1.1.E: Essential Ideas of Chemistry (Exercises)
- Page ID
- 393409
Chemistry in Context
Explain how you could experimentally determine whether the outside temperature is higher or lower than 0 °C (32 °F) without using a thermometer.
- Answer
-
Place a glass of water outside. It will freeze if the temperature is below 0 °C.
Identify each of the following statements as being most similar to a hypothesis, a law, or a theory. Explain your reasoning.
- The pressure of a sample of gas is directly proportional to the temperature of the gas.
- Matter consists of tiny particles that can combine in specific ratios to form substances with specific properties.
- At a higher temperature, solids (such as salt or sugar) will dissolve better in water.
- Answer
-
(a) law (states a consistently observed phenomenon, can be used for prediction); (b) theory (a widely accepted explanation of the behavior of matter); (c) hypothesis (a tentative explanation, can be investigated by experimentation).
Identify each of the underlined items as a part of either the macroscopic domain, the microscopic domain, or the symbolic domain of chemistry. For any in the symbolic domain, indicate whether they are symbols for a macroscopic or a microscopic feature.
a. A certain molecule contains one H atom and one Cl atom.
b. Copper wire has a density of about 8 g/cm3.
c. The bottle contains 15 grams of Ni powder.
d. A sulfur molecule is composed of eight sulfur atoms.
- Answer
-
(a) symbolic, microscopic; (b) macroscopic; (c) symbolic, macroscopic; (d) microscopic.
The amount of heat required to melt 2 lbs of ice is twice the amount of heat required to melt 1 lb of ice. Is this observation a macroscopic or microscopic description of chemical behavior? Explain your answer.
- Answer
-
Macroscopic. The heat required is determined from macroscopic properties.
Phases and Classification of Matter
What properties distinguish solids from liquids? Liquids from gases? Solids from gases?
- Answer
-
Liquids can change their shape (flow); solids can’t. Gases can undergo large volume changes as pressure changes; liquids do not. Gases flow and change volume; solids do not.
How does a homogeneous mixture differ from a pure substance? How are they similar?
- Answer
-
The mixture can have a variety of compositions; a pure substance has a definite composition. Both have the same composition from point to point.
How does a heterogeneous mixture differ from a homogeneous mixture? How are they similar?
- Answer
-
A heterogeneous mixture has different composition at different points. A homogeneous mixture has constant composition throughout.
How do molecules of elements and molecules of compounds differ? In what ways are they similar?
- Answer
-
Molecules of elements contain only one type of atom; molecules of compounds contain two or more types of atoms. They are similar in that both are comprised of two or more atoms chemically bonded together.
Many of the items you purchase are mixtures of pure compounds. Select a commercial product and prepare a list of the ingredients that are pure compounds.
- Answer
-
You answers will vary depending on what commercial product you chose. Sample answer: Gatorade is a mixture. It contains water, sugar, dextrose, citric acid, salt, sodium chloride, monopotassium phosphate, and sucrose acetate isobutyrate.
- Classify each of the following as an element, a compound, or a mixture:
- iron
- oxygen
- mercury oxide
- pancake syrup
- carbon dioxide
- a substance composed of molecules each of which contains one hydrogen atom and one chlorine atom
- baking soda
- baking powder
- Answer
-
(a) element; (b) element; (c) compound; (d) mixture, (e) compound; (f) compound; (g) compound; (h) mixture.
How are the molecules in oxygen gas, the molecules in hydrogen gas, and water molecules similar? How do they differ?
- Answer
-
In each case, a molecule consists of two or more combined atoms. They differ in that the types of atoms change from one substance to the next.
When elemental iron corrodes it combines with oxygen in the air to ultimately form red brown iron(III) oxide which we call rust. (a) If a shiny iron nail with an initial mass of 23.2 g is weighed after being coated in a layer of rust, would you expect the mass to have increased, decreased, or remained the same? Explain. (b) If the mass of the iron nail increases to 24.1 g, what mass of oxygen combined with the iron?
