Yr 9 Science Notes Term 1 PDF

[Science Term 1-2 Study Notes] **Chapter 13** **Elements:** **[What are Elements?]** - Pure substances made up of one type of atom - May be synthetic/natural - Atoms are the smallest unit of elements - Each element has a unique universal symbol **Elements- Protons, Neutrons, Electron...

[Science Term 1-2 Study Notes] **Chapter 13** **Elements:** **[What are Elements?]** - Pure substances made up of one type of atom - May be synthetic/natural - Atoms are the smallest unit of elements - Each element has a unique universal symbol **Elements- Protons, Neutrons, Electrons** - Every element has a unique number of protons - Elements are classified based on their number of protons - Same atoms of elements may have different numbers of electrons and neutrons- but same amount of protons, e.g. carbon-12 (6 protons, 6 neutrons), carbon-14 (6 protons, 8 neutrons) - Atoms of the same elements with different neutron numbers are called isotopes - An atom with the same amount of electrons and protons is a neutral atom - An atom with more protons/electrons than electrons/protons is called an ion (a charged atom) - To find the number of neutrons subtract the atomic number from the mass number of an element Charge Mass (amu- atomic mass unit/Daltons) Location Symbol ---------- -------- -------------------------------------- ---------- -------- Proton +1 1 nucleus p+ Neutron 0 1 nucleus n^o^ Electron -1 1/1840 shells e- **Periodic Table** - The periodic table is used to organise all 118 elements - Its organisation groups together elements with similar properties, shows the atomic mass and number of elements - The atomic number is the amount of protons the element has - The elements are arranged by the atomic number increasing, with lowest first and highest last - Mass number is the mass of the neutrons and protons in an atom (the electron is almost massless) - The periodic table doesn't list the individual mass of an elements' atom (mass number), because isotopes with different amounts of neutrons have different mass, therefore it lists the atomic mass of an element (the average mass number for all natural isotopes of an element **[Groups]** - Elements are arranged into 18 groups (vertical columns) based on properties - The groups show the number of valence electrons (amount of electrons on outermost shell) - Valence electrons of each group; - Alkali metals; 1 - Alkaline earth metals; 2 - Transition metals; 0-12 - Boron family; 3 - Carbon family; 4 - Nitrogen family; 5 - Chalcogens; 6 - Halogens; 7 - Noble Gases; 8 (except helium = 2) **Alkali Metals (1)** - Alkali metals are metals with one valence electron (except for hydrogen, non-metal but has 1 valence electron) - They are the most reactive metal group due to their ionic charge of +1 - They are shiny, reactive, soft, malleable, ductile, conduct heat and electricity, solid at room temperature - Hydrogen is not a metal and does not contain these properties but is there because it has one valence electron **Alkaline Earth Metals (2)** - Alkaline earth metals are metals with two valence electrons - They are the second most reactive metal group - Same metallic properties as alkali metals - Solid at room temperature **Transition Metals (3-12)** - Transition metals are metals with zero to twelve valence electrons - Less reactive metals than alkali and alkali earth metals - All solids at room temperature except for mercury, liquid **Boron Family (13)** - Boron family includes metals (except for boron metalloid) - They all have three valence electrons - All solid at room temperature **Carbon Family (14)** - Carbon family is made up of non-metal, metalloids, and metals - They all have four valence electrons, their ionic charge may be +4/-4 - They all are solids - Not very reactive **Nitrogen Family (15)** - Metals, metalloids, non-metals - All solid at room temperature except for nitrogen (gas) - Five valence electrons **Chalcogens (16)** - Non-metals, metalloids, and metals - Solid and gases - Six valence electrons **Halogens (17)** - Seven valence electrons - Non-metals, metalloids, metals - Solids, liquids, gases (all gases except for liquid bromine, solid iodine, and astatine and tennessine) - Very reactive due to its need for only one electron (ionic charge of -1) **Noble Gases (18)** - Unreactive due to full shell of electrons - Full valence shell, all 8 valence electrons except for helium (2) - All non-metal gases - Non-metal properties, low melting/boiling point, cannot conduct heat/ electricity, brittle, dull, solid, gas and liquid at room temperature **[Periods]** - Horizontal rows are called periods - There are 7 periods - Periods indicate the amount of electron shells within each element - Lanthanides and actinides are separate periods as the elements are rare and have very similar properties, so they're separated to not disrupt the organisation of table **Metals** - Metals contain properties such as: - Lustre/shiny - High melting point/ boiling point - Solid at room temperature (except for mercury) - Good conductors of electricity and heat - Malleable (can be bent and shaped) - Ductile (can be stretched into wires) **Metalloids** - Metalloids contain properties of both metals and non-metals - Semi-conductors - Brittle - Solid at room temperature **Non-Metals** - Non-metals contain properties such as: - Dull appearance - Low melting point/ boiling point - Mostly solid, gas and liquid at room temperature - Cannot conduct heat/electricity - Brittle **Periodic Table Origins** - The periodic table has been developed over years and years - The main order of scientists who composed it; - John Dalton 1808 ; - produced first periodic table - 20 elements - made own difficult symbols and put incorrect mass numbers - after proposing atomic theory - Johnann Döbereiner 1829; - studied trends in chemical/physical properties - 55 discovered elements - made 'triads', groups of three elements each based on physical/ chemical properties - John Newlands 1864; - 60 known elements - arranged in order of increasing atomic mass number - law of octaves, put elements into 7 groups of 8 each, 54 total, - every eighth elements in the octave had similar properties, but this pattern failed for some elements - Dmitri Mendeleev 1869; - elements in order of increasing atomic mass - placing known 'families' into vertical rows - left gaps in periodic table for undiscovered elements - predicted unknown elements would share properties with their 'family', predictions proved similar - later this periodic table was similarly used by Lothar Meyer - Henry Moseley 1913; - proposed that atomic number is related to physical/chemical properties, not atomic mass - modified periodic table, more accurate and more elements **[Terminology:]** - Atom; smallest particle/ unit of matter (made up of electrons orbiting a nucleus of protons and neutrons) - Chemical symbol; one or two letters representing an element - Element; a pure substance (made up of one type of atom) - Period; horizontal row of the periodic table that indicates the amount of electron shells - Group; vertical column of the periodic table that indicates the amount of valence electrons - Mass number; the total amount of protons and neutrons in an atom - Atomic number; the amount of protons in an atom - Ductile; can be made/drawn into a wire - Malleable; can be stretched/ bent - Metalloid; a semi metal consisting of both metal and non-metal properties - Chemical property; a substances' property that can be observed during a chemical reaction (reactivity, flammability, acidity, solubility, toxicity, radioactivity, basicity) - Dalton's atomic theory; all matter is made up of particles - Physical property; a property of substance that can be physically measured (colour, boiling point, melting point, lustre, density, hardness, texture) - Matter makes up any physical substance - Matter is anything that takes up space and has mass - Matter is what makes up all physical substances which takes up space and has mass - A substance is a form of matter which has properties - Substances can be pure or impure **Pure Substances** - Pure substances are made up of only one type of particle in a fixed structure/ ratio - Pure substances include: - Elements; made up of one type of atom - Compounds; made up of two or more elements chemically bonded in a fixed ratio (cannot be physically separated) **Impure Substances** - Impure substances are made up of two or more elements and/ or compounds not chemically bonded (can be physically separated) **[Elements ]** **Monatomic** - A monatomic element is an element that naturally occurs with only one atom alone as the element - The reason for monatomic elements is because their outer shell of electrons is full and therefore are stable naturally, they do not need to form bonds with other atoms to gain this and hence do not - Noble gases are monatomic - A monatomic element must be a non-metal gas **Molecule** - A molecule is a cluster of atoms - Non-metals usually occur in the form of molecules as elements in order to achieve stability by gaining a full electron outermost