Name: ______Date: ______Period: ______
Study Guide for Chemistry Fall Midterm 2017 – ANSWER KEY
1
Midterm Exam Facts
The midterm exam is scheduled for ______. You will have 90 minutes.
The midterm exam is cumulative. This means it covers everything we have studied in chemistry this semester.
How Does the Midterm Exam Affect My Grade?
The midterm exam counts 10% of your overall Quarter grade for chemistry.
Students historically score within 10% of their test average on the midterm exam. So, If Polly Perfect’s test average is an 85%, she can expect to score 75-95% on the midterm – if she studies!
What Should I Review/Study?
Unit Tests and Quizzes
Previous study guides
Online review resources (both on the midterm page and the unit pages)
This Study Guide & Answer Key
Which Reference Sheets Can I Use on the Midterm?
You will need to remember to bring all of these with you on the day of the midterm!
4” x 6” notecard (hand-written front & back)
Periodic Table (Miss Scott’s class set)
Unit Conversion Factors Reference Sheet (i.e. 1 inch = 2.54 cm)
Periodic Table Flipbook
VSEPR Reference Sheet
What if I Need Extra Help?
It is much better to study a little every day than to leave things until the last minute. Seek help early.
Find a study buddy/friend/significant other who is in chemistry and study together.
Last Piece of Advice
Chemistry is a challenging college preparatory class. Recognize that your college/university instructors will not provide you with a study guide that covers “everything” that will be on their exams. In fact, most professors won’t provide you with a study guide at all. You can thank Miss Scott for putting together this study guide for you. Please view this as a “guide,” and understand it will not tell you everything that is on the midterm exam. However, if you are able to answer all of the questions successfully in this guide, and you truly understand all of the bulleted concepts listed for you to study, your chances of success are very good.
Unit 1– Measurements, Scientific Method, Math
1.How are matter and mass related? Matter is anything that has mass and takes up space (volume)
2.Describe the difference between mass and weight.Mass is the amount of matter in a substance. Weight is the amount of matter times the gravity (so your mass won’t change if you go on the moon, but your weight will)
3.What is volume?3D space occupied by a substance
4.What is a scientific theory? Theory is a well-established explanation that has been tested
5.What is the difference between a hypothesis, a theory, and a law?Hypothesis is an educated guess (can be tested). Theory is a well-established explanation that has been tested. A law is theory with no known exceptions (extensively tested)
6.What is an observation?
7.Describe quantitative and qualitative observations.Quantitative observations are measurements (numbers). Qualitative measurements are made using the 5 senses –smell, touch, sight (color/texture/appearance), etc.
8. Explain if the shape is definite and if the volume is definite for:
- Solid: definite shape and volume
- liquid: definite volume, not a definite shape.
- Gas: not a definite volume nor shape.
9.Graphing: Table 1 shows data collected about the study habits of law school students. For each candidate, they recorded how much time they spent studying and the score they received on the test. Graph the following data on the graph to the right, then answer the questions. Remember to include a title, axis labels, and an appropriate scale.
- What is the dependent variable? ___Score earned__
- What is the independent variable? ___days studied____
- Draw a line of best fit on the graph.
- Does the graph have a positive or negative correlation? _positive__
- If a student studied for 10 days, what would you expect their score to be? __depends on line of fit__
- Is this extrapolation or interpolation? ___extrapolation (off the line)___
- Write a sentence describing the relationship between days studied and score earned. Answers will vary.
10.What is a physical property?Describes the appearance of a substance.
11.What is a physical change?Substance remains the same, but appearance changes (size, shape, state of matter, etc).
12.What is a chemical property?How a substance will react
13.What is a chemical change?Substance reacts to form a new substance (change in color, temperature, formation of bubbles, etc).
