Chem Test #1 - Matter and Measurement PDF

Matter: all the substances that make up our world - Anything that has mass + takes up space Mass: a measure of the amount of material in an object (a body’s resistance to accelerate) - Measured in grams (kg) Weight: a measure of the force with which an object is attracted by gravity...

Matter: all the substances that make up our world - Anything that has mass + takes up space Mass: a measure of the amount of material in an object (a body’s resistance to accelerate) - Measured in grams (kg) Weight: a measure of the force with which an object is attracted by gravity - Measured in Newtons (N) Volume: the amount of space an object occupies in 3-D Solid → Liquid → Gas Compact → Spread apart A pure substance: matter that consists of just one type of atom or one type of molecule Elements: the simplest form of a pure substance - Composed of only one type of atom - Cannot be broken down into simpler substances by ordinary chemical changes Compound: a substance that consists of molecules or ions of two or more different atoms always chemically joined in the same proportion Mixtures - consist of two or more substances that are mixed together but not chemically joined. (physically mixed) - Homogenous mixture: a mixture in which the components are uniformly distributed - Heterogenous mixture: a mixture in which the components are not uniformly distributed  Compounds Mixtures 1. Chemically combined can be 1. Physically combined; can be separated or formed by chemical separated by physical changes changes 2. Each constituent retains its 2. Have properties that are different properties from properties of constituents Ex. sweet + sour = sweet and sour 3. Elements are combined in definite 3. Substances may be combined in any ratio ratio or proportion Ex. H2O → water Ex. SWEET + sour = SWEET and sour H2O2 → hydrogen chloroxide Separation of Mixtures: 1. Filtration: the process of separating a mixture of a solid and a liquid 2. Distillation: a process used to separate a mixture based on differences in boiling points - Selective evaporation and condensation 3. Evaporation: a process used to separate mixtures by heating a solution → evaporate liquid solvent + leave behind the solid solute 4. Chromatography: the components of a mixture separate as they move at different rates up the surface of a piece of paper - Rates depend on differences in solubility in a solvent Physical properties: can be observed, or measured, without changing a substance into another substance Ex. temp, mass, volume, phase Chemical properties: how a substance reacts or changes during a chemical reaction Ex. flammability, pH, acidity, Physical changes: changes in matter that does not change the identity (composition) of a substance Ex. changes in state of matter, temperature, volume, mass Chemical changes: changes that result in new substances with their own set of properties Ex. combustion, oxidation, decomposition Measurement: a technique in which the properties of an object are determined by comparing them to a standard of quality Standard: an unchanging body of each unit to serve as a primary reference Metric system: a decimal system of measurement based on multiples of 10 Quantity: a measured property of a substance International System (SI System): - Uses a different unit for each quantity - Two types of SI units 1. Fundamental or Basic 2. Derived or Calculated (must be calculated using fundamental/basic) Density: property of matter that describes how closely packed together the particles of a substance are - density = mass/volume ★ In scientific measurements, Celsius is used ★ When estimating/guessing a measurement, you can only guess ONE unknown digit Accuracy: the proximity of a measurement to the value of a quantity (if known) - Percent error is calculated to evaluate the extent of deviation % error = ((measured value - accepted value) / accepted value) x 100 Precision: a measure of how closely individual measurements agree with one another - ^ # of decimal places → ^ precision - Standard deviation is calculated to evaluate precision of data Measured Numbers: - Certain digits: values that are marked on the measuring device - Uncertain digits: the last digit which is always estimated Significant figures: the # of digits used to express a measured or calculated quantity Counting Significant Figures: - Nonzero numbers are always counted as significant figures - Zeros may or may not be significant figures depending on their position in a number Rules: 1. A zero is a significant figure if it is a. Between nonzero digits b. At the end of a decimal number 2. A zero is not a significant figure if it is a. At the beginning of a decimal number b. Used as a placeholder in a large number without a decimal point ★ If a number ends in a decimal point, then ALL numbers before it are significant Significant Figures in Calculations:  - In multiplication or division, the final answer is written so that it has the same number of SFs as the measurement with the fewest SFs - In addition or subtraction, the final answer is written so that it has the same number of decimal places as the measurement having the fewest decimal places Unit Conversions Steps: 1. Start w/ the given measurement 2. Set up the conversation factors to permit the cancellation of unwanted units 3. Cancel unwanted units 4. Use as many conversion factors as needed Mole: a group or set of 6.022 x 10^23 particles Molar mass (gram-formula mass): the mass in grams of 1 mole of substance - Measured in units of g/mol Development of the Atom: 1. Dalton’s Atomic Theory: a. Billiard Ball Model: the atom is a small solid sphere b. Elements are made of tiny particles called atoms c. Atoms of one element are identical while atoms of different elements are different d. Conservation of atoms–rearrangement in RXN e. Different atoms form compounds in constant ratios 2. Plum Pudding Model (J.J. Thomson): a. Atoms are positive spheres of matter w/ negative electrons embedded b. Discovered atoms have negative particles called electrons c. Electrons are dispersed in a uniform positive charge (plum pudding/chocolate chip cookie model) 3. Rutherford’s Nucleus Theory: a. Positive charge (proton) is concentrated in the nucleus as shown in Gold Foil (alpha particle) experiment → concluded that most of an atom is empty space  b. Discovered neutron in nucleus which has no charge Law of Constant Composition/Definite Proportions: a given compound always contains exactly the same proportions of elements by mass Law of Conservation of Mass: matter cannot be created nor destroyed during a chemical reaction (an equal amount of matter exists both before and after an experiment) Subatomic Particles: - Protons: positive electrical charge (found in nucleus) - Neutrons: no electrical charge (found in nucleus) - Electrons: negative electrical charge (found outside/around nucleus in electron cloud) ★ Protons and newtons have essentially the same mass ★ Mass of electron is so small we ignore it ★ Atoms are overall neutral Atomic number (z): # of protons or electrons ★ All atoms of the same element have the same number of protons Mass number (A): the total # of protons + neutrons in the nucleus of ONE atom (total # of nucleons) Isotopes: atoms of the same element w/ different masses - Isotopes have different #s of neutrons Atomic mass: a weighted average of all isotopes, resulting in fractional values Weighted average: Atomic mass = ((mass of isotope 1)(%1) + (mass of isotope 2)(%2))/100 Properties of a Wave: - Crest: highest point of a wave - Trough: lowest point of a wave - Wavelength (λ): the distance between 2 successive peaks or troughs (in meters) - Frequency (v): the # of waves (cycles) per second that passes a given point - Measured in units of hertz (Hz) - 1 Hz = 1/s (s^-1) ★ There is an inverse relationship between wavelength and frequency - Velocity: equals the speed of light in a vacuum (2.998 x 10^8 m/s) Electromagnetic spectrum: the complete range of all types of radiation that has both electric and magnetic fields and travels in waves Electric field: the electric force per unit charge Electromagnetic waves: carry energy through space at a speed equal to the speed of light in a vacuum Quantum theory: energy is not absorbed nor released continuously Quantize: to limit the possible values of a magnitude or quantity to a discrete set of values A quantum is the minimum amount of energy that can be gained. Photons: packets of energy that carry a fixed amount of energy but have no mass Energy of one photon: hv or h(c/λ) (v = c/λ)