Unit 1 · Segment 1: Organisms and Nonliving Things Are Made of Atoms · printed p. 6 (PDF p. 42)
The Composition of Matter
To create stage makeup, chemists must account for the properties of the substances they will use.
Anchoring phenomenon
Chapters
- 01 Atoms and Elements
What are the smallest pieces of matter, how do we know they exist, and how do scientists keep track of the different kinds?
1 presentation10 worksheets3 labs - 02 Molecules and Extended Structures
How can fewer than a hundred kinds of atoms build millions of different substances, and how do scientists model the ways atoms join?
1 presentation10 worksheets3 labs - 03 Substances and Their Properties
How can you tell one substance from another when they look the same, and which measurements can be trusted to do it?
1 presentation10 worksheets3 labs
Standards in this unit
Unit vocabulary
matterAnything that has mass and takes up space. Solids, liquids and gases are matter; light and sound are not.Chapter 1
atomA single particle of an element, the smallest piece of a substance that still counts as that element.Chapter 1
elementA substance made of only one kind of atom. Carbon, iron and neon are elements; water and air are not.Chapter 1
atomic scaleThe range of sizes where atoms live, roughly a hundred to a few hundred picometers across, far below what any eye or light microscope can show.Chapter 1
picometer (pm)A unit of length equal to one trillionth of a meter, written 10⁻¹² m. Most atoms are about 100 to 300 pm wide.Chapter 1
criteriaThe requirements a design must satisfy for the solution to count as a success.Chapter 1
constraintA limit on what solutions are possible, such as time, money, available technology or the physical conditions of the work.Chapter 1
scanning tunneling microscope (STM)An instrument that maps a surface atom by atom by moving an extremely sharp probe just above it and tracking a tiny electric current that grows when the probe is closer to the surface.Chapter 1
atomic massThe mass of an atom, measured in daltons. The value printed on the periodic table is an average for the element's atoms, which can differ slightly from one another.Chapter 1
periodic table of the elementsA chart of every known element arranged in rows and columns so that elements with similar properties line up in the same column.Chapter 1
groupA column of the periodic table. Elements in a group tend to share properties and react in similar ways.Chapter 1
chemical symbolA one- or two-letter shorthand for an element's name, used by scientists in every language. Some come from older names, such as Pb for lead from the Latin plumbum.Chapter 1
chemical bondA strong connection that holds two atoms together inside a particle. Bonds are what turn separate atoms into a molecule or an extended structure.Chapter 2
moleculeA particle built from a definite number of atoms (at least two) joined to one another by chemical bonds, so every particle of a substance has the same count of each kind of atom. The atoms can all be one element (O₂) or several elements (H₂O).Chapter 2
chemical formulaShorthand that lists a substance's elements by symbol. For a molecule the small numbers count the atoms in one molecule (no number means one); for an extended structure the numbers give the ratio of the elements instead.Chapter 2
modelA simplified stand-in for something too small, too large or too complex to see directly, built to make the important features easy to notice and reason about.Chapter 2
ball-and-stick modelA model of a molecule or extended structure in which spheres stand for atoms, sticks stand for bonds, and a color key tells which element each sphere represents.Chapter 2
atomic compositionWhich elements a substance contains and how many atoms of each (for a molecule) or in what ratio (for an extended structure).Chapter 2
chemical structureThe way the atoms in a substance are connected and arranged in space.Chapter 2
extended structureA structure built by repeating the same small subunit over and over, so it has no fixed size but keeps a constant ratio of its elements. Crystals and polymers are extended structures.Chapter 2
repeating subunitThe small group of atoms or molecules that is copied again and again to build an extended structure.Chapter 2
crystalA solid whose atoms or molecules sit in a regular pattern that repeats in all three directions. Diamond, quartz, salt, ice and table sugar are all crystals.Chapter 2
polymerAn extended structure made of many small repeating units linked into a long chain. Polyethylene bags, PET bottles and PVC pipes are polymers.Chapter 2
ratioA comparison of two amounts, written with a colon. In quartz the silicon-to-oxygen ratio is 1:2, so any quartz crystal has twice as many oxygen atoms as silicon atoms.Chapter 2
substanceA kind of matter with one fixed makeup throughout, such as water, oxygen gas or pure copper. Every pure sample of a substance shares the same identifying properties.Chapter 3
macroscopicAt the everyday scale of things you can see, hold or measure directly, which means trillions upon trillions of atoms or molecules acting together.Chapter 3
propertyA trait of matter that can be observed or measured, such as color, mass, density or melting point.Chapter 3
massHow much matter an object or sample contains, measured in kilograms or, for small samples, in grams. Mass depends on how big the sample is.Chapter 3
volumeHow much space an object or sample takes up, often measured in cubic centimeters (cm³) or milliliters (mL); 1 mL equals 1 cm³.Chapter 3
densityHow much mass is packed into each unit of volume: density = mass ÷ volume, usually in g/cm³. Every pure sample of a substance has the same density at the same temperature.Chapter 3
melting pointThe temperature at which a solid turns into a liquid. A large sample takes longer to melt than a small one, but both melt at the same temperature.Chapter 3
boiling pointThe temperature at which a liquid boils into a gas. Tables list it at normal sea-level air pressure, because lower air pressure lowers the boiling point.Chapter 3
solubilityThe amount of a substance that can spread out, particle by particle, into a particular liquid until the mixture looks like one clear liquid. Solubility always names a pair: the substance that dissolves and the liquid it dissolves in.Chapter 3
flammabilityWhether, and how easily, a substance burns. Burning turns the substance into new substances, so flammability is a chemical property and the test uses up the sample.Chapter 3
mixtureTwo or more substances mingled together without becoming one new substance. Each part keeps its own properties and can, in principle, be separated out again.Chapter 3
alloyA mixture of a metal with other metals or elements, made to give useful properties such as hardness. Steel, brass and the gold used in coins are alloys.Chapter 3