14.Classify each of the following as a physical property or a chemical property:
a. ability to conduct heat PP
b. ability of a compound to decompose into its elements CP
c. ability of a compound to change from a gas to a liquid PP
d. compressibilityPP
15.Classify each of the following as a chemical change or a physical change:
a. sleet (watery hail) is formed into rain PC
b. a piece of paper is burned CC
c. butter is melted PC
d. clothes are dried PC
e. a piece of bread is toasted CC
16.Identify each of the following as an example of a physical (P) change or a chemical (C) change:
a. the baking of bread C b. the melting of iron P c. the dissolving of sugar in waterP d. tarnishing of silverC
17.What is the equation for percent error?
18.Describe accuracy and precision. Accuracy is how close your measured value is to the accepted value. Precision is how close your measurements are to each other.
19.What is the percent error of a length measurement of 0.229 cm if the correct value is 0.225 cm? 1.78%
20.What are the SI units for length? _m_ for mass? _g_for volume? _L_ for temperature? _K_
21.What is the density of 5.3 lbs of oak that has a volume of 25.7 cm3? Give your answer in g/ml!
5.3 lbs 2404 grams25.7cm3 25.7mLD = m/V = 2404/25.7 = 94 g/mL
22.How many kilometers in 15 miles? 24 km
23.How many seconds are in 1 year? Show your work in proper format!! 3 x 107 seconds
24.How many cm in a 100 yard football field? Show your work in proper format!! (Hint: 2.54 cm = 1 inch)
9000 cm
25.How many significant figures does each number have?
- 0.00003 1
- 8 000 000 1
- 203.050 6
- 0.003050 4
- 500.033 6
- 4.0 x 1032
26.Express the following in scientific notation:
- 55 000 000 000 5.5x1010
- 0.0022 2.2x10-3
- 65 200 6.52x104
27.Take the following out of scientific notation and write them in long/standard form:
- 4.5 x 1034500
- 3.90 x 10-40.000390
- 6.02 x 105602000
28.Perform the calculations and round off each answer to the correct number of significant figures.
a. 162.1g + 38.73g + 1.554g =202.4 gb. 21.9m - 6.34m + 157m =173 m
c. 9.88cm x 7.2 cm =71 cm2d. 44.75 g / 1.62 L=27.6 g/L
29.Express the following quantities in scientific notation
a. 6006x102b. 7770 7.77x103 c. 0.125 1.25x10-1d. 0.00000252.5x10-6
30.At a track meet, you time a friend running 100 m at 11.00 seconds. The official time of her race is 10.87 seconds. What is your % error?1.196%
31.Express each of the following as a whole number or decimal (not in scientific notation).
a. 2.5 x 1032500b. 6.25 x 10-6 0.00000625
32.How many significant figures are there in each of the following measurements? What type of measurement are they?
a. 7.009 km 4 lengthb. 0.008 m 1 length c. 48.2 g 3 massd. 0.0080 m 2 length
33.Calculate the following quantities using dimensional analysis
a. 100 cm = 1m b. 1000 cm = 10m c. 752 m = 0.752 km d. 53 km = 53000m
Unit 2 – Heat & Energy in the Earth’s System
34.What is energy? What are the two types of energy? What are the 3 types of energy transfer?Energy is the ability to do work or transfer heat. Kinetic & potential. Radiation, convection, conduction. You should be able to define them all!
35.What is Radioactivity? How do half-lives relate to radioactivity?Radioactivity is when an unstable nucleus releases energy in the form of particles to get more stable. Half-life is how long it takes half of the radioactive material to decay (change into a more stable nucleus)
36.What is the difference between temperature and heat (enthalpy)?Temperature is average kinetic energy. Heat is the transfer of energy between objects.
37.What is calorimetry & what is a calorimeter? Calorimetry is the study of energy changes as they related to chemical reactions. A calorimeter is an insulated structure used to measure the energy transfer between two objects by measuring the change in temperature.
