Revision notes – Psychology A2 – Overt behaviour and Private subjective experience

Distinctions that have been made between behaviour and experience are that behaviour is external or overt and amenable to scientific enquiry whereas, experience is internal, subjective and not open to scientific enquiry.

These distinctions are in fact misleading. Biological psychologists study internal events using ‘scientific’ techniques such as EEG recordings can be classed as behavioural. Cognitive psychologists attempt to investigate thought processes, memory, perception and attention which are all part of internal, private and conscious experience yet, are amenable to scientific enquiry. Insights into these mental processes may be inferred from an individual’ observable response.

Private subjective experience – personal subjective phenomena and unique to the individual. Private subjective experiences are not easily investigated using scientific procedures.

A better distinction is the criterion of accessibility. Behaviour, whether external or not, can be directly observed by a researcher or at least inferred using empirical methods, whereas private subjective experience cannot.

William James, ‘stream of consciousness’ – a internal monologue that is always present, unique, private and accessible only to the individual. People are aware of external events through the combined information from all senses but this cannot be fully verbalised as it is fleeting and therefore, there is too much report. Private subject experience cannot therefore be fully accessed or replicated. People can never perceive the same experience twice because on the second occasion, the event is a different experience.

Introspective reports – report what went through their mind whilst carrying out some action.

Introspective reports couldn’t be verified, were subjective and accessible only to the individual reporting the experience. Only those processes of which the participant was aware could be reported.

Phenomenology – the study of an individual’s subjective and contemporary experience or unique perception of the world. The emphasis is on understanding events from the person’s point of view rather than focusing on behaviour.

Chemistry A level – Kinetics

*I apologise to my followers for spamming your feed with all these chemistry related posts! I’m throwing my notes away so I wanted to get these revision notes up onto the blog before I scrapped them. Bear with me please, I’ll post something that isn’t related to science soon!*

Increasing the temperature – this increases the rate of reaction because the particles have more kinetic energy therefore, they move faster, the frequency of collisions increase. More particles will have the minimum activation energy and therefore, it is most likely to have more successful collisions.

Increasing the pressure – this increases the rate of reaction because there are more particles in the same unit volume so, there are more collisions with the minimum activation energy and therefore, more successful collisions.

Increasing the concentration – increases the rate of reaction because there are more particles in the same unit volume so, there are more collisions with the minimum activation energy and therefore, more successful collisions.

Adding a catalyst – this increases the rate of reaction by providing an alternative pathway of lower minimum activation energy, so more particles have the minimum activation energy and therefore, there are more successful collisions.

Chemistry A level – Equilibria

Important definitions and concepts that need to be known for equilibrium

LE CHATELIER’S PRINCIPLE – a system as dynamic equilibrium will shift its equilibrium position to oppose any external change applied to it.

DYNAMIC EQUILIBRIUM – the rate of the forward reaction exactly equals the rate of the reverse reaction, maintaining constant concentration of reactants and products.

Factors affecting the equilibrium position:

Concentration – Le Chatelier’s principle predicts that if a reactant’s concentration is increased, the equilibrium position will shift to the right/the product’s side in order to decrease the concentration.

If the reactant’s concentration is decreased, the equilibrium position will shift to the left/the reactant’s side in order to increase the concentration.

if a product’s concentration is increased, the equilibrium position will shift to the left/the reactant’s side in order to decrease the concentration.

If the product’s concentration is decreased, the equilibrium position will shift to the right/the product’s side in order to increase the concentration.

Pressure – The pressure depends on the number of gas molecules in the system. Le Chatelier’s principle predicts that if the pressure is increased, the equilibrium position will shift to the side with fewer gas moles.

If the pressure is decreased, the equilibrium position will shift to the side with more gas moles.

If the number of gas moles is the same on both sides, then changing the pressure has no effect on the equilibrium position.

Catalyst – adding a catalyst will have no effect on the position of equilibrium. The addition of a catalyst will increase the rate of the forward and reverse reactions but by the same amount.

Temperature – in order to understand how temperature change may affect the equilibrium position, you must know how to identify whether a reaction is exothermic (gives heat out therefore, increasing the temperature of the system) or endothermic (takes heat in therefore, decreasing the temperature of the system).

Le Chatelier’s principle predicts that if the forward reaction is exothermic, an increase in temperature will cause the equilibrium position to shift to the left. If the forward reaction is exothermic, a decrease in temperature will cause the equilibrium position to shift to the right.

If the forward reaction is endothermic, an increase in temperature will cause the equilibrium position to shift to the right. If the forward reaction is endothermic, a decrease in temperature will cause the equilibrium position to shift to the left.

