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Chemistry: explore STEM content (page 38 of 47) · openstem

All fields Software Mathematics Physics Chemistry Biology Engineering Astronomy Environmental Other Chemistry Chemistry groups

Explore STEM Content

Search the community's STEM library — free to study, yours to make your own.

Chemistry

Reactions, bonding and organic chemistry on openstem — flashcards, notes, quizzes and molecule structures shared by the community. Study free, or clone into your library.

Content Groups1

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Flashcards10 cards

What three structural criteria must a ring system meet to be aromatic?1 / 10

It must be cyclic, planar, and have a continuous (fully conjugated) ring of p orbitals overlapping all the way around — with the right number of π electrons to satisfy Hückel's rule. Miss any one of these (a non-planar ring, a broken conjugation path, or the wrong electron count) and the ring is not aromatic.

Chemistry

Chemistry · L4 · Aromatic Chemistry & EAS

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Chemistry · L4 · Aromatic Chemistry & EAS

Flowchart10 objects

Chemistry

Chemistry · L2 · Curing Homemade Soap

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Chemistry · L2 · Curing Homemade Soap

Flashcards10 cards

State the third law of thermodynamics. Why does it single out a perfect crystal?1 / 10

The entropy of a perfectly ordered, pure crystalline substance approaches zero as the temperature approaches absolute zero:

Chemistry

Chemistry · L5 · The Third Law and Absolute Entropy

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Chemistry · L5 · The Third Law and Absolute Entropy

Note~775 words · 4 min

What Is Electronegativity? Electronegativity is a measure of how strongly an atom pulls the pair of electrons it shares in a covalent bond toward itself. Every bonded atom has some pull on the shared pair — electronegativity just says how s

Chemistry

Chemistry · L3 · Electronegativity and Bond Polarity

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Chemistry · L3 · Electronegativity and Bond Polarity

Flashcards12 cards

Define chemiluminescence, and contrast it with photoluminescence.1 / 12

Chemiluminescence is the emission of light produced when a chemical reaction releases enough energy in a single step to directly populate an electronically excited state of one of its products — no photon is ever absorbed beforehand. Photoluminescence (fluorescence/phosphorescence) instead starts by absorbing a photon to create the excited state. Both end the same way: an excited-state molecule relaxing to its ground state by emitting a photon. The difference is entirely in how the excited state is FIRST created.

Chemistry

Chemistry · L5 · Chemiluminescence

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Chemistry · L5 · Chemiluminescence

Flashcards8 cards

What is femtochemistry, and why is the femtosecond timescale significant for chemical bonds?1 / 8

Femtochemistry is the study of chemical reaction dynamics on the femtosecond timescale (1 fs = 10⁻¹⁵ s), pioneered by Ahmed Zewail (1999 Nobel Prize in Chemistry). This timescale matters because it is comparable to the period of a single molecular vibration (roughly 10–100 fs for typical bond stretches), meaning femtosecond pulses are the only tool fast enough to directly capture the actual motion of atoms as a bond breaks or forms, rather than only the reactant and product states before and after.

Chemistry

Chemistry · L5 · Ultrafast Femtochemistry

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Chemistry · L5 · Ultrafast Femtochemistry

Flowchart7 objects

Chemistry

Chemistry · L4 · Lanthanide Contraction — Zr vs Hf Radii

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Chemistry · L4 · Lanthanide Contraction — Zr vs Hf Radii

MoleculeO=[N+]([O-])c1ccccc1

Chemistry

Chemistry · L4 · Nitrobenzene

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Chemistry · L4 · Nitrobenzene

Note~1163 words · 6 min

Taming the randomness of chain growth Earlier polymer chemistry topics classified finished polymers by cross-link density and asked how chain structure sets bulk properties like Tg and crystallinity. This note steps back one stage further,

Chemistry

Chemistry · L5 · Controlled and Living Polymerization

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Chemistry · L5 · Controlled and Living Polymerization

Flowchart6 objects

Chemistry

Chemistry · L1 · Ship vs. Pebble

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Chemistry · L1 · Ship vs. Pebble

Collection4 items

01Chemistry · L1 · Fizzy Drinks and Dissolved Gas

02Chemistry · L1 · Fizzy Drinks and Dissolved Gas

03Chemistry · L1 · Fizzy or Flat?

