atoms:

• Atoms are the particles that make up materials in the world
• They are neutrally charged overall
• They are made up of a nucleus (containing protons and neutrons) and electrons in shells
• Protons: positively charged
• Neutrons: neutrally charged
• Electrons: negatively charged

compounds-and-mixtures:

• Elements are made up of exclusively one type of atom, but can be in molecules of those atoms (examples include oxygen and sulfur, which string together in molecules)
• Compounds are 2 or more elements chemically bonded together
• Mixtures are 2 or more substances not chemically bonded together

Cells:

2 types:

• Eukaryote: Contains a nucleus, is larger
• Prokaryote: Smaller, doesn't contain a nucleus. Instead has a single loop of DNA

cell features:

eukaryote:

• Mitochondria: Facilitates chemical reactions within the cell to provide energy
• Nucleus: Contains DNA (how to reproduce itself)
• Ribosome: Makes proteins
• Cytoplasm: Maintains cell shape and structure
• Cell membrane: Provides protection for the cell, decides what goes in and out

  prokaryote:

• single loop of DNA: Contains how to replicate itself
• slime capsule: Acts as protection
• cell wall: Maintains cell shape
• cell membrane: Provides protection for the cell, decides what goes in and out
• cytoplasm: Maintains cell shape and structure
• ribosomes: Makes proteins
• plasmids: More loops of DNA floating around in cytoplasm

misc:

• 2 types of eukaryote, plant and animal
• Plant cells have cell walls, vacuoles and chloroplasts
• Vacuole: handles waste
• Chloroplast: facilitates photosynthesis

Specialised-cells:

Sperm cell

• Function: Fertilise an egg cell to pass your DNA onto a child
• Specialised features:
  • Tail (to swim)
  • Middle piece contains many mitochondria to release energy to swim and fertilise the egg
  • Acrosome contains enzymes to penetrate the egg

Nerve Cell

• Function: receive and send messages from the body to the brain and back again
• Specialised features:
  • Nerve cells are long, to conduct nerve impulses between different areas of the body
  • Branched connections at each end to connect to other nerve cells

Egg cell

• Function: To connect with the male sperm cell to become fertilised and produce offspring
• Specialised features:
  • The cytoplasm contains nutrients for the embryo in the form of yolks
  • The cell membrane changes to ensure no more sperm enter after one sperm cell enters.

Muscle cell

• Function: Contract to produce movement
• Specialised features:
  • Lots of mitochondria to release energy for contracting
  • Layers of fibres (protein filaments) which can slide over each other when contracting

Palisade cell

• Function: Photosynthesis (produce energy from sunlight)
• Specialised features:
  • 70% chloroplast to maximise photosynthesis output
  • Ridges on their cell walls to increase surface area

Root hair cell

• Function: To absorb water and minerals from soil
• Specialised features:
  • Has “hairs” which increase the surface area of the cell that is in contact with the soil to maximise absorption
  • Thinner cell walls to reduce diffusion time

Guard cell

• Function: Help to regulate transpiration (exhalation of water vapour by a plant) by opening and closing their stomata
• Specialised features:
  • Thick cell walls facing the stoma and outside air

Xylem and phloem cells

• Xylem function: Transports water and minerals from the roots to the leaves
• Xylem specialised features:
  • Thick cell wall
  • One way flow only
  • No top or bottom, so form an uninterrupted tube
• Phloem function: Transports sugar and amino acids around the plant

• Specialised features:

  • Join by holes in the top and bottom of the cell called sieve plates
  • Very few sub-cellular structures to avoid obstructing flow of substances
  • 2 way flow

  Law of conservation of energy

  The total energy of a closed system is constant, energy cannot be created or destroyed, but it can transfer from one form to another

Types of energy stores

• Chemical energy
• Kinetic energy - movement
• Gravitational potential energy - height, gravity
• Elastic potential energy - squashing and stretching
• Thermal energy - heat
• Nuclear energy
• Magnetic energy
• Electrostatic energy

Types of energy transfer

• Heating (conduction, convection)
• Radiation
• Mechanical
• Electrical
• Sound/Waves

diffusion :

• Spreading out of the particles of a substance in a solution. this results in the net movement (overall movement) of particles
• Net movement: movement from an area of higher concentration to an area of lower concentration
• This is possible because of random movement of particles

rates of diffusion:

The rate of diffusion is how quickly diffusion takes place, and can by impacted by these:

Difference in concentration

• If there is a large difference between concentration in 2 areas, diffusion will happen faster
• "this is because many particles will move randomly towards the area of low concentration, but only relatively few will move randomly in the other direction" - Activate AQA GCSE Biology textbook
• The difference in concentration is called the concentration gradient

Temperature

• An increase in temperature makes the particles move quicker, and with diffusion being the movement of particles, if the particles are moving quicker then diffusion takes place quicker

