Key:  Homework Set 1 

1.  A junked car is neatly crushed into a compact cube.  Which of the following physical quantities remain constant as a result of this action?  Circle all that apply AND explain why each circled physical quantity remains constant.

Volume        Mass        Density        Weight        Phase of Matter

Phase of Matter - remains a solid
Mass - still same amount of matter when crushed
Weight - still same amount of matter in same gravitational field when crushed

***Volume decreases upon compacting and therefore density also must increase

2.  Circle the best answer to complete this statement:  The “Scientific Method” is a systematic means of _______________.

a.      proving a hypothesis is true.

b.     creating models to interpret experimental data.

c.      revealing if a hypothesis is consistent with experimental data.

d.      All of these are correct.

3.  Provide a definition and an example for each of the following terms:

a.      Kinetic Energy    definition: energy of motion

                               example:  arrow in flight

b.     Potential Energy   definition: energy possessed by virtue of location or position

                                example:  arrow loaded in a drawn bow

c.      Physical Property  definition: charactistic of matter such as color, melting point, 
                                                 or ability to conduct electricity

                                 example:  water is colorless, melts at 0^oC, and does not conduct
                                            electricity well (as a pure substance)

d.  Chemical Property  definition:  reactivity of matter, what other matter it does or does not
                                                     react wtih

                                 example:  elemental magnesium reacts with elemental oxygen to form
                                           magnesium oxide (a compound)

4.  The helium atoms inside a helium filled birthday balloon all slowly escape through 
the walls of the balloon and are contained inside a house.  What happens to the density 
of the helium gas as a result of this process (i.e. in the balloon versus in the house)?
            *Quantity (mass) of He remains constant.
         Inside balloon:  the density of He is relatively high (relatively small volume)
          Inside room:  the density of He is relatively low (relatively large volume)

5.  What is the difference between an element and a compound?

          Elements are made from only one type of atom, while compounds are made
          from two or more types of atoms.  Example:  Cl₂ = element, CO₂ = compound

6.  How many liters are in 1000 centiliters?  Show your work.

        1000 cL  x  (1 L / 100 cL)  =  10 L

7.  How many kilograms are in 235 pounds if there are 2.2 pounds per 1 kilogram?  Show your work.

      235 lbs  x  (1 kg / 2.2 lbs)  =  107 kg

8.   Why are elements grouped into columns (a.k.a. groups, families) on 
the Periodic Table?

        Elements in a Group, families or columns (all same) on the Periodic Table share
          similar chemical and physical properties.

9.  At what temperature does water freeze on the Kelvin scale if it 
freezes at 0^o on the Celsius scale?  Show your work.

        0^oC + 273 = 273 K

10.  Provide a definition for a theory that clearly differentiates it 
from a hypothesis or a law.  

        A detailed explanation of a natural process born out of an abundance of experimental
           data that can be used to confidently make predictions about the results of 
           (as yet) untested experiments.

11.  Describe a situation when an object can have mass without having weight.  

        Weight is the measure of mass IN A GRAVITATION FIELD.  So measuring in a zero 
        gravitational field like in outerspace would result in an object having zero weight.
        (*It would have the same mass on earth as in outerspace.)        

12.  An aspirin contains 250 milligrams of active ingredient.  How many micrograms of active ingredient does it contain?  Express your answer in scientific notation.   Show your work.

        250 mg  x  (1000 ug / 1 mg)  =  2.5 x 10⁵ ug

13.  Name the unit name and give the unit symbol abbreviation 
for energy.  (The answer is NOT energy, E !!)
        Joule, J       or       calorie, cal       or       Calorie, Cal

14.  Circle ALL the substances that are elements in the following list.     
                      Cl₂          NaCl         Co          O₃.  

        *Only NaCl is a compound.  The others are elements.

15.  (a)  Circle the atom below that is the biggest (volume, radius).    
                    F          Na          Al          Ar
     (b)  Is this atom a metal or a non-metal?

                metal

     (c)  What is the atomic number of this atom?

                11

16.  The name of an atom with the symbol, ³²S, is __sulfur_.  This (neutral) atom contains __16___

neutrons and ____16___ electrons.

17.  Which one of the following atoms (a, b, or c) corresponds to Iron-56?  Iron is atomic number 26 on the periodic table.  
(Circle the correct atom letter.)   

18.  Every atom is uniquely identified by its ______atomic number_______ which is the number of

       _____protons_____ located_____inside____  the nucleus of the atom.