- Answer
-
(a) Increased as it would have combined with oxygen in the air thus increasing the amount of matter and therefore the mass. (b) 0.900 g
- Yeast converts glucose to ethanol and carbon dioxide during anaerobic fermentation as depicted in the simple chemical equation here: \[\ce{glucose\rightarrow ethanol + carbon\: dioxide}\]
- If 200.0 g of glucose is fully converted, what will be the total mass of ethanol and carbon dioxide produced?
- If the fermentation is carried out in an open container, would you expect the mass of the container and contents after fermentation to be less than, greater than, or the same as the mass of the container and contents before fermentation? Explain.
- If 97.7 g of carbon dioxide is produced, what mass of ethanol is produced?
- Answer
-
(a) 200.0 g; (b) The mass of the container and contents would decrease as carbon dioxide is a gaseous product and would leave the container. (c) 102.3 g.
Physical and Chemical Properties
Classify each of the following changes as physical or chemical:
- condensation of steam
- burning of gasoline
- souring of milk
- dissolving of sugar in water
- melting of gold
- Answer
-
(a) physical; (b) chemical; (c) chemical; (d) physical; (e) physical.
The volume of a sample of oxygen gas changed from 10 mL to 11 mL as the temperature changed. Is this a chemical or physical change?
- Answer
-
physical
Explain the difference between extensive properties and intensive properties.
- Answer
-
The value of an extensive property depends upon the amount of matter being considered, whereas the value of an intensive property is the same regardless of the amount of matter being considered.
The density (d) of a substance is an intensive property that is defined as the ratio of its mass (m) to its volume (V).
\(\mathrm{density=\dfrac{mass}{volume}}\) \(\mathrm{d=\dfrac{m}{V}}\)
Considering that mass and volume are both extensive properties, explain why their ratio, density, is intensive.
- Answer
-
Being extensive properties, both mass and volume are directly proportional to the amount of substance under study. Dividing one extensive property by another will in effect “cancel” this dependence on amount, yielding a ratio that is independent of amount (an intensive property).
1.4: Measurements
Indicate the SI base units or derived units that are appropriate for the following measurements:
a. the mass of the moon
b. the distance from Vancouver to Toronto
c. the speed of sound
d. the density of air
e. the temperature at which alcohol boils
f. the area of the province of BC
g. the volume of a COVID-19 vaccine
- Answer
-
(a) kilograms; (b) meters; (c) kilometers/second; (d) kilograms/cubic meter; (e) kelvin; (f) square meters; (g) cubic meters
Give the name of the prefix and the quantity indicated by the following symbols that are used with SI base units.
- (a) c
- (b) d
- (c) G
- (d) k
- (e) m
- (f) n
- (g) p
- (h) T
- Answer
-
(a) centi-, \(\times\) 10−2; (b) deci-, \(\times\) 10−1; (c) Giga-, \(\times\) 109; (d) kilo-, \(\times\) 103; (e) milli-, \(\times\) 10−3; (f) nano-, \(\times\) 10−9; (g) pico-, \(\times\) 10−12; (h) tera-, \(\times\) 1012
A large piece of jewelry has a mass of 132.6 g. A graduated cylinder initially contains 48.6 mL water. When the jewelry is submerged in the graduated cylinder, the total volume increases to 61.2 mL.
- Answer
-
10.5 g/mL
Pure silver has a density of 10.5 g/mL, so it is a likely substance that the jewelry is made of.
Measurement Uncertainty, Accuracy, and Precision
Express each of the following numbers in exponential notation with correct significant figures:
- (a) 704
- (b) 0.03344
- (c) 547.9
- (d) 22086
- (e) 1000.00
- (f) 0.0000000651
- (g) 0.007157
- Answer
Indicate whether each of the following can be determined exactly or must be measured with some degree of uncertainty:
(a) the number of seconds in an hour
(b) the number of pages in this book
(c) the number of grams in your weight
(d) the number of grams in 3 kilograms
(e) the volume of water you drink in one day
(f) the distance from Vancouver to Calgary
- Answer
-
(a) exact; (b) exact; (c) uncertain; (d) exact; (e) uncertain; (f) uncertain
How many significant figures are contained in each of the following measurements?
