Chemical Compounds and Observations Quiz

Properties of Matter

• Matter is anything that has mass and takes up space

• Volume describes how much space matter occupies

• Chemistry studies the composition and properties of substances, and how they change.

• Chemical properties describe how substances react with other substances

• Physical properties describe the matter itself, examples include: color, temperature, mass, volume, density, luster, ductility, malleability, hardness, solubility, boiling point

• Melting and freezing points are temperatures where substances change states between solid and liquid.

• Boiling and condensation points are temperatures where substances change states between liquid and gas or vice versa.

• Methane gas is an example of a substance that can catch fire and burn in air

• Intensive properties depend on the type of matter.

• Extensive properties depend on the amount of matter.

• A physical change is when the matter stays the same before and after the process.

• A chemical change happens when the matter becomes new material.

Classifying Matter

• Composition describes what something is made up of

• Pure substances are uniform in their composition and cannot be separated physically; they have unique chemical and physical properties

• Mixtures have variable compositions and their components can be physically separated.

• Mixtures can be solids, liquids or gases

• Mixtures display some properties of each of its components

• Elements are substances consisting of one type of atom and found on the Periodic Table.

• Compounds are formed when two or more elements chemically combine in fixed proportions.

• Elements are one type of particle and cannot be broken down by chemical means.

Density

• Mass is a measure of the amount of matter (force) and is measured in grams.
• Volume is measured in cubic units (cubic centimeters = milliliters)
• Density is the amount of matter in a given space.
• Density can be calculated by comparing mass and volume
• Experimentally, density can be calculated by determining the mass and volume of a sample.

Mixtures

• Mixtures are made of two or more substances combined physically

• The original substances in a mixture keep their properties

• Percent by mass = (mass of part / mass of whole) x 100

• Percent by volume = (volume of part / volume of whole) x 100

• Percent mass/volume = (mass of part / volume of whole) x 100

• Mixtures can be separated based on their different properties

Scientific Notation

• The number part has to be between 1 and 10

• Positive exponent indicates a large number

• Negative exponent indicates a small number

• Add/subtract: exponents match in order to add or subtract; multiply/divide: add the exponents to multiply or subtract them to divide

Density Worksheet

• Density calculations are based on mass and volume
• Objects do not always have the same density

Significant Figures

• Accuracy refers to how close a measured value is to the correct or accepted value.

• Precision refers to how closely a series of measured values are to each other

• Exact numbers are known with certainty.

• Approximate numbers are measured.

• Significant figures are digits in a measurement that are believed to be valid.

• Significant figures help in rounding

Metallic Bonding

• Metallic bonding is a force of attraction between positively charged metal ions and the many electrons in a metal.
• Valence electrons can be modeled as a "sea of electrons" that move freely around the metal ions.

Configurations and Valence

• Electron configurations are shorthand for the electronic structure of an atom

The Octet Rule

• Atoms will lose or gain electrons (to match the valence electrons).
• Nonmetals gain electrons to form negative ions (anions).
• Metals lose electrons to form positive ions (cations).
• Metals names do not change when losing electrons

Ionic Bonding

• Nonpolar covalent bonds: electrons evenly shared
• Polar covalent bonds: electrons unequally shared
• Ionic bonding in compounds: high melting points, brittle

Diatomic Molecules

• Diatomic molecules consist of two atoms bonded together.
• Elements in specific groups on the periodic table commonly form diatomic molecules.
• The relative number of valence electrons in elements can show the types of bonding in diatomic molecules

Other Math in Chemistry

• Physical quantities are measured using units
• Using prefixes can help convert from one unit to another

Temperature Conversions

• 1 Kelvin = 1 degree Celsius.
• The formula to convert between the units of Celsius and Kelvin is C° = K- 273 or K = C°+ 273

Dimensional Analysis

• Dimensional analysis is a method of converting between different units.
• Use equivalence statements to compare quantities.
• Use conversion factors, a fraction that equals 1.

Atoms

• Atomic number is the number of protons in an element.

• Mass number is the number of protons and neutrons in an element

• Charge is the number of electrons (+ or -) in an atom.

• The average mass is the weighted average mass of an element's isotopes.

• Ion is an atom or molecule with a net electric charge due to the loss or gain of one or more electrons.

There are positive and negative charges.

Short-hand Notation for Atoms

• The shorthand notation for atoms shows the atomic number, mass number, the number of protons and electrons for an element.

Radioactive Atoms

• Radiation is the emission of energy as particles or waves.

• Radioactivity comes from an unstable nucleus.

• The strong force holds protons and neutrons together.

• The number of protons and neutrons determines stability.

• Types of radiation include alpha, beta, gamma, X-rays, and neutrons(non-ionizing).

• Ionizing radiation can cause ionization of atoms.

Alpha Decay, Beta Decay, and Gamma Decay

• Alpha decay: alpha particles are emitted from the nucleus consisting of 2 protons and 2 neutrons -Beta decay: beta particles; identical charge to an electron and mass much less. Beta + and Beta- occur with a change in neutron to proton ratio in the nucleus- Gamma decay: gamma rays are high energy light with no mass and no charge to be emitted during nuclear decay.

The Story of the Atom

• Leucippus and Democritus were early Greek philosophers who proposed the idea of atoms.
• Aristotle and Plato challenged the notion that matter is made of atoms.
• Robert Boyle was a key figure in modern chemistry.