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@openstem · Joined Jul 2026
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Flashcards10 cards
How does lemon juice taste?1 / 10
Sour.
Chemistry · L1 · Sour or Soapy? Acids and Bases in the Kitchen
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Chemistry · L1 · Sour or Soapy? Acids and Bases in the KitchenFlashcards10 cards
What three things does a candle's flame need to keep burning?1 / 10
Fuel (the wax), oxygen from the air, and enough heat.
Chemistry · L1 · Why a Candle Burns
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Chemistry · L1 · Why a Candle BurnsFlashcards10 cards
What happens when you stir sugar into warm tea?1 / 10
The sugar dissolves — it spreads out into tiny pieces you can no longer see.
Chemistry · L1 · Dissolving vs. Melting
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Chemistry · L1 · Dissolving vs. MeltingFlashcards10 cards
What happens to a puddle on the sidewalk after a sunny afternoon?1 / 10
It slowly disappears — the water evaporates into the air.
Chemistry · L1 · Evaporation and Condensation
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Chemistry · L1 · Evaporation and CondensationFlashcards10 cards
Why do people sprinkle salt on icy sidewalks in winter?1 / 10
Because salt makes ice melt faster, and helps keep the sidewalk from refreezing as easily.
Chemistry · L1 · Why Salt Melts Sidewalk Ice Faster
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Chemistry · L1 · Why Salt Melts Sidewalk Ice FasterFlashcards10 cards
What happens when you add a splash of vinegar to milk?1 / 10
The milk curdles — it turns lumpy, with soft white clumps floating in watery liquid.
Chemistry · L1 · Milk and Vinegar Curdling
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Chemistry · L1 · Milk and Vinegar CurdlingFlashcards10 cards
What is a mixture?1 / 10
Two or more things stirred together, without becoming a new substance.
Chemistry · L1 · Mixtures vs. Solutions
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Chemistry · L1 · Mixtures vs. SolutionsFlashcards10 cards
Do oil and water mix together?1 / 10
No. Oil and water do not mix, no matter how long you stir them.
Chemistry · L1 · Oil and Water Don't Mix
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Chemistry · L1 · Oil and Water Don't MixFlashcards10 cards
Is a black marker really made of just one plain color?1 / 10
No — a black marker is often a mix of several hidden colors that only look black together.
Chemistry · L1 · Hidden Colors in a Black Marker
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Chemistry · L1 · Hidden Colors in a Black MarkerFlashcards10 cards
What are the three main states of matter?1 / 10
Solid, liquid, and gas.
Chemistry · L1 · Solid, Liquid, or Gas?
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Chemistry · L1 · Solid, Liquid, or Gas?Flashcards5 cards
What is an atom?1 / 5
An atom is the smallest particle of an element. It is far too small to see, but everything around you is made of atoms.
Chemistry · L2 · Atoms and Molecules
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Chemistry · L2 · Atoms and MoleculesFlashcards5 cards
What is a physical change?1 / 5
A physical change alters the shape or state of a substance, but no new substance is formed. Tearing paper and melting ice are physical changes.
Chemistry · L2 · Physical vs Chemical Change
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Chemistry · L2 · Physical vs Chemical ChangeFlashcards9 cards
How are elements arranged in the periodic table?1 / 9
By atomic number — the number of protons in each atom. Element 1 (hydrogen) comes first, element 2 (helium) comes next, and so on.
Chemistry · L2 · Periodic Table Basics
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Chemistry · L2 · Periodic Table BasicsFlashcards7 cards
What is the pH scale?1 / 7
A number line from 0 to 14 that measures how acidic or basic (alkaline) a substance is.
Chemistry · L2 · The pH Scale
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Chemistry · L2 · The pH ScaleFlashcards10 cards
Roughly where does lemon juice sit on the pH scale?1 / 10
Around pH 2 — strongly acidic.
Chemistry · L2 · pH in Everyday Life
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Chemistry · L2 · pH in Everyday LifeFlashcards8 cards
What is a reactant?1 / 8
A reactant is a substance you start with in a chemical reaction. Reactants get used up as the reaction happens.
