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Midterm Review ANSWERS 2009 - Greenwich Pulic Schools

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Midterm Review ANSWERS 2009 - Greenwich Pulic SchoolsPulic,pulic

Chemistry Name

    Midterm Exam Review 2009 Date Block

Units 1- 7 included on review sheet;

Unit 1. Measurement, Matter and Change

Measurement

1. Rank these measurements from the smallest to the largest: (hint: change all numbers to

    scientific notation) 4 md) 0.005 7 m a) 5.3 x 10

    3 -3b) 7.7 x 10 me) 5.1 x 10 m

    -2c) 4.9 x 10 m f) 0.072 m

    Correct order: e d c f b a

    2. For each of the following pairs of units, which is the larger unit?

    a) centigram or milligram centigram

    b) liter or centiliter liter

    c) calorie or kilocalorie kilocalorie

    d) millisecond or centisecond centisecond

    e) milliliter or kiloliter kiloliter

    33 3 f) mm or m m

    3. Round each of the answers given to the correct number of sig. figs.:

    a) 8.7 g + 15.43 g + 19 g = 43.13 g 43 g

    22b) 4.32 cm x 1.7 cm = 7.344 cm 7.3 cm

    c) 853.2 L ? 627.443 L = 225.757 L 225.8 L

    3 22d) 38.742 m ? 0.421 m = 92.023 m 92.0 m

4. Round off each of the following measurements to 3 significant figures:

    a) 98.473 L 98.5 L

    b) 0.000 763 21 cg 0.000 763 cg

    c) 57.048 m 57.0 m

     1

     3 and a mass of 27.2 g. What is the density of the 5. An object has a volume of 3.5 cm

    object? Show all work, units on every number, cancel units where possible, pay attention

    to sig. figs. and units in answer.

    33 D = ? g/cm m = 27.2 g V = 3.5 cm

    D = m/V = 27.2 g = 7.7714 g = 7.8 g 333 3.5 cm cm cm

    6. What is the volume of an object having a density of 1.05 g/mL and a mass of 4.85 mL?

     Show all work. units on every number, cancel units where possible, pay attention to sig. figs

     and units in answer.

     D = 1.05 g/mL m = 4.85 g

     D = m/V V = m/D = _ 4.85 g = 4.6190 mL = 4.62 mL

     1.05 g

     mL

7. Write the following measurements in scientific notation:

    2a) 572.5 km 5.725 x 10 km

    -3 b) 0.005 725 m 5.725 x 10 km

8. Write the following measurements in standard notation:

    -3a) 4.45 x 10 g 0.004 45 g

    7b) 4.45 x 10 mg 44 500 000 mg

9. A watch loses 0.15 seconds, (symbol for second is s), every day. How many minutes will

     the watch lose in 1.0 day? Show all work.: units on every number, cancel units where

     possible, pay attention to sig. figs and units in answer.

     0.15 s x 1 min = 0.0025 min

     1 day 60 s 1 day

2

Matter and Change

1. Identify each of the following as an element, a mixture, or as a compound:

    a) iced tea mixture

    b) ice compound

     c) table sugar compound

    d) silver element

     2. Classify each of the following as either a physical change or as a chemical change:

    a) bending a piece of glass PC

    b) melting an ice cube PC

    c) cooking a steak CC

    d) cutting grass PC

    e) burning wood CC

    f) sugar dissolving in water PC

    g) boiling water PC

3. Give the correct symbols for each of the following elements:

    a) sodium Na e) copper Cu

    b) aluminum Al f) magnesium Mg

     c) chlorine Cl g) iron Fe

    d) sulfur S h) nitrogen N

4. List the three common phases or states of matter: __solid_______________________,

     _________liquid__________________, and __________gas_______________.

5. Which of the following is NOT a physical property of matter? __flammability_____

     density color odor melting point boiling point

     texture flammability malleability luster

     3

Unit 2. Phase Changes and Thermochemistry

____ 1. Energy of motion is called

    A) potential B) chemical C) standard D) kinetic

____ 2. As the temperature of a substance increases, the ___ of its particles also increases.

    A) PE B) KE C) mass D) number

    ____ 3. The temperature of an object is a measure of the

    A) average KE of the particles that make up the object

    B) energy stored in the chemical bonds of the object

    C) number of joules released by the object

    D) heat content of the object

____ 4. The condensation point of pure water on the Celsius scale is ooooC B) 32.0 C C) 273.0 C D) 100.0 C A) 0.0

     o____ 5. The amount of heat energy released when 1.0 gram of a substance is cooled by 1.0 C, o (or is absorbed when 1.0 gram of the substance is heated by 1.0 C), is known as the

     ____ of the substance.

    A) heat of fusion C) heat of vaporization

    B) specific heat D) heat of cooling

    ____ 6. In order to melt ice at its melting point,

    A) crystals of ice must be physically removed

    B) heat must be removed from the ice

    C) heat must be added to the ice oD) the temperature of the ice must be above 5.0 C

7. What is temperature?

     measure of the average kinetic energy of a sample of matter

8. What does a decrease in the temperature of a substance mean with respect to the average KE

    of the particles of the substance?

