Science Department: Science Flash Cards

Pure substance = one element/compound only

Formulation = useful mixture designed as product

Chromatography separates dissolved substances.
Mobile phase = solvent, stationary phase = paper

R_f = distance moved by substance ÷ distance moved by solvent

Gas test:
• Hydrogen = squeaky pop
• Oxygen = relights a glowing splint
• Carbon Dioxide = turns lime water milky/cloudy
• Chlorine = bleaches damp blue litmus paper white

Flame colour tests:
• Lithium → Crimson
• Sodium → Yellow
• Potassium → Lilac
• Copper → Green

The early atmosphere was mainly carbon dioxide

Oxygen levels increase when bacteria began to photosynthesise

Grenhouse gases are Carbon Dioxide, Methane and Water Vapour

Human activity increases atmospheric carbon dioxide levels through burning fossil fuels and deforrestation

Climate change causes global warming, sea level rise and habitat loss

Atmospheric pollutants:
Sulfur dioxide → acid rain
Nitrogen oxides → acid rain & respiratiry issues
Particulates → smog/global dimming/health issues

Electron shells are limited to 2 in the first shell then a maximum of 8 in the others.

Protons and neutrons are in the nucleus of the atom, electrons orbit in shells

Protons: mass = 1, charge = +1
Neutrons: mass = 1, charge = 0
Electrons: mass = 1/2000, charge = -1

Atomic number = number of protons
Atomic mass = number of protons + neutrons together

Isotope = atoms with the same number of protons but varying number of neutrons. Isotopes have identical chemical properties

Models of the atom over time:
1, Dalton → solid spheres
2, Thomson → plum pudding (first charges)
3, Rutherford → nuclear model (tiny positive nucleus, mainly empty space)
4, Bohr → electron shells

Periods (horizontal) = same as number of shells
Groups (vertical) = same as number of electrons in the outer shell

Group1: Alkali metals
Soft, low density, more reactive as you go down the group

Group 7: Halogens
Diatomic (in pairs) non-metals, more reactive as you go up the group

Group 0: Noble gases
Inert/unreactive as they already have a full outer shell of electrons

Development of the periodic table:
Dalton created a list by atoic weight (not mass, protons had not been discovered)
Newlands noted that every 8th element had similar properties (Li, Na,K then F, Cl, Br) Law of Octaves
Mendeleev ordered by weight AND properties and he left gaps for undiscovered elements

Photosynthesis occurs in chloroplasts, it is an endothermic reaction as light energy is taken in.

The rate of photosynthesis is affected by light intensity, carbon dioxide concentration, temperature and amount of chlorophyll

The limiting factor, is the factor that runs out first

Glucose is used in: respiration, making cellulose, making amino acids and it is stored as starch and stored as lipids

Aerobic respiration:
C₆H₁₂O₆+ 6O₂ → 6CO₂ + 6H₂O
Photosynthesis:
6CO₂ + 6H₂O → C₆H₁₂O₆+ 6O₂

Respiration is an exothermic reaction that releases energy for metabolic reactions (never say produces energy)

Anaerobic respiration in muscles:
Glucose → lactic acid
This causes an oxygen debt and cramp

Metabolism = all chemical reactions that occur in cells/the body

Inonic bonding:
Metal loses electon(s) → positive ion.
Non-metal gains electron(s) → negative ion. (Each ion now has a FULL OUTER SHELL)
Oppositely charged ions are held together by strong electrostatic forces

Covalent bonding:
Non-metals overlap their outer shells to share electrons and gain a FULL OUTER SHELL. The shared pair of electrons is a covalent bond.

Metallic bonding:
Metal atoms eject outer electrons (to gain a FULL OUTER SHELL) and form positive ions. They remain surrounded by delocalised electrons. The attraction (oppositely charged) holds the metal together

Giant ionic compounds (giant because of the 3D lattice).
High melting point - lots of energy to overcome the strong electrostatic forces
Only conduct electricity when molten or in solution as the ions need to be free to move.
Brittle as the layers cannot slide

Simple molecules are covalent:
They have low melting/boiling points as the molecules are held together by weak intermolecular forces (not much energy needed to separate)

Giant covalent:
Diamond very high melting point/very hard, held together by strong covalent bonds in a 3D lattice. Each carbon is bonded to 4 others.
Graphite only has 3 bonds per carbon so forms sheets that can slide over each other and the unused electons are delocalised so it conduscts electricity

Metals:
Conduct heat and electricity (delocalised electrons free to move through the structure
Malleable and Ductile because the layers can slide over each other

Alloys:
Adding a different sized metal atom to another disrupts the layers so they can no longr slide over each other, this makes alloys stronger than the original metal

Nanoparticles: between 1 and 100 nanometers in size, have a very large surface area to volume ratio. Used in self cleaning class and higher protection suncream

All cells contain:
• cell membrane,
• cytoplasm,
• genetic material,
• ribosomes.

