52 terms

Chemistry Chapter 2 Review

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Why must a measurement include both a number and a unit?
To improve specificity and clarity
Explain why standard units of measurement are particularly important to scientists.
So that measurements and results can be understood and compared universally
What role do prefixes play in the metric system?
Prefixes modify the units, making them easier and faster to write
How many meters are in one kilometer? In one decimeter?
1000 m in a km and 10m in a dm
What is the relationship between the SI unit for volume and the SI unit for length?
The SI unit for volume is the cubic meter and the SI unit for length is the meter. Volume and length are related by the fact that you can take three lengths and multiply them together and you will get the volume
Explain how temperatures on the Celsius and Kelvin scales are related
Celsius and Kelvin have a linear relationship. Meaning, in order to go between any value in Celsius to kelvin one merely needs to add 273 and when going from kelvin to Celsius simply subtract 273
A 5-mL sample of water has a mass of 5 g. What is the density of water?
1 g/mL
The density of aluminum is 2.7 g/mL. What is the volume of 8.1 g?
3 mL
Formula for density
Density= mass over volume
Or
D=m/v
An object with a mass of 7.5 g raises the level of water in a graduated cylinder from 25.1 mL to 30.1 mL. What is the density of the object?
1.5 g/mL
The directions in the candy recipe for pralines instruct the cook to remove the pot containing the candy mixture from the heat when the candy mixture reaches the soft-ball stage. The soft-ball stage corresponds to a temperature of 236°F. After the soft-ball stage is reached, the pecans and vanilla are added. Can a celsius thermometer with a range of -10°C to 110°C be used to determine when the soft-ball stage is reached in the candy mixture?
No
How does scientific notation differ from ordinary notation?
Scientific notation adds uniformity to answers and puts them in terms of a number times a power of 10 instead of just a number
If you move the decimal place to the left to convert a number to scientific notation, will the power of 10 be positive or negative?
Positive
Two undefined numbers are expressed in regular notation are shown below, along with the number of places the decimal must move to express each in scientific notation. If each X represents a significant figure, write each number in scientific notation.
a. XXX.XX (move decimal 2 places to the left)
b. 0.000000XXX (move decimal 7 places to the right)
a. X.XXXX x E2
b. X.XX x E-7
When dividing numbers in scientific notation, what must you do with the exponents?
Subtract
When you convert from a small unit to a large unit, what happens to the number of units?
The number decreases
When converting from meters to centimeters, how do you decide which values to place in the numerator and denominator of the conversion factor?
M/1 = 100cm/m
Write the following numbers in scientific notation.
a. 0.0045834 mm
b. 0.03054 g
c. 438,904 s
d. 7,004,3000,000 g
a. 4.5834 x E-3 mm
b. 3.054 x E-2 g
c. 4.38904 x E5 g
d. 7.0043 x E9 g
Convert the following measurements.
a. 5.70 g to milligrams
b. 4.37 cm to meters
c. 783 kg to grams
d. 45.3 mm to meters
e. 10 m to centimeters
f. 37.5 g/mL to kg/L
a. 5700 mg
b. 0.0437 m
c. 783000 g
d. 0.0453 m
e. 1000 cm
f. 37.5 kg/L
A troy ounce is equal to 480 grains, and 1 grain is equal to 64.8 milligrams. If the price of gold is $560 per troy ounce, what is the cost of 1 g of gold?
$18 per gram
The average mass of a kernel of popcorn is 0.125 g. If 1 pound = 16 ounces, and 1 ounce = 28.3 g, then how many kernels of popcorn are there in 0.500 pounds of popcorn?
1811 kernels
You have 15 g of hemoglobin in every 100 mL of your blood. 10.0 mL of your blood can carry 2.01 mL of oxygen. How many millimeters of oxygen does each gram of hemoglobin carry?
1.34 mL of oxygen
The recommended calcium intake for teenagers is 1300 mg per day. A glass of milk contain 305 mg of calcium. One class contains a volume of 8 fluid ounces. How many liters of milk should a teenager drink per day to get the recommended amount of calcium? One fluid ounce equals 29.6 mL.
1.0093 L
Which zero is significant in the number 50,540? What is the other zero called?
In the number 50,540 the first zero in the 50 is considered to be a significant number, while the second (in the 540) is not. The second zero is a called a placeholder zero and can be removed by converting the number into scientific notation
Why are the percent error values negative?
Because a line graph is used to depict change over time
If you report two measurements of mass, 7.42 g and 7.56 g, are the measurements accurate? How might you evaluate the precision of these measurements? Explain your answer.
There is no way to assume that the two measurements are not accurate, as they have nothing to be accurate to. However, they are within .1g of each other, so we can assume that they are precise. In order to be accurate, they must have a scientifically measured and trusted measurement to be accurate with. But to be precise, they only need to be the same or similar with each other
Which produce the same number when rounded to three significant figures: 3.456, 3.450, or 3.448?
3.450 and 3.448
When subtracting 61.45 g from 242.6 g, which value determines the number of significant figures in the answer? Explain.
The one with the smallest number of significant figures
Round each number to four significant figures.
a. 431,801 kg
b 10,235.0 mg
c. 1.0348 m
d. 0.004384010 cm
e. 0.00078100 mL
f. 0.0098641 cg
a. 431800 kg
b. 10240 mg
c. 1.0350 m
d. 0.004384 cm
e. 0.0007810 mL
f. 0.009864 cg
The accepted length of a steel pipe in 5.5 m. Calculate the percent error for each of these measurements.
a. 5.2 m
b. 5.5 m
c. 5.7 m
d. 5.1 m
a. 5.5%
b. 0%
c. 3.6%
d. 7.3%
The accepted density for copper is 8.96 g/mL. Calculate the percent error for each of these measurements.
a. 8.86 g/mL
b. 8.92 g/mL
c. 9.00 g/mL
d. 8.98 g/mL
a. 1.12%
b. 0.446%
c. 0.446%
d. 0. 223%
Which type of graph would you use to depict how many households heat with gas, oil, or electricity? Explain.
A bar graph because it is depicting quantitative data about unrelated qualitative x values
Which type of graph would you choose to depict gasoline consumption over a 10-year period? Explain.
A line graph because you're observing over a 10 year period and line graphs depict change over time
base unit
a defined unit in a system of measurement that is based on an object or event in the physical world is independent of other units
second
the SI unit for time
meter
the SI base unit for length
kilogram
the SI base unit for mass
kelvin
the SI base unit of temperature
derived unit
a unit defined by a combination of base units
liter
the metric unit for volume equal to one cubic decimeter
density
the amount of mass per unit volume; a physical property
scientific notation
expresses any number as a number between 1 and 10 (known as a coefficient) multiplied by 10 raised to a power (known as an exponent)
dimensional analysis
a systematic approach to problem solving that uses conversion factors to move from one unit to another
conversion factor
a ration of equivalent values used to express the same quantity in different units; is always equal to 1 and changes the units of quantity without changing its value
accuracy
refers to how close a measured value is to an accepted value
precision
refers to how close a series of measurements are to one another; precise measurements show little variation over a series of trials but might not be accurate
error
the difference between an experimental value and an accepted value
percent error
the ration of an error to an accepted value
significant figures
the number of all known digits reported in measurements plus one estimated digit
graph
a visual display of data
Percent error equation
PE= error/accepted value X 100
Kelvin-Celsius Conversion Equation
K= C + 273
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