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OpenStem
@openstem · Joined Jul 2026
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Flashcards10 cards
What does VSEPR theory say determines a molecule's shape?1 / 10
The electron pairs (bonding pairs AND lone pairs) around a central atom repel each other and arrange themselves to be as far apart as possible. The resulting positions of the ATOMS give the molecular shape.
Chemistry · L3 · VSEPR shapes
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Chemistry · L3 · VSEPR shapesFlashcards10 cards
What is a mole, in everyday terms?1 / 10
A dozen always means 12, however many you're counting. A mole is the same idea for atoms and molecules: it always means 6.02 × 10²³ particles — Avogadro's number — no matter which substance you're counting.
Chemistry · L3 · Stoichiometry & the Mole
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Chemistry · L3 · Stoichiometry & the MoleFlashcards8 cards
What does Boyle's Law say about pressure and volume?1 / 8
At constant temperature, the pressure and volume of a fixed amount of gas are inversely proportional: squeeze the gas into a smaller space and its pressure rises by the same factor.
Chemistry · L3 · Gas Laws
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Chemistry · L3 · Gas LawsFlashcards8 cards
What does the 'equivalence point' of an acid–base titration mean?1 / 8
The point where the moles of base added exactly equal the moles of acid originally in the flask — the acid and base have exactly neutralised each other.
Chemistry · L3 · Titration curves
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Chemistry · L3 · Titration curvesFlashcards9 cards
What does the equation q = mcΔT let you calculate, and what does each symbol mean?1 / 9
It calculates q, the heat energy transferred, in joules. m is the mass being heated or cooled, in grams; c is the substance's specific heat capacity, in J/(g·°C) — how much energy it takes to raise 1 g of it by 1 °C; and ΔT is the temperature change, in °C.
Chemistry · L3 · Thermochemistry Basics
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Chemistry · L3 · Thermochemistry BasicsFlashcards8 cards
What two conditions does collision theory say a collision must meet to cause a reaction?1 / 8
The particles must collide with enough energy — at least the activation energy — AND in the correct orientation. Meet only one and the collision fails.
Chemistry · L3 · Reaction rates & kinetics
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Chemistry · L3 · Reaction rates & kineticsFlashcards9 cards
What does the ⇌ symbol mean in a chemical equation?1 / 9
The reaction is reversible — it can run forward (reactants → products) and in reverse (products → reactants) at the same time, under the same conditions.
Chemistry · L3 · Chemical Equilibrium & Le Chatelier's Principle
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Chemistry · L3 · Chemical Equilibrium & Le Chatelier's PrincipleFlashcards8 cards
What does the mnemonic OIL RIG stand for?1 / 8
OIL — Oxidation Is Loss (of electrons). RIG — Reduction Is Gain (of electrons). It's a quick way to remember which direction each half-process moves electrons.
Chemistry · L3 · Redox & Electrochemistry
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Chemistry · L3 · Redox & ElectrochemistryFlashcards8 cards
Why can carbon form so many more compounds than almost any other element?1 / 8
Carbon forms four covalent bonds, and — unusually — it bonds happily to itself, chaining into long strings, branches, and rings almost without limit. That single property (catenation) is why organic chemistry, the chemistry of carbon compounds, is such a vast field.
Chemistry · L3 · Organic Chemistry: Functional Groups & Naming
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Chemistry · L3 · Organic Chemistry: Functional Groups & NamingFlashcards10 cards
What particle is emitted in alpha decay?1 / 10
A helium nucleus — 2 protons and 2 neutrons bundled together (written α, or ⁴₂He).
Chemistry · L3 · Nuclear Chemistry
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Chemistry · L3 · Nuclear ChemistryFlashcards6 cards
What does molarity (M) measure?1 / 6
The concentration of a solution — how many moles of solute are dissolved per litre of solution. Its unit, mol/L, is written M for short.