Eukaryotic cells have a nucleus.

Prokaryotic cells have no nucleus; DNA is free in cytoplasm.

Bacteria are prokaryotes.

Plant cells have a cell wall, permanent vacuole and chloroplasts (if exposed to sunlight).

Specialised cell examples:
Sperm cells: tail and many mitochondria.
Nerve cells: long to carry impulses, branches to join a network
Muscle cells: many mitochondria,
Root hair cell: large surface area.

Light microscopes = lower magnification/resolution.
Electron microscopes = much higher magnification/resolution

Required formula:
Magnification = image size ÷ real size

Mitosis produces 2 identical diploid cells. This is used for growth, repair and asexual reproduction

Stem cells are unspecialised cells that can differentiate. They are found in early embryos, some adult tissue and in meristems in plants

Diffusion is the movement from high concentration → low concentration. This is a passive process.

Osmosis is the movement of water particles, Dilute → Concentrated through a partially permeable membrane.

Active transport is movement from Low concentration → High concentration (against the concentration gradient). Requires energy from respiration.

Ionic substances must be melted or dissolved in water to conduct electricity, there must be free moving ions

Most reactive: K→ Na → Ca → Mg → Al → C → Zn → Fe → Sn → Pb → H → Cu → Ag → Au → Pt Least reactive

More reactive metals displace less reactive metals

Oxidation = Gaining oxygen/locing electrons

Reduction = Losing oxygen/gaining electrons

General formulae:
Acid + Metal → Salt + Hydrogen
Acid + Metal oxide → Salt + Water
Acid + Alkali → Salt + Water
Acid + Metal Carbonate → Salt + Water + Carbon Dioxide

Electrolysis is decomposition of a compound using electricity (reverse of an ionic reaction)

pH scale: 0-6 = acid, 7 = neutral, 8-14 = alkali

Electrolysis of melts: Metal ions go to the negative electrode (cathode) become elements. Non-metals go to the positive electrode (anode) become elements.

Electrolysis of solutions: Least reactive positive ion is reduced back to an element. If a halide ion is present, it is produced at the anode, if none are present, then oxygen is produced.

Food chain: Producer → Primary consumer → Secondary consumer

Producers are plants or algae. They produce through photosynthesis

Interdependence is when different species depend upon each other

Abiotic factors (non-living):
Light, Temperature, Moisture level. pH, Mineral content, Wind speed, CO₂ and O₂ levels

Biotic factors (living):
Food availability, predators, Competition, Pathogens

Types of adaptations:
Structural, Behavioural, Functional

Carbon cycle:
Photosynthesis removes CO₂ from the atmosphere and respiration & decay put it back

Water cycle is linked to transpiration, evaporation and condensation

Biodiversity = variety of different species in an ecosystem

Current is the flow of charge. This is often the flow of electrons though a conductor

Charge = current x time (Q=It)

Potential difference = energy transferred per coulomb

Reseitance opposes the flow of current

Ohm's law gives us: voltage = current x resistance or V=IR

In a series circuit, the current stays the same, the pd is shared across the devices and the resistance is simply added up

In a parallel circuit, the pd stays the same and the current splits at junctions

UK mains electricity: Alternating Current (AC), 230V and 50Hz

The National Grid uses step-up and step-down transformers to reduce energy loss. When the voltage is very high, the current is very low so much less energy is lost as heat

Energy cannot be created of destroyed, it simply gets transferred or stored

Energy stores:
Kinetic, thermal, chemical, gravitational, elastic, magnetic, electrostatic, nuclear

If energy is transferred into a store that you wanted, it is useful, if not it is wasted. A bicycle transfers energy into the kinetic store (useful) and thermal store (waste as heat through friction)

Power = Energy transferred ÷ time taken

Efficiency = ( Useful output ÷ total input) x100

Work done = Force x distance moved in the direction of the force

Endothermic reactions absorb heat from their surroundings (feel cold)

Exothermic reactions release heat into the surroundings (feel hot)

Combustion, neutralisation, displacement reactions and respiration are all exothermic

Photosynthesis and thermal decomposition are both endothermic reactions

In an energy profile for an exothermic reaction, the reactants are higher up than the products (endothermic is the other way around)

