + H2SO4 => SO2 (g) +2H2O(l) + Br(l) [Brown fumes]


Eqn3 ...
- NaI(s) + H2SO4(l) => NaH2SO4(s) + HI(g) [Steamy fumesof HI]
-- 2H+ + 2I- + H2SO4(aq) => H2S(g) + 4H2O(l) + I2(s) [Black solid forms, (I2), bad egg smell.]

Group Two Metals

Trends that are needed to know:

1. The solubilities of group two Hydroxides increase as you go up the group (Radium to Beryllium)
2. The solubilities of Group two Sulphate decrease as you go down the group (Beryllium to Radium)
   

Group two are all metallic and therefore, have high melting points. The sea of delocalised electrons are further from the nuclei as you go down the group, and therefore, the strength of the bond decreases and the melting point decreases.

Haemoglobin

Is a protein consisting of:

• 4 Polypeptide chains
• These are coiled into a helix
• Which is folded into a specific shape
  
• These are linked to form a spherical molecule.
  

Each polypeptide is associated with a haem group, containing and Fe2+ ion.

Ferrous (Fe2+)attaches to the middle of the heam group.

Hb+ 4O2 = HbO8
or
Haemoglobin + Oxygen = Oxyhaemoglobin

Has to associate/load with oxygen in the lungs. High affinity. Disociates at the tissues that require it.

Carbon Dioxide makes a weak acid when in water (solution), this changes the pH, and therefore, the shape of the protein, (temporarily.)

Why can haemoglobin unload? :

• Low partial pressure of O2 means the oxygen is used in aerobic respiration, which means there is a higher CO2 concentration.
  
• This reduces the pH (as CO2 is acidic in solution)
  
• Haemoglobin changes it's shape in high CO2 concentrations.
  
• This means it binds to the oxygen more loosely.
  
• And can, therefore, unload where needed.
  

Erythrocytes- Red Blood Cells
Leucocytes- White Blood Cells.

Plasma % in blood is important, makes it fluid, and flows easier.

Adaptations of a red blood cell:

• Small size (7 micrometres.)
  
• Flattened biconcave disc shape.
• Thin central section
• Absence of organelles.
  
• Filled with haemoglobin

Oxygen dissasociation curve: Shows how much oxygen is combined with Hb at different concentrations of oxygen.

Haemoglobin is never 100% saturated.

Pp of oxygen is lower in lungs due to presence of CO2 and water vapour so it would be less.

Thoughts?
-Nin.

Tissue fluid, etc. :D

Tissue fluid carries oxygen to cells, takes waste products. Important substance.

What is tissue fluid?

• formed from blood plasma, leaking out of the capillaries.
• Is a watery liquid that contains glucose, amino acids, fatty acids, salts and oxygen. Tissue fluid supplies all these substances to the tissues and also recieves waste materials, for example, carbon dioxide from the tissues.
• Is the means by which materials are exchanged between the blood and cells of the body
• It provides a very constant environment for cells.

Lymphatic system starts in capillaries, series of tubes, join to make bigger lymph nodes.

Formation of tissue fluid and return to circulatory system:

• Blood leaving heart passes along arteries, narrower arterioles, and then even narrower capillaries.
• This creates a pressure called hydrostatic pressure at the arterial end of the capillaries
• Hydrostatic pressure forces fluid (and plasma) out.
• This is opposed by the hydrostatic pressure of the tissue fluid outside, and the lower water potenital in the due to the plasma proteins that pulls water back into the arteries.

Thoughts?

-Nin.

Transport systems and stuff.

Why do some organisms need a transport system?

• Large organism: Small surface area to volume ratio, needs can't be met by the surfaace of the body.
  
• Diffusion is inadequate over large distances.
  
• Transport system required to take materials from cells to exchange surface and vice versa.

The lower the SA/V ratio, and the more active the organism, the greater the need for a specialised system with a pump.

Main function of a blood system is to transport substances around the body. Allows organism to move substances around in bulk, quickly, over large distances. Blood vessels, a closed system of tubular vessels contain blood and transport it. The heart is the mechanism that pumps. Valves maintain this flow in one direction.

