STAR Testing ReviewChemical Reactions&Chemistry of Life
Chemical & Physical ChangePhysical Changes: Any change thatalters the form, shape, or appearanceof a substance but does not change itinto a new substance. EXAMPLE: If I were to toss fresh berriesinto a blender and make a fruit smoothie-it would still be fruit, just mashed intosmaller pieces.
Chemical & Physical ChangeChemical Changes: a change that asubstance undergoes where a totallynew substance is the result. EXAMPLE: In the magnesium lab, weburned magnesium and after it’s chemicalchange the result was magnesium oxide.It was no longer metal!!
Did a chemical reaction occur??Was light given off? It was chemical.Was gas released? It was chemical.Was heat given off? It was chemical.Was energy released? It waschemical.
Chem vs. Phys PropetiesChemical Properties- Thecharacteristic of a substance thatdescribes its ability to change into anew substance Example: Burning of Magnesium intoMgOPhysical Properties- A characteristic ofa substance that can be observedwithout changing the substance into anew substance Example: Ice Melting, Cutting a piece ofpaper
Bonding & Chemical ReactionsIn order for a chemical reaction tohave taken place, bonds must havebeen broken and re-created!! Atomsrearrange to create something totallynew. Bonds can change from one form toanother; covalently bonded atoms canrearrange to create ionic bonded atoms(like with the Mg lab)
ReactionsRemember, when atoms cometogether to form compounds, the newcompounds produced have differentproperties than the atoms did before. No exploding salt!!!!
Balancing equationsDue to the conservation of matter,equations MUST be balanced! Atoms cannot be created or destroyed! Thus, the atoms in the products mustequal the total atoms in the reactantsREMEMBER: The atoms are only beingrearranged!
Let’s try one…N2 + O2 ---> N2O52 N 2 N2 O 5 OWe need to balance out the Oxygen first, then theNitrogen. This gives us…2N2 + 5O2 ---> 2N2O54 N 4 N10 O 10 O
Let’s do another, for fun!!Fe + HCl ---> FeCl2 +H21 Fe 1 Fe1 H 2 H1 Cl 2 ClFe + 2HCl ---> FeCl2 +H2
One More…C2H4 + O2 ---> CO2 + H2O2 C 1 C4 H 2 H2 O 3 OC2H4 + 3O2 ---> 2CO2 + 2H2O
Acids and BasesAn Acid is a chemical compound, that,when dissolved in water has a pH ofless than 7.Acids taste sour, react with metals andcarbonates and will turn blue litmuspaper red.Acids are corrosive- they eat away atother materials.
Acids and BasesBases are chemical compounds that,when dissolved in water, have a pH ofabove 7.Bases taste bitter, feel slippery andturn red litmus paper blue.Bases are corrosive- they eat awaymaterials.
Uses for Acids:Acids are naturally in many of the foodswe eat :Tomatoes, lemons, oranges,and even leafy green veggies!Acids are also used in many fertilizers.Acids can also be found in batteries
Uses for BasesCement is made using basesMany cleaning solutions used in thehome are bases (drain cleaner, glasscleaner, bleach, soap)Bases can also be found in bakedgoods such as breads, cakes, andcookies!
The pH scale!!!!The pH scale is a range of values from0-14 that express the concentration ofhydrogen ions in a solution. The more hydrogen ions, the lower thenumber on the pH scale.
Acids & Bases: pH scaleAcids range from 0-6Acids have the most amount ofhydrogen ions.Bases range from 8-14Bases have the least amount ofhydrogen ions.7 on the scale is neutral (neither)
Neutralizing Acids & BasesThe reaction between acids and basesis a called neutralization.The neutralization of acids and basesdepends on the identities, volumesand concentrations of the reactants. Salts will typically form as a result ofacids and bases neutralizing.
Chemistry of Life!A quick (very quick) introduction!
Carbon! It’s special!Because of it’s very special ability tocombine in any ways with itself andother elements it has a central roll inthe chemistry of living organisms!
CHONPS!Living organisms are made ofmolecules consisting largely of:CarbonHydrogenOxygenNitrogenPhosphorusSulfur