Science Yearly 2026

pure substance def

Pure substance: a type of matter only made up of one type of particle (atom or molecule)

mixtures def

Mixture: a substance made by physically combining 2 or more different materials together

mixtures and compounds difference

Compounds are chemically bonded together, while mixtures are physically bonded together. Mixtures can be separated through physical means like evaporation, while compounds cannot

reactant, products write an equation using them

Reactant + reactant -> products

systems, energy and matter flow yes or no

Isolated system: X energy transfer and matter

Closed system: O energy, X matter

Open system: O for both

period and group, which way is it, describe

Period: horizontal row of elements

Group: vertical row of the periodic table

Same period: increasing atomic number

Same group: same number of electrons on its valence shell

valency def

Valency: How many electrons it may lose or gain to gain stability

octet rule def

Octet rule: when atoms have a full outer shell that is stable (such as 2 or 8 electrons). Noble gases often follow this rule bc they have a stable valence shell

Molecular compound def

Molecular compound: when one type of atom or a compound atom with chemically bonded atoms form a structure where molecules do not bond to each other

molecule def

Molecule: a group of 2 or more atoms bonded together, molecules do not bond with each other

Diatomic molecule def

Diatomic molecule: A molecule containing exactly two atoms, H₂, N₂, O₂, F₂, Cl₂, Br₂ and I₂.

lattice def

Lattice: when one type of atom or chemically bonded one/more type of atom form a structure where all atoms are bonded tgt, usually a solid

Difference between elements/compounds and molecule/lattice

Elements/compounds classification: types of atoms it is bonded with and whether they are bonded with atoms different from themselves

Molecule/lattice classification: depends on structure. Molecules composed of structures of bonded atoms while lattices all bonded tgt (type of atom does not matter)

ions def

Ions: charged particles that are formed when atoms lose or gain electrons. Atoms form ions in order to achieve a full valence shell (by transferring, receiving or sharing electrons with other atoms). Their valency determines the number of electrons needed to lose/gain

negative and positive ions are called what

Lose electrons -> positive -> cations

Gain electrons -> negative -> anions

metals and non-metals form cations or anions

Metals form cations, nonmetals form anions

what forms the ionic bond

Electrostatic attraction between positive and negative ions form ionic bonds.

ionic compound, what is it, formed between what ions, what structure

• Ionic compound: A compound formed of one or more ions held tgt by an ionic bond after the transfer of electrons to each other.

  • formed between anions and cations (often metals and nonmetals)

  • lattice structure only

do transition metals have same valencies, give examples of some that do

Transition block metals have variable valencies (except Zn (always 2+) and Ag (always 1+)

polyatomic ions def

Polyatomic ions (charged molecules, more than one element)

ionic naming, what comes first, anion or cation, and what changes are made

cation then anion, Cation: name of atom, Anion:ending changed to -ide (eg bromine to bromide)

covalent compounds def and explanation of why they dont form ions, what do they form between, structure

• Covalent compound: a substance made when 2 or more nonmetal atoms bond by sharing valence electrons

  • (nonmetals are on the right side of the periodic table, where they only require a few electrons to be full, so ions will not form because they don't want to give up their electrons. Instead, they share electrons)

  • Lattice and molecules

covalent naming

• Prefix (eg mono, di, tri, tetra etc) for each atom’s number per molecule

• SO3 = sulfur trioxide

• N2O4 = dinitrogen tetraoxide

single covalent bond and double covalent bond what r they

Single covalent bond: when two atoms share one pair of electrons

Double covalent bond: when two atoms share two pairs of electrons

metallic bonding def

Metallic bonding: Formed between metals when they all discard valence electrons, leaving a sea of delocalised electrons that are free to carry charge. Holds the positive atoms together

In metallic bonding what does the force of attraction form between

The strong electrostatic force of attraction between positively charged ions and a sea of moving, delocalised electrons

what is a structural formula

Structural formula: a representation that depicts the bonding of atoms in a compound eg. C-C-C

Molecular formula def

Molecular formula: a formula that shows the number and type of atoms in a molecule of a compound eg. Co2, P2O5

Electron dot diagram/Lewis structure def

Electron dot diagram/Lewis structure: shows the valence electron structure and bonding of atoms

organic compound def

Organic compound: any compound that contains carbon-hydrogen (C-H) bonds. Examples include Methane, Ethane, Ethanol

Inorganic compound def

Inorganic compounds: lack C-H bonds. Common examples include water, sodium chloride

What are groups of organic molecules called?

homologous series

How are homologous series recognised?

recognised by their functional group.