Chemistry · L2 · Chemical Reactions & Word Equations
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Chemistry · L2 · Chemical Reactions & Word EquationsFlashcards7 cards
What is the law of conservation of mass?1 / 7
In a chemical reaction, no atoms are created or destroyed — they are only rearranged into new substances. So the total mass of the products equals the total mass of the reactants.
Chemistry · L2 · Conservation of Mass
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Chemistry · L2 · Conservation of MassFlashcards8 cards
What is filtration used for?1 / 8
Filtration separates an insoluble solid from a liquid. You pour the mixture through filter paper sitting in a funnel — the solid is trapped on the paper, and the liquid runs through. Example: separating sand from water.
Chemistry · L2 · Separating Mixtures
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Chemistry · L2 · Separating MixturesFlashcards7 cards
What is a mixture?1 / 7
A mixture is two or more substances combined together but not chemically joined. Each substance keeps its own properties, and the mixture can usually be separated back into its parts.
Chemistry · L2 · Mixtures and Solutions
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Chemistry · L2 · Mixtures and SolutionsFlashcards8 cards
What is the reactivity series?1 / 8
The reactivity series is a list of metals ordered from most reactive to least reactive. It helps predict how strongly a metal will react with things like water, acid, or oxygen.
Chemistry · L2 · The Reactivity Series
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Chemistry · L2 · The Reactivity SeriesFlashcards9 cards
How can you tell how reactive a metal is just by watching it react with acid?1 / 9
Watch how fast bubbles form. Fast, vigorous fizzing means a more reactive metal. Slow, weak fizzing (or none at all) means a less reactive metal.
Chemistry · L2 · Evidence, Rust, and Uses
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Chemistry · L2 · Evidence, Rust, and UsesFlashcards8 cards
What is a chemical symbol?1 / 8
A chemical symbol is a short code, one or two letters, that stands for one element. O stands for oxygen, Fe stands for iron.
Chemistry · L2 · Chemical Symbols
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Chemistry · L2 · Chemical SymbolsFlashcards7 cards
What does a chemical formula show you?1 / 7
Which elements a substance is made of, and exactly how many atoms of each element are joined together in one unit of it.
Chemistry · L2 · Reading Chemical Formulae
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Chemistry · L2 · Reading Chemical FormulaeFlashcards7 cards
What is a solute?1 / 7
A solute is the substance that gets dissolved. Sugar stirred into tea is the solute.
Chemistry · L2 · Solute, Solvent, and Solution
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Chemistry · L2 · Solute, Solvent, and SolutionFlashcards7 cards
What is a saturated solution?1 / 7
A saturated solution is one that cannot dissolve any more solute at that temperature. If you add more, it just sinks to the bottom instead of dissolving.
Chemistry · L2 · Saturation, Temperature, and Concentration
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Chemistry · L2 · Saturation, Temperature, and ConcentrationFlashcards8 cards
What three things make up the fire triangle?1 / 8
Fuel, oxygen, and heat. A fire needs all three at the same time — take away any one and the fire goes out.
Chemistry · L2 · The Fire Triangle
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Chemistry · L2 · The Fire TriangleFlashcards6 cards
What two substances form when a fuel burns completely in plenty of oxygen?1 / 6
Carbon dioxide and water. Both are released as gases (water leaves as water vapour).
Chemistry · L2 · Burning Fuels — Products and Extinguishers
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Chemistry · L2 · Burning Fuels — Products and ExtinguishersFlashcards10 cards
What is density?1 / 10
Density tells you how tightly packed the matter in an object is — how much mass is squeezed into each unit of volume. A dense object has a lot of mass in a small space.
Chemistry · L2 · Density
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Chemistry · L2 · DensityFlashcards7 cards
What is a crystal?1 / 7
A crystal is a solid whose particles (atoms, ions, or molecules) are arranged in a regular, repeating pattern. That orderly pattern is what gives crystals their flat faces and straight edges.
Chemistry · L2 · Crystals — The Basics
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Chemistry · L2 · Crystals — The BasicsFlashcards6 cards
What is the first step in growing sugar or salt crystals at home?1 / 6
Dissolve as much sugar or salt as possible into hot water, stirring until no more will dissolve. This makes a saturated solution — one packed with as much dissolved solid as it can hold.
Chemistry · L2 · Growing Crystals
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Chemistry · L2 · Growing Crystals