Chemistry Exam 1 Flashcards
Chapters 1-5
Compounds
A substance composed of two or more different chemical elements that are chemically bonded together in a fixed ratio
Mixtures
A substance made up of two or more different components that are physically combined but not chemically bonded together
Element
A pure substance that cannot be broken down into simpler substances by chemical means
Pure Substance
A material that has a constant composition and distinct properties throughout, with no variation in its chemical make-up
Homogenous Mixture
The components are uniformly distributed with no visible boundaries between them. Examples: air, salt water, vinegar
Heterogenous Mixture
The components are not uniformly distributed and have visible boundaries between different phases/components. Examples: sand and water, salt and oil
Changes In State: Which ones require an input of energy?
Melting, Boiling, Sublimination (solid to gas)
Changes in State: Which ones release energy?
Condensation, Freezing, Deposition (gas to solid)
Chemical vs Physical Changes
Chemical changes alter the chemical composition (tarnishing of silver), while physical changes just change in color, boiling point, etc
Steps of Scientific Method
Step 1: Make Observations
Step 2: Develop a Hypothesis
Step 3: Test the hypothesis through experiments
Step 4: Develop a law (summarize consistent outcomes)
Step 5: Develop a theory (explanation of law)
Scientific Notation
- Move the decimal point so there is only one non-zero digit to the left of the decimal
- Count the number of places the decimal moved
- The digit(s) left is the coefficient
- The number of places the decimal moved becomes the exponent of 10
Sig Fig Rules
- Answer can’t have more sig figs than lowest # sig figs in the calculation
- Leading zeros are not significant UNLESS marked by decimal (3500.)
- Trailing zeros are signif. (.3000)
Density equation
D=M/V
Specific Heat Capacity
Amount of energy needed to raise a certain mass of a substance by 1 degree Celsius
Exothermic Reactions
Release Energy
Endothermic Reactions
Absorb energy
Law of Conservation of Matter (Dalton)
When a reaction takes place, matter is neither created nor destroyed
Percent by Mass
mass of oxygen in compound divided by total mass of compound times 100
Dalton’s Atomic Theory
- All matter is made up of atoms
- Atoms can neither be created or destroyed
- Atoms of a particular element are alike
- Atoms of different elements are different
- A chemical reaction involves the union or separation of individual atoms
Rutherford’s Gold Foil Experiment
- Fired alpha particles at metal foil
- Expected a straight flight path for the particles
- Some particles flew through and some deflected at a wide angle or “bounced backward”
- made him realize there must be something dense inside the atom and negative space
Rutherford’s Model of the Atom
- An atom is mostly negative space
- A nucleus is a tiny, massively dense, positive-charged unit in the atom (contains protons and neutrons)
Atomic Number
- # of protons in the nucleus
- Determines identity of the atom
- An atom with one proton is always a hydrogen
Mass Number
Number of protons plus neutrons
Isotopes
Atoms with the same number of protons but differing numbers of neutrons (exhibit same chemical properties still)
Atomic Mass
The actual mass of an atom (given in AMUs or Daltons)
Law of Octaves
Elements that are 8 elements apart by mass react in a similar manner (aka chemical periodicity)
Law of Mendelev
Properties of elements recur in regular cycles (periodically) when elements are arranged in increasing atomic mass