Chemistry
Ages 6–8 · Grades 1–2
- Solid, Liquid, GasMatter comes in solids, liquids and gases.
- What Happens When You Mix ThingsSome things dissolve and some do not.
- Some Changes Cannot Be UndoneSome changes, like melting, can be undone by cooling.
- The Right Stuff for the JobEvery material has properties: hard or soft, see-through or not, bendy or stiff.
- Heavier or Lighter?Big things are not always heavy, and small things are not always light.
- Which Holds More?Pouring water into a different shape does not change how much water there is.
- Built From Small PiecesMany big things are made of small pieces joined together.
- Where Do Puddles Go?Water can turn into an invisible gas and go into the air. This is evaporation.
- Slow Changes: Rust and Brown ApplesSome changes happen slowly and on their own, like rusting and apples browning.
- The Bubbles in BreadYeast is made of tiny living things that turn sugar into a gas.
Ages 8–11 · Grades 3–5
- What Makes a Reaction Speed Up?Reactions happen at very different speeds.
- How Much Will Dissolve?Dissolving spreads a substance through a liquid; it does not destroy it.
- Acids, Bases and Cabbage WaterAcids and bases are two opposite families of substance.
- How You Know Something ReactedA chemical reaction makes a new substance.
- Does It Weigh Less When It Disappears?Mass is how much matter there is; volume is how much space it takes up.
- Is Air Really Something?Air is matter: it takes up space and it has mass.
- The Mystery Powder TestEvery material has properties that can be observed and measured.
- Getting a Mixture ApartIn a mixture, each part keeps its own properties.
- Every Substance Melts at Its Own TemperatureTemperature is measured with a thermometer, in degrees Celsius.
- Just Enough VinegarThe amount of product depends on the amounts of the starting materials.
Ages 11–14 · Grades 6–8
- What Everything Is Made OfAll matter is made of atoms.
- Where Does the Mass Go?Mass is conserved in a chemical reaction.
- Why Some Metals React and Some Do NotMetals differ enormously in how readily they react.
- Telling One Gas From AnotherGases are different substances even when they all look like nothing.
- Heavy for Its Size: DensityDensity is mass divided by volume, and it belongs to the material, not the object.
- How Strong Is a Solution?A solution is a solute dissolved in a solvent, the same all the way through.
- Pure Substances and MixturesElements contain one kind of atom; compounds contain elements joined in a fixed ratio.
- Heating ParticlesTemperature measures how fast a substance’s particles move on average.
- Reactions That Get Hot or ColdExothermic reactions release energy and warm their surroundings; endothermic reactions take energy in and cool them.
- Plastic From Milk: What Polymers AreA polymer is a very long molecule made of many small repeating units called monomers.
Ages 14–18 · Grades 9–12
- Counting Atoms: The MoleA balanced equation gives fixed ratios between substances.
- Reactions That Go Both WaysSome reactions are reversible and reach equilibrium.
- Where the Electrons Go: Oxidation and ReductionOxidation is the loss of electrons and reduction is the gain; the two always happen together.
- Why Water Is StrangeWater is polar, and hydrogen bonds between its molecules are far stronger than the attractions between molecules of similar size.
- Why the Periodic Table Has Its ShapeElements are ordered by atomic number, and each new period starts a new electron shell.
- Salt, Sugar and Copper: Three Kinds of BondIonic bonds form when electrons transfer from metal to non-metal atoms, making oppositely charged ions.
- Collision Theory: What Sets the Speed of a ReactionParticles react only when they collide with at least the activation energy, in a suitable orientation.
- The pH Scale: Counting in Powers of TenAcids release hydrogen ions in water, and pH measures their concentration on a logarithmic scale.
- Where the Energy in a Reaction Comes FromBreaking bonds takes in energy; making bonds gives energy out.
- When the Nucleus Itself ChangesUnstable nuclei decay by alpha, beta or gamma emission, and may become a different element.