Arteries take blood away from the heart into ARTERIOLES, thinner branches of arteries in organs. CAPILLARIES- mass of very narrow vessels which penetrate tissues. Link ARTERIOLES to VENULES. VENULES, blood flows back from capillaries into veins, which transports blood back to the heart.

Structure of blood vessels:
Arteries, arterioles, and veins have the same basic layered structure. Relative proportions of each layer differ between each type of blood vessel:-

• Tough outer layer- resists pressure changes, inside and out, (OUTER LAYER)
  
• Muscle layer, can contract and control the flow of blood.
  
• Elastic layer, helps maintain pressure by stretching and recoiling.
  
• Endothelium- thin inner lining, smooth to prevent friction, and thin to allow diffusion. INNER LAYER.
  
• Lumen - central cavity of blood vessel.
  

Have different proportions of these features in different types.

Arteries- thick walls to maintain pressure, thin to absorb it and keep it constant.

Arteries Have a smooth endothelium, inner layer, cells are flat. This ensures the blood flows freely and doesn't stick to the walls. It has a layer of elastic fibresm, which allows it to expandand recoil each time the heart beats, smoothing out pressure changes. The have a realtively thick muscle layer, so that smaller arteries can be constricted to control the volume of blood passing through them. There is a tought outer layer of protein fibres, which allows the wall to resist bursting under pressure.

Arteriole's muscle layers are relatively thicker then that of the arteries. This allows contraction of the muscle allowing constriction of the lumen of the arteriole, restricting bloodflow and controlling it. Also the elastic layer is thinner then that in the arteries, as the blood pressure is lower.

Veins have a realtively thin muscle layer, as they carry blood away from the tissues, and therefore, cannot control blood flow to the tissues. The elastic layer is thin, becuase there is a low blood pressure, and the recoil action cannot be made. The walls are thinner then the arteries walls are. This is because blood pressure is lower and pressure is resisted less. There are valves throughout (the body muscles contract and compress them), this ensures that blood flows one way.

Capillaries are one cell thick, and their function is to exchange metabolic material. The flow of blood is slow in capillaries, which allows more time for exchange of materials. Also, the walls are extremely thin, which makes for a short diffusion distance. There are numerous capillaries, which provides a large SA for diffusion. They are narrow in diameter, so they can penetrate tissues.

Potometer , other random notes about fish and that.

Potometer:

It is difficult to measure transpiration, because it is difficult to collect and condense, and you can't measure vapour.

A leafy shoot would be cut under water, because otherwise, an air bubble would go into the xylem, breaking the transpiration stream, and stopping the movement up the shoot. If it is in water, water will be drawn in instead, and the column maintained.

The syringe in a potometer is to refill the capillary tube when the bubble reaches the stem so water can continue to be measured.

Assumption made if potometer is used to measure the rate of transpiration - all water taken up is being transpired.

Small organisms have a sufficient gas exchange system as the have a large sa/v ratio.

Large animals have blood systems because with a large animal, gas exchange diffusion distance to cells would be too far, so, blood system is needed for rapid oxygen supply.

Small fish, no gill, because exchange/diffusion can take place through body surface, as they have a high surface area to volume ratio and a short diffusion distance.

Mackerel swim faster then toadfish => Mackerel have thinner lamellae, short diffusion distance, rate of gas exchange is quicker, get oxygen for respiration faster, to release ATP for muscle contraction.

Gill makes oxygen efficient => Thin lamellae, short diffusion distance to blood capilaries

Counter current flow maintains a concentration gradient, doesn't reach an equilibrium, takes place along whole gill.

Yet more plant shiz. (:

Transport up the stem, due to:

• Root Pressure- generated by the active transport of ions in the endodermis, creating a water potenital gradient.
  
• Cohesion Tension.

Xylem Vessels are thinner when not transpiring.

Water molecules are polar, form hydrogen bonds. Water molecules form hydrogen bonds to make continuous stream. Water is constantly lost by transpiration. When one molecule is lost, another is pulled along. Transpiration pull is the main cause of water movement, putting the water under tension.

Water attraction = COHESION.

Cohesion Tension:

• Water lost from respiritory surface in leaves during transpiration is replaced by water from xylem in leaves.
  
