Sunday, February 7, 2010

Which of the follownig is a true statement about a 10-liter air sample?

...that has been compressed to a volume of 1-liter


a. the density of the gas remains constant


b. the density of the gas increases


c. the number of gas particles decreases


d.the mass of the sample decreases





and


A student performs an experiment three times. The results for each are as follows: 33.4 g/mL; 33.6 g/mL; and 33.5 g/mL. The actual value for the density being tested is known to be 45.7 g/mL. What can be said of the student's work?


a. the student had low precision and high accuracy


b. the student had high precision and high accuracy


c. the student had low precision and low accuracy


d. the student had high precision and low accuracy





and


true or false ? A measurement of 23.56 mL has more uncertainty than a measurement of 23.5 mL.





and


Which is an example of a chemical change?


boiling ethanol , burning gas, melting gold , dissolving sugar in water?





thanksWhich of the follownig is a true statement about a 10-liter air sample?
1) As volume goes down, with constant mass, density increases (B is the correct answer)


2) The answers are close to each other, but miss the bullseye by a lot.


(D is the correct answer, check the Wiki link below for good explanation)


3) False, its the other way around. 23.56 could range from 23.555 to 23.564 while 23.5 ranges from 23.45 to 23.54.


4) Burning gas, you cannot take the byproducts of the reaction and go backwards to make gas. The other two are phase changes, and sugar water is just dissolving sugar.

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