UNIT 1, ALL LESSONS VOCAB / KEY CONCEPTS

Question 1

atom

Answer 1

basic building blocks matter; small particles consisting of neutrons, protons, and electrons along with a nucleus

Question 2

mass

Answer 2

amount of matter in a substance or an object

Question 3

law of definite proportions

Answer 3

a law that states that any chemical compound will always have the same proportions, (fixed ratio), or amount of each element by weight, no matter what the amount is, or source

Question 4

law of conservation of mass

Answer 4

mass is neither lost nor created during chemical reactions; mass is conserved

Question 5

chemical symbol

Answer 5

a letter or pair of letters used to represent a chemical element

Question 5

atomic theory

Answer 5

created by John Dalton, 1766-1844, states that all matter is made up of atoms
› matter consists of tiny particles called atoms
› in any sample of a pure element, all the atoms are identical in mass and other properties
› the atoms of different elements differ in mass and other properties
› when atoms of different elements combine to form compounds, new and more complex particles form. however, in a given compound the constituent atoms are always present in the same fixed numerical ratio
› atoms are indestructible. in chemical reactions, the atoms rearrange but they do not themselves break apart

Question 6

molecules

Answer 6

a group of two or more atoms that are held together by chemical bonds

Question 7

compound

Answer 7

a substance that is made up of two or more different chemical elements that are bonded together in a fixed ratio
› types of chemical compounds: ionic compounds (compounds made up of charged particles called ions), covalent compounds (compounds composed of atoms that share electrons), and organic compounds (covalent compounds containing carbon atoms bonded to hydrogen atoms)

Question 8

chemical substances

Answer 8

a type of matter with a fixed chemical composition and characteristic properties; can be elements (simplest form of a chemical and can be the building blocks of other chemicals), compounds (formed when elements combine in a fixed ratio), and mixtures (formed when two or more chemical substances are combined without reacting)

Question 9

ionic compound

Answer 9

a compound made up of ions that are held together by ionic bonding
› ionic bonding occurs when one atoms transfers electrons to another atom
› ions form when atoms gain or lose electrons, which is called electron transfer (process of atoms gaining or losing electrons- atom loses electron turns into a positively charged ion called a cation- atom gains an election, it becomes a negatively charged ion called an anion)

Question 10

chemical formula

Answer 10

a formula/representation of a compounds chemical composition, showing the types and number of atoms in a molecule or compound
› use symbols to represent the elements that make up a compound
› shows the ratio in which the atoms of the elements combine to form a molecule
›subscripts are used to indicate how many of a particular atom are in a compound
›three main types of chemical formulas: empirical (shows the simplest whole number ratio of atoms in a compound), molecular (shows the number of each type of atom in a molecule), and structural (shows how the atoms in a molecule are bonded to each other)

Question 11

diatomic molecules

Answer 11

a molecules made up of two atoms that are bonded together

Question 12

free element

Answer 12

a chemical element that is not chemically bonded to or combined with elements; can be found in nature in their pure form and can be monatomic or polyatomic

Question 13

polyatomic atoms

Answer 13

a group of three or more atoms that are held together by covalent bonds and are electrically neutral

Question 13

chemical bonds

Answer 13

the force of attraction between atoms or ions that holds them together to form molecules, crystals, and other structures

Question 14

structural formula

Answer 14

a diagram that consists of elemental symbols that represent the atoms in a molecule that are connected by one, two, or three lines that represent the chemical bonds

Question 14

atomic composition

Answer 14

structure of an atom & ratio; which is made up of three subatomic particles: protons (located in the nucleus, these particles have a positive charge), neutrons (located in the nucleus and have no charge and a similar mass to protons), and electrons (particles orbit the nucleus in electron shells and have a negative charge

Question 15

ball and stick model

Answer 15

three-dimensional representation of a chemical substance that shows the positions of atoms and the bonds between them

Question 16

space filling model

Answer 16

a 3D model of a molecule that shows the relative size and shape of the molecule

Question 17

mixture

Answer 17

combination of two or more pure substances that are physically blended together, where each substance retains its individual properties and are not chemically combined
› can either be homogeneous (uniform composition throughout, meaning all the components of the mixture are evenly distributed throughout, essentially appearing as a single consistent substance), or heterogenous (non-uniform composition, meaning the different components of the mixture are not evenly distributed throughout, and does not appear a single substance)

Question 18

homogeneous mixture

Answer 18

a mixture where the components are evenly distributed throughout › looks the same, and you cannot visually distinguish between the individual components that make up the mixture
› is a consistent mixture at the molecular level

Question 19

heterogeneous mixture

Answer 19

a mixture where the components are not evenly distributed
› does not look the same throughout
› can visually distinguish the different components that make up the mixture (separate phases or particles)
› is not blended smoothly