38.What is specific heat? What are the units of specific heat? What is the specific heat of water?Specific heat is the amount of energy required to raise one gram of a substance by 1°C. Specific heat is different for every substance. Units are J/g°C or cal/g°C. The specific heat of water is 4.184J/g°C
39.A student must use 225 mL of hot water in a lab procedure. Calculate the amount of heat required to raise the temperature of 225 g of water from 20.0°C to 100.0°C. 75300 J
40.A 40.0 g sample of ethanol releases 2952 J as it cools from 50.0 °C. Calculate the final temperature of the ethanol. (Specific heat of ethanol is 2.46J/g°C) 20.0°C releases means the Q value was negative to start with.
41.Calculate the heat change involved when 2.00 kg of water is heated from 20.0°C to 99.7°C in an electric kettle.
667,000 J (need to convert kg to g first)
42.Calculate the specific heat capacity of titanium if a 43.56 g sample absorbs 0.476 kJ as its temperature changes from 20.13°C to 41.06°C. 0.522J/g°C (need to convert kJ to J first)
43.A 63.5 g sample of an unidentified metal has a specific heat capacity of 1.23J/g°C. How much energy (in calories) is absorbed when its temperature changes by 4.56°C? 85.1 cal
44.A 125 gram block of iron at 95°C is placed in 25.5 grams of water at 45°C. The iron cools to 75°C. What is the specific heat of the iron? (Hint: Qwater = -Qiron) 1.28J/g°C
45.Uranium-238 is one of the radioactive nuclides sometimes found in soil. It has a half-life of 580 years. What percentage of a sample is left after 1740 years? 12.5%
46.Cesium-133, which is used in radiation therapy, has a half-life of 15 years. What was the size of the original sample if after 120 years you now have 16.0 grams? 4096 grams
47.The half life of plutonium-239 is 24,110 years. If an original mass is 100. g, how much will be left after 96,440 years? 6.25g
48.What is the theory of plate tectonics? What are the three types of plate boundaries? What topographical (land) features are formed at each boundary? Plates (lithosphere/crust of the earth) float on the asthenosphere and move (slowly) because of convection cells in the asthenosphere. Convergent, divergent, transform. Continental-continental Convergent = mountains, continental-oceanic = volcanoes, oceanic-oceanic = island arc, oceanic-oceanic divergent= seafloor spreading. Transform = earthquakes
49.How do convection currents in the asthenosphere get created? How do convection currents relate to plate tectonics?Heat from earth’s core heats up the asthenosphere as it gets close so it rises towards the surface where it cools and falls back down. Circular motion. Currents are what move the plates.
Unit 3 – The Atom, Nuclear Chemistry & The Periodic Table
50.Name and describe the 3 subatomic particles (describe their charge, location in the atom, & mass)
Proton (positive in nucleus), neutron (neutral in nucleus), electron (negative orbits nucleus)
51.How do you find the neutrons in an atom? Mass # (rounded) – Atomic Number
52.For Lithium find:
- Atomic number –3c. Protons -3e. Neutrons -4
- Mass number –7d. Electrons -3
53.Define an ion. Define an isotope. Atom that gains or loses electrons. Isotope is the same element, different number of neutrons
54.Two isotopes of Iodine-127 and iodine-131. Compare their:
a. atomic numbersboth are 53b. mass numbers 127 and 131
c. number of protons & neutrons 53 protons for each, I-127 has 74 neutrons, I-131 has 78 neutrons
d. complete nuclear symbols
55.12. Fill in the missing data in the table below
symbol / He / W / Pb / U / MoAtomic # / 2 / 74 / 82 / 92 / 42
Mass # / 4 / 184 / 210 / 235 / 95
# of protons / 2 / 74 / 82 / 92 / 42
# of neutrons / 2 / 110 / 128 / 143 / 53
# of electrons / 2 / 74 / 82 / 92 / 42
56.Fill in the following table. Watch out for IONS and ISOTOPES!