Surface area

• The available surface area can increase the amount and rate of diffusion that happens
• some cells and even organs have adaptations that increase surface area for more diffusion to take place

diffusion in living organisms

• Substances move in and out of cells by diffusion across the cell membrane
• Substances that do this include:
  • Simple sugars (like glucose)
  • Gases (Oxygen, Carbon dioxide)
  • Waste products such as urea ( formula: CO(NH2)2, organic compound, also called carbamide)
• "Gases are exchanged in organs like lungs, gills and leaves. Gases like Oxygen and Carbon dioxide move down concentration gradients from a region of higher concentration to a region of lower concentration" - Activate AQA GCSE Biology textbook
• "Dissolved food molecules such as glucose, and waste substances such as urea, also move from one area of an organism to another by diffusion. In many animals, food substances diffuse from the digestive system to the blood and then into the cells. In plants, they move by diffusion from the leaves to the transport system and then to the cells that need them" - Activate AQA GCSE Biology textbook

$$ Efficiency=\frac{\textrm{Useful output energy (J)}}{\textrm{Total input energy (J)}}(*100\textrm{ for percentage}) $$ Efficiency has no set units, and percentage is a common way of representing it

How to reduce wasted energy (increase efficiency) by circumstance:

Electronic structures

How shells work:

• each shell can only have a certain number of electrons
• For the first 20 atoms in the periodic table, at GCSE spec, the shells work like this
  • The first shell can only hold 2 electrons
  • All other shells after that can hold 8 electrons
• Elements with the same number of electrons in their outer shells are in the same group and will react with water similarly

partially permeable membrane

• Doesn't let all types of particles through, but water can move across partially permeable membranes by osmosis
• Can also be called semipermeable

hypotonic

having a lower osmotic pressure than a particular fluid, typically a body fluid or intracellular fluid.

hypertonic

having a higher osmotic pressure than a particular fluid, typically a body fluid or intracellular fluid.

isotonic

denoting or relating to a solution having the same osmotic pressure as some other solution, especially one in a cell or a body fluid.

turgid

If the solution surrounding a plant cell is hypotonic and therefore less concentrated than the contents inside the cell, water will enter the plant cell by osmosis.

This causes there to be more pressure against the cell walls,
The cells will be firm and swollen and will therefore
become turgid.

plasmolysed

The cytoplasm shrinks and pulls away from the cell wall

$$ \textrm{Change in Ep} = \textrm{mass (kg)} \textrm{gravitational field strength (G)} \textrm{change in height (m)} $$

• When an object moves upwards, its gravitational potential energy increases
• Could also be weight (N) X change in height (m)
• Earth's gravitational field strength: 9.8 N/kg or 9.8G
• Greek letter delta - Change in

Democritus

• (470-380BC)
• Came up with the concept of the atom, the smallest particle that cannot be further broken down

Charles Augustin de Coulomb

• (1736-1806)
• Released work on electrostatic forces and how opposite charges attract

John Dalton

• (1766-1844)
• Introduced the first atomic theory
• Atoms are tiny, invisible particles
• Atoms of one element are the same
• Atoms of different elements are different
• Compounds are formed by combining atoms

JJ Thompson

• (1856-1940)
• discovered electrons and how atoms were made up of event smaller things. Introduced the "plum pudding model", electrons being seen as raising inside the pudding

Ernest-Rutherford

• (1871-1937)
• Published the "Gold leaf" experiment, disproving the plum pudding model
• He claimed there was a dense central component in the atom, called the nucleus
• He claimed it was made entirely of protons, a positively charged particle that would make the atom neutrally charged

NielsBohr

• (1885-1962)
• Claimed electrons moved around in atoms in energy levels (shells), and orbited the nucleus instead of floating randomly

Schrodinger and Heisenberg

• (1887-1961, 1901-1976)
• Schrodinger published the quantum wave equation that treats electrons as waves in particles
• Heisenberg published the uncertainty principle, stating you can never know the exact location and energy of an electron within an atom
• These theories led to the electron cloud theory, locations where electrons are likely to be in the atom

James Chadwick

• (1891-1974)
• Discovered the neutron, a neutrally charged particle that is in the nucleus

Ions

Ions are particles that contain a different number of protons and electrons and so they are electrically charged

$$ Charge = \textrm{number of protons} - \textrm{number of electrons} $$ ion electronic structure is written like this:

[2,8] ^{(+ or -) (charge)}

Group 0 elements, called the noble gases, have stable electron structures (the outer shell is full). Ions have this same electronic structure

Atoms often react to gain or lose electrons. They gain or lose electrons in order to get a stable electron structure of a noble gas

Mass numbers and atomic numbers

• Atoms are often presented with 2 number alongside them
• The smaller of the 2 is the atomic number, and refers to how many protons are in the atom
• The larger is the mass number, and is the total number of protons and neutrons in the atom

Osmosis required practical

method :

1. Peel potato (potato skin may interfere with osmosis)
2. Use cork borer to cut small potato cylinders of equal length
3. Prepare beakers with an equal amount of various concentrations of sugar or sodium chloride salt solution, these measured in M (Molarity)
4. Measure and record the starting mass of the potato cylinders
5. Put the potato cylinders in the beakers
6. Wait however long is available (the longer the better)
7. Take the cylinders out, dab them on a paper towel before measuring and recording their final mass.
8. Calculate the change in mass by subtracting the starting mass from the final mass
9. Calculate the percentage change in mass by dividing the change by the starting mass and multiplying by 100
10. Plot and draw appropriate graph

