HESI A2 Chemistry Latest Update 2024

HESI A2 Chemistry Latest Update 2024 Chemistry The study of matter and its properties and how those properties relate to one another Three states of matter solid, liquid, gas Scientific notation The scientific system of writing numbers. A method to write very big or very small numbers easily. Is composed of three parts: a mathematical sign, + or -, the significand, and the exponential, sometimes called the logarithm. Mathematical sign designates whether the number is positive or negative (+ or -) Significand the base value of the number or the value of the number when all the values of ten are removed Exponential A multiplier of the significand in powers of ten. Move the decimal in the significand the number of places equal to the exponent of 10. positive to the right, negative to the left. Numbers between -1 and 1 always place a zero to the left of the decimal. Temperature systems Fahrenheit, Celsius, and Kelvin Fahrenheit (F) Used only in US, Belize, and Jamaica. 0 degrees is the freezing point of sea water or heavy brine at sea level. 32 degrees is the freezing point of pure water at sea level, 212 degrees is the boiling point of pure water at sea level. most people body temp s 98.6 degrees Celsius (C) sometimes called Centigrade and is used in the rest of the world and by the scientific community. 0 degree is the freezing point of pure water at sea level, 100 degrees is the boiling point of pure water at sea level. most people body temp is 37 degrees Kelvin (K) Used only in the scientific community. 0 degrees Kelvin is -273 degrees celsius and is thought to be the lowest temp achievable, 273 degrees Kelvin is the freezing point of water, 373 degrees Kelvin is the boiling point of water, most people body temp 310 degrees Kelvin but this is never used. Absolute zero 0 degree Kelvin, -273 degrees Celcius. thought to be the lowest temp achievable Melting ice 21 degrees Celcius and 32 degrees Fahrenheit Normal body temp 37 degrees Celcius and 98.6 degrees Fahrenheit Boiling water 100 degrees Celcius and 212 degrees Fahrenheit Atom The basic building block of all molecules. most stable when an orbital is full. The simplest form of matter that can naturally exist in nature. Physical structure of an Atom nucleus and orbits, which are sometimes called electron cloud. Nucleus at the center of the atom and composed of protons and neutrons Orbits sometimes called electron cloud, located at the outermost part of the atom and is where the electrons are Electron spins around (orbits) the nucleus at various energy levels called orbits or shells so fast forming electron clouds. Shell or Orbits various energy levels around the nucleus Proton charge has a positive electrical charge Electron charge has a negative charge Neutron charge has no charge at all Ground state atom tend to have equal numbers of protons and electrons making them electrically neutral. Ion or Ionic state An atom that is electrically charged (+ or -) either by losing or gaining electrons Cation An atom with a positive charge Anion An atom with a negative charge Periodic Table A table made up of a series of rows and columns of the known elements arranged according to their properties. Period The rows on a periodic table Group The columns on a periodic table Group 1A +1 charge 1 electron in the outer shell Group 2A +2 charge 2 electrons in the outer shell Group 3A +3 charge 3 electrons in the outer shell Group 4A +4 or -4 charge 4 electrons in the outer shell Group 5A -3 charge 5 electrons in the outer shell Group 6A -2 charge 6 electrons in the outer shell Group 7A -1 charge 7 electrons in the outer shell Group 8A called noble gases has no charge, these gases are very stable and chemically inert Transition metals The groups 3 3B through 12 2B Atomic number The number of protons in the nucleus. Is located at the top of each of the squares in a periodic table. Is always a whole number. Atomic mass The average mass of each of that element's isotopes. Is the number at the bottom of each of the squares in the periodic table, and is usually a decimal number Isotopes Different kinds of the same atom that vary in weight based on the number of neutrons in the nucleus. written as an abbreviation with the symbol of the element preceded by a superscript number indicating the atomic mass Compound A combination of elements Mixtures of different elements to create a single matter Chemical equations recipes Reactants ---> Products Reactant the ingredients in a chemical reaction Products desired end result or compound Law of conservation of mass mass cannot be created or destroyed during a chemical reaction. Equilibrium A state in which reactants are forming products at the same rate that products are forming reactants. Reactions may stop before all of the reactants are used to make products A reaction at equilibrium can be said to be reversible. A+B <---> C+D 4 Ways to increase the reaction rate 1. Increase temperature 2. Increase surface area 3. Add a catalyst 4. Increase the concentrations of reactants