Chemistry · L3 · Molarity Basics
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Chemistry · L3 · Molarity BasicsFlashcards6 cards
Write the dilution equation and say what each symbol means.1 / 6
C₁, V₁ are the concentration and volume BEFORE diluting; C₂, V₂ are the concentration and volume AFTER. It works because the moles of solute (C×V) don't change — only the volume of solution around them does.
Chemistry · L3 · Dilution — C₁V₁ = C₂V₂
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Chemistry · L3 · Dilution — C₁V₁ = C₂V₂Flashcards10 cards
What is the difference between a covalent bond and an intermolecular force?1 / 10
A covalent bond is a strong force WITHIN a molecule, holding its atoms together by sharing electrons. An intermolecular force is a much weaker force BETWEEN separate molecules.
Chemistry · L3 · Intermolecular Forces
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Chemistry · L3 · Intermolecular ForcesFlashcards10 cards
What oxidation number does an atom have when it is part of a free, uncombined element — for example, the Zn in solid zinc, or each O in O₂ gas?1 / 10
Zero. Any atom in a free element — whether monatomic (Zn) or a molecule of just that element (O₂, Cl₂) — has oxidation number 0. There's no other element around to shift electrons toward or away from it.
Chemistry · L3 · Assigning Oxidation Numbers
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Chemistry · L3 · Assigning Oxidation NumbersFlashcards6 cards
What must a monomer have to undergo ADDITION polymerization?1 / 6
A carbon–carbon double bond (C=C), like the one in ethene above. The double bond opens up so the monomer can bond directly to its neighbours on each side.
Chemistry · L3 · Addition vs Condensation Polymerization
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Chemistry · L3 · Addition vs Condensation PolymerizationFlashcards8 cards
What does recycling code #1 stand for, and name one common product.1 / 8
PET (polyethylene terephthalate) — used for soft-drink and water bottles.
Chemistry · L3 · Plastic Recycling Codes
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Chemistry · L3 · Plastic Recycling CodesFlashcards10 cards
What flame colour does a lithium salt give, and which other common metal ion gives the exact same colour?1 / 10
Red (crimson). Strontium salts give the same red colour, so flame colour alone cannot tell the two apart.
Chemistry · L3 · Flame Tests & Ion Tests
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Chemistry · L3 · Flame Tests & Ion TestsFlashcards6 cards
What does it mean to call a property "colligative", and which three properties does that cover?1 / 6
A colligative property depends on HOW MANY particles are dissolved in a solvent — not what those particles are.
Chemistry · L3 · Freezing & Boiling Point Shifts
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Chemistry · L3 · Freezing & Boiling Point ShiftsFlashcards6 cards
In plain terms, what is vapor pressure?1 / 6
A measure of how many molecules are escaping a liquid's surface to become vapor. Liquids that evaporate easily (like rubbing alcohol) have a high vapor pressure; liquids that evaporate slowly have a low one.
Chemistry · L3 · Vapor Pressure Lowering
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Chemistry · L3 · Vapor Pressure LoweringFlashcards10 cards
What is electrolysis, and how is it the OPPOSITE of what a galvanic cell does?1 / 10
Electrolysis uses electrical energy from an external supply to force a non-spontaneous reaction — splitting an ionic compound into its elements. A galvanic cell runs the opposite direction: it lets a spontaneous redox reaction generate electrical energy. One converts electrical energy into chemical energy; the other converts chemical energy into electrical energy.
Chemistry · L3 · Electrolysis
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Chemistry · L3 · ElectrolysisFlashcards10 cards
What is a limiting reagent?1 / 10
The reactant that runs out first in a chemical reaction, stopping the reaction before the other reactant is fully used up. It caps the maximum amount of product that can possibly form — like running out of cheese partway through making sandwiches, even with bread left over.