shell (e.g. H2 = two hydrogens chemically bond to form a full outer shell 1+1) - Covalent bonds form molecules **Lattice** - A lattice is a rigid structure containing fixed, repetitive patterns of atoms - Metals form metallic lattices (except mercury liquid) - Atoms in lattices can be bent and hammered in sheets due to structure **Compounds** **(atoms only form compounds for valence stability)** **Molecular (Formed by covalent bonds)** - Molecular compounds are formed by covalent bonds (bonds formed through sharing valence electrons between two or more atoms in order to gain full shell) - All non-metals exist as molecules except for noble gases (full outer shells) - Molecules are clusters of atoms (two or more atoms chemically bonded) which are formed through covalent bonding - Metals CANNOT form covalent bonds nor be a molecule, ONLY non-metals can, metalloids CAN also form covalent bonds when bonding with non-metals - Non-metal plus metalloid = molecular compound **Ionic (Forms Lattice)** - An ionic compound is when a non-metal and metal bond chemically - Swap drop method (swap iconic charges and remove the negative/ positive) - Involves gaining/ losing electrons to contain a full shell for both atoms - This produces ions (atoms with a charge) - Atoms will lose or gain electrons depending on what's easier, for example hydrogen will lose an electron as that's easier therefore its ionic charge would be 1+, (its positive by 1 because it lost 1 electron in ratio to protons and is no longer neutrally charged) however nitrogen has 5 valence electrons, so it'd gain three to form a full shell, so it has an ionic charge of -3 - A metalloid plus metal = ionic compound **Subatomic Particles-**   **Atomic Theories + Models** **Atomic Theories** - Many atomic theories and models have been made by scientists over the years, the main ones are; - Democritus 400 BCE - John Dalton 1803 - J.J (Joseph John) Thomson 1904 - Ernest Rutherford 1910 - Niels Bohr 1913 - Erwin Schrödinger 1926 - James Chadwick 1932 **Democritus 400BCE** - Ancient Greek philosopher, 400BCE - Proposed everything is made of indivisible particles- atoms - He called them atomus which mean 'cannot be divided' **John Dalton 1803** - English chemist, 1803 - Proposed atomic theory- all matter is made of atoms, and atoms of the same element share an identical size, mass, and properties - Each element has unique properties, and these elements combine to form compounds, bonded in ratios **J.J Thomson 1904** - English physicist, 1904 - Studied cathode rays (beams of electrons shot from a cathode) shot through different gases - He labelled the negative particles as electrons based on their behaviour - Stated that if every atom has negative particles it must have positive matter too to balance the electrical charge - Made the atomic model of 'plums in a pudding', negative electron particles sitting within positive matter **Ernest Rutherford 1910** - New-Zealand physicist, 1910 - Was a student of J.J Thomson, and tested his plum pudding model - Bomb barded piece of gold foil with alpha particles (particle of two protons and two neutrons), expecting them to pass through as the plum pudding model stated the positive matter was spread out so the charge would be too weak to deflect the fast-moving particles, however some deflected - This indicated the positive matter being a dense small nucleus in centre, and the negative particles are electrons orbiting, with most an atom being empty space **Niels Bohr 1913** - Danish physicist, 1913 - Used maths to figure out that the electrons in Rutherford's model must move around the nucleus in orbits of fixed sizes and energy levels like planets orbiting the sun - The energy was explained by emission spectra - Emission spectrum- when atoms absorb energy in the form of heat, light, or electricity etc, they are usually going to re-emit that energy in the form of light (photons), passing light through a prism separates the colours as your eyes reflect the light and perceive different wave lengths as certain colours, however the emission spectrum is the spectrum of light given off by atoms, it is made of bright lines within a dark background, this is a line spectrum, each element has its own unique line spectrum (like a finger print for humans), he used this to argue electrons themselves in these specific orbits in these energy levels do not emit energy, but absorb energy when they jump from a lower level to a higher, and emit when they jump from a higher to lower, because electrons cannot be observed between the shells, the jump occurs instantaneously (instantly) - As the electrons jump down from a higher to lower shell, as stated earlier, they will re-emit the energy gained as light, so this visible light will appear depending on the wavelength, from whatever shell to whatever shell - The lines left in these line spectra are called spectral lines, bright or dark lines in a uniform spectrum - A picture containing text, colorfulness, line, diagram Description automatically generated - Proposed that each orbit shell has a fixed number of electrons - The arrangement of electrons could explain how chemical bonds are formed in reactions **Erwin Schrödinger 1926** - Austrian physicist, 1926 - Used math to depict probable location of electron - Worked out that electrons do not move in orbits around the nucleus, but move in clouds; their location is uncertain - It is impossible to locate exactly where an electron is, but math can be used to work out where they most likely are **James Chadwick 1932** - English physicist, 1932 - Worked with Rutherford - Bombarded beryllium atoms with alpha particles (particles with two protons and two neutrons), and a new particle was ejected that had similar mass to a proton - He discovered the particle had mass but no charge, it was neutral - This was the neutron particle, 1932, during WWII, his finding and him was used to study nuclear fission to produce nuclear weapons    A picture containing text, design Description automatically generated  atomic model timeline \| Timetoast timelines **Radiation** **Radiation** - When atoms are unstable due to too many neutrons or protons, the nucleus breaks down and releases energy, this is a nuclear reaction and this energy is known as radiation and can be in three different forms; - Alpha radiation - Beta radiation - Gamma rays - Atoms are transformed into new elements after releasing radiation, in the form of energy or particle **Radioisotopes** - Atoms of the same element that have different number of neutrons are isotopes, e.g. Carbon-12 has 6 neutrons, and is most common, while carbon-14 has 8 and is an isotope - Most atoms contain stable nuclei, with enough neutrons to balance out the protons therefore they do not need to break down, unstable atoms have too many protons or neutrons, so to balance its nucleus breaks down, radioisotopes are radioactive isotopes, they break down to stabilise releasing electromagnetic energy from nucleus - An unstable nucleus of a radioisotope may occur naturally rarely, or be due to artificial alters - When a sample of radioisotope decays (nuclear decay), it emits radiation - Overtime, the level of radioactivity falls as the amount of radioisotope in the sample decreases - The half-life of a radioisotope is the time taken for half the radioactive substance/nucleus to decay - The rate at which nuclear decay takes place is measured in half lives of the radioisotope - A half-life of a radioisotope is the amount of time it takes for half the nuclei to decay - The half-life can be graphed numerically in a decay curve   - As stated earlier, radioisotopes have half lives and can be measured by those - Carbon-14, a radioisotope of carbon (carbon-12), can be used to depict the age of ancient materials found through this, in the process of carbon dating - Every living thing contains carbon within, and so a small amount of carbon-14 must be there too - The amount stays within the organism, as they absorb it through food and air - When an organism dies the absorbed carbon-14 begins to undergo beta nuclear decay because it has too many neutrons, this means a neutron becomes a proton and electron while the proton stays the electron leaves - This means the mass stays the same, but an extra proton is gained, transforming the element carbon into nitrogen-14 (7 protons) - As carbon decays into nitrogen, the radioisotope has a half-life of 5730 years, it takes that long for half the radioisotope to decay - Scientists take the found things and measure the amount of carbon-14, to determine how long it's been there and estimate how old the thing is  A picture containing sphere, circle, light Description automatically generated   **Nuclear Decay** - In chemical reactions, reactants rearrange to form new products but the atoms themselves are not changed as chemical reactions involve the interactions of electrons, but not the nuclei of atoms (protons/neutrons)A picture containing circle, emoticon Description automatically generated - In order to make change to the atom and transform it into something new (another