What type of bond do alkanes have?

C-C single bond

Do alkanes have a functional group?

Alkanes (C-C single bond) does not have a functional group.

Aliphatic homologous def

Aliphatic homologous: straight chain (branched or cyclic)

Aromatic homologous def

Aromatic homologous: benzene ring (ring of 6 carbon atoms)

naming for organic compounds, prefix up to 8

Meth- 1 carbon, Eth-2 carbons, Prop-3 carbons, But-4 carbons, pent-5 carbons, hex-6 carbons, hept-7 carbons, oct-8 carbons

in naming, what is the suffix, how many bonds do alkanes, alkenes and alkynes have

Suffix- functional group. Alkanes- single bond, Alkenes - C=C double, Alkynes triple bond

what does the number mean if there are no side chains in naming

Number- the position of the functional group on the carbon chain

how to name with side chains and halogens

Longest straight chain with functional group

Identify the side chain eg. methyl, ethyl etc Identify halogen eg. bromo, chloro

Number the C so the side chain is on the lowest possible C

Number of each side chain

Alphabetical order

OH (carboxyl/hydroxyl group) has precedence; must be included as the main chain

R-OH (hydroxyl) group ends with -ol eg. Ethanol

Carboxyl group. (COOH) -oic acid.

Halogen groups: -F, -Cl, -Br, -I Eg: H-C-C-Br (Bromoethane)

Isomers def

Isomers: made of the same molecular formula (composed of the same molecules) but of a different structure. Eg. 1-butene and 2-butene is of a different structure, both C4H8

hydrocarbon fuel def

Hydrocarbon fuel: combustible energy sources composed of carbon and hydrogen atoms Eg. Methane

complete combustion formula, give an example

Complete combustion: hydrocarbon fuel + oxygen -> water + CO2 + energy (ATP)

Blue bunsen burner flame

incomplete combustion formula, give example

Incomplete combustion: hydrocarbon fuel + oxygen -> water + CO2 + carbon monoxide + Carbon (soot) + energy (ATP)

Yellow bunsen burner flame

energy produced for complete combustion vs incomplete

Complete combustion results in 100% energy produced, incomplete results in 50%

do exothermic reactions produce or absorb heat

Exothermic -> produces heat.

plastic def

Plastic: a synthetic material made of polymers, which is formed by the chains of bonded monomers- made of hydrocarbon molecules

what is plastic made from

• Plastic is made from hydrocarbons extracted from crude oil and natural gas. The liquids and gases are extracted via distillation.

polymer def

Polymers: chains of monomers (repeating units)

monomer def

Monomer: materials that bond together to form long chains (mostly organic molecules)

what is polymerisation

Polymerisation: a chemical process in which monomers join in a chain to form polymers

how are polymers named

Polymers are named with an added poly- in front of the monomer name. Eg. ethene becomes polyethylene

what are examples of natural polymers

Natural polymers: carbs, fats, protein, DNA, rubber, Cellulose, starch, glycogen (natural condensation polymers)

synthetic polymers examples

Synthetic polymers: polyethylene, Nylon, PET, polyesters (synthetic condensation polymers)

addition polymerisation def and describe, 4 examples

Addition polymerisation: requires an initiator. PE, PVS, PS, Teflon

Monomer -> break double bond -> an electron free at each end -> new C-C bonds form -> polymerisation

Unsaturated HC monomer, double/triple bond, break the bond and add across. No by-product.

Condensation polymerisation def and describe

Condensation polymerisation: removing atoms. Needs a functional group at each end. Includes NH2, hydroxyl (OH), carboxyl (COOH) or -COCL. Water or other small molecules as a by-product. Free bond, monomers join.