Name(hyphen notation) / Symbol () / Atomic Number / Mass Number / Protons / Neutrons / Electrons
Calcium—39 / 3920Ca+2 / 20 / 39 / 20 / 19 / 18
Bismuth – 207 / / 83 / 207 / 83 / 124 / 86
Technetium – 98 / 9843Tc+1 / 43 / 98 / 43 / 55 / 42
Barium – 138 / 13856Ba+2 / 56 / 138 / 56 / 82 / 54
Xenon—130 / 13054Xe / 54 / 130 / 54 / 76 / 54
57.The most abundant isotope of lead contains 82 protons & 124 neutrons packed closely together in the nucleus. Why do protons stay together in the nucleus rather than fly apart?
a. Electrons in neighboring atoms neutralize repulsive forces between protons.
b. Neutrons effectively block the protons and keep them far apart to prevent repulsion.
c. Electrostatic forces between neutrons and protons hold the nucleus together.
d. Nuclear forces overcome repulsive forces between protons in the nucleus.
58.What is the History of the Atom? (Democritus, Dalton, Thomson, Rutherford, up to Bohr) Review your notes and video notes online!
59.Which statement best describes the density of an atom’s nucleus?
a. The nucleus occupies most of the atom’s volume but contains little of its mass.
b. The nucleus occupies very little of the atom’s volume and contains little of its mass.
c. The nucleus occupies most of the atom’s volume and contains most of its mass.
d. The nucleus occupies very little of the atom’s volume but contains most of its mass.
60.What is the neutron –proton ratio of the most stable nuclei according to the ‘band of stability’?
Even numbers.
61.Describe what happens in the following nuclear processes.
- alpha –releases a helium particleb. beta –releases an electronc. gamma –releases energy
d. Positron emission – releases a positrone. electron capture – electron on reactants side
62.Complete the following nuclear reactions, then give the type of decay:
- 23993Np 0-1β + 23994PuType of decay: ___beta______
- 158O 157N + 0+1eType of decay: __positron emission______
- 94Be 52He + 42HeType of decay: ___Alpha___
- 33*15P 3315P +00ɣType of decay: ___gamma____
63.Types of nuclear decay (Alpha, beta, gamma, positron emission, and electron capture)
(a) Identify the types of decay:
Rn Po +42HeThis is ___alpha decay___.
F + 0-1e OThis is ____electron capture______.
U He + 23190ThThis is ____alpha decay______.
Xe 0+1e + 11853IThis is positron emission.
(b) Write the following nuclear decay equations:
Sodium-23 undergoes electron capture. 2311Na + 0-1e 2310Ne
An alpha particle is shot at an unstable isotope to produce Barium-138. 42He + 13454Xe13856Ba
Lead-208 is produced from alpha decay.21284Po 20882Pb + 42He
Ru-103 goes through positron emission.10344Ru 0+1e + 10343Tc
Beta decay of Tin-119 resulted in a stable isotope and a gamma particle.
11950Sn 00ɣ + 0-1e + 11951Sb
64.Draw a wave and label the wavelength and frequency.
65.How is energy related to wavelength? How is it related to frequency?
66.Which color of light is the highest energy? Which color is the lowest energy?Violet (purple). Red
67.What is thermoluminescence (think of the flame test lab)? Explain using words like ground state, excited state, absorb energy, release energy, and light. Heat (energy) is absorbed by the electrons so they jump from ground state (low energy level) to excited state (high energy level). When they release the energy (in the form the light) they go back to ground state.
68.Give the names and symbols of the elements that correspond to the atomic numbers 10, 16, & 3.
Neon (Ne), Sulfur (S), Lithium (Li)
69.Name, by number, both the period and group that each element in the previous question is in.
Neon is in period 2 and group 18. Sulfur is in period 3 and group 16. Lithium is in period 2 and group 1.