element), there must be change in the nucleus (protons neutrons), in order to achieve this a nuclear reaction must occur - Nuclear- referring to the nucleus, this means the reaction involves the nucleus - As the protons and neutrons rearrange in the nucleus, they release nuclear decay, which is high-energy electromagnetic radiation (energy that can travel through a vacuum) - This can be in the form of a particle or wave, and can be three types; - Alpha radiation - Beta radiation - Gamma rays - Nuclear decay can cause atoms to transform into others due to the changed nucleus, this is called transmutation - When an atom has too many protons in its nucleus it becomes unstable, this is due to Coulomb's law on repulsion, like charges repel while unlike charges attract - With too many protons in ratio with neutrons, the nucleus will be unstable in terms of charge and produce excess energy, an atoms' goal is to stay stable no matter what, whether through nuclear or chemical reactions, to keep a full outer shell and a stable nucleus - Therefore, the nucleus releases an alpha particle, an alpha particle is a positively charged particle with a nucleus identical to a helium atom - It has no electrons, so its charge is 2+, as it contains two protons and two neutrons - As an atom releases an alpha particle, the atomic number will drop down two numbers, and the mass will drop down four as its lost two protons, and two neutrons - It will always release a helium ion as alpha particle - Alpha particles are a sort of ionising radiation, AKA alpha rays - Ionising means to give or take electrons from a substance, in order to turn it to an ion - This means that when alpha particles are released, they will take the first two free electrons they can find and become noble gas helium, ionising other elements - Alpha decay occurs in heavy atoms usually, with a mass more than 100 - Alpha particles have low penetrating power (ability to pass through matter), due to their large mass and high ionisation which takes energy) however their high charge and mass is the reason for their high ionising power, as their charge allows them to take electrons, so alpha particles cannot travel far and lose excessive amounts of energy as they do travel, so that's why they ionise atoms quickly and take any free electrons, due to its high charge it can simply pass by atoms and attract electrons - When an atom contains too many neutrons within its nucleus, its nucleus becomes unstable - To stabilise itself during this, the nucleus splits a neutral nucleus, into one positive proton and one negative electron - After obtaining these two charged particles, the atom then keeps the proton and releases the electron, this electron is released as a beta particle, beta decay/ radiation - An electron is identical to a beta particle, a beta particle is just an electron that's emitted specifically due to nuclear decay - As the atom releases an electron and keeps a proton, the mass stays the same as the proton substitutes for the neutron, and the atomic number rises by one due to the proton, changing the element - Beta particles are a form of ionising radiation known as beta rays - Beta particles ionise particles they penetrate (pass through), but not as strongly as alpha particles since they have a higher charge and take more electrons, they're also slower so they can ionise multiple in short distances, beta particles however are small and have a single charge, half the amount of an alpha, so they need to travel further and faster, penetrating more as they hope to ionise other atoms, this causes them to use up all their energy before they have to stop - The atom is now stable in its nucleus with protons and neutrons as it transformed a neutron into a proton and electron - When a nucleus is unstable, instead of releasing particles sometimes the atom will simply release waves due to rearrangement of the nucleus - Gamma rays are a form of electromagnetic radiation and are waves - Gamma rays have no charge or mass, as they are not a particle, meaning they simply just transfer energy - They are transverse waves and have highest frequency on electromagnetic spectrum with lowest wavelength, they have higher penetrating power than alpha and beta as they are small and fast (high frequency) - Because they have no charge or mass, and are not a particle, they don't interact with particles as much as charged particles, so they pass through easier and faster - Ionisation occurs when electrons gain enough energy to move from the electromagnetic forces of the atom, forming an ion when atoms give or take electrons - As gamma rays have a lot of energy, when they collide with atoms or penetrate they may share this with the electrons, which can lead to potential ionisation as the electrons gain energy to move away - Nuclear energy can be used to diagnose and recognise medical threats - In medical imaging, technologies such as PET scans make use of radiation to recognise cancer cells - In a PET scan the patient will be injected with diagnostic isotopes into their blood, which will then be detected on the scanner which will locate tumours and other medical concerns as the radiation passes through the blood where the isotopes are - Radiotherapy is treatment of cancer through radiation, radiation can kill cancer cells as it can penetrate and ionise matter destroying DNA of cancer cells, however through doing this surrounding healthy cells will be killed, this is why symptoms occur such as hair loss, vomiting etc, those cells are being killed - Nuclear energy is used in the industry for many things - Nuclear energy is more efficient in producing electricity than fossil fuels, this is because when fossil fuels are used to make electricity they need to be burnt and combustion causes other harmful gases such as CO2 and SO2, nuclear energy also uses less fuel (in the form of uranium) than coal power plants do, coal is also non-renewable and nuclear energy doesn't need it - Nuclear energy produces less background radiation than coal power plants and are overall more efficient - Radiation is used in the food industry to sterilise products so that they last longer on shelves for consumers, this is helpful for stores - Radiation can also check for underground pipes that have cracks, and can check the thickness of paper when manufacturing **Nuclear Energy- Safety Concerns** - Expose to radiation can damage cells as it damages DNA, this is because it is ionising meaning it can make atoms into ions by moving electrons - As radiation damages DNA, it can cause diseases such as leukemia, cancer, and birth defects if someone pregnant or has eggs experiences radiation - Because of the dangers of radiation, rules have been put into place to prevent the damages - People who work near radiation, health workers, nuclear workers etc have to use methods or use certain devices to help protect themselves, which are made mandatory through guidelines - Workers must wear dosimeters, which are devices which detect the amount of radiation absorbed by a worker and monitor it to limit exposure and the harm it can do - The workers also wear protective clothing and work within thick glass to prevent the amount of radiation - A issue in the nuclear industry is nuclear waste as nuclear waste is let off in such environments - Some forms of nuclear waste have very long half-lives, impacting and ionising their surroundings which is dangerous - Dangerous radioactive waste must be gathered together and then treated and stored away somewhere it cannot reach other places - A disadvantage of nuclear energy being used is that nuclear power plants are very expensive especially to be made safe and only last 40 years before being safely destroyed - Atom; smallest unit/particle of matter, made up of electrons orbiting a nucleus of protons and neutrons - Electrically neutral; no charge, equal ratio of protons and electrons - Element; pure substance made up of one type of atom - Matter; makes up all physical substances that takes up space and has mass - Molecule; cluster of atoms chemically bonded - Nucleus; central part of atom containing protons, and neutrons - Alpha particle; a positively charged particles with two protons and two neutrons - Cathode ray; a beam of electrons emitted from a cathode, observed in a tube - Dalton's atomic theory; theory that states all matter is made of atoms, particles - Electron shell; space around nucleus in which electrons orbit - Spectral line; bright or dark line in a uniform spectrum - Atomic number; amount of protons in atom - Half-life; amount of time it takes for half a radioisotope to decay - Ionise; to give or take electrons to or from an atom - Isotope; an atom of an element with a different amount of neutrons - Penetrating power; ability to pass through matter - Radioisotope; an unstable isotope that emits radiation - Dosimeter; a worn device used to measure the amount of ionising radiation absorbed, a detector used to detect and monitor how much radiation a worker has been exposed to - Ionising radiation; radiation that is able to make other atoms into ions