Chemistry A2 notes – Optical isomers

  • An optical isomer occurs when the carbon atom (chiral centre; this is marked by a *) is attached to 4 different groups.
  • this results in 2 isomers (pair of enantiomers) that are mirror images
  • they are NOT identical and can’t superimpose
  • the 2 isomers differ in the way that they rotate the plane of polarisation of polarised light

How to distinguish between the pair of enantiomers

  • the 2 isomers differ in the way that they rotate the plane of polarisation of polarised light
  • (plane-polarised light is light that has been filtered into 2D plane)
  • the light passes through a polaroid or liquid containing a chiral molecule which causes the plane of light to rotate. This is detected using a polarimeter
  • chiral molecules rotate plane-polarised light.
  • the 2 isomers rotate equally but in opposite directions.
  • The + isomer (dextrorotatory) rotates the plane of polarisation CLOCKWISE.
  • The – isomer (laevorotatory) rotates the plane of polarisation ANTI-CLOCKWISE.
  • a substance which can rotate plane of polarised light is optically active

The importance of optical isomers in biochemistry

Many drugs and enzymes are chiral so only 1 of the optical isomers can interact effectively with the target molecule.

Many drugs work by a molecule of the active ingredient fitting the receptor on the cell, similarly enzymes have a specific active site that only a specific substrate can fit into.

Receptors have a 3D structure so only 1 of the pair of optical isomers will fit. So one optical isomer will be the effective drug and the other optical isomer will be inactive.

Racemates

The oppostie effect they have on the rotation of plane polarised light is no overall rotation, so an equimolar mix of 2 optical isomers will have no effect on the plane of polarised light. So they are NOT optically active.

Racemic mixtures – equimolar mixture of 2 optical isomers that aren’t optically active.

Separating the 2 isomers is difficult and expensive as they have similar properties.

Chiral molecules show optical activity if 1 isomer is in greater quantity than the other.

Chemistry A2 notes – stereoisomerism

STEREOISOMERISM

Geometrical isomers occur in alkenes when both carbon atoms forming the double bond are attached to 2 different groups. It has a restricted rotation.

Optical isomers

  • When the carbon atom is attached to 4 different groups
  • It is asymmetric but cannot be superimposed on its mirror image
  • The mirror images cannot be interconverted without breaking covalent bonds
  • 2 non-superimposable images are optical isomers or enantiomers

Biology AS revision notes – The Digestive System

Summary of the digestion process

Food enters the mouth and is physically broken down by teeth into smaller food pieces to ingest the food and provide a large surface area for chemical digestion. (The salivary glands pass their secretions which contain amylase to break starch down into maltose, into the mouth via the duct). The pharynx is responsible for the food going down the right passage through the oesophagus. The epiglottis prevents food getting into the respiratory system.

The food goes down the oesophagus which carries food from the mouth to the stomach and is made up of a thick muscular wall so that it is adapted for transport.

The food goes to the stomach which is a muscular sac with an inner layer. The stomach stores and digests foods and has glands that produce enzymes (protease) to digest proteins. The other glands produce mucus to stop the stomach being digested by its own enzymes.

The muscles in the stomach wall also churn the food (physical digestion).

The food is then further digested by enzymes that are produced within the walls of the small intestine and by the glands that pour their secretions into it. The small intestine is a long muscular tube with the inner walls folded into villi to increase surface area. The surface area of the villi has microvilli to further increase the surface area for absorbing products into the bloodstream.

The liver is made up of glandular tissue and produces bile and the gallbladder stores the bile.

The pancreas is a large gland that produces alkaline pancreatic juice which contains proteases to digest proteins, lipases to digest lipids, and amylase to digest starch.

The large intestine is a muscular tube that absorbs water and the rectum is where the faeces are stored before being removed via egestion.

Microscopes – Biology AS A Level – Revision notes

In Biology AS, you will need to know about 3 types of microscopes: light microscopes, scanning electron microscopes and transmission electron microscopes.

Most of the time, the exam paper will have questions asking about the advantages and disadvantages of using these microscopes but in order to understand this, it is best that you first have a brief overview of how each type of microscope works.

How a light microscope works

  • A condenser is used to gather light from a source and focus it on a small area of the thin specimen.
  • The specimen is illuminated by the light shone from beneath it.
  • The objective lens are small and have a shorter focal length which allows light to be gathered from the illuminated specimen and brings the image into focus at a shorter distance.
  • The ocular lens magnify the image as it is brought to your eyes.
  • The objective lenses can be used to bring even smaller areas of the specimen into view.

How scanning electron microscopes (SEM) works

  • An SEM is a microscope that uses electrons to allow you to see objects smaller than the wavelength of light
  • The electron gun at the top of the column generates a beam of electrons that is fired at the sample surface (the lenses help to direct the electrons onto the target).
  • The surface of the sample is scanned with a high energy beam of electrons which causes the electrons to collide with the atoms in the sample
  • The detectors pick up on the movement of the secondary electrons and it is then fed through to the sensor/monitor that collects the image.

How transmission electron microscopes (TEM) work

  • The TEM also works by using a beam of electrons to create an image of the specimen but, unlike the SEM that produces an image by bouncing electrons off the surface of the sample, the TEM fires the electrons through the sample.
  • The magnetic lenses form a high voltage electron beam that is emitted by the cathode and shot through the sample
  • The electromagnetic lenses help to control the path of electrons to hit a fluorescent screen and produce an image.

 

*note – the diagrams do not belong to me*