Amorphous regions def

Amorphous regions: linear polymer chains that can move around. Tangled, disorders, no structure. Lower softening/mtps, more flexibility, permeable

Crystalline regions def

Crystalline regions: packed tightly together Higher rigidity and mtp. Harder plastic. Prevents the transmission of light. Opaque appearance, not permeable

Cross-links def and how does it change the plastic

Cross-links: links between polymers that prevent the chains from sliding past one another. Makes the plastic hard and rigid

Branching polymer chains def and how does it change the plastic

Branching polymer chains: makes it so that polymer chains cannot pack close together giving it a light and flexible quality.

Plasticisers def and how they change the plastic

Plasticisers: small molecules weaken the forces of attraction between molecular chains so they can easily slide over to each other. Gives it a soft and elastic property

Intermolecular forces def

Intermolecular forces: the attraction and repulsion forces that exist between separate molecules. holds the polymer chains together. The stronger they are, the stronger and denser the plastic is with a high melting point as the forces are harder to overcome

Thermosoftening plastics def

Thermosoftening plastics: plastics that soften or melt when heated bc the bonds between the polymer chains are weaker so chains are free to change shape, easier to recycle as they are easily remoulded, can be repeatedly melted and shaped

Thermosetting plastics def

Thermosetting plastics: hard plastics that don’t melt and are not easily recycled. Do not decompose or melt, only burns with heat. Bonds are strong so not moldable

Qualities of plastics, and what does each one test

Flexibility- whether it can be bended without breaking (brittle if it breaks)

Density- how tightly the particles are packed together. High density -> sinks underwater

Tensile strength- the maximum pulling strength it can withstand

Transparency- whether it is see-through (opaque when it is not)

Flammability- a material’s ability to ignite and sustain the flame

landfill def

Landfill: A site where solid waste is deposited, compacted and covered for long-term disposal

bioplastics def

Bioplastics: A plastic material made partially or entirely from renewable resources

time to degrade for synthetic vs bio polymers

Polymers made from hydrocarbons are unnatural and synthetic consisting of long chains of polymers that are difficult to break. They take a long time to break.

Some biopolymers are degradable, taking less time to degrade than hydrocarbons

microplastics def

Microplastics: A piece of plastic that is less than 5mm in size

briefly describe the digestive system

Digestive system: breaks down food into nutrients like glucose, amino acids, responsible for absorbing these essential nutrients and water into the body, providing fuel while eliminating waste products

briefly descrbe the circulatory system

Circulatory system: primary transportation network, pumps blood through a vast network of vessels, delivers nutrients and oxygen to every single cell in the body. Collects byproducts and delivers them to appropriate organs

Respiratory system briefly describe

Respiratory system: draws fresh oxygen from lungs, where it crosses into bloodstream, also expels carbon dioxide byproduct through exhalation.

Urinary system/excretory system briefly describe

Urinary system/excretory system: maintains internal chemical balance (homeostasis) by filtering the blood to remove excess water, salts and other waste products, produces urine to do so

Cellular respiration def

Cellular respiration: The process of turning nutrients like glucose into energy (ATP) in cells.

Receptor (nervous system) def

Receptor (nervous system) : specialised cells that detect inputs from our bodies, including senses

types of inputs, what body parts are associated with each, examples

• Type of inputs:

  • Mechanical: skin, ears, hearing a phone buzz, putting hand on soft blanket

  • Chemical: nose, tongue, tasting icecream, smelling old pair of socks

  • Electromagnetic: eyes, skin, feeling warmth from fire, seeing rainbow on a cloudy day

nervous system def

Nervous system: the body system that senses the environment and controls actions

Central nervous system def

Central nervous system: the brain and spinal cord

Peripheral nervous system def

Peripheral nervous system: the nerves extending from the brain and spinal cord

Neuron def

Neuron: A specialised nerve cell in the nervous system, transmitting information through electrical and chemical signals

Stimuli def

Stimuli: any detectable changes in an internal or external environment that can cause a living thing or cell to react

Synapse def

Synapse: The gap between neurons where signals are sent from one to another

The somatic nervous system def

The somatic nervous system controls voluntary movements, such as walking, writing and moving your arms. It carries signals to skeletal muscles.