through moving electrons, can cause cancer - Radiotherapy; treatment of cancer using radiation to destroy the cells **Chapter 14** **Matter:** **Isotopes** - Isotopes are atoms of the same element with a different number of neutrons **Rates of Reactions** - The rate of a reaction is the speed at which the chemical reaction occurs - The rate can be increased or decreased depending on certain factors; - [Catalyst]; chemicals that can speed up reactions without being used through either reducing the amount of energy required or easening the ability for reactants to collide and react (e.g. sunlight and chlorophyll in photosynthesis) - [Concentration] (of reactants); the higher concentration of reactants will increase the rate of the reaction as there are more reactants to collide and react - [Agitation]; mixing/ stirring will increase collision of reactants and keep them in contact while excess/ products are moved to side - [Temperature;] the higher temperature will increase rate of reaction as heat enables particles to move faster due to kinetic energy produced - [Surface area;] dividing the reactant into smaller pieces allows more surface area as the smaller pieces can react from their outer layers and in which takes less time as its small however if the reactant was left as a huge substance it'd take ages for it to react from the outside all the way in **[Atomic Bonding]** - Atoms form compounds in order to gain stability through achieving a full outermost shell of electrons, in order to form compounds they must bond with other atoms chemically, this can be done in three ways; **Covalent Bonds** - Covalent bonds are bonds between atoms through sharing valence electrons to achieve a full outershell - Two or more non-metals form covalent bonds - The shared electrons then orbit all nuclei and form a covalent compound/ molecule (cluster of chemically joined atoms) - Drawing covalent bonds;  Examples of covalent compounds; Graphical user interface, text, application Description automatically generated **Ionic Bonding** - Ionic bonding involves a non-metal and metal atom forming a bond through losing/ gaining electrons to create a full outershell for each - Ionic compounds can be worked out chemically through swap drop method by looking at ionic charges on periodic table - Ions are charged atoms, therefore ionic bonds are named so as when electrons are gained/ lost the atoms become ions, if they gain electrons they will be negative and if they lose they will be positive due to the proton electron ratio - Atoms will either give or gain electrons based on what's easier, for example chlorine has 7 valence electrons, so it'd take 1 in an ionic bond to fill its shell easily, therefore its charge is -1 as there'd be one more electron than proton breaking their neutral charge - Some ions' charges need to be memorised; - Silver (Ag) = +1 - Zinc (Zn) = +2 - Lead (Pb) = +2/4 - Iron (Fe) = +2/3 - Copper (Cu) = +1/2 **Polyatomic Ions** - Polyatomic ions are two or more atoms chemically bonded behaving as a single charged unit (ion), they are formed through covalent bonds as they are sharing electrons and act as a single particle - The polyatomic ions have their own charges based on the covalent bonds they've formed, for example, NO3 has a charge of -1 because nitrogen shares its 5 electrons with the three oxygens which in total have 18 electrons, together there are 23 valence electrons, however a full shell would need 24, so its charge is -1 as it'd gain one extra electron from another substance in order to attain this stability of a full shell, another example would be SO4, it has one sulfur atom which has 6 valence electrons, and four oxygens with 6 (24), 24 and 6 equals 30, however a full shell would have 32, so it'd gain an extra 2 from another substance to attain the full shell, therefore its ionic charge would be -2 - Polyatomic ions need to be memorised; - Ammonium= NH4, +1 - Hydroxide= OH, -1 - Nitrate= NO3, -1 - Sulfate= SO4, -2 - Sulfite= SO3, -2 - Nitrite= NO2, -1 - Phosphate= PO4, -3 - Hydrogen sulfate= HSO4, -2 - Carbonate= CO3, -2 - The ion who has gained electrons is negatively charged and now known as an anion, and the ion who has lost electrons is positively charged and now known as a cation, their ionic bond is very strong due to the opposing charges and the electrostatic attraction this produces, cations always come first in the chemical name, and is usually a metal (always place metal first in compound)  **Metallic Bonds** - Metallic bonding occurs between two or more atoms of the same element, it is how metals form - All atoms of the metal 'lose' their electrons to form a free sea of electrons between them all, which all surround the positive metal ions of protons and neutrons, this is due to law of attraction between the positive and negative charges the electrons and nuclei hold - Due to the free sea of electrons dispersed among all the nuclei, a lattice structure is formed, and metallic compounds are good conductors for heat and electricity due to the electronic flow - Metallic bonds however are weaker than ionic bonds - The electrons of each atom are delocalised meaning they don't have a single atom to orbit **[Naming Compounds]** **Covalent Compound Naming** - If a chemical compound has two non-metals, its covalent, if it has a metal and non-metal, its ionic, if its covalent, name it this way; - If the first element contains one atom, leave it as the simple name, e.g. sodium, hydrogen, you do not need to add 'mono', however if there is more than one of it, clarify it, e.g. dihydrogen monoxide, tetraboron dichloride - Now for the second element, always end the second element in 'ide', e.g. fluoride, iodide, chloride, now add a prefix to clarify the amount of atoms of that element contained, even if there is one, e.g. 5 oxygens would be pentoxide Table Description automatically generated **Ionic Compound Naming** - In an ionic compound, the metal is always named first, e.g. NaCl, sodium, the metal will always come first because metals are cations (have positive charge) and nonmetals are anions (negative charge) - In some cases, a polyatomic ion (elements bonded to form a sole particle behaving as an ionic unit ) bonds with another ion to form the compound; Always place the metal before the polyatomic ion, e.g. Na2SO4 - In order to find the chemical compound to name between two ions bonding, use the swap drop method; - Find the ionic charge of the elements bonding, and/ or polyatomic ion bonding - Once you've found it on the periodic table, you may move onto the next step, however if not, memorise it, but if the element has two different charges, you will need to work backwards to figure this out, as shown later on - Now that you have found the two charges, simply swap them between the ions, if 1 is swapped, simplify it to nothing, if they both have the same amount, simplify to nothing, if a polyatomic ion with subscripts gains a charge, make sure to include subscripts in brackets and charge outside, for example, Cl has a charge of -1, SO4 has a charge of -2, swap drop = Cl2(SO4) - To name an ionic compound, you simply just include the metal normally, and end the non-metal in ide, for example, sodium bromide, even if there is a certain amount of each do not use prefixes or include it - If you need to name an ion which has more than one charge, clarify this in roman numerals, e.g. iron (II), if you are given a compound with one of these ions and need to name work backwards, e.g. Fe3N2, swap backwards, Fe2N3, therefore iron (II) - Some polyatomic ions have their own names used in this, for example sulfate (SO4), nitrate (NO3), hydroxide (OH) - Polyatomic ions to memorise; **[Chemical Equations]** **Writing Chemical Equations** - Writing chemical equations involves listing the reactants on the left side being added with each other, and an arrow which is followed on the right side by the products, this is written chemically and in words, e.g. hydrogen + oxygen = water, H2 + O2 = H2O - However in the equation we notice on one side there is more of an element than on the other, this cannot be true as matter cannot be destroyed nor created, which is why we balance **Balancing Chemical Equations** - Law of conservation states that matter cannot be destroyed nor created - Therefore in chemical equations when there appears more of an element on one side than the other, it makes no sense, so we must balance this amount of both sides by adding coefficients (numbers before the chemical formula) to balance it, you must never change the subscripts however which are the little numbers next to the elements, they depict how much of an element is within the substance and cannot be changed - For example; H2 + O2 = H2O, there is an uneven amount of oxygen atoms, so we must add coefficients to balance this= (2)H2 + O2 = (2)H2O **[Acids + Bases]** **Acids** - An acid is a corrosive (highly reactive and damaging to other substances) substance - Acids always consist of H+, and when mixed with pure water they produce amounts of H+ as water is neutral H2O, it will leave excess H+ ions - The