As temperature decreases, the average KE of the particles of the substance also decreases.

9. What does the term absolute zero on the Kelvin scale mean?

    Absolute zero on the Kelvin scale is the theoretical lowest temperature of matter; all molecular

    and atomic motion stops (atoms and molecules no longer would vibrate).

4

10. What is heat?

    Heat is a form of energy that travels from one region or object to another region or object when there is a difference in temperature between the two regions or objects. Heat will travel from the region or object at the higher temperature to the region or object at the lower temperature until the two regions or objects are at the same temperature.

11. What is the difference between evaporation and boiling?

    Evaporation is the change of state from a liquid to a gas AT THE SURFACE of the liquid; evaporation can occur at temperatures BELOW the normal boiling point of the liquid.

    Boiling is the change of state from a liquid to a gas WITHIN THE LIQUID when the vapor pressure of the liquid is equal to the atmospheric pressure on the surface of the liquid.

     ooC cools to 10.0 C ? 12. What quantity of heat is released when 44.0 g of liquid water at 24.0. o (Specific heat of water = 4.18 J/(g)(C) ) (SHOW ALL WORK!)

     oooQ = m x ;T x c; Q = ? J; m = 44.0 g; ;T = (T-T) = (10.0 C ? 24.0 C) ?14.0 C; 21o c = 4.18 J/(g)(C)

     o Q = 44.0 g x ?14.0 C x 4.18 J = ?2 574.88 J = ? 2570 J o (g)(C)

     o413. What quantity of water at its melting point will be warmed to 10.0 C by 1.18 x 10 J of o heat? (Specific heat of water = 4.18 J/(g)(C) ) (SHOW ALL WORK!)

Q = m x ;T x c; m = Q/ ;T x c 4ooooQ = 1.18 x 10 J; m = ? g; ;T = (T-T) = (10.0 C - 0.0 C) = 10.0 C; c = 4.18 J/(g)(C) 21

     4m = 1.18 x 10 J = 282.297 g = 282 g o (10.0 C x 4.18 J o (g)(C)

     oo14. What is the specific heat of silver if a 93.9 g sample cools from 215.0 C to 196.0 C with

     the loss of 428 J of heat energy? (SHOW ALL WORK!)

Q = m x ;T x c; c = Q/ m x ;T

    ooooQ = - 428 J; m = 93.9 g; ;T = (T-T) = (196.0C - 215.0 C) = -19.0 C; c = ? J/(g)(C) 21

c = - 428 J_________ = 0.239 89 J = 0.240 J ooo93.9 g x -19.0 C (g)(C) (g)(C)

     5

    oC? 15. How many calories of heat are required to evaporate 250.00 g water at 100.0

     ( H = 540.0 cal/g ) (SHOW ALL WORK!) v

Q = H x m Q = ? cal H = 540.0 cal/g m = 250.00 g vv

    5Q = 540.0 cal x 250.00 g = 135 000 cal = 1.350 x 10 cal

     g

Unit 3. Energy and Energy Transformations

    ____ 1. A flowing stream of water that turns a paddle wheel is an example of

    A) chemical energy transformed to mechanical energy

    B) mechanical energy transformed to potential energy

    C) mechanical energy being used to do work

    D) potential energy being used to do work

____ 2. You plug in a radio and turn the radio on. As you are listening to the music, the energy

    transformations that are occurring are

    A) chemical energy to electrical energy to sound energy

    B) electrical energy to sound energy

    C) mechanical energy to chemical energy

    D) sound energy to electrical energy

    ____ 3. In the lab Heat of Fusion of Ice, the primary source of heat energy was the

    A) ice cubes

    B) ice and water mixture

    C) hot water

    D) room air

____ 4. Heat energy flows

    A) between bodied regardless of their individual temperatures

    B) between bodies that are at the same temperature

    C) from a body at a lower temperature to a body at a higher temperature

    D) from a body at a higher temperature to a body at a lower temperature

6

    5. A metal spoon is placed in a cup of hot tea. After a short time, the handle of the spoon is

     too hot to hold in your hand. Explain why and how the spoon handle became too hot to

     handle.

a) WHY (give the reason) the spoon handle became too hot: heat energy from the hot water

    was absorbed by the metal atoms in the spoon; the temperature of the spoon handle

    increased and became much hotter than the temperature of your hand;

    b) HOW (explain the process) the spoon handle became too hot: heat energy was absorbed

    by the metal atoms in contact with the hot water by conduction (particle to particle transfer

    of energy); the metal atoms continued to conduct the heat energy along the length of the

    spoon; at the spoon handle, heat energy was radiated into the air (and conducted to those

    air molecules that were in contact with the spoon handle) surrounding the spoon handle

    but the density of air is very low compared to the density of the metal so the spoon handle

    became very hot since heat didn’t radiate very quickly.

