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OpenStem
@openstem · Joined Jul 2026
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Flashcards10 cards
Is air a single substance or a mixture?1 / 10
Air is a mixture of several different gases, not a single substance. The main ones are nitrogen, oxygen, argon, and carbon dioxide.
Chemistry · L2 · Gases in the Air
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Chemistry · L2 · Gases in the AirFlashcards8 cards
What is a polymer?1 / 8
A polymer is a very long chain made of many small, repeating units called monomers joined together — like a paper-clip chain made of thousands of identical clips.
Chemistry · L2 · Polymers and Monomers
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Chemistry · L2 · Polymers and MonomersFlashcards8 cards
Name two natural polymers found in living things.1 / 8
Starch (made by plants) and rubber (from rubber trees) are natural polymers. Wool and silk, made by animals, are natural polymers too.
Chemistry · L2 · Plastics — Useful but Tricky
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Chemistry · L2 · Plastics — Useful but TrickyFlashcards8 cards
What does a flammable hazard symbol mean?1 / 8
The substance catches fire easily. Keep it away from flames, sparks, and other heat sources.
Chemistry · L2 · Hazard Pictogram Categories
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Chemistry · L2 · Hazard Pictogram CategoriesFlashcards6 cards
Why do you wear safety goggles in the lab?1 / 6
Goggles protect your eyes from splashes, fumes, and flying particles — eyes are easily and permanently damaged by chemicals.
Chemistry · L2 · Lab Safety Rules
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Chemistry · L2 · Lab Safety RulesFlashcards8 cards
What is an exothermic reaction?1 / 8
A reaction that releases energy to its surroundings, usually as heat. The reaction mixture and container get warmer.
Chemistry · L2 · Exothermic Reactions
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Chemistry · L2 · Exothermic ReactionsFlashcards8 cards
What is an endothermic reaction?1 / 8
A reaction that absorbs energy from its surroundings, usually as heat. The reaction mixture and container get colder.
Chemistry · L2 · Endothermic Reactions & Spotting the Difference
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Chemistry · L2 · Endothermic Reactions & Spotting the DifferenceFlashcards12 cards
What is a salt, in the chemistry sense?1 / 12
A salt is a compound formed when the hydrogen in an acid is replaced by a metal (or a similar positive ion). It is always one of the products when an acid reacts with a metal, a base, or a metal carbonate.
Chemistry · L2 · Making Salts
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Chemistry · L2 · Making SaltsFlashcards11 cards
What is the general word equation for a metal reacting with an acid?1 / 11
metal + acid → salt + hydrogen. This pattern holds for any reactive metal and any acid.
Chemistry · L2 · Metals Reacting with Acids
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Chemistry · L2 · Metals Reacting with AcidsFlashcards10 cards
How do you test for oxygen gas?1 / 10
Put a glowing splint into the gas. If it relights into a flame, the gas is oxygen.
Chemistry · L2 · Testing for Gases
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Chemistry · L2 · Testing for GasesFlashcards10 cards
What is fermentation?1 / 10
Fermentation is a chemical reaction in which yeast — a living microorganism — breaks down sugar without using any oxygen. It is a type of anaerobic respiration.
Chemistry · L2 · Fermentation
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Chemistry · L2 · FermentationFlashcards10 cards
Paint and galvanizing work well for fences and nails, but how do engineers protect something huge and expensive like a ship's hull or a pipeline?1 / 10
They scale up the same ideas and add a few more tools: mixing chromium into steel to make it self-protecting, bolting on sacrificial blocks of a more reactive metal, or plating on a thin barrier of another metal.
Chemistry · L2 · Protecting Metal Structures
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Chemistry · L2 · Protecting Metal StructuresFlashcards12 cards
Is evaporation endothermic or exothermic?1 / 12
Endothermic — evaporation absorbs energy from its surroundings as liquid water turns into vapour.
Chemistry · L2 · Energy in the Water Cycle
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Chemistry · L2 · Energy in the Water CycleFlashcards10 cards
What is an alloy?1 / 10
An alloy is a mixture of a metal with one or more other elements — often another metal, sometimes carbon. It's mixed on purpose to give the metal better properties than it would have on its own.
Chemistry · L2 · Alloys — Mixing Metals for a Purpose
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Chemistry · L2 · Alloys — Mixing Metals for a PurposeFlashcards12 cards
Where is the energy involved in a chemical reaction actually stored?1 / 12
In the chemical bonds holding atoms together, both in the reactants and in the products. A reaction changes energy because it changes which bonds exist.
Chemistry · L2 · Energy Stored in Chemical Bonds
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Chemistry · L2 · Energy Stored in Chemical BondsFlashcards12 cards
What is a natural pH indicator?1 / 12
A substance found in nature — usually in a plant — that changes colour depending on whether it touches an acid or a base, instead of being manufactured in a lab like universal indicator.
