chemistry unit notes 7th grade science. basic vocabulary matter : anything that has mass and volume...
TRANSCRIPT
Basic Vocabulary
Matter: Anything that has mass and volume
Mass: Amount of matter in an object
Weight: Measure of the force of attraction between objects due to mass and gravity
Volume: Amount of space an object takes up
Density: Measurement of how much mass is contained in a given volume
More Vocabulary
Atoms: Smallest particle of an element that has all the properties of matter: Protons- particles in the nucleus with positive charge Electrons- particles orbiting around nucleus with negative
charge Neutrons- particles in the nucleus with no charge
Elements: Simplest form of a pure substance Compounds: Two or more elements chemically combined to
form a new substance
Sub-Atomic ParticlesSub-Atomic Particles
Part of Part of AtomAtom
ChargeCharge LocationLocation Mass/SizeMass/Size
ElectronElectron - negative- negative outside outside nucleusnucleus
.0006 amu.0006 amu(too little to (too little to count)count)
ProtonProton + positive+ positive inside inside nucleusnucleus
1 amu1 amu
NeutronNeutron no chargeno charge inside inside nucleusnucleus
1 amu1 amu
Using the Periodic Table Atomic NumberAtomic Number
– Equal to # protons = # electronsEqual to # protons = # electrons– Periodic Table is arranged by this Periodic Table is arranged by this
numbernumber
Symbol Symbol – ““ShorthandShorthand”” for the element – Note 2 for the element – Note 2ndnd
letter is always lowercaseletter is always lowercase
Atomic Mass NumberAtomic Mass Number – Total AVERAGE mass of Protons + Total AVERAGE mass of Protons +
Neutrons + ElectronsNeutrons + Electrons
17
Cl
35.5
More PracticeMore Practice
Determine the name, number of Determine the name, number of protons, neutrons and electrons for protons, neutrons and electrons for each element shown and draw…each element shown and draw…
1
H
1
8
O
16
6
C
12
IsotopesIsotopes
An isotope is a variation of an An isotope is a variation of an element (same protons) but can element (same protons) but can have diff. # of neutronshave diff. # of neutrons
Ex: carbon (atomic mass = Ex: carbon (atomic mass = 12.011)12.011)– Carbon (14) and carbon (12) exist in Carbon (14) and carbon (12) exist in
nature nature
Chemical vs. Physical Change
Physical Change: A change that can occur without changing the identity of the substance.
Ex. Solid, Liquid, Gas (Phase change)
Chemical Change: Process by which a substance becomes a new and different substance
Ex. Fire
Chemical ReactionsChemical Reactions
Chemical Reaction:Chemical Reaction: a process in a process in which the physical which the physical andand chemical chemical properties of the original substance properties of the original substance changechange as new substances with as new substances with different physical and chemical different physical and chemical properties are formedproperties are formed
Chemical Reaction BasicsChemical Reaction Basics
H2 + O2 --> H2O
Reactants- substance that enters into a reaction
Products- substance that is produced by a chemical reaction
Reactants Products
Evidence of Chemical Evidence of Chemical ChangeChange
EPOCH is an acronym that stands for evidence EPOCH is an acronym that stands for evidence that a chemical reaction has occurred.that a chemical reaction has occurred.
– – Effervescence (bubbles and/or gives off Effervescence (bubbles and/or gives off gas)gas)
– – Precipitate (solid crystals form)Precipitate (solid crystals form) – – Odor (change of smell is detected)Odor (change of smell is detected) – – Color changeColor change – – Heat (reaction either heats up or cools Heat (reaction either heats up or cools
down)down)
Does sighting evidence of a chemical reaction mean Does sighting evidence of a chemical reaction mean that a chemical reaction has undoubtedly taken place?that a chemical reaction has undoubtedly taken place?
EEP P OO
CCHH
Conservation of Mass
Atoms cannot be created or destroyed in a chemical reaction.
What goes in must come out.
So we must balance equations to conserve mass.