The autonomic nervous system def

The autonomic nervous system controls involuntary functions, such as heart rate, digestion and breathing regulation.

Sympathetic nervous system def

Sympathetic nervous system (fight or flight): Prepares the body for stress by increasing heart rate, breathing rate and energy availability while slowing digestion.

Parasympathetic nervous system def

Parasympathetic nervous system (rest and digest): Helps the body recover by slowing heart rate, stimulating digestion and conserving energy.

Neurotransmitters def

Neurotransmitters: A chemical messenger that nerve cells use to send messages to other cells, like dopamine

what are the parts of a neuron and how do they help sned messgaes around the body

Dendrite: receives messages from from another cell/environment

Cell body: controls the action of the cell

Axon: carries messages away from the cell body

Myelin sheath: Allows signals to travel faster

Axon terminal: Passes messages to another cell

what is the stimulus response pathway

Stimulus -> receptor -> sensory neurons carry message from skin to spinal cord -> spinal cord sends message to the brain -> brain processes -> sends response signal back out to motor neuron -> effectors receive info -> you act upon stimulus

explain the proccess of Transmitting information from neuron to neuron in detail

1. Receptors on the end of dendrites pick up neurotransmitters from the previous neuron through the synapse. The neurotransmitters, like dopamine, bind to receptors and trigger a new action potential by letting ions flood into the dendrite

2. The action potential travels along the neuron, across the cell body, axon to the axon terminal. When the action potential occurs, the overall charge is extremely positive, and lowers back down to negative when the message has been passed on. The myelin sheath allows the signal to jump quickly across the axon

3. The action potential arrives at the axon terminals, where it causes calcium channels to open and calcium ions to flood into the cell. This causes vesicles, which hold neurotransmitters, to activate. 

4. Once the vesicles are activated, they bind to the cell wall/membrane, and release the neurotransmitters that they hold into the synapse. Neurotransmitters are cleared by diffusion, special enzymes breaking the chemicals down, or they go back into the original cell, or they disperse. 

Membrane potential describe

Membrane potential: When there is a difference between the electrical charge of the inside vs the outside of the cell, making the cell overall negative. This happens when there are more ions(cations) outside the cell than in the cell. It is maintained by the sodium potassium pump.

Polarised cell def

Polarised cell: A cell that is charged and at its resting stage, with a negative electrical charge compared to the outside

Depolarised cell def

Depolarised cell: A cell has experienced a shift where positive sodium ions enter the cell during an action potential

Electrochemical gradient, electrical and chemical gradient def

Chemical gradient: Ions naturally flow from an area of higher concentration to an area of lower concentration

Electrical gradient: the difference in electrical charge across the membrane. Inside the cell is negative, which pulls positive ions inwards.

Sodium potassium pump def

Sodium potassium pump: A protein pump that transports 3 sodium ions out of the cell and 2 potassium ions into the cell. Helps to maintain higher concentration of sodium ions outside the cell than potassium ions inside the cell, which maintains the membrane potential. Function is critical for neurons to be able to fire action potentials

Action potential def

Action potential: The action potential is a electrical signal that travels through a neuron and is used to get information to different parts of the body. It is triggered by stimuli or neurotransmitters at the dendrites, which open ion channels and depolarise the cell. This creates an electrical signal, which spreads down the cell and moves onto the next cell. -55mV threshold is the critical point, once its past that there is no return, usually membrane potential around -70mV

Reflex arc def

Reflex arc: built in or innate behaviours. When danger is sensed, a quick response is needed. Signals from sensory neurons bypass the brain and are acted upon soon as they read the spinal cord. These shorter paths are called the reflect arc

Learned response/conditioned reflex def

Learned response/conditioned reflex: Reflexes that require prior thought or learning and the body responds subconsciously as a result of this. It doesn’t involve subconscious thought. E.g a dog is always fed with a bell sound, so it starts salivating at the sound of a bell

Effector def

Effector: A molecule, cell or organ that responds to a certain stimulus to change or control a biological activity (the muscles/glands that produce a response to the stimulus)