UNIT 2 REVIEW ANSWERS
1. Scientific Notation
a. Know how to write numbers
Convert the following numbers into scientific notation.
1. 0.000000009543 km
9.543 x 10-9 km
2. 856400000 mL
8.564 x 108 mL
3. .0253 cm
2.53 x 10-2 cm
4. 23186 dg
2.3186 x 104 dg
b. Know to add/subtract and multiply and divide using calculator
1. 6.23 x 106 kL + 5.24 x 106 kL =
1.15 x 107 kL
2. 9.87 x 104 g – 6.2 x 103 g =
9.3 x 104 g
3. 3.3 x 10-4 mL2 ÷ 1.1 x 10-6 mL =
3.0 x 102 mL
4. 3 x 10-4 m ● 4 x 10-5 m =
1 x 10-8 m2
2. Know definition and SI units for mass, length, time, temperature, volume and the name of the
equipment used to measure these.
a. Next to the equipment pictures write the name of the equipment, what it measures,
and the unit it measures in.
Beaker
Volume
SI Unit Liters
Lab unit mL
Triple Beam Balance
Mass
SI Unit kilogram
Lab unit gram
Graduated cylinder
Volume
SI Unit Liters
Lab unit mL
Thermometer
Temperature
SI unit Kelvin
Lab unit °C
Ruler
Length
SI unit meters
Lab unit cm
3. A 2.70-kg block of aluminum is melted. The resulting liquid is divided equally between 36
square molds. What is the mass, in grams, of each square that is produced when the liquid
solidifies? Report your answer to the correct number of significant figures.
75g
4. What type of property is density, physical or chemical? If physical, is it extensive or
intensive? Give the definition of the property you chose? What does it mean? Under what
conditions could a substance’s density change? Explain
Density is a physical intensive property. An intensive property is the same no matter how
much of the substance is present. So as long as the state of the substance you are
comparing is the same, then the density will be the same. However, if a substance’s state
changes, then the density will change especially from a solid to a gas because a gas fills
the container so the volume increases thereby decreasing the density.
5. Know the units for density and given the density of two objects, which will float.
The units for density are g/mL or g/cm3. The less dense object will float.
a.
The table shows some properties of four different substances. The picture shows a solid
sphere of one of the four substances in a water-ethanol solution (D = 0.9319 g/mL). The
sphere is most likely composed of which substance?
Substance Q
6. Calculate density, volume, or mass using the density formula. In addition, be able to identify
metal from a table after calculating density.
a. Find the density when mass = 3.04 g and volume V= 33.4 mL
D = m/V = 3.04 g/33.4 mL = .0910 g/mL
b. Find mass when density is 3.25 g/mL and volume is 12.45 mL
m = D●V = 3.25 g/mL ● 12.45 mL = 40.5 g
c. Find volume when density is 1.35 g/mL and mass is 33.63 g
V = m/D = 34. g/1.35 g/mL = 25 mL
d. Read the volume below and then calculate the mass of a substance having a density of
.79 g/mL.
V = 43.0 mL
m = V●D = 43.0 mL ● .79 g/mL = 34 g
e. If an empty graduated cylinder has a mass of 5.66 g and the cylinder with liquid
measures 10.22 g, what is the density of the liquid if the volume is 6.8 mL?
m = 10.22 g – 5.66 g = 4.56 g
D = m/V = 4.56 g/6.8 mL = .67 g/mL
f. Use the diagram below to calculate the density of a solid having a mass of 27 g.
V = 23.0 mL – 20.0 mL = 3.0 mL
D = m/V = 27 g/ 3.0 mL = 9.0 g/mL
g. A student finds a shiny piece of metal that she thinks is gold. In the lab she
determines that the volume of the metal is 31.1 cm3 and a mass of 600g. Is this metal
gold? (Density of gold = 19.3g/mL)
D = m/V = 600 g/31.1 cm3 = 20 g/cm3 Yes.
7. a. Define accuracy and precision.
Accuracy is how close a measurement is to the known value.
Precision is how close a group of measurements are to each other.
b. The following length measurements were taken by students. The known value is 16.3 cm. Is the
data set below accurate, precise, neither or both?
15 cm, 14.9 cm,15.1 cm, 14.8 cm,15.2 cm
Precise
C. The actual density of iron is 7.86g/cm3. Scott ran his experiment three times and
calculated the following densities for iron: 7.88, 7.86, 7.87. Are his answers accurate,
precise or both?
Both accurate and precise
8. a. Be able to determine the number of sig figs.
1. 0.0670
sig figs=___3_____
2.
3.0 x 107
sig figs=___2_____
1. 1008.
sig figs=___4_____
4.
6060.
sig figs=____4____
5. 500
sig figs=____1____
b. Know and apply the rules for sigfigs. +/-, */÷
1. 43.2 cm + 102.0 cm + 1.635 cm=_______146.8 cm___________
2. 589.7165 L – 56.323 L – 7.5 L = ________525.9 L__________
3. 12560 g x 25.0314 g = __________314400 g2_______
4. 65000 m / 234 m = ________280_________
5. 2.070 mL x 10.5 mL x 3000 mL = _____70000 mL3_____________
c. Know how to round to the proper sig figs.
Round each number to 4 sig. figs.
1. 431801 kg
431800 kg
3. 1.0348 m
1.035 m
2.
0.004384010 cm
4.
0.0098641 cg
0.004384 cm
0.009864 cg
9. a. Be able to do Metric conversions
1. 550g= .550 kg
2. 1.5cm= .015 m
3. 0.2L= 200 mL
4. 1.2m=
1200 mm
b. Need to memorize the prefixes, kilo, milli, deci, centi
1 kilo = 1000 1 milli = 1/1000
1 deci = 1/10
10. Be able to do dimensional analysis
a. Given 5280 feet = 1 mile, 12 inches = 1 foot, 2.54 cm = 1 inch
Convert the following:
8.5 miles=_______inches
8.5 miles‫ ׀‬5280 feet ‫ ׀‬12 inches‫׀‬
‫ ׀‬1 mile ‫ ׀‬1 foot
.
= 540000 in
1 centi = 1/100
Graphing
a. Be able to read a graph
b. Be able to interpolate, extrapolate
c. Know how to graph, i.e. what axis is the dependent variable? independent variable?