Physical Sciences 1000 - Term 1 2005 - MidTerm B
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4) How might you distinguish a sodium-vapor street lamp from a mercury-vapor street lamp? 4) ______
A) Ask your local utility company to identify these lamps for you.
B) Use binoculars to look for printing adjacent to the bulb.
C) Look at the street lamps through a spectroscope and match their spectral patterns to their respective atomic spectra.
D) The shadows cast from a sodium-vapor street lamp tend to be more diffuse around the edges.
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10) The circles in the boxes shown above represent the submicroscopic particles of a material in its three phases. From left to right these are 10) ______
A) gas, solid, and liquid. B) gas, liquid, and solid.
C) solid, liquid, and gas. D) liquid, solid, and gas.
11) During a chemical reaction 11) ______
A) old atoms transform into new ones.
B) old atoms disappear to be replaced by new ones.
C) old atoms stick around merely switching partners.
D) none of the above
12) Is the following transformation representative of a physical change or a chemical change?
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A) physical change because a new material has been formed
B) chemical change because of the formation of elements
C) chemical change because the atoms are connected differently
D) physical change because of a change in phase
13) Mixtures can be separated into their components by taking advantage of differences in the chemical properties of the components. Why might this separation method be less convenient than taking advantage of differences in the physical properties of the components? 13) ______
A) A chemical property involves a chemical change so that you no longer have what you had.
B) The chemical properties of the components of a mixture are too similar to each other.
C) The chemical properties of the components of a mixture are too different from each other.
D) Chemical properties are not as apparent as are physical properties.
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15) The oceans are salt water, and yet evaporation over the ocean surface produces clouds that precipitate fresh water. Explain. 15) ______
A) The salts are too heavy to evaporate with the water.
B) Fresh rainwater falls only after the salts have been removed by the action of the clouds.
C) Salt ions are too attracted to the liquid water to evaporate.
D) Two of the above are reasonable answers.
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21) A refrigerator delays the spoilage of food by 21) ______
A) killing microorganisms.
B) slowing down the rate of chemical reactions within microorganisms.
C) diminishing the supply of oxygen to microorganisms.
D) expanding the water found within microorganisms.
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23) Suggest why people once washed their hands with ashes. 23) ______
A) The ashes act as a base and reacts with skin oils to produce solutions of soap.
B) After being burnt in the fire, the acids and bases of the log are neutralized, making it a gentle material to use on the hands.
C) The ashes act as an acid and reacts with the skin oils to produce soap.
D) The oils on the skin act as a base and reacts with the ashes to produce soap.
24) A pH of 7 signifies 24) ______
A) an acidic solution. B) a salt solution.
C) a neutral solution. D) a basic solution.
25) A fuel cell differs from a battery in that 25) ______
A) a battery runs by oxidation while a fuel cell runs by reduction.
B) while a battery produces electricity, a fuel cell consumes it.
C) it can run indefinitely provided a continuous supply of fuel.
D) they are typically much lighter.