Chapters 2 & 3 Review Sheet - Loudoun County Public Schools



Foundations of Matter Review Sheet

POINTS 1-5: (1 point, min 5)

1. Classify the following materials as heterogeneous mixtures, homogeneous

mixtures, compounds, or elements.

a. milkshake Mixture f. plutonium element

b. coca-cola heterogeneous mixture g. pond water heterogeneous mixture

c. multivitamin heterogeneous mixture h. Spanish omelet heterogeneous mixture

d. diamond element i. chunky peanut butter heterogeneous mixture

2. Classify the following properties as chemical or physical.

a. stability chemical b. ductility physical

3. Classify the following as chemical or physical changes.

a. flat tire ___ physical __________________

b. explosion of gas ___ chemical _________________

c. silver tarnishing ___ chemical _________________

d. scorching a shirt with an iron ___ chemical _________________

4. In gaseous substances, the individual molecules are relatively (close/far apart) and are moving freely, rapidly, and randomly.

5. How did the outcome of Rutherford’s gold foil experiment indicate the existence of a nucleus? The positive alpha particles were deflected by something very small and positively charged.

6. Write the atomic symbol ([pic]) for each of the isotopes described below. (1 point, min 3) Example: Z = 8, number of neutrons = 9 [pic]

a. the isotope of chlorine in which A= 37 [pic]

b. Z = 27, A = 60 [pic]

c. Number of protons = 26, number of neutrons = 31 [pic]

d. The isotope of iodine with a mass number of 131 [pic]

e. Z = 3, number of neutrons = 4 [pic]

Average atomic mass(7-9) (3 point, min 6)

7. Explain the difference between the mass number and average atomic mass.

Mass number is the sum of the protons and neutrons in the nucleus of an atom. Average atomic mass is a weighted average of all isotopes (mass numbers) of an element

8. The element potassium consists of two isotopes: 40K, which has a mass of 40.01 amu, and 39K, which has a mass of 39.01 amu. The average atomic mass of potassium is 39.31 amu. What is the percent abundance of each of the isotopes?

%40K = x %39K = 100% - x

39.31amu = [(x * 40.01amu) + (100% - x)* 39.01amu] / 100%

3931%amu = (x * 40.01amu) + (100% - x)* 39.01amu

3931%amu = (40.01amu)x + 3901%amu - (39.01amu)x

3931%amu = (1.00amu)x + 3901%amu

30.%amu = (1.00amu)x

30.% = x, 30.% 40K , 70.% 39K

9. If element X consists of 32.0% of atoms with a mass of 48.0 amu, 12.0 % of atoms with a mass of 49.0 amu, and 56.0% of the atoms with a mass of 50.0 amu, what is the atomic mass of element X?

AAM = [ (32.0% * 48.0amu) + (12.0% * 49.0amu) + (56.0% * 50.0amu)]/100%

AAM = [1540%amu + 588%amu + 2.80x103 %amu] / 100 = 4928% amu / 100%

= 49.28 amu

Match the scientist with their contribution to our understanding of the atom. Write the letter of the correct contribution next to each scientist's name. (½ point, min 6)

|Scientist |Contribution |

|__J___ Rutherford |a. Developed the "Uncertainty Principle" |

|__D___ Democritus |b. Measured the charge of an electron with the oil drop experiment. |

|__L___ de Broglie |c. Rejected the idea of atoms |

|__E___ Planck |d. First philosopher to describe possibility of atoms. |

|__G__ Chadwick |e. Discovered atoms emit quantum waves |

|__K__ Schrӧdinger __C__ Aristotle |f. Discovered the electron with the cathode ray experiment |

|__H__ Bohr |g. Proved the existence of neutrons |

|__B___ Millikan |h. Proposed that electrons orbit the nucleus on energy levels |

|__I___ Dalton |i. Developed the first Atomic Theory of Matter |

|__A__ Heisenberg |j. Discovered that atoms are made of mostly empty space |

|__F___ Thomson |k. Used a math equation to show that waves can describe electrons |

| |l. Proposed that electrons can behave as both particles and waves. |

Complete and classify the following nuclear equations. (1 point, min 3)

12. [pic] → [pic] + ? [pic] Beta decay

13. [pic] → [pic] + ? [pic] Beta decay

14. [pic] → [pic] + ? [pic] Alpha decay

15. ? → [pic] +[pic] [pic] Alpha decay

16. ? → [pic] +[pic] [pic] Beta decay

17. [pic] → [pic] + ? [pic] Alpha decay

Half-life (2 points, min 2)

18. After 4797 years, how much of an original 0.250 g sample of radium-226 remains? Its half-life is 1599 years.

4797 years / 1599 years = 3 half-life = 1/8 remains

1/8*0.250g = .0313g left over

19. A half-life of iodine 131 is approximately 8 days. How many mg of the original 12 mg sample will be left after 24 days?

24 days / 8 days = 3 half-life = 1/8 remains

1/8*12mg = 1.5mg left over

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