Velocity, Displacement and Force are all vector quantities, as well as a magnitude, they have a direction

Velocity = distance ÷ time taken

Acceleration = change in velocity ÷ time taken

Newton's First Law:
If the resultant force = 0, then velocity will remane constant

Newton's Second Law:
Acceleration is directly proportional to the net force applied
Or Force = Mass of object x acceleration

Distance time graphs:
Gradient = velocity
Flat line = object has stopped

Velocity time graphs:
Gradianet = acceleration
Area under the line = distance travelled

Overall stopping distance = thinking distance + braking distance

Thinking distance is affected by tiredness, drug use, alcohol consumption and the speed of the car

Breaking sistance is affected by the efficiency of the brakes, tread depth of the tyres, air pressure in the tyres and condition of the road (mud, wet, ice etc)

Momentum is the tendancy of an object to keep moving
Momentum = mass x velocity

Hooke's law:
The extension of an object is directly proportional to the force applied up until the elastic limit is reached
F = ke

Homeostasis is maintaining constant internal conditions like temperature, blood glucose and water content

Nervous system pathway:
Stimulus → Receptor → Coordinator → Effector → Response

Reflex actions are rapid, automatic and there to protect us

Endocrine system: glands release hormones into the bloodstream e.g. Pancreas releases insulin and glucagon

Type 1 diabetes = not enough insulin to lower blood sugar levels

Negative feedback restores levels back to normal

Hormones of the Menstrual cycle:
• FSH - matures and egg
• LH - releases an egg
• Oestrogen - thickens the uterus lining
• Progesterone - maintains the uterus lining for pregnancy (also prevents release of more FSH/LH)

Contraception is prevention of pregnancy:
•Oral pill
•Barrier methods (condoms etc)
•Implants
•IUD

A pathogen is a microorganism that causes an infection disease

The 4 types of pathogen are:
Bacteria, Viruses, Fungi and Protists

Examples:
Measles = virus
Salmonella = bacteria
Gonorrhoea = bacteria
Rose black spot = fungus
Malaria = protist

The body defends itself with skin, nose hairs & mucus, stomach acid and finally, white blood cells if the pathogen gets in.

3 actions of white blood cells:
Phagocytosis (engulf & break down the pathogen)
Antibodies (attack the antigens on the pathogen)
Antitoxins (make you feel better)

Vaccinations introduce a weak or dead pathogen (its antigens), this stimulates the production of antibodies and memory cells

Antibiotics kill bacteria but do not affect viruses

Painkillers treat symptoms (pain and fever), they do not affect the pathogen

Drugs have been discovered from nature. Aspirin from willow bark & Penicillin from mould

DNA carries genetic information and is found in chromosomes in the nucleus

Gene = a small section of DNA that codes for a specific sequence of amino acids to make a particular protein

Genome = all genetic material of an organism

Sexual reproduction = 2 parents → variation

Asexual reproduction = 1 parent → genetically identical offspring

Allele = different form of a gene (eye colour)
Dominant = an allele that is always expressed
Recessive = an allele that is only expressed if it appears twice
Homozygous = two alleles are different
Heterozygous = two alleles are the same
Genotype = the specific combination of alleles an organism possesses
Phenotype = The observable characteristics

Variation is caused by genetics, environment or a mixture of both

Evolution is the gradual change of inherited characteristics over time

Natural selection: where there is variation, the best adapted survive and reproduce to pass on their alleles

Antibiotic resistance: Caused by naturals selection due to antibiotic overuse

Selective breeding: Humans select the parent organisms with the desired traits

Genetic engineering: inserting a gene from one organism into another's DNA

Permanent magnets produce magnetic fields

Opposite poles attract and like poles repel

Magnetic field lines travel from the North to the South

The strength of an electromagnet can be increased by increasing the number of coils or increasing the current through the wire and adding an iron core.

The motor effect is the force on a wire that is carrying a current inside a magnetic field

A generator works by moving a wire through a magnetic field which induces a current to flow

Transformers work using electromagnetic induction across a laminated iron core. They can 'step up' the voltage (while reducing the current) or 'step-down' the voltage (while increasing the current)

Crude oil is a mixture of hydrocarbons

Hydrocarbons are made of only hydrogen and carbon

Fractional distillation separated hydrocarbons into fractions (groups of similar size) by their boiling point

Alkanes are saturated hydrocarbons with the general formula of C_nH_2n+2

Alkenes are unsaturated hydrocarbons (contain a carbon to carbon double bond C=C) with the general formula of C_nH_2n