Osmosis :

• Special type of diffusion that applies only to water molecules
• The movement of water molecules down a water potential gradient from a higher water potential (a more dilute solution) to a lower water potential gradient (a more concentrated solution) through a partially permeable membrane (selectively permeable)

Water potential :

• Water potential is a measure of the concentration of water molecules
• Pure water has the highest water potential and the more concentrated a solution becomes, the lower the water potential

Permeable :

(of a material or membrane) allowing liquids to pass through it

Partially permeable:

• Doesn't let all types of particles through, but water can move across partially permeable membranes by osmosis
• Can also be called semipermeable

Osmosis in plants

• When a plant doesn't receive adequate water for its needs, the plant will wilt and become flaccid
• When water enters the vacuole it causes the cell to swell
• This pressure is what makes the plant stay stood up

Relative atomic mass

A_r = relative atomic mass Relative atomic mass is an average value that takes into account the abundance of the isotopes of the element.

Carbon 12 is the standard reference unit:

• it is given a "mass" of 12 units for its 6 protons and 6 neutrons (each proton/neutron being 1 mass unit)
• All other elements are compared to this

\[ Ar = \frac{\sum (\mathrm{isotope\ abundance} \times \mathrm{isotope\ mass\ number})}{\sum \mathrm{isotope\ abundances}} \]

example:

\[ \mathrm{Ar\ Cl} = \frac{(25 \times 37) + (75 \times 35)}{100} = 35.5 \]

Mixtures

• Physical process: Processes that don't involve chemical reactions - no new substances are made
• Chemical process: Processes involving a chemical reaction - new substances are made
• Soluble: A substance that can be dissolved into a solvent
• Insoluble: A substance that cannot be dissolved into a solvent
• Immiscible: 2 liquids that do not mix

Separating mixtures

• Distillation: Mixture is boiled. substance with lowest boiling point evaporates and its vapour travels through the condenser, where it is cooled by water and flows into a beaker at the end, leaving residue in the starting round-bottomed flask
• Filtration: Filter paper in filter funnel, liquid soaks through holes into conical flask, leaving solid residue in filter paper
• Crystalisation: Bunsen burner at base with tripod suspending a beaker containing water on top, on top of beaker is an evaporating basin. Bunsen burner heats water, which gently heats the evaporating basin, evaporating the substance with the lowest boiling point, letting the residue solidify

Chromatography

• Can be used to separate mixtures of soluble solids
• Involves a stationary and mobile phase
• Stationary phase: The paper that doesn't move
• Mobile phase: Solvent that moves up the paper
• Solvent front: The furthest the solvent has travelled
• Rf value: Rf = distance moved by substance/distance moved by solvent
• Loose method:
  • Draw pencil line 1-2cm from bottom of chromatography paper
  • Draw crosses where each spot will go, and label them if needed
  • On the crosses, put a drop of each solution (in case of demo, pen ink)
  • Fill a beaker with cold water
  • Clip chromatography paper to something that can balance on top of the beaker
  • Place chromatography paper in beaker, avoiding it touching the edges as that could change how the solvent moves
  • Make sure substance isn't submerged, as the substance will just dissolve into the solvent instead of travelling up the paper

The microscope:

Light-microscopes :

• Has an eyepiece lens magnification of 10x
• 3 objective lenses, usually with magnification 4, 10 and 40 x
• Almost always the microscope chosen by schools
• Robert Hooke first saw cells using this kind of microscope
• 2 methods of focus adjustment, fine focus wheel and coarse focus wheel

  parts

• Eyepiece
• Neck
• Clips
• Coarse focus wheel
• Fine focus wheel
• Objective lens(es)
• Stage
• Condenser
• Light

  Electron-microscopes:

  2 types, TEM and SEM

  TEM:

• Transmission electron microscopy
• Uses transmitted electrons to create a 2D projection of a sample's inner structure
• Uses a beam of electrons that passes through a very thin sample
• Requires the sample to be very thin and flat
• Can provide detailed information about a sample's inner structure

  SEM:

• Scanning electron microscopy
• Uses reflected electrons to create a 3D image of a sample's surface
• Uses a beam of electrons that hits a sample's surface
• Requires little to no sample prep
• Can provide information about a sample's surface composition, and can be faster and less restrictive than TEM

  Order of magnitude:

  Used to make approximate comparisons between numbers or objects 1000 micrometers = 1mm

  Magnification calculations:

• Actual size = image size (micrometers) / magnification
• Image size = Actual size (micrometers) x magnification
• Magnification = Image size (micrometers) / actual size (micrometers)

Units helper

J - Joules, universal unit of energy W - Watts, unit of power N - Newtons, unit of force

Work done

\[ \mathrm{Work\ done\ (J)} = \mathrm{Force\ applied\ (N)} \times \mathrm{Distance\ (in\ direction\ of\ the\ force,\ m)} \]

Power

\[ \mathrm{Power\ (W)} = \frac{\mathrm{Work\ done\ (J)}}{\mathrm{Time\ (s)}} \]