Notes about the atom, etc. *Matter: Anything that has mass and takes up space *Properties of matter: Physical properties: • These properties can be observed or studied without changing the matter into something else. • Density, color, size, shape, melting point, boiling point, freezing point Chemical properties • These properties can only be known when there is a change to the matter- we will end up with something new • Frequently the changes that occur are irreversible • Flammability, reactivity with other substances *Changes that can occur to matter: *Physical changes do not change the substance. Think about a piece of wood, a piece of paper and a piece of metal. What could happen to these things that would not change them into something different? *A chemical change will produce something new and different than what we started with. Think about a piece of wood, a piece of paper, a piece of metal, and an egg. What could happen to these things that would change them into something different? ( we end up with something that is very different than what we started with) *Substance: • A substance, sometimes called a pure substance, always has the exact same compositioneverywhere in the universe. • Elements, and compounds are substances *The Atom: • An atom is the smallest piece of matter that cannot be broken down into other substances without losing the properties of the matter. • Elements (on the periodic table) are made up of a single type of atom. *Compounds: • A compound is a combination of two or more DIFFERENT atoms bonded together. • Examples: NaCl, C6H12O6 ,MgBr2 , CH3OH *Molecule: • A molecule is a combination of two or more atoms bonded together. The atoms may be of the same element or different elements. Examples: H2O, CO2, O2 *Mixtures: • A mixture is a combination of substances. They do not have definite and constant composition. • Two types of mixtures: 1. Homogeneous mixtures • A homogeneous mixture is a mixture that has the same composition throughout. • It is called a solution • Examples: a beaker of salt water, a glass of Koolaid, a balloon full of air • Difficult to separate* (Might require a lot of work, or energy to separate) • A Solution consists of two parts : Solute What “dissolves” ( frequently a solid) Solvent what does the “dissolving” ( freq. liquid) 2. Heterogeneous mixtures: • A heterogeneous mixture is one that does not have the same composition throughout. • Examples: muddy water; a bucket of sand, salt, and nails; blood; milk generally called suspensions. A lot of the time, we can see different types of stuff in the mixture. • Easier to separate The Atom! The atom consists of Protons, Neutrons, and electrons Protons and Neutrons make up the nucleus, and the electrons are outside of the nucleus Protons: protons have a positive charge P+, a mass of 1.673x 10 -24 g ( mass of 1 amu) ((atomic mass unit)) Neutrons: neutrons are neutral in charge N0 , a mass of 1.673x 10 -24 g (1 amu) Electrons: electrons have a negative charge e-1, a mass of 9.109 x 10 -28 g ( 1/1678 amu… 0 amu!) electrons are going around the nucleus os an atom at the speed of light, very fast, and actually have some specific energy levels an orbitals that we will discuss later! The periodic table: a “list” of all of the elements known to man! The periodic table has lots of important information on it, The symbol- a one or two letter symbol from either the Latin or English name. the first letter is always capitalized any other letters are lowercase The atomic number is the smaller number, it is a whole number. This number tells us how many protons are in the atom. The periodic table is arranged by how many protons the element has. This number also tells us how many electrons there are- in a neutral (uncharged) atom. The atomic mass number is the larger number, it almost always has a decimal, as this number is actually an average of the different isotopes* that each element has. We generally consider the atomic mass to be the total number of protons and neutrons in an element. Since electrons have very very very little mass, we use the atomic mass number to help us figure out number of neutrons in an element. We generally round the atomic mass number to the nearest whole number, and then subtract the atomic number to get the number of neutrons. For example… oxygen has a mass of 15.99 which we will round to 16, its atomic number is 8, so 16 – 8 = 8 neutrons, similarly, Phosphorous has a mass of 30.97 which we round to 31, and with 15 protons, 31-15 = 16 neutrons! Isotopes: An isotope is an element that has different number of neutrons than another atom of the same element. They will be the same element, but will have different masses. For example, we can have oxygen 16 with 8 protons and 8 neutrons and we can have oxygen 17 with 8 protons and 9 neutrons. We can write these symbols in a few ways- O-16, and O-17 is one example Ions: An ion is an element that has gained or lost electrons and therefore has a charge. If we lose electrons, we have more protons than electrons and thus have a positive charge, and if we gain electrons, we then have more electrons than protons, and therefore have a negative charge We can write ion symbols like Al+3, S-2, etc.