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Chemistry Review Classification of Matter Chemistry – What is it? Chemical vs. Physical Change Chemical change (or reaction): new substances with different properties are formed. Physical change: no new substances are formed. A change in state or shape is a physical change. How do you know if a chemical reaction has occurred? 1) 2) 3) 4) 5) Formation of a gas Formation of a precipitate (solid) Color change Energy is released (exothermic) Energy is needed (endothermic) Please note that with any chemical change, there is also a change in energy. Lab Safety Recognize hazards!!!! No book bags or large jackets in the lab Always wear safety goggles and lab aprons, especially when working with hazardous materials and liquids Do not eat or drink in the lab. Long hair should be tied up. Do not have combustible materials near a flame Clean up your lab bench once you are done. Look for WHMIS labels on chemical bottles (see page 35 in text) Compressed gas Flammable and combustible material Oxidizing material Materials causing immediate and serious toxic effects Materials causing other toxic effects Biohazardous infectious material Corrosive material Dangerously reactive material Use safe procedures & techniques Tie back long hair Always wear safety glasses Do not eat or drink in the lab. Never taste chemicals Do not directly inhale chemicals Please stand while doing labs Respond to emergencies sensibly Inform a teacher if someone requires assistance If chemicals are spilled on skin, rinse with water for 20 minutes If you break something or spill something, please inform a teacher immediately. Do NOT handle broken glass! If a fire starts, inform a staff member immediately – STOP… DROP… ROLL!!! IF YOU ARE NOT SURE ABOUT SOMETHING… ASK A TEACHER!!!! V. Classifying Matter Matter is anything that has mass and occupies space Matter can be classified into two main categories: Heterogenous & Homogenous Matter Heterogeneous Homogeneous (Non uniform mixture) i.e. cookie dough (uniform matter) i.e. water Homogeneous Mixture / Solution i.e. NaCl Pure Substances i.e. Lead (aq) Compounds i.e. NaCl(s) Elements i.e. O2(g) * This chart found on page 36* - An atom is the smallest particle of an element which still has the characteristics of the element. (O2(g), Cl2(g), K(s)) - Compounds contain more than one type of atom combined in a definite proportion. (NaCl(s), KBr(s), HCl(aq)) 1) Gravel and Sand 2) Vinegar 3) Nitrogen 4) Salt Elements I. Classifying Elements Metals -Solids @ SATP Nonmetals -solids, liquids, gases -Gain electrons to -Ductile form negative -Good conductors ions -Lose electrons -Brittle to form positive -Poor conductors ions -Lack luster -Shiny Metalloids -Have characteristics of metals & nonmetals -Located near staircase II. The Periodic Table John Alexander Newlands Arranged elements in order of increasing atomic masses Noticed some properties recurring over and over again – he called this the periodic law Dmitri Mendeleev Published the periodic table of elements Very confident as he left spaces empty – assumed those elements were not yet discovered - Mendeleev used the terms FAMILY and PERIOD to describe the table’s organization. FAMILY/GROUP: elements in vertical columns – have similar properties. Reactivity INCREASES from top to bottom within groups 1 and 2 Reactivity DECREASES from top to bottom in groups 17 & 18. (Fluorine is the most reactive non-metal) PERIOD: elements in horizontal rows – these elements change from metals to nonmetals. Groups of Elements Alkali Metals: Group 1 metals Soft, silver coloured metals that react violently with H2O to form basic solutions Most reactive: cesium & francium Alkaline Earths: Group 2A metals Light, reactive metals that form oxide coatings when exposed to air Transition Metals: Elements in groups 3 to 12 Exhibit a wide range of properties Metalloids: Metals very close to the “staircase” line They have properties of metals and non-metals. Halogens: Group 17, non-metals, highly reactive. Fluorine is the most reactive Noble Gases: Group 18 Generally unreactive (inert) Lanthanides: atomic numbers 58-71 Actinides: atomic numbers 90-103 III. Atomic Theories Dalton: all matter is composed of tiny indivisible particles called atoms atoms of the same element have identical properties atoms can be combined to form new substances Thompson: Discovered the electron – a subatomic particle with a negative charge. He proposed the atom was a positive sphere with negative electrons embedded in the sphere. Rutherford: Suggested the existence of the proton – subatomic particles with positive charge His “gold” experiment led to the discovery of the proton Proposed that all atoms have a positive central region called the nucleus Bohr: Electrons orbit the positive nucleus in certain orbitals – electrons cannot exist between orbitals The higher the energy level of an electron, the further it is from the nucleus Energy Level Maximum Number of electrons (e-) 1 2 2 8 3 8 Quantum Mechanics: Highly mathematical There is a region around the nucleus in which there is a high probability of finding an electron – the motion of the electron is unknown. Currently accepted model VI. Back to the Periodic Table… What do these tell us? - atomic number - group number - atomic mass - period number In each atom, the number of protons equals the number of electrons. The number of neutrons can be found by subtracting the atomic number from the atomic mass V. Simple Ions Ions are charged atoms. Metals lose electrons to become positively charged. Groups 1, 2, & 3 will lose electrons to become similar to the nearest noble gas. Non-metals will gain electrons to obtain a net negative charge Ion Formation All atoms want to have a stable (full) outer energy ring They want to be more like noble gases To become stable the atoms will gain or lose electrons (whichever is easiest) to fill the outer energy level. When they lose electrons, they become positively charged When they gain electrons, they become negatively charged When atoms lose or gain electrons, they become IONS. To name an ion, follow these rules: 1) If ion is non-metal, change the ending to “-ide” - ex. Chlorine → Chloride Bromine → Bromide 2) If ion is a metal, call it the same and add the word “ion” after it. - ex. Sodium → Sodium ion Iron → Iron ion How do you calculate the charge of an ion? 1) 2) 3) 4) Find the noble gas that the element is closest to on the periodic table (does not have to be in the same period) Calculate if it would be easier to gain or lose electrons to get the same number of electrons as the closest noble gas. Calculate how many electrons the element would gain or lose. (When you gain electron the ion becomes positive, when you lose, the ion becomes negative) Record the charge as a superscript following the element’s symbol. O Gain electrons 2 electrons O2- VI. Isotopes ISOTOPES are elements that have the same atomic number but different atomic masses. The differences in atomic masses are due to the addition or removal of neutrons. Protons? Neutrons? Electrons? Protons? Neutrons? Electrons? Protons - 10 Neutrons - 10 Electrons - 10 Protons - 35 Neutrons - 45 Electrons - 36