hydrogen ions (H+) within acids react with other substances to produce salts (ionic substances), salt means the product of a neutralisation reaction (acid + base) - The higher the concentration of produced hydrogen ions when an acid is mixed with pure water means the higher the acidity - Acids are dangerous as they are reactive and damaging - Types of acids- H2SO4 (sulfuric acid), HNO3 (nitric acid), HCl (hydrochloric acid) **Bases** - A base is a caustic (able to burn through organic tissue chemically) substance that produces hydroxide (OH-) ions when mixed with pure water - Acids are also dangerous - Acids and bases neutralise each other and produce H2O as the simplest formula - Three types of bases; - Metal hydroxides (metal bonds with OH-) - Metal oxides (metal bonds with O2-) - Metal carbonates (metal bonds with CO3\^-2) - Types of bases- Sodium hydroxide, calcium carbonate **pH Scale** - The pH scale (potential hydrogen) is a scale that measures acidity - It is called potential hydrogen as it measures whether there are more or less hydrogen ions H+ - It is a unit of measurement - The higher the number, the more alkaline, basic a substance is (contains more OH-), the lower the number, the more acidic the substance is (contains more H+) - Water (H2O) has a pH of 7, and is neutral, this is because OH- + H+ = H2O (neutral), so when h2O is mixed with an acid it leaves excess hydrogen ions, when with a base it leaves excess hydroxide ions - H+ has one less electron, OH- has one extra electron, together they form the neutral H2O, neutralisation, and that's why H2O is used to depict acids and bases - Anything above 7= a base, anything under 7= an acid   **Indicators** - Indicators are chemicals that can be used to depict whether a substance is acidic or basic, this is indicated by the colour change of the indicator - There are many types of indicators, litmus paper is an indicator that when dipped in an acid, blue litmus paper turns red, and when dipped in a base, red litmus paper turns blue - A universal indicator is a more specific indicator as it uses 14 different shades of colours to indicate the 14 numbered pH levels, with dark red as 0, fading across to a neutral 7 green, continued to the end resulting in a dark blue for 14 - Litmus paper is a binary indicator, with only two values, however a universal indicator is more accurate with 14 values, but universal indicators are harder to distinguish between the shades, while litmus paper is clear, they both have pros and cons **[Reactions With Acids]** **Neutralisation (Acid + Base)** - In a neutralisation reaction, an acid and base react and form a salt and water, the production of H2O is due to the OH within the base and H within the acid - In order to name the salt, look at the acid and indicate what the element beside hydrogen is, for example, HCl, exclude hydrogen and take Cl, then look at the base, indicate what element there is besides OH, for example, NaOH, take the Na, then with the metal first, use these two elements to make a salt, NaCl, and leave the remaining H and OH to form H2O, NaCl + H2O are our products - When naming the salt, keep in mind the salt is ionic, use the charges of the metal and non-metal to find the chemical formula of salt, for example Mg and F = MgF2 as a salt - At the end of writing the reaction in words and chemically, finally balance the equation to make sure the amount of each element is the same on each side **Acid + Metal** - When an acid and metal react, a salt and hydrogen is produced, the production of hydrogen is due to the hydrogen contained in the acid, and the salt is the metal and the element within the acid besides hydrogen (all acids are just substances which contain amounts of hydrogen ions while bases contain OH ions) - Acids to memorise; - HCl (hydrochloric acid), salt- chloride - HNO3 (nitric acid), salt- nitrate - H2SO4 (sulfuric acid), salt- sulfate **Acid + Metal Carbonate** - When acids react with metal carbonates, salt, water, and carbon dioxide are produced, the production of salt is due to the substance within the acid other than hydrogen and the metal reacting bonding, the production of water is due to the hydrogen within the acid and oxygen within the carbonate, and the carbon dioxide is due to the carbon and oxygen within carbonate - Carbonate; CO3, -2 - Example; Nitric acid + potassium carbonate = potassium nitrate + water + carbon dioxide, HNO3 + K2(CO3) = K(NO3) + H2O + CO2, balance after Reactivity Series - Reactivity of Metals, Features and Applications **[Oxidation Reactions]** **Combustion Reactions- Burning Oxygen** - A combustion reaction releases energy - Combustion reactions require burning in the presence of oxygen in order to release energy, heat and light - An oxidation reaction is a reaction that involves oxygen, combustion and corrosion are both the two types of oxidation reactions - A combustion reaction involves the two reactants of oxygen and a compound to produce heat energy and a new substance - An example of combustion is burning wood in a fire, heat energy is produced, along with a substance including carbon, such as CO2 or CO - All products formed by a combustion reaction are oxides - If a metal is burnt in oxygen, a metal oxide and heat and light energy are products - E.g. magnesium + oxygen \-- \> magnesium oxide - In combustion reactions, chemical energy (energy stored in the atomic bonds of chemical substances) is transformed to heat energy - In combustion reactions, chemical energy (energy stored in the atomic bonds of chemical substances) is transformed to heat energy **Hydrocarbons in Combustion** - Hydrocarbons are compounds consisting of only carbon and hydrogen atoms, in different ratios depending on the compound itself, e.g. propane C3H8, ethane C2H8, methane CH4   - When a hydrocarbon (containing hydrogen and carbon) is burnt in the presence of oxygen, the products are H2O and CO2, as there are only hydrogen and carbon atoms being burnt in the presence of oxygen to rearrange atomic bonds - Methane is a hydrocarbon (CH4) used as fuel in many objects to undergo combustion, for example in cars - Combustion energy is used daily, e.g. in cars the petrol is burnt to release energy, usually heat energy, and transform into another - In combustion reactions, chemical energy (energy stored in the atomic bonds of chemical substances) is transformed to heat energy - As combustion reactions require oxygen, when there isn't enough present when a combustion reaction occurs it can lead to different products - As hydrocarbons are burnt in the presence of oxygen and produce CO2 and H2O, this is a complete reaction as enough oxygen was available to produce the typical products - When there isn't enough oxygen present as a hydrocarbon is burnt, the typical products of H2O and CO2 cannot be produced, and something else will - Due to the lack of oxygen, instead of carbon dioxide (CO2), carbon monoxide (CO), with one less oxygen atom can be produced, or carbon soot, a black powder made up of particles produced in an incomplete hydrocarbon combustion, these are harmful as carbon monoxide will bind to hemoglobin in the blood, less oxygen will bind needed **Corrosion Reactions- Degradation Of Metals** - Corrosion is an oxidation reaction, as metals react with oxygen present compounds are produced and form on the metals' surface - The oxygen present reacting can be found within air and water (salt and fresh), as long as oxygen is involved - Some metals corrode faster than others - Corrosion affects a metals' physical and chemical properties such as appearance, strength, structure, etc. - Corrosion and combustion are both oxidation reactions, and both give off heat - Combustion- fast and more heat, corrosion- slow and less heat - Once a metal corrodes, the left of the metal beneath the layer is left exposed, which eventually all corrodes **Iron Corrosion- Rust** - Iron is a metal which undergoes corrosion as others, the scientific name for rust is iron oxide (Fe2O3), iron undergoes corrosion very frequently and easily so pure iron is rare to find - The compound of iron oxide formed on the surface is seen as a red-brown flaky solid - Rust causes a lot of damage due to no protective layer to stop it **Corrosion- Avoidance** - Corrosion can be avoided by creating a barrier between the surface of the metal and substances containing oxygen atoms, water, and oxygen - This can be done through; - Painting metal - Electroplating (coating in another metal) - Galvanising (specifically covering iron in zinc) - - Sacrificial protection (attaching a more reactive metal to the metal so the reactive one will be sacrificed to oxygen while the other one stays safe underneath) - Creating an alloy (two or more metals mixed), this makes it resist corrosion, e.g. stainless steel- iron + chromium/ nickel - Passivating metal (reacts with oxygen to instead forms inactive surface layer to protect metal beneath) **Decomposition- Breaking Substances Down** - Decomposition involves the process of a substance breaking down into two or more substances - Majority of decomposition processes