Significant Figures

• all non-zero digits

• any zeros that are contained between non-zero digits

• leading zeros don’t count

• trailing zeros may not count if there is no decimal point

Scientific Notation

• shorter way to write a long number

  Steps:

• put the decimal after the first significant figure

• indicate how many places the decimal moved by the power of 10

  • positive = decimal moved to the left

  • negative = decimal moved to the right

The Basics of Matter

Vocab

matter - anything that has mass + takes up space

atom - smallest particle of an element

Element - a substance composed of atoms having an identical number of protons in each nucleus. Elements cannot be reduced to simpler substances by normal chemical means.

Compound - a pure, homogeneous substance consisting of atoms or ions of two or more different elements in definite proportions that cannot be separated by physical means. A compound usually has properties unlike those of its constituent elements.

Mixture - a composition of two or more substances that are not chemically combined with each other and are capable being separated.

Pure substance - a sample of matter, either an element or a compound, that consists of only one component with definite physical and chemical properties and a definite composition.

Chemical change - a process where bonds are broken and new bonds are formed between different atoms.

Physical change - a usually reversible change in the physical properties of a substance, as size or shape.

Gas – a substance having no definite shape and no definite volume. The molecules are spread out and free to move.

Liquid – a substance having a definite volume, but no definite shape. The inter-molecular forces hold these atoms or molecules loosely together but do not force them into a rigid structure allowing liquids the ability to flow.

Solid - a substance having a definite shape and definite volume. The atoms or molecules are held in rigid structure. Although they are free to vibrate, they cannot move around

Plasma - gases that have been so energized that their atoms have been stripped of some or all electrons

Pressure - the force exerted on a surface per unit area

Volume - the amount of space that a substance or object occupies

• Mixtures

  • a mix of elements and compounds NOT chemically bonded

  • can be Heterogeneous or Homogeneous

    • heterogeneous is when the arrangement of particles in not uniform

    • homogeneous is when the arrangement of particles is uniform

• Pure Substances

  • can be elements

    • singular atoms

  • can be compounds

    • chemically bonded elements

• Volume

  • cube/rectangular prism: l x w x h

  • use the Water Displacement method for irregularly shaped objects

• Density

  • mass/volume

Phase Changes + Heat

• Phase Changes

  • Melting - solid to liquid

  • Freezing - liquid to solid

  • Vaporization - liquid to gas

  • Condensation - gas to liquid

  • Sublimation - solid to gas

  • Deposition - gas to solid

• kinetic energy: the energy of an object because of motion

• temperature measures the average kinetic energy of the particles of on object or substance

  • measured in degrees Celsius or Kelvins

• heat is the flow of energy from warmer places to cooler places due to a difference in temperature

• thermal equilibrium is when heat flows from a higher temperature object to a lower temperature object, until they are the same temperature

• heat can transfer in 3 different ways

  • Conduction: the transfer of heat energy between materials that are in direct contact with each other.

    • ex: the handle of a metal spoon that has been placed in a bowl of hot soup. The hot soup transfers heat to the end of the spoon; the heat is then transferred through the spoon to the handle.

  • Convection: the transfer of heat energy by the mass movement of fluids containing heated particles

    • convection currents

    • when particles of a fluid are heated, the particles move farther apart, causing the fluid to expand

    • ex: home heating systems force heated air into rooms by way of convection currents; these currents heat the colder air in the room.

  • Radiation: the transfer of heat energy through electromagnetic waves.

    • electromagnetic waves originate from accelerated charged particles

    • electromagnetic waves travel through matter or through empty space

    • heat transfer through empty space is unique to radiation.

    • ex: since the space between the Sun and Earth is essentially a vacuum, the heat energy from the Sun is transferred to Earth only by radiation.

  • endothermic: energy going into the system

  • exothermic: energy going out of the system

  • specific heat is the energy needed to raise substance temperature

  • varies for each substance

  • measured in joules per gram per degree Celsius (J/g°C) or calories per gram per degree Celsius (cal/g°C)

  • The equation Q = mcΔT can be used to calculate heat gained or lost, where Q is heat energy, m is mass, c is specific heat, and ΔT is temperature change.

