Matter anything that occupies space and has mass Atoms are the basic particles that compose ordinary matter and about 91 different types of atoms naturally exist Molecules formed when atoms bind together in specific geometrical arrangements the protertis of substances radically depend on the structure of the particles that compose them chemistry the science that seeks to understand to properties of matter by studying the structure of the particles that compose it the state of matter depends on the relative positions of the particles and how strongly they interact with one another relative to temperature the composition of matter depends on the types of particles solid matter the particles attract one another strongly and therefore pack close to each other in fixed locations particles vibrate but do not move around or past each other liquid matter the particles pack about as xlosely as particles do in a solid but slightly weaker attractions between the particles allow the to move relative to each other giving liquids a fixed volume but not a fixed shape liquids assume the shape of their container at room temp gaseous attract eachother only very weakly so weakly that they do not clump together as particles do in a liquid or solid instead the particles are free to move large distances before colliding with one another the large space between the particles make gases compressible always assume the shape and volume of their container at room temp pure substance made up of only one type of particle one component and its composition is invariant doesn t vary from one sample to another Ex helium water table salt mixture is a substance composed of two or more particles in proportions that can vary from one sample to another Ex tea heterogeneous the composition varies form one region of the mixture to another the different particles that compose sand don t mix uniformly homogenous the same composition throughout the particles that compose sweetened tea mix uniformly element a substance that cannot be chemically broken down into simpler substances compound a substance composed of two or more elements in a fixed definite proportions chemical reaction a process in which one or more substances are converted into one or more different substances according to law of conservation of mass the total mass of the substances involved in the reaction does not change since these particles are merely rearranged in chemical reactions and not created or destroyed the total amount of mass remains the same law of conservation of mass in a chemical reaction matter is neither created nor destroyed mass if reactants mass of products law of definite proportions all samples of a given compound regardless of their source or how they we prepared have the same proportions of their constituent elements PG 11 Examples the law of multiple proportions when two elements A and B form two different compounds the masses of element B that combine with 1 g of element A can be expressed as a ratio of small whole numbers refer to notes A B compound 1 and compound 2 Dalton used these laws with his atomic theory atomic theory matter is composed of small indestructible particles called atoms all atoms of a given element have the same mass and other properties that distinguish them from the atoms of other elements atoms combine in simple whole number ratios to form compounds atoms of one element cannot change into atoms of another element in a chemical reaction atoms only change the way that they are bound together with other atoms the nuclear theory most of the atoms mass and all of its positive charge are contained in a small core called the nucleus most of the volume of the atom is empty space throughout which tiny negatively charged electrons are dispersed there are many negatively charged electrons outside the nucleus as there are positively charged particles protons within the nucleus so that the atom is electrically neutral realized this wasn t complete didn t account for neutrons neutral particles within the nucleus atomic mass number of protons plus neutrons atomic number the number of protons defines the elements the periodic table arranged by atomic number number of protons number of protons never changes Isotopes atoms with the same number of protons but different number of neutrons Natural abundance of the isotope is percent that this isotope is naturally occurring Cations positively charged ions Anions negatively charged ions Atomic mass the average mass based on the different isotopes and the percentage of how often they naturally occur PAGE 23 EXAMPLE Law of conservation of energy energy is neither created or destroyed Desity m v Energy is the capacity to do work Potential energy the energy associated with its position or composition Kinetic energy the energy associated with its motion Thermal energy the energy associated with the temperature of an object Ch 3 Ball dropped final thermal energy released is equal to initial potential energy Tendency for systems with high potential energy to change in a way that lowers their PE objects or systems with high potential energy tend to be unstable Exothermic system gives off energy to the surroundings change in energy is negative Endothermic system absorbs energy from the surroundings to the system change in energy is positive Dimensional anlysis P43 Moles The mass of 1 mol of atoms of an element elements molar mass g mol the elements atomic mass 6 022 X 10 23 atoms of the element Electrons and light both share a wave particle duality Amplitude verticle height of a crest or depth of a trough determines lights intensity and brightness Wave length the distance between adjacent crests determines the light s color Frequency the number of wave crests that pass through a stationary point in a given period of time second V c lambda The color something appears is which color is reflected electromagnetic spectrum includes all wavelengths of electromagnetic radiation threshold frequency below which no electrons are emitted from the metal no matter how long the light shines on the metal o low frequency long wavelength light does no eject and electrons from a metal regardless of whether the intensity if high or low or if the light is shone on it for a long time o but high frequency short wave length light ejects electrons even if the intensity is low or high came to the conclusion light energy must come in packets photon the amount of E in a photon h v frequency can also be