Complete combustion:
Hydrocarbon + Oxygen → Carbon Dioxide + Water

Incomplete combustion:
Hydrocarbon + less Oxygen → Carbon (soot) + Carbon Monoxide + Water

Catalytic cracking breaks longer/lower demand alkanes into smaller/more useful ones and an alkene

Many alkenes join together to make plastics in a process called Addition Polymerisation

Crude oil is formed when plankton dies → sinks and is burried → heat, pressure, lack of oxygen → millions of years → crude oil

Smallest first, the order is: Cell→Tissue→Organ→Organ System→Organism

Amylase (carbohydrase): carbohydrates → sugars
Protease: proteins → amino acids
Lipase: lipids → fatty acids & glycerol

Enzymes are biological catalysts that have an optimal temperature & pH. High temperatures change the active site and denature the enzyme.

A double circulatory system (like in humans), blood travels:
Heart→Lungs→Heart→Body

Arteries = away from the heart = thick walls
Veins = return to the heart = valves
Capillaries = one cell thick

Blood contains:
Red blood cells that carry oxygen in the haemoglobin.
White blood cells that defend against pathogens
Platelets to form clots/scabs
Plasma that transports substances

Coronary Heart Disease (CHD) is a build up of fatty material in the coronary arteries that restricts blood flow.

Xylem transports water & mineral ions up
Phloem transports dissolved sugars around the plant

Transpiration is the loss of water from leaves

Translocation is the movement of sugars in the phloem

The states of matter are: Solid (s), Liquid (l) and Gas (g).

Total internal energy is equal to the kinetic energy of the particles and their potential energy combined

Density = mass of object (kg) ÷ volume of object (m³)

Gas pressure is caused by the particles colliding with the walls.

When the temperature increases the particles have gained kinetic energy

The Relative Formula Mass or M_r, is all of the relative atomic masses (A_r) of the atoms in a compound added together

The number of moles of a substance = mass ÷ M_r

Mass is always conserved. The mass of all of the reactants is always equal to the mass of all of the products. The Conservation of Mass

Percentage mass is the A_r of the element (x abundance in the compound) ÷ M_r of the compound. Multiply the decimal by 100 to get the percentage

Concentration = mass ÷ volume or = moles ÷ volume

1 mole of gas occupies 24 dm³ at room temperature and pressure

The three types of nuclear radiation are:
Alpha α = 2 protons + 2 neutrons
Beta β = high speed electron
Gamma γ = electromagnetic wave

Half-life is the time take for half of the radioactive nuclei to decay or the time take for the activity to halve (same time)

Background radiation comes from the rocks below and from cosmic rays

Radiation is used for radiotherapy, tracers and smoke alarms

Nuclear fission involved the splitting of unstable nuclei into smaller "daughter' nuclei and neutrons (which propogate the reaction)

The rate of a reaction is affected by:
• Temperature
• Surface area
• Catalyst
• Concentration (if a solution)
• Pressure (if a gas)

Reactions are faster if there are more successful collisions per second

In a graph of product (a gas given off) against time, the steeper the curve, the faster the rate

The rate of a reaction falls during the reaction, this is because as reatants are used up, the concentration falls so there are fewer collisions per second

When a reverisble reaction reaches dynamic equilibrium, the reaction has not stopped, the rate of the forward reaction is equal to the rate of the reverse reaction

In a reversible reaction, LeChatelier's principle shows:
Add heat → moves in the endothermic direction
Add reactant → makes more product
Increase pressure of gas → moves to side with fewest moles

Potable water is water that is safe to drink

Waste water treatment:
Screening → Sedimentation → Biological treatment

Life Cycle Assessments (LCAs) assess the environmental impact from manufacture to disposal

Earth's resources are running out so we must Reduce, Reuse and Recycle

Sustainable Development ensures that we have the resources that we need without preventing future generations from also having enough

Transverse waves: Particles move at 90° to direction of the wave.
Examples : electromagnetic waves, waves on water, seismic S-waves

Longitudinal waves: Particles move parallel to the direction of the wave.
Examples: sound waves (including ultrasound), seismic P-waves

Wave speed = frequency x wavelength
V = f x λ

Electromagnitic spectrum:
Longest wavelength/lowest frequency
Radio waves
Microwaves
Infrared
Visible light
Ultraviolet
X-rays
Gamma rays
Shortest wavelenght/highest frequency

Sound waves need a medium (a substance to travel in), electromagnetic waves can travel through the vacuum of space

Waves undergo reflection, refraction and absorption

Science Flash Cards

Key Facts: Flash Cards