chem midterm study guide (vocab)

this is only the vocabulary

solid

fixed shape and volume, particles touching, not moving 

liquid

fixed volume, unfixed shape, particles touching and moving a little 

gas

no fixed volume or shape, particles far apart and moving a lot, not charged

plasma

no fixed volume or shape, particles far apart and moving a lot, charged

**physical property** 

anything you can see **without changing** the substance 

**physical property ex.**

transparency, boiling point, density, elasticity, malleability, brittleness, melting point

**chemical property** 

you can only see by **changing** the substance 

**chemical property ex.**

flammability, ability to rust, reactivity with vinegar

**physical change?** (is it reversible?)

when the identity of the substance **doesn’t change (reversible)** 

**physical change ex.**

shattering, melting, separating (sand from gravel), dissolving, mixing, evaporating

**Chemical change** 

when the identity of the substance **changes (irreversible),** during a chemical reaction 

**Chemical change ex.**

rusting, bleaching, cooking, burning, exploding

**extensive property** 

**depends on how much matter** there is 

**extensive property ex.**

mass, weight, volume

**intensive property** 

**doesn’t matter how much matter** there is 

**intensive property ex.**

color, combustibility, density, melting point, malleability

5 signs of a chemical reaction

* formation of a gas 
* color change/ emission of light 
* odor change 
* temp change 
* formation of a precipitate

**parts of a chemical reaction** 

reactant, yield arrow, product

**Law of conservation of mass**

in a closed system, mass cannot be created or destroyed 

the 2 classifications of matter

__pure substances__ and __mixtures__

pure substance

only one type of molecule, ex. water or carbon

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compound

a __molecule__ made of different atoms, ex H20 (water)

* can be broken down into molecules using chemical charges
* compounds can be molecular, ionic, or intermetallic

element (define, examples)

an __atom__ with specific characteristics, **ex**. hydrogen, iron, copper

* can be metals or nonmetals, can’t be broken down further

mixture

a combo of 2 substances, not chemically bonded

* can be __solutions__ or __heterogeneous__ mixtures
* CAN be separated physically

solution (aka homogenous) (how are the molecules distributed? example?)

group of molecules that are **evenly** distributed, **ex**. gasoline, air, soda

heterogeneous mixture

a solution (group of molecules) that is **unevenly** distributed, **ex.** salad dressing

accuracy

“the extent to which a measurement approaches the true value of a quantity “

* **how correct is it?**

precision

“the extent to which a series of measurements of the same quantity made in the same way agree with each other, not necessarily accurate.”

* **how close together** are your answers? (they don’t have to be right)

**percent error formula**

\[(experimental - accepted) / accepted\] \* 100  

mass

* the **amount of matter** an object contains. Doesn’t change unless you add/remove matter 
* find with a balance, use **grams** 

volume (define, what units?)

* the **amount of space** an object occupies  
* find with liquid or a ruler, use **mL for liquids** or **cm³ for solids** or **L for gases** 

density (define)

* The **compactness** of the molecules or particles of a substance 
* more compact molecules = greater density 

density formula

**mass**/ volume

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remember:

* mL – volume
* g – mass
* **g/mL** or**g/cm³** or**g/L**- density

billiards ball atomic model

small, hard sphere

created by dalton in 1808

plum pudding atomic model (what? when? who?)

negative electrons in a positive atom

created by thompson in the 1890s

nuclear model (what? who?)

nucleus with electron shell

created by rutherford around 1911

modern atomic model (who? what?)

discovered neutrons, current model used today

created by chadwick around 1932

atom

the smallest particle of an element that still has the chemical properties of the element

nucleus

* very small thing in the center of the atom 
* made of at least one proton (p+) and usually at least 1 neutron (n\*) 
* surrounding the nucleus is a cloud of electrons (e-) 

protons (p+) (define)

located in nucleus, positive charge, big and heavy 

neutrons (n\*)

located in nucleus, no charge, big and heavy 

electrons (e-)

outside the nucleus, negative charge, tiny and light 

isotopes

2 atoms with different # of neutrons  

* have the same atomic #, different mass #s 

\
* protons never change
* neutrons can change

ions

* **an atom with a charge**, # of electrons change
* if atom loses electrons, atom is + and (vice versa)
* protons, neutrons, atomic # and atomic mass stay the same

1st periodic table

created by Dmitri Mendeleev, 1869

Elements arranged: 

* Groups had similar properties 
* Increasing atomic mass 
* Spaces left for undiscovered elements 

current periodic table

created by Henry Mosely, 1913

Elements arranged: 

* By atomic #, not mass 
* You already know what it looks like

periodic law

*“When elements are arranged by increasing atomic #, there is a periodic repetition of physical and chemical properties.”*

* Or in simple words: **when you put elements in order by atomic #, you can see some patterns.** 

what’s the only metal that’s liquid at room temp

mercury

the most reactive element groups

alkaline metals, then alkaline earth metals cause they only have 1 valance electron

what are the most reactive nonmetals

halogens

what do noble gases (except helium) bond with

nothing

metals (where? describe)

left side of stairsteps

* In the A block 
* conduct heat, electricity 
* high luster, solid at room temperature (not mercury) 
* ductile, can be made into wire 
* malleable, can be made into a sheet

nonmetals (where? describe, example)

right side of stairsteps

* In the A block
* Most are gases at room temperature (not bromine, it’s a liquid)
* Poor conductors, brittle, dull
* ex. chlorine and oxygen

metalloids

along stairsteps

* In the A block 
* Properties of metals and nonmetals 
* Conductors and insulators 
* Ex. Semiconductors are Selenium, Germanium, arsenide

catalyst

the thing on top of the yield arrow, speeds up a chemical reaction

dalton

(what model? what discoveries?)

discovered the atom, did billliards ball model

thompson

discovered electrons, did cathode ray tube and plum pudding

rutherford

what experiment? what discoveries?

nucleus, protons on nucleus, discovered that the atom is mostly empty space…………

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nuclear model (nucleus with electron shell)…………

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gold foil experiment

bohr (discoveries? models?)

atomic energy levels, atomic model, planetary model.

electrons shell is made of orbits/shells

heisenberg and schroedinger (created, discovered?)

electron cloud and orbitals, heisenberg uncertainty principle, quantum model

hyphen notation

* (element name) dash (mass number) 
* ex. uranium-235 

isotope notation (nuclear symbol)

* top - mass #                      bottom - atomic # 
* ex. U²³⁵₉₂ (pretend like that’s lined up) 

atomic number =

\# protons (# electrons if neutral)

mass number =

protons + neutrons

atomic mass =

the decimal in the element box

neutrons =

mass # - atomic #

reactivity

**⇙ How easily an element reacts** with other elements **⇙**

ion

an electron with a charge

shielding effect

when the inner shells shield the outer shells from the nucleus’s pull

metallic character

**⇙** how metallic it is **⇙**

atomic radius

**⇙** how big the atom is **⇙**

ionization energy

**⇗** amount of energy required to remove an electron from the valance shell **⇗**

electronegativity

**⇗** how attractive an atom is **⇗ smaller atoms have higher attractivity**

cation

positive, lost electrons, smaller than neutral, metal

anion

negative, gained electrons, larger than neutral

* ex. iodide, chloride, hydroxide

octet rule

usually there’s 8 electrons in a valance shell

ionic compounds

metal, nonmetal

when an electron is taken from another atom

molecular (covalent) compounds

(what are they made of, what process?)

nonmetal, nonmetal

when electrons are shared between atoms