Chemistry · L2 · Natural pH Indicators
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Chemistry · L2 · Natural pH IndicatorsFlashcards12 cards
What is a gas actually made of?1 / 12
A gas is made of countless tiny particles spread far apart, all moving around freely and quickly in every direction.
Chemistry · L2 · Gas Pressure — the Particle Picture
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Chemistry · L2 · Gas Pressure — the Particle PictureFlashcards11 cards
Why do candle wax, propane, and petrol all produce carbon dioxide and water when they burn completely?1 / 11
They are all hydrocarbons — molecules made only of carbon and hydrogen. When any hydrocarbon burns completely in plenty of oxygen, its carbon always ends up as carbon dioxide and its hydrogen as water.
Chemistry · L2 · What Comes Out of a Flame
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Chemistry · L2 · What Comes Out of a FlameFlashcards12 cards
What is the first step when raw water arrives at a treatment plant?1 / 12
Screening. The water passes through a coarse screen or mesh that catches large debris like leaves, litter, sticks, and other floating rubbish before anything else happens to it.
Chemistry · L2 · Treating Water for Drinking
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Chemistry · L2 · Treating Water for DrinkingFlashcards12 cards
What is an ore?1 / 12
An ore is a rock found in the ground that contains enough of a metal (usually combined with other elements, like oxygen) to be worth extracting.
Chemistry · L2 · Getting Metals from Ores
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Chemistry · L2 · Getting Metals from OresFlashcards11 cards
What makes cotton comfortable to wear in hot weather?1 / 11
Cotton is breathable and absorbs sweat and moisture well, so it feels cool and comfortable when it's hot — though it does wrinkle easily and takes a long time to dry.
Chemistry · L2 · Natural and Synthetic Fibers
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Chemistry · L2 · Natural and Synthetic FibersFlashcards11 cards
What two things do you need to make a simple homemade battery?1 / 11
Two different metals (like zinc and copper) and an electrolyte — a liquid that can carry a charge, such as salty water, lemon juice, or potato juice.
Chemistry · L2 · How Batteries Work
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Chemistry · L2 · How Batteries WorkFlashcards12 cards
What is photosynthesis?1 / 12
The process plants use to make their own food. Using energy from sunlight, a plant combines carbon dioxide and water to produce glucose (a sugar) and releases oxygen as a byproduct.
Chemistry · L2 · The Carbon Cycle
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Chemistry · L2 · The Carbon CycleFlashcards12 cards
What is soap traditionally made from?1 / 12
A fat or oil — such as animal fat, olive oil, or coconut oil — heated together with a strong base called lye (sodium hydroxide, NaOH).
Chemistry · L2 · How Soap Is Made — Saponification
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Chemistry · L2 · How Soap Is Made — SaponificationFlashcards10 cards
How does salting meat or fish help stop it from spoiling?1 / 10
A high concentration of salt on the surface draws water out of any bacteria or mould cells that land on the food. Water always moves toward the saltier side across a cell membrane, so the microbe's own water is pulled out of it, drying it out and stopping it from growing.
Chemistry · L2 · The Chemistry of Food Preservation
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Chemistry · L2 · The Chemistry of Food PreservationFlashcards12 cards
What is an electrolyte?1 / 12
A substance that splits apart into charged particles called ions when it dissolves in water, letting the resulting solution carry an electric current.
Chemistry · L2 · Electrolytes and Sports Drinks
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Chemistry · L2 · Electrolytes and Sports DrinksFlashcards6 cards
Name this reaction — and say which species is the nucleophile.1 / 6
Nucleophilic substitution (Sₙ2). Hydroxide is the nucleophile; bromide is the leaving group.
Chemistry · L3 · Reactions at a glance
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Chemistry · L3 · Reactions at a glanceFlashcards9 cards
What are the three subatomic particles in an atom, and where is each one found?1 / 9
Protons (positive charge) and neutrons (no charge) are packed together in the nucleus, the tiny, dense centre of the atom. Electrons (negative charge) are found outside the nucleus, arranged in shells at various distances from it.
Chemistry · L3 · Atomic Structure & Electron Shells
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Chemistry · L3 · Atomic Structure & Electron ShellsFlashcards9 cards
How does atomic radius change as you move across a period (left to right), and why?1 / 9
Atomic radius decreases. Moving across a period adds protons to the nucleus one at a time, but the new electrons are added to the SAME outer shell. The extra positive charge pulls that whole electron cloud in tighter, so the atom shrinks.
Chemistry · L3 · Periodic Trends
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Chemistry · L3 · Periodic TrendsFlashcards9 cards
What happens to electrons when an IONIC bond forms?1 / 9
One atom (a metal) transfers one or more electrons to another atom (a non-metal). Both end up with full outer shells, but now as oppositely charged ions that attract each other electrostatically.
Chemistry · L3 · Ionic, Covalent & Metallic Bonding
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Chemistry · L3 · Ionic, Covalent & Metallic Bonding