require energy to begin - There are different types of decomposition; - Thermal decomposition: thermal decomposition requires heat energy to decompose the substance, it is an endo-thermic reaction (involves the absorption of heat and cools surroundings). This can be done by heating a reactive substance over heat: - The heat energy promotes kinetic energy which can cause particle collision to break chemical bonds, decomposing the substance - The carbon carbonate is heated, decomposing into carbon oxide and carbon dioxide, two simpler substances - Released carbon dioxide can be checked for through limewater test, an alkaline liquid solution of solute calcium hydroxide Ca(OH)2 in the solvent water, (alkaline due to the OH) A picture containing text, font, number, screenshot Description automatically generated - An example of this in real life is airbags, Sodium Azide (NaN3) is used in airbags, when heated it decomposes into nitrogen gas which inflates airbags during an accident or collision to protect the persons impact    Diagram of air bag inflation device Description automatically generated with low confidence  - Electrical decomposition: electrical decomposition is known as electrolysis, involving an electrical current breaking down a substance into simpler ones - Electrolysis occurs in liquids mostly as it occurs in only ionic solutions, and the ions need to move freely (this cannot occur in solids) - Electrolysis can only occur in substances where ions can move freely, therefore it does NOT occur in covalent compounds, or solid ionic compounds - Electrolysis requires ions (atoms with a charge), so only electrolytes can undergo electrolysis (a liquid/gel which contains ions and can undergo electrolysis to decompose) - Water (H2O) is covalent, not ionic, yet it undergoes electrolysis as it is self-ionising and can produce OH- and H+ by itself, as acids and bases react with each other, H2O being made of OH- and H+ can do this too, and undergoes auto-ionization, this is when an excited atom releases an electron, when this happens it can be gained by another H2O molecule and form hydronium (H3O), an ion, and H+, OH- ions will also be formed A picture containing text, font, white, number Description automatically generated   - Photochemical decomposition: photochemical decomposition AKA photolysis involves light energy, photons breaking down substances into smaller ones, this is usually a slow reaction and unnoticed (lysis means break down) - Example of photochemical decomposition: silver chloride decomposes into chlorine and silver ions overtime, this is due to the atom gaining light energy from a photon entering a transient (short) excited state, where it changes original properties and starts to decompose **Limewater Test** - Released carbon dioxide can be checked for through limewater test, an alkaline liquid solution of solute calcium hydroxide Ca(OH)2 in the solvent water, (alkaline due to the OH) - Released carbon dioxide can be checked for through limewater test, an alkaline liquid solution of solute calcium hydroxide Ca(OH)2 in the solvent water, (alkaline due to the OH), when CO2 reacts with limewater, it produces the precipitate of calcium carbonate (CaCO3) and H2O, the calcium carbonate as precipitate makes the limewater appear milky - Reaction- CO2 + Ca(OH)2 = CaCO3 + H2O (already balanced) The Reaction Of Carbon Dioxide With Lime Water **Hydrogen Pop Test** - Add acid and metal in test tube, place stopper on top - Remove stopper and add match with flame - If pop sound produced, hydrogen is present **[Terminology]** - Atom; smallest unit of matter - Compound; substance made up of two or more types of atoms bonded chemically in fixed ratio - Element; a pure substance made up of one type of atom - Isotope; atoms from the same element with different amounts of neutrons - Mass; amount of matter in object - Matter; any physical substance that takes up space and has mass - Covalent bond; bond between atoms formed by shared valence electrons - Ion; charged atom - Ionic bond; bond between atoms through losing/gaining electrons - Lattice; a rigid, large structure of repetitive patterns of atoms arranged - Metallic bond; bond between two metals where electrons are all lost and move freely around metal positive ions - Molecule; a cluster of atoms/smallest unit of covalent compound - Valency; an element's ability to combine with another through outermost shell - Chemical formula; chemical symbols indicating a ratio between two or more elements - Polyatomic ion; elements chemically bonded behaving as a sole ionic unit - Prefix; a word placed before another - Coefficient; number placed before another - Conservation of mass; matter cannot be created nor destroyed - Product; substance produced in chemical reaction - Reactant; substances which form products through reacting - Caustic; able to corrode, burn organic tissue chemically - Concentration; the amount of substance within a volume of solution - Corrosive; highly reactive and damaging to other substances - Neutralise; make something chemically neutral - pH; a figure representing potential hydrogen, used to measure the acidity of a substance - Carbonate; a substance containing a carbon atom with three oxygen atoms with a charge of negative two - Neutralisation reaction; a reaction between a base and acid to produce a salt and water - Strong acid; an acid with a lower pH, ionises in water completely (produces many H+ and changes charge of water) - Weak acid; an acid with higher pH, partially ionises in water (doesn't produce that much H+) - Combustion; a reaction that involves burning in the presence of oxygen to give off heat - Hydrocarbon; a compound consisting of only carbon and hydrogen atoms - Oxidation; a chemical reaction involving oxygen - Soot; carbon in the form of black powder produced due to incomplete combustion - Transform; change from one thing to another - Alloy; a mixture of two or more metals - Degrade; wear down a substance **Chapter 1** **Energy:** **[Energy Transfer]** - Heat is a form of energy, transferred through objects as any form of energy does, this can be done in two ways; - Conduction: through solids - Convection: through liquids/gases **Conduction** - Conduction is the transfer of heat through solids - Solid particles vibrate, as heat energy is gained by solid particles, this is transformed into kinetic energy, which causes the particles to vibrate more and at faster speed, this causes the particles to collide and bump transferring the heat energy as kinetic energy, and it spreads throughout the whole solid - The best solid conductors of heat are metals, such as iron, copper, etc. - There are also solid insulators who are not good at conducting heat, such as plastic, cotton, wood, wool A picture containing text, screenshot, font Description automatically generated  - Convection is the transfer of heat through liquids/gases - Particles in liquids/gases are less dense than those of solids - Convection currents occur to keep heat moving through liquids and gases - As the liquid or gas is heated, particles spread out and the substance expands - If a liquid or gas is heated from beneath, the particles will heat up below and become less dense, so they rise up to the cooler areas, where they will then lose heat energy once again due to lack of heat, and will become cool and dense, dropping down back to the heat source and the convection current continues - Waves are the travel of energy without the movement of matter - There are two main categories of waves; - Electromagnetic waves; an electric and magnetic field sharing vibrations creating a wave of energy that can travel through vacuums (empty space), a form of radiation - Mechanical waves; a wave of energy that is an oscillation of matter (motion repeating), it requires matter to pass through, they are caused by a disturbance or vibration in matter, e.g. sound waves - There are two types of waves that then fall under these; - Transverse; can travel through both matter and vacuum, doesn't need matter as it can be produced by electromagnetic fields sharing vibrations or matter vibration, e.g. light - Longitudinal; requires medium, needs matter to travel due to a disturbance or vibration within causing it, e.g. sound, that's why sound is not heard in space but light travels A close up of a logo Description generated with high confidence **Wave Properties** - Regardless of the type of wave, all waves share some properties; - Amplitude; All waves have amplitude, which means half the height of the wave, this in sound causes louder sound, a wave with high amplitude carries more energy - Frequency; All waves have frequency, amount of waves/ vibrations passing per second, is measured in Hertz - Wavelength; the wavelengths in waves can be measured as the distance between one peak of a wave to the next, in transverse waves this is measured as one trough and crest meeting again at the centre, or one-half crest/ trough to the same other **Longitudinal Waves** - A longitudinal wave is mechanical, meaning it requires matter to pass through disturbance - Particles vibrate in the same direction of wave, they move back and forth causing rarefactions (where particles are most far apart), and compressions (where particles are most close), these are the peaks of the wave - To measure a wavelength in longitudinal wave is to mark the centre of a compression to the centre of the next - As the waves travel in a medium (matter that allows waves to pass through), they disturb the particles causing them to vibrate in the direction of the wave transferring it through - Longitudinal waves travel faster in denser matter as there's more particles to vibrate - Longitudinal wave example is sound  **Transverse Waves** - Transverse waves vibrate up and down rather than back and forth in direction of the energy transportation to move it along - Transverse waves can be both mechanical and electromagnetic - Transverse waves travel at right angles to their direction of motion - To measure a wavelength is to have both a full crest and trough meeting at node, but it can also be one crest to another, half the centre of a crest to another, or trough **To Find Speed** - To find speed of wave, we need wavelength and freq, vice versa as they are all related V (velocity/speed) = f (frequency) x  λ(wavelength) A screenshot of a cell phone Description generated with very high confidence **Sound Waves** - Sound waves are longitudinal, mechanical waves - They require matter to pass through as they are mechanical, and cannot travel through a vacuum (empty space), this is why in space you hear no noise - Sound travels faster through denser matter as it requires particles to pass through, so having more present allows it to travel faster with ease - Sound travels faster through solids, e.g. put your ear on a desk and smack it you'll hear it louder - Sound in liquid travels slower than in solids as particles are more spread out, this is why sound is slower in water - Sound in gas travels the slowest as particles are very spread out, this means sound in water is faster than air - For gas particles, it takes longer vibrations to be passed from one to another which takes more time - Heat increases kinetic energy, so sound travels faster in heated substances than cooled ones **Sound Reflection/Absorption** - Hard surfaces reflect sound waves, causing an echo because sound cant penetrate it due to the dense structure and change of medium - Soft surfaces absorb sound waves due to fibrous structure and convert it into heat - This is why unfurnished rooms have echoes and are colder - Places where plays occur are made to reflect sound waves with hard materials and lots of space  - Electromagnetic waves come from the sun and stars originally, they travel through vacuums as they are all transverse waves which don't require particles to move through - Electromagnetic waves are made up of magnetic and electric fields travelling together sharing vibrations - All electromagnetic waves travel at the speed of light 300,000km/s - Electromagnetic waves on the spectrum all differentiate based on frequency and wavelength - When the wavelength increases, the frequency decreases as less waves can transfer within a second if they're longer, the energy also decreases as the energy is stretched out in long waves rather than there being enough to be a lot of small ones - The spectrum which has all these waves, is called the electromagnetic spectrum - When the wavelength decreases, frequency, and energy increases, as the waves are smaller so more can fit in the second and that means more energy - In the order of increasing energy, gamma rays are highest frequency, then x-rays, then UV, then visible light, then infrared, then microwaves, then radio waves Electromagnetic spectrum \| Definition, Diagram, & Uses \| Britannica - Gamma rays can penetrate materials, even dense hard ones such as lead/ concrete - Gamma rays are dangerous because they can damage your body cells - Gamma rays are used in the industry to detect cracks in metal structures and underground pipes - Gamma rays can be used to sterilise metal equipment, can be used to treat cancer and in CT scans **X-Rays** - X-rays are second highest frequency and are made when electrons with a lot of energy hit a metal surface, this affects photographic film and can help find cracks in bones etc - Denser materials absorb more X-rays because there are more subatomic particles to react with radiation with the more amount of atoms - X-rays produce images of bones as they are dense and hard, the soft materials such as organs and tissue instead allow the x-rays to penetrate, pass through them rather than absorb it - X-rays are used in airports to see luggage, kill cancer cells and detect bone cracks **UV (Ultraviolet)** - Ultraviolet means 'beyond violet', this is because it is the section of the electromagnetic spectrum where it has shorter wavelengths and higher frequencies than violet visible light rays, which has the highest frequency - You can't see UV light, but some insects can such as bees - UV light is used to detect blood, checking signatures and other substances **Visible Light** - Light is known as visible light because it's the only type of electromagnetic wave our eyes can see which is due to special cells in our eyes **Infrared Light** - Infrared light has a lower frequency and a longer wavelength than red does on the visible light spectrum, which has the longest wavelength and lowest frequency, meaning infrared has less energy - Infrared light is given off as heat - Infrared is used in electrical heaters, short-range communications (remote controls), and thermal imaging cameras (detect people in the dark) **Microwaves** - Microwaves have shorter wavelengths than radio waves and are given off by mobile phones, microwaves are used in telecommunications, satellite telephone towers, shorter microwaves are used in cooking food **Radiowaves** - Radiowaves used for broadcasting television and radio and can be used in communications and satellite transmissions - The radiowaves are produced by vibrating electrons which then cause the antennas of tv to vibrate, this then converts into images on TV and sound on the radio **Light and Electromagnetic Wave** - Light is an electromagnetic wave made up of magnetic and electric fields which alter and share their vibrations - Light travels very fast, at 300,000km per second - Light may be reflected, absorbed, or refracted when it hits a surface - Transparent materials; allow light to pass through - Translucent materials; allow some light to pass through but not all - Opaque materials; reflect or absorb light, so it is not able to pass through and it appears solidly that colour  **Light- Reflected and Absorbed** - When light hits a shiny smooth surface, it reflects off at the angle (angle of reflection) that is the same angle at which it is hitting the surface (angle of incidence) - Opaque materials that have very rough surfaces do not reflect light in this way so you cannot see a reflection, some of the light is also absorbed and transformed into heat - This is why only some materials have reflections A close up of a map Description generated with high confidence **Light- Bends Travelling Different Mediums** - When light travels from one medium to another, it will refract, bend - Light travels at different speeds in different mediums - When light moves from air to water, it slows down as water is more dense - The sudden change in speed causes the light to bend, causing the object to appear in another position A close up of a map Description generated with very high confidence **Convex and Concave** - Lenses are useful as they can bend light - Concave lenses make the light spread out so people using these lenses can see further, people who are short-sighted use this - Convex lenses make light meet at a point through a bulge, to make things seem bigger, people who are long-sighted use this to see objects closer - Conduction; transfer of heat through solids - Convection; transfer of heat through liquids/gases - Conductor; substance that allows heat to pass through - Insulator; substance that resists the transfer of heat, doesn't allow it to pass through - Amplitude; half the height of the wave - Frequency; number of waves that pass per second - Longitudinal; going length wise, straight horizontal rather than across - Transverse; across horizontal rather than horizontal straight - Vacuum; empty space - Wavelength; the distance from the peak of one wave to the next, or one crest and trough included where they meet again at the node - Reflect; send back sound/ light, not absorbing it - Sonar; sound navigation - Electromagnetic spectrum; all the different electromagnetic waves - Gamma ray; radiation emitted by radioactive materials with the shortest wavelength and highest frequency - Infrared light; an electromagnetic wave with longer wavelength than red light, given off as heat - X-ray; a high-energy ray that can penetrate materials and comes after gamma rays with lower frequency, and longer wavelengths but still strong - Angle of incidence; the angle at which light hits the surface - Angle of reflection; the