Chemistry · L3 · Limiting Reagents and Percent Yield
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Chemistry · L3 · Limiting Reagents and Percent YieldFlashcards10 cards
What does an empirical formula tell you, and what does it NOT tell you?1 / 10
An empirical formula gives the simplest whole-number ratio of atoms in a compound — it tells you the PROPORTION of each element, but not the actual number of atoms in one real molecule.
Chemistry · L3 · Empirical and Molecular Formula
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Chemistry · L3 · Empirical and Molecular FormulaFlashcards11 cards
In a pure metal, why can layers of metal ions slide past each other without breaking the metallic bond?1 / 11
The bonding electrons are delocalised into a shared sea that surrounds the whole lattice rather than belonging to any fixed pair of atoms. When a layer slides, the electron sea simply flows to keep surrounding whichever ions are now nearby — no fixed bond has to break in a particular direction.
Chemistry · L3 · Metallic Bonding and Why Alloys Are Harder
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Chemistry · L3 · Metallic Bonding and Why Alloys Are HarderFlashcards10 cards
In the Haber process, N₂(g) + 3H₂(g) ⇌ 2NH₃(g) is exothermic. Why isn't the reaction simply run at a low temperature, where equilibrium favours more ammonia?1 / 10
Because a low temperature also makes the reaction very slow. It would take far too long to reach equilibrium to be economical — temperature isn't chosen for yield alone, it has to balance yield against how fast the plant can actually produce ammonia.
Chemistry · L3 · Industrial Equilibrium — Haber and Contact Processes
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Chemistry · L3 · Industrial Equilibrium — Haber and Contact ProcessesFlashcards10 cards
What does a buffer solution do?1 / 10
It resists changes in pH when small amounts of acid or base are added — the pH shifts only slightly instead of swinging sharply.
Chemistry · L3 · Buffers — Resisting pH Change
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Chemistry · L3 · Buffers — Resisting pH ChangeFlashcards11 cards
In everyday terms, what does 'entropy' actually measure?1 / 11
Entropy measures how spread out or disordered energy and matter are. Low entropy means energy or particles are concentrated and orderly; high entropy means they are spread out and jumbled up.
Chemistry · L3 · Entropy and the Second Law
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Chemistry · L3 · Entropy and the Second LawFlashcards11 cards
What is a reaction mechanism?1 / 11
The sequence of small, individual collision steps (elementary steps) that a reaction actually proceeds through on the way from reactants to products — as opposed to the overall balanced equation, which only shows the start and end points.
Chemistry · L3 · Reaction Mechanisms and the Rate-Determining Step
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Chemistry · L3 · Reaction Mechanisms and the Rate-Determining StepFlashcards10 cards
What is one of the two big patterns that make transition metals (like iron, copper, chromium, and manganese) stand out from main-group metals (like sodium and magnesium)?1 / 10
Most transition metals can exist in more than one oxidation state across different compounds — for example, iron forms both Fe²⁺ and Fe³⁺ compounds. A main-group metal like sodium or magnesium essentially only ever forms one fixed oxidation state (Na⁺, Mg²⁺).
Chemistry · L3 · Transition Metals — Variable States and Color
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Chemistry · L3 · Transition Metals — Variable States and ColorFlashcards10 cards
What two products form when a hydrocarbon undergoes complete combustion in plenty of oxygen?1 / 10
Carbon dioxide and water. Complete combustion also releases a lot of useful energy — the whole reason hydrocarbons are burned as fuels.
Chemistry · L3 · Combustion and Cracking of Hydrocarbons
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Chemistry · L3 · Combustion and Cracking of HydrocarbonsFlashcards11 cards
HDPE and LDPE are both made from the same monomer, ethene. Why is HDPE rigid while LDPE is flexible?1 / 11
HDPE has long, mostly straight chains that pack tightly and tangle, resisting sliding — rigid and strong. LDPE has shorter, highly branched chains that pack loosely and slide past each other easily — soft and flexible.
Chemistry · L3 · Polymer Structure and Properties
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Chemistry · L3 · Polymer Structure and Properties