• This causes a negative pressure in the xylem of the leaves which pulls up a column of water with dissolved ions up with xylem.
  
• Column of water does not break as, 1) Hydrogen bonds hold water together, and 2) water molecules are attrated to the xylem vessels.
  

Transpiration:

• Water evaporates from the mesophyll cells into the air spaces in the leaf.
  
• It diffuses out of the stomata to the atmosphere. (Air has a low water potential, as it usually has a low % of water vapor.)

Rate of transpiration is affected by four main factors:

• TEMPERATURE: temperature rises and increases the kinetic energy, and therefore, the particles move faster, and the diffusion of water vapor is quicker.
• HUMIDITY: Air spaces in the leaf are normally saturated with water, whereas the air outside is much less humid. The greater the difference in humidity, the faster the water will diffuse out.
• AIR MOVEMENTS: The more rapidly the air is moved away from the leaf surface, the more rapid the rate of transpiration, as it takes away the layer of moisture that forms, and maintains a constant water potential gradient.
  
• LIGHT: This is an indirect effect, stomata are usually open during daylight hours, to allow carbon dioxide in, but it also lets water out.
  

More plant bits.

Water/minerals go through the cell wall, can pass through fibres (apoplasric)

Endodermis controls what goes in.

Apoplastic Pathway:

• Water can move freely between fibres in the cellulose cell wall.
  
• There is very little resistance, and, as the water moves it pulls move water behind is due to the cohesive properties of water.
  

Symplastic Pathway:

• Takes place across the cytoplasm of cells of the cortex as a result of osmosis.
  
• Water passes from cell to cell along tiny passages/openings called Plasmodesmata. Each plasmodesmata is filled with a thin strand of cytoplasm.
  
• Water moves down a water potential gradient, since the cells near the centre have a more low water potential then those near the outside of the root.
  
• It is a slow route, because the membranes and cytoplasm restrict the rate at which water can move.
  

Passage of water into Xylem:

• Before water enters the xylem it has to pass through the endodermis.
• Water traveling the apoplastic way (along the cell wall) can't continue as there is the water proof barrier, the casparian strip.
  
• It has to pass through the membrane and cytoplasm and join the symplastic pathway.
  
• The ions must be actively transported through the cell, which builds up a high concentration, and the gradient goes backwards.
  
• This establishes a water potential gradient, from the root hairs, to the centre of the root, as the ions would lower the WP in the centre, and the water coming in makes it high at the tip. This is called root pressure.

Evidence for the existence of root pressure:

• The pressure increases with an increase in temperature.
  
• Metabolic inhibitors e.g. cyanide, cause root pressure to cease to exist. (It would stop the active transport, and therefore, no WP gradient is created.)
  
• A decrease in oxygen can cause a reduction in root pressures.
  

Transport into Xylem:

• ACTIVE SECRETION of mineral ions into the xylem.
  
• This lowers the water potential of the solution in the xylem
• This makes a water potenital gradient, and water passes into xylem via osmosis froma high water potential to low.
  

• 
  

Structure of root and stem (:

Plant adaptations for mass transport.

'Root Pressure'
'Cohesive Theory'

Needs water for photosynthesis in pallisade cells, and to keep it turgid. Also, evaporation from leaves has a cooling effect, stopping them from overheating, and enzymes denaturing.

Epidermis- one cell thick, single cell have out growths called root hairs.
Exodermis- protection against pathogens.
Cortex- nonspecializing cells that often store starch.
Endodermis- Surrounds Xylem/Pholem, waxxy layer called casparian strip. Impermeable to water and mineral ions, selective.
Xylem- transports water and mineral ions.
Phloem- Transports organic substances (e.g. sucrose) around the plant.

Big thick roots are used for anchoring, not taking up water.
New xylem doesn't have any lignin, lignin can take on different patterns. Thin areas in vessels called pits allows water to move laterally. When fully ligininfied, moving laterally is the only option.

Xylem Vessels:

• Responsible for the movement of water and ions in the plant.
  
• Long tubes linked end to end of dead cells containing NO cytoplasm
  
• Develop near tip of root as elongated cells and become thickened with lignin.
  
• Young cells have rings of lignin.
  