angle at which the light that has hit now reflects off the surface - Opaque; a material that absorbs or reflects light energy and doesn't let it pass through, so you don't see any clear surface it instead appears solidly colour - Refract; light bending because it passes from a medium to a very different one - Translucent; material that allows some light to pass through only, so it is clear but very blurry - Transparent; a material that allows all light to pass through, appears clear completely **Chapter 4:** **Energy- Usage:** **[Conservation of Energy]** - Energy cannot be made nor destroyed, this is stated in law of conservation of energy, as energy cannot be made nor destroyed, it can transform into other types of energy, or transfer - All the existing energy right now has been recycled since it all came from the big bang - Energy exists in multiple forms in which it transforms to other forms; Energy Type Description ------------------------- ---------------------------------------------------------------------------- Heat Energy that raises the temperature (average kinetic energy) of a substance Kinetic Energy that allows substances to move Light Energy that can be seen Nuclear Energy within the nucleus of an atom Chemical Energy stored within bonds of atoms Sound Energy that causes vibrations that can be heard by ear Elastic potential Energy stored when substance is stretched, compressed, twisted Gravitational potential Energy stored when an object is at a high position Electrical Energy produced by movement of electrons **Energy Transfer** - Energy can be transferred from one substance to another - If a rolling ball hits another ball it transfers kinetic energy **Energy Transformation** - Energy can transform from one form to another - For example, a ball thrown at first will have kinetic energy, when it reaches a peak it will lose kinetic energy and gain gravitational potential energy, then this will convert into kinetic energy again and continues faster falling until it hits the ground **Energy Lost in Transfers/Transformations** - Whenever an energy transfer/transformation occurs, some energy is always lost as a result of the change - A ball falling from a height, starts off with gravitational potential energy, then it transforms into kinetic energy, and as it hits the ground elastic potential energy is stored then it bounces back up, but not to the same height as it originally bounced to, this isn't because some of the energy was destroyed, it's because it was lost in the process; - Some energy was lost due to air resistance, a form of friction, that occurs when something is surrounded by air, this forms heat as it is friction and the heat is lost, when the ball hits the ground heat will also be produced and transferred to the ground - As the ball hits the ground some of the kinetic energy that allowed it to hit the ground will be transformed into sound energy and also lost - All of these minor contributions overall lead to the loss of energy in the ball, so the remaining kinetic energy goes as high as it can with the new amount of energy **Energy Devices Efficiency** - All devices lose some energy, devices with mostly usable energy are desired and made to that standard - Wheels produce friction and lose some kinetic energy as heat - Lights lose energy as heat - Vacuums lose energy as heat, sound, when they only require kinetic - Devices that contain mostly usable energy are energy efficient - To work out the efficiency of a device, place the useful energy output over total energy input, then times by 100/1 to get it as a percentage - E.g, if a smartphone uses 200J, and 50J is sound, 50J is light, and 100 is heat, it is 50% efficient as you only need sound and light, which is 100/200, add them in joules (J) - If the percentage is over half, its energy efficient, if its below, it's not - Most of the energy produced worldwide is by fossil fuels, about 80% - Fossil fuels are burnt to produce electricity - A fossil fuel is a material that is a hydrocarbon and is formed in the Earth's crust from dead organisms remains and takes millions of years with the high temperature and pressure of the crust - This means fossil fuels are non-renewable as they take ages to form, and we may run out of them - These resources are finite, and we can run out, they also produce greenhouse gases which are harmful to the atmosphere and environment - This makes us search for new ways to generate electricity - We need to make sure we don't waste much energy, and use energy efficient devices, using devices that lose a lot of energy as extra lowers the quality and efficiency of the device, as not enough usable energy is being produced **Energy-Efficient Devices** - Energy efficient devices are becoming more important and desired as the cost of energy production increases and the dangers of non-renewable sources producing energy are aware, like electricity produced by fossil fuels - Switching to an energy efficient device, such as LED lights, will save the long-term costs as it will require more energy input to use inefficient devices - With the less waste of energy, the products can take on tasks without wasting produced energy and it can be used for other useful devices - Incandescent light bulbs waste 90% of their energy as heat, only 10% is useful and used which is very inefficient - Fluorescent lightbulbs and LED lights use less energy, and incandescent and halogen light bulbs are being used less - LED lights convert about 95% of their input to useful light energy, wasting only 5% as heat, this is very efficient, doesn't let heat out into environment contributing to global warming, require less energy and are cheaper in electricity bills due to this - The fossil fuel industry contributes a lot to Australia's economy - Australia contains plenty of fossil fuels which makes them cheap - 85% of Australia's electricity supply comes from coal and gas power - Australia's fossil fuel related industries, gas and coal give jobs to more than two hundred thousand people, and coal and gas is sold overseas too to contribute to Australia's economy - Australia could stop relying on fossil fuels eventually, but this will require investments in renewable resources, so more money will be spent, and a lot of employees will lose jobs, however the renewable energy source may create new employment opportunities to take place **Fossil Fuels- The Environment** - Fossil fuels being burnt causes pollution - When burnt, dangerous chemicals are given off in the combustion reaction - These chemicals destroy the ecosystems - Acid rain is caused when pollutants enter the atmosphere and dissolve into water and produce acid rain in the water cycle, the pollutants that cause this include nitrogen and sulfur oxides, e.g. S dissolves with H2O = H2SO4, N + H2O = NHO3 - Acid rain destroys the ecosystems and causes multiple deaths of organisms - The pollutants also cause diseases as they enter the air, such as lung diseases, asthma, cancer, heart disease etc - Burning fossil fuels, coal, releases heavy metals such as lead and mercury which make up the substance naturally occurring, which may enter water sources and contaminate marine life and the water cycle **Fossil Fuels- Climate Change** - Carbon dioxide is a greenhouse gas released when fossil fuels are burnt as carbon dioxide is released in combustion as fossil fuels are hydrocarbons - Greenhouse gases released in the atmosphere trap heat energy, as the molecules of them absorb light, heating up the atmosphere raising the planet's temperature - This is global warming and is a symptom of climate change, which may cause; sea levels rising as ice melts causing floods at coast, animals in polar regions lose habitats, organisms we rely on for food may not survive due to heat stress reducing livestock growth, reproduction and milk production, extreme weather events, diseases due to heat as fungi spread in places that were too cold before, coral bleaching due to rising water temperatures can cause coral to lose their algae **Terminology** - Energy the ability to do work - Energy transfer; energy moving from one substance to another, or through a substance without transformation - Energy transformation; energy changing from one form to another - Efficient; does not waste much, effective in use - Energy efficiency; most energy produced is usable and effective - Friction; the force that opposes motion, kinetic energy, and produces heat, caused by objects rubbing against each other - Joule; measure of energy - Usable energy; energy produced by a device that is meant for use, not extra - Finite; can run out, limited, not forever - Fossil fuel- a hydrocarbon substance naturally occurring within the Earths' crust due to organism remains and high pressure and temperature - Generate; produce or make something - Abundant; plentiful - Economy; the system of a country involving the production and usage of money with goods and services - Ecosystem; a community of organisms within the environment - Pollution; harmful substances entering the environment and causing negative side effects