    6 a. Describe HOW magma moves between the hot core of the earth and the crust of the earth. Magma is molten rock and is much more liquid near the hot core of the earth that it is near the crust of the earth. The hotter more liquid magma rises toward the crust; once near the crust, the magma then sinks back toward the core.

b) What is the name of the process by which magma moves between core and crust of the earth?

    ______convection currents___________________________________

c) Explain WHY the magma moves as it does between core and crust?

    Magma moves as it does because the hotter more liquid magma near the core is less dense than the cooler magma near the crust. The less dense magma rises toward the crust. As it rises, the magma cools and becomes more dense the closer it gets to the crust. This cooler more dense magma sinks back toward the core and the cycle is repeated.

     7

Unit 4. Atomic Structure

    1. Complete the following table assume neutral atoms. Use your periodic table as a reference.

     Element # protons Mass # # electrons Atomic # # neutrons

     K 19 39 19 19 20

     P 15 31 15 15 16

     Ca 20 40 20 20 20

     Mg 12 24 12 12 12

    2. For each of the following atoms, give the atomic number and mass number:

    36a) Ar atomic #: 18 mass #: 36 18

    79b) Br atomic #: 35 mass #: 79 35

Complete the following sentences:

    3. The atomic number is determined by the number of protons in an atom.

    4. In a neutral atom, the number of protons equals the number of electrons .

    5. The mass number is determined by the total number of protons and neutrons .

    6. The difference in mass of isotopes of the same element is due to different numbers of

     _neutrons__ in the nucleus of the atoms.

     7 _____ 7. How many electrons are in a neutral atom of Li? 3

    A) 7 B) 10 C) 3 D) 4

     19_____ 9. The nucleus of a fluorine atom, F, has a total electrical charge of 9

    A) 1+ B) 9+ C) 19+ D) 0

    _____ 10. The atomic mass number of any atom is equal to the total number of its

     A) electrons only C) electrons and protons

     B) protons only D) protons and neutrons

8

Unit 5. Electrons in Atoms and Electromagnetism

_____ 1. As the wavelength of light increases, the frequency

     A) increases C) approaches the speed of light

     B) remains the same D) decreases

_____ 2. The number of wave cycles that pass a given point per unit of time is called the

     A) frequency B) amplitude C) wavelength D) crest

    _____ 3. The color of the bright lines in an emission spectrum are due to

    A) low wave amplitudes of energy being absorbed by electrons

    B) specific frequencies of energy being emitted by electrons

    C) high wave amplitudes of energy being emitted by an electron

    D) low frequencies of energy being absorbed by electrons

    _____ 4. Which of the following does NOT involve electromagnetic radiation?

    A) getting a suntan C) listening to the radio

     B) shining a flashlight at night D) floating on a raft in the ocean

_____ 5. Each color of visible light has its own

     A) amplitude C) frequency only

     B) wavelength only D) frequency and wavelength

    _____ 6. A photon of red visible light has more energy than

    A) a photon of yellow light C) radiowaves

    B) ultraviolet light D) a photon of green visible light

_____ 7. The light energy emitted by an “excited” electron is

    A) lost as the electron returns to a higher energy level

    B) lost as the electron returns to a lower energy level

    C) gained as the electron returns to a lower energy level

    D) gained as the electron returns to a higher energy level

     9

_____ 8. The major weakness in Rutherford’s model of the atom was that

    A) negatively charged electrons orbited the positively charged nucleus

    B) there was no explanation of why there were no neutrons in the nucleus

    C) there was no explanation of why the negatively charged electrons didn’t fall

    into the positively charged nucleus

    D) there was a dense positively charged nucleus

    _____ 9. A correct listing of electromagnetic radiation, in order of increasing energy, is

    A) X-rays, visible yellow, infrared, microwaves, radiowaves, visible violet

    B) radiowaves, infrared, ultraviolet, X-rays, gamma rays

    C) visible blue, infrared, ultraviolet, radiowaves, microwaves

    D) infrared, radiowaves, microwaves, ultraviolet, visible violet

    _____ 10. When an element is heated sufficiently to excite its electrons and the emitted light is

    passed through a diffraction grating or a prism, you would expect to observe

     A) a continuous spectrum C) a single color

    B) a bright-line spectrum D) white light

Match the atomic model with the appropriate scientist or theory name

    _D_ 11. John Dalton A) dense positively charged nucleus with negatively

     charged electrons moving around the nucleus

    _A__ 12. Ernest Rutherford B) positively charged sphere in which negative charges

    are uniformly distributed

    _B__ 13. J.J. Thomson C) tiny, indivisible bits of matter; different kinds of

     matter made of different kinds of atoms

    _E__ 14. Niels Bohr D) tiny invisible spherical bits of matter having a

    uniform density and which combine in definite

    proportions to form compounds

    _C__ 15. ancient Greeks E) dense positively charged nucleus with negatively

    charged electrons moving at fixed distances from the

    nucleus; electrons could move from one level to a

    higher level if sufficient energy is absorbed

    _F_ 16. modern atomic theory F) dense positively charged nucleus around which

    electrons move in areas of highest probability

    10

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