70.Mendeleev arranged the modern periodic table in order of increasing:
a. atomic numberb. atomic massc. both of thesed. none of these
71.Why is cobalt (Co) placed before nickel (Ni) on the periodic table of the elements even though it has a higher average atomic mass than nickel?
a. Nickel has one more proton.b. Cobalt was discovered first.
c. Nickel has fewer electrons.d. Cobalt has a lower density.
72.Which of the following atoms has the largestatomic radius?
a. barium b. chlorine c. iodine d. magnesium
73.List the following atoms in order of increasing electronegativity: Na, I C, K, Br. K, Na, I, C, Br
74.Identify the atom with the larger radius in each of the following pairs.
a. S and Ob. O and F c. Na and K
75.Which of the following ordered pairs of elements shows an increase in atomic number but a decrease in average atomic mass?
a. Ag to Pd b. Co to Ni c. Ge to Sn d. Cr to Mo
76.Iodine would have chemical properties most like
a. manganese b. tellurium c. chlorine d. xenon (Xe)
77.What are valence electrons? What is the octet rule? What does it mean? Outermost electrons. Each element (except hydrogen/helium) wants to get a stable octet (8 electrons) in their outmost shell (energy level) because that’s the most stable.
78.Describe anions. Describe cations. Anions are atoms that have gained electrons (negative charge). Cations are elements that have lost electrons (positive charge).
79.Why are the noble gas elements so stable (inert)? They have a stable octet so their energy level is full and they won’t react.
80.Define ionization energy –Energy required to turn the atom into an ion.
81.Define electronegativity –How badly the atom wants to gain/lose an electron to get a stable octet. Fluorine is the most electronegative.
82.Define atomic radius – The distance from the nucleus to the electron cloud edge.
83.Define electron affinity –How badly an atom wants to get an electron.
84.Define reactivity – How likely the atom is to form bonds.
Unit 4 – Matter, Molecules & Bonding
85.Name 2 categories of matter. Pure Substances and Mixtures
86.What is the difference between a homogenous mixture and a heterogeneous mixture? How can you tell them apart?Homogeneous is uniform throughout. Heterogeneous you can see distinct differences/layers throughout the mixture.
87.What is the difference between an element and a compound?Element is one type of atom. Compound is 2+ atoms of different elements.
88.Indicate which of the following is an element, compound, heterogeneous mixture or homogeneous mixture (solution).
a. ocean waterHOMf. milkHOMk. zinc nailE
b. calciumEg. sugarCl. woodHET
c. vitamin Ch. paperHOMm. airHOM
d. dry ice (carbon dioxide)Ci. Aluminum foilEn. distilled water C
e. copper Ej. table saltCo. peanutHET
89.What is the equation for density?D = m/V
90.What is volume of a cube that weighs 250 g and has a density of 3.5 g/mL? 71mL
91.What is the mass of a substance that has a volume of 30 mL and a density of 40 g/ mL? Give your answer in kilograms. 1.2kg
92.You are given a blue liquid. You determine the mass to be 64.8 g. You observe the volume to be 54.0 cm3. What is the liquid’s density? 1.2g/cm3
93.Describe metallic bonds (what happens with the electrons and their properties) Between metal atoms – sea of electrons
94.Describe ionic bonds (what happens with the electrons and their properties)between metal and a nonmetal. Metal gives up the electrons, nonmetal takes the electrons. (TRANSFER/STEALING)
95.Describe covalent bonds (what happens with the electrons and their properties) between two nonmetals. Share electrons to get a stable octet.
96.Use electronegativity to explain why metal + non-metal is an ionic bond while non-metal + non-metal is a covalent bond. Metal’s electronegativity is VERY low and nonmetal is very high. So the difference is great and the metal is too “weak” to hold on to its electrons. When it’s two nonmetals their electronegativities are close so they share because neither is strong enough to steal.
97.Draw dot diagrams for the following molecules and ions:
a. H2Ob. O2
c. H2SO4 d. OH-