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Chemistry

Chemistry · L1 · Fizzy Drinks and Dissolved Gas

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Chemistry · L1 · Fizzy Drinks and Dissolved Gas

Flowchart5 objects

Chemistry

Chemistry · L3 · Hydrogenation of Vegetable Oil to Margarine

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Chemistry · L3 · Hydrogenation of Vegetable Oil to Margarine

Note~636 words · 3 min

What a buffer does A buffer solution resists changes in pH when small amounts of acid or base are added to it. Add a splash of acid to plain water and the pH crashes; add that same splash to a buffer and the pH barely moves. Buffers do not

Chemistry

Chemistry · L3 · Buffers — Resisting pH Change

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Chemistry · L3 · Buffers — Resisting pH Change

Flowchart7 objects

Chemistry

Chemistry · L1 · Cabbage Juice Colour Clues

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Chemistry · L1 · Cabbage Juice Colour Clues

Plot1 plot · 2 params

Chemistry

Chemistry · L3 · Concentration vs Time (Reactant Decay)

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Chemistry · L3 · Concentration vs Time (Reactant Decay)

Collection4 items

01Chemistry · L5 · Controlled and Living Polymerization

02Chemistry · L5 · Controlled and Living Polymerization

03Chemistry · L5 · Block Copolymer Synthesis via Living Chain Ends

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Chemistry

Chemistry · L5 · Controlled and Living Polymerization

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Chemistry · L5 · Controlled and Living Polymerization

Flashcards8 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

Chemistry · L3 · Gas Laws

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Chemistry · L3 · Gas Laws

Flashcards6 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

Chemistry · L3 · Addition vs Condensation Polymerization

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Chemistry · L3 · Addition vs Condensation Polymerization

Note~550 words · 3 min

What Is Gas Pressure, Really? A gas is made of an enormous number of tiny particles, spread far apart and moving around constantly in every direction. They are far too small and far too fast to see individually, but together they do somethi

Chemistry

Chemistry · L2 · Gas Pressure — the Particle Picture

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Chemistry · L2 · Gas Pressure — the Particle Picture

Collection5 items

01Chemistry · L5 · Electrocatalysis & Fuel Cells

02Chemistry · L5 · Electrocatalysis and Fuel Cells

03Chemistry · L5 · Fuel Cell Polarization Curve Loss Regimes

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Chemistry

Chemistry · L5 · Electrocatalysis & Fuel Cells

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Chemistry · L5 · Electrocatalysis & Fuel Cells

Note~303 words · 2 min

Two Secret Inks You can write a message that is completely invisible — until you use a trick to make it appear! Here are two fun ways to do it. Lemon Juice Ink Dip a cotton swab or a toothpick into lemon juice and write your message on pape

Chemistry

Chemistry · L1 · Secret Messages with Invisible Ink

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Chemistry · L1 · Secret Messages with Invisible Ink

Quiz5 questions

How much heat is required to raise 200.0 g of water from 20.0 °C to 45.0 °C? (c_water = 4.18 J/(g·°C))

A20 900 JB16 720 JC8360 JD37 620 J

Chemistry

Chemistry · L4 · Calorimetry Calculations — 5 Q

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Chemistry · L4 · Calorimetry Calculations — 5 Q

MoleculeCCC(=O)C

Chemistry

Chemistry · L4 · 2-Butanone (methyl ethyl ketone)

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Chemistry · L4 · 2-Butanone (methyl ethyl ketone)

Note~1027 words · 5 min

Crystal defects and semiconductors The unit-cell picture of a crystal — atoms sitting on perfectly regular lattice sites, with no gaps or extras — is an idealization. Real crystals almost always contain a small population of point defects:

Chemistry

Chemistry · L5 · Crystal Defects and Semiconductors

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Chemistry · L5 · Crystal Defects and Semiconductors

Collection4 items

01Chemistry · L1 · Growing Crystals at Home

02Chemistry · L1 · Growing Crystals at Home

03Chemistry · L1 · How a Crystal Grows

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Chemistry

Chemistry · L1 · Growing Crystals at Home

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Chemistry · L1 · Growing Crystals at Home

Flashcards12 cards

Enzyme catalysis follows the mechanism E + S ⇌ ES → E + P. Which approximation from the generic two-step mechanism (A ⇌ I → P) applies directly here, and to which species?1 / 12

The steady-state approximation, applied to the enzyme-substrate complex ES — exactly as you set d[I]/dt ≈ 0 for a generic intermediate I, here you set d[ES]/dt ≈ 0.

Chemistry