• Old cells are completely ligninfied, apart from small gaps called pits.
• Pits allow water to move sideways into tissues if vessels get blocked.
  

Uptake of water by root hair:

• Larger roots anchor plant into soil (waterproof)
  
• Branch to form finer roots, not waterproof.
  
• Epidermis have extensions called root hairs. Increase surface area.
  
• Root hairs are exchange surfaces for uptake of water and minerals.
  

Root hairs are efficient because they have a large surface area, and a thin surface layer, so there's a shorter diffusion distance.

The soil solution is mostly water and has a very high water potential. The root hairs have sugars and amino acids dissolved in them, and have a low water potential. So, water moves by osmosis down this water potenital gradient into the root hair cell. Ion can also go in by active transport, as this gradient is in reverse.

Water movement take two route across the cortex. Apoplastic and Symplastic.
Apoplastic: Has to go between fibres, and join the symplastic when it reaches the non permeable casparian strip.
Symplastic: Pushes through the membrane, and faces far more resistance.

Xerophytes :D

Xerophytes: Plants that live in very dry conditions, and have additional adaptations that enable them to conserve water effectively.

Cactus, for example:

• Have a thinner waxy cuticle
• A reduced surface area
• Stem is adapted for photosynthesis, lots of chloroplasts.
  
• Less leaves = low sa/v ratio, which reduces water loss.
  
• Stem stores water in tissues.
  
• Reduced number of stomata, water can't escape from them.
  

These factors increase the rate of transpiration:

• Windy - As water diffuses, a vapour accumulates around the stomata on the outside on the leaf. This increases the water potential, lowering the water potential gradient. Rate of transpiration is therefore, reduced, however, if it is windy, this layer of moisture is blown away, and the area become drier, allowing the water potential to lower, increasing the gradient, and speeding up the rate of transpiration.
• Light- Stomata are open in the light, when the stomata are open, water moves out and into the atmosphere, therefore, light increase rate of transpiration.
  
• Temperature- increases the kinetic energy so particles move faster, and lowers the water potential to make a gradient.
  
• Humidity- low humidity, = less water in air, better WP gradient.
  

Marram Grass:

• Leaf rolls up, only one surface expose, inside gap will be humid, creates gradient.
  
• Expose surface has thick cuticle, and no stoma. (No water can escape)
  
• Stomata on inside in grooves (microclimate, humid, gradient is backward, can't get out.)
• Hairs trap water and increase water potential.
  

Planty bits (:

Dicotelydon - 2 cotelydon- two seed leaf
Monocotelydon - one seed leaf.
In a plant, water and CO2 go in, and glucose and oxygen out go out. Oxygen and carbon dioxide are the gas exchange products.

Photosynthesis takes place in daylight hours.

Respiration takes place all the time, as all cells need to respire.

Stoma (singular)
Stomata (plural)

- Large surface area = numerous stomata.
- Thin= Short diffusion distance.
- Concentration gradient is great.

Spongy mesophyll, lots of air spaces.

Layer of moisture, gas dissolves and gas diffuse through membrane.

Vascular bundle, where xylem and phloem are. Xylem brings water into the leaf.

Gases enter the leaf through the stomata, usually in the lower surface. Stomata are enclosed by guard cells that can swell up and close the stomata to reduce water loss. The gases then diffuse through the air spaces in the leaf which are in direct contact with the spongy pallisade mesophyll cells. Plants do not need a ventilation mechanism as their leaves are exposed, so the air surrounding them is constantly being replaced.
During the hours of daylight, photosynthesis increases the oxygen concentration in the sub-stomal airspaces.
When a green plant is expose to bright light, both photosynthetic and respiritory gas exchange are taking place in the leaves. However, since the rate of photosynthesis exceeds the rate of respiration during the day, there is a net uptake of carbon dioxide and release of oxygen.
In the dark, the non photosythetic parts of the plant, that respire, there is a net uptake of oxygen and a net release of carbon dioxide.

• Long thin pallisade cells, large Surface Area.
• loosely packed, whole surface covered.
• moist layer, gases can dissolve and diffuse easily.
  
• air spaces give a constant circulation of air.
  
• thin - short diffusion distance.
  
• numerous stomata.