Boyle’s Law

the volume of a given mass of gas varies inversely with the pressure when the temperature is kept constant

We use P₁ and V₁ to stand for the initial pressure and initial volume of a gas. After a change has been made, P₂ and V₂ stand for the final pressure and volume. The mathematical relationship of Boyle's Law becomes:

P ₁ × V ₁ = P ₂ × V ₂

• 2 changing variables - pressure + volume

• constant variable - temperature

• inverse relationship

• real life example: syringe with marshmallow inside

Charles’s Law

the volume of a given mass of gas varies directly with the temperature of the gas when the pressure is kept constant

We will use V₁ and T₁ to stand for the initial volume and temperature of a gas, while V₂ and T₂ stand for the final volume and temperature. The mathematical relationship of Charles's Law becomes:

• 2 changing variables - volume + temperature

• constant variable - pressure

• direct relationship

• real life example: tire cold in the winter (temperature decreases) ➡ pressure decreases

Gay-Lussac’s Law

the temperature of gas varies directly with the pressure when the volume is kept constant

We will use V₁ , P₁, and T₁ to stand for the initial volume, pressure, and temperature of a gas, while V_2, P_2, and T₂ stand for the final volume, pressure, and temperature. The mathematical relationship of Charles's Law becomes:

• 2 changing variables - pressure + temperature

• constant variable - volume

• direct relationship

• real life example: rice cooker gets heated up (temperature increases), and pressure increases inside of the cooker; this causes the whistle to blow

Atoms

• Bohr Model

• electrons

  • negative charge

  • makes up the least amount of mass in an atom

  • orbit the nucleus

• protons

  • positive charge

  • mass = 1 amu

  • inside nucleus

• neutrons

  • neutral/no charge

  • mass = 1 amu

  • inside nucleus

• ● Isotopes - atoms with different numbers of neutrons

  ● Ions - atoms with a charge

  ● Average atomic mass - the number of protons + neutrons

  ● Mass number - the average atomic mass rounded to the nearest

  whole number

  

• Periodic Table

  • 18 groups

  • 7 periods

  • Same group = same properties + # of valance electrons

  • Same period = same number of shells

  • the one’s place in a group’s number tells the # of valance electrons

• metals on right

• metalloids in middle

• non-metals on right

• alkali metals

  • highly reactive

  • group 1

• alkaline earth metals

  • quite reactive

  • group 2

• halogen family

  • most reactive non-metals

  • group 17

• noble gases

  • stable

  • group 18

• Octet Rule - the max number of valence electrons any element can have is 8 (stable)

• Lewis Dot Diagrams

  • the amount of valance electrons in an atom represented with dots

Chemical Bonding

• ionic bonding

  • metal and nonmetal

  • gives/takes valance electron(s)

  • swap oxidation numbers to find the bond

  • can conduct electricity

  • use Lewis Dot Diagrams

• covalent bonding

  • nonmetal (x2)

  • shares valance electron(s)

  • use Lewis Dot Diagrams

• ionic naming

  • name of metal

  • name of non-metal + “ide”

  • subscript DOESN’T change the name

• covalent naming

  • 1st non-metal name + prefix (subscript)

  • 2nd non-metal name + “ide”

    

• Law of Conservation of Mass - Mass can neither be created nor destroyed; it can only be changed from one form to another.

Solutions + Acids + Bases

• Solute - smaller part that gets dissolved

• Solvent - larger part that dissolves the solvent

• Water = universal solvent

• Solute + solvent = solution

• Solubility - grams of solute that can be dissolved into 100 grams of H2O at a given temperature

• Saturated Solution - cannot take anymore solution; will settle at the bottom

• Unsaturated Solution - can hold more solution

• Super-saturated Solution - holding more solute than the solution can actually hold

• Dilute - very little solute in solvent

• Strong - a lot of solute in solvent

• Acids

  • Hurt skin

  • Can corrode metals

  • Sour to taste

  • Turns blue litmus paper to red

  • Acids turn red cabbage juice pink

  • When submerged in water, acids release the H+ ion

• Bases

  • Slippery to touch

  • Bitter to taste

  • Turns red litmus paper to blue

  • Bases turn red cabbage juice green

  • When submerged in water, bases release the OH- ion