Sem 1 Final Review Chapters 1- 5

States of Matter Fixed = solid Variable shape = liquid Variable shape and volume = gas

Physical vs. Chemical Physical properties can be measured without changing the substance Examples: color, shape, mass, density, conductivity, malleability, melting point Chemical properties are only apparent when the substance reacts Examples: reacts with oxygen, burns, rusts, decomposes when heated

Elements vs. Compounds Elements have only one type of atom – they are listed on the periodic table Examples: Ag, Cu, Br2, F2, S8 Compounds have different types of atoms combined as molecules Examples: CO, H2O, NH3

Pure vs. Mixture Pure substances are either elements (all same atom) or compounds (all the same molecules) Mixtures must have more than one substance.

Homogeneous vs. Heterogeneous Homogeneous means the ‘same’ throughout All pure substances are homogeneous. SOLUTIONS are homogeneous mixtures. Examples: air, kool-aid, steel (Fe and C) Many mixtures are heterogeneous, different areas have different properties Example: chicken noodle soup

Periodic Table Families (columns) have similar characteristics Important families: alkali metals, alkaline earth metals, halogens, noble gases Most elements are metals because most elements have 1,2, or 3 outer electrons Metals tend to lose electrons to become cations (+) when they form compounds

Diatomic Elements When these elements are alone and uncharged, they will exist as molecules H2 N2 O2 F2 Cl2 Br2 I2

Atomic Structure The nucleus of an atom is made of protons and neutrons It is positively charged and VERY small. The electrons surround the nucleus and create an electron cloud. The electron cloud is negatively charged and 10000x bigger than the nucleus. Remember – you are mostly empty space.

Atomic notation Zn-65 p = 30 n = 35 e = 30 Zn-66 p = 30 n = 36 e = 30 The bottom number is the ATOMIC NUMBER = number of protons. The top number is the MASS NUMBER = protons and neutrons Elements with the same # of protons but different # of neutrons are called ISOTOPES. Zn-65 p = 30 n = 35 e = 30 Zn-66 p = 30 n = 36 e = 30

Ionic Compounds Write the correct formula for these: Sodium sulfide Magnesium oxide Iron(III) nitrate Aluminum phosphate

Ionic Compounds Write the correct formula for these: Sodium sulfide = Na2S Magnesium oxide = MgO Iron(III) nitrate = Fe(NO3)3 Aluminum phosphate = AlPO4

Naming Compounds Write the name for these: AlCl3 CrCl3 PCl3 BeI2 Cu(NO3)2 NO2

Naming Compounds Write the name for these: AlCl3 = aluminum chloride CrCl3 = chromium(III) chloride PCl3 = phosphorous trichloride BeI2 = beryllium iodide Cu(NO3)2 = copper(II) nitrate NO2 = nitrogen dioxide

Scientific Notation Good notation has only one number before the decimal. All of the digits shown in scientific notation are significant digits. Decimal notation Scientific notation 0.003505 25500 4.2x103 2.50x10-2 3.505x10-3 2.55x104 4200 0.0250

Significant Figures Measure all the marks and estimate one digit between the marks. When you write the number, the last digit is always a ‘guess’ because its your estimate. All the known digits and your estimate are the ’significant figures’

Counting Sig Figs All non-zeros are sig figs (123456789) Zeros at the beginning are never sig figs 0.00345 Zeros bewteen numbers are always sig figs 42005 Zeros at the end are only sig figs if there is a decimal point 3700 3700. 25.00

Using Sig Figs Sig figs allow us to round our answers correctly When multiplying or dividing, round to the smallest number of sig figs in the problem When adding or subtracting, round to the smallest number of places after the decimal (or the last column with sig figs for ever number in the problem.) 525.55 x 16.2 = 8513.91 (round to 3 sig figs) 8510 525.55 + 16.2 = 541.75 (round to 1 decimal) 541.8

Dimensional Analysis Use equalities to convert numbers/solve problems Set-up so the units cancel Multiply the tops, divide by the bottoms How many seconds in 3.25 hours? 60 min 60 sec (3.25)(60)(60) 3.25 hr 11700 sec = = X X (1)(1) 1 hr 1 min

Density Density = mass/volume The density of water is 1 g/mL Things that are more dense than water will sink in water. If there are less dense they will float on water. Put these objects in the cylinder of water. floats D = 0.80 g/mL 1.0 g/mL D = 1.25 g/cm3 sinks