(a) 53 cm
(b) 2.05 \(\times\) 108 m
(c) 86,002 J
(d) 9.740 \(\times\) 104 m/s
(e) 10.0613 m3
(f) 0.17 g/mL
(g) 0.88400 s
- Answer
-
(a) two; (b) three; (c) five; (d) four; (e) six; (f) two; (g) five
Round off each of the following numbers to two significant figures:
(a) 0.436
(b) 9.000
(c) 27.2
(d) 135
(e) 1.497 \(\times\) 10−3
(f) 0.445
- Answer
-
(a) 0.44; (b) 9.0; (c) 27; (d) 140; (e) 1.5 \(\times\) 10−3; (f) 0.44
Perform the following calculations and report each answer with the correct number of significant figures.
(a) 628 \(\times\) 342
(b) (5.63 \(\times\) 102) \(\times\) (7.4 \(\times\) 103)
(c) \(\dfrac{28.0}{13.483}\)
(d) 8119 \(\times\) 0.000023
(e) 14.98 + 27,340 + 84.7593
(f) 42.7 + 0.259
- Answer
-
(a) 2.15 \(\times\) 105; (b) 4.2 \(\times\) 106; (c) 2.08; (d) 0.19; (e) 27,440; (f) 43.0
Consider the results of the archery contest shown in this figure.
(a) Which archer is most precise?
(b) Which archer is most accurate?
(c) Who is both least precise and least accurate?
- Answer
-
(a) Archer X; (b) Archer W; (c) Archer Y
Mathematical Treatment of Measurement Results
Write conversion factors (as ratios) for the number of:
- yards in 1 meter
- liters in 1 liquid quart
- pounds in 1 kilogram
- Answer
-
(a) \(\mathrm{\dfrac{1.0936\: yd}{1\: m}}\); (b) \(\mathrm{\dfrac{0.94635\: L}{1\: qt}}\); (c) \(\mathrm{\dfrac{2.2046\: lb}{1\: kg}}\)
Soccer is played with a round ball having a circumference between 27 and 28 in. and a weight between 14 and 16 oz. What are these specifications in units of centimeters and grams?
- Answer
-
68–71 cm; 400–450 g
How many milliliters of a soft drink are contained in a 12.0-oz can?
- Answer
-
355 mL
Many medical laboratory tests are run using 5.0 μL blood serum. What is this volume in milliliters?
- Answer
-
5.0 \(\times\) 10−3 mL
Use scientific (exponential) notation to express the following quantities in terms of the SI base units in [link]:
(a) 0.13 g
(b) 232 Gg
(c) 5.23 pm
(d) 86.3 mg
(e) 37.6 cm
(f) 54 μm
(g) 1 Ts
(h) 27 ps
(i) 0.15 mK
- Answer
-
(a) 1.3 \(\times\) 10−4 kg; (b) 2.32 \(\times\) 108 kg; (c) 5.23 \(\times\) 10−12 m; (d) 8.63 \(\times\) 10−5 kg; (e) 3.76 \(\times\) 10−1 m; (f) 5.4 \(\times\) 10−5 m; (g) 1 \(\times\) 1012 s; (h) 2.7 \(\times\) 10−11 s; (i) 1.5 \(\times\) 10−4 K
Make the conversion indicated in each of the following:
(a) the length of a soccer field, 120 m (three significant figures), to feet
(b) the height of Mt. Kilimanjaro, at 19,565 ft the highest mountain in Africa, to kilometers
(c) the area of an 8.5 t 11-inch sheet of paper in cm2
(d) the displacement volume of an automobile engine, 161 in.3, to liters
(e) the estimated mass of the atmosphere, 5.6 t 1015 tons, to kilograms
(f) the mass of a bushel of rye, 32.0 lb, to kilograms
(g) the mass of a 5.00-grain aspirin tablet to milligrams (1 grain = 0.00229 oz)
- Answer
-
(a) 394 ft
(b) 5.9634 km
(c) 6.0 \(\times\) 102
(d) 2.64 L
(e) 5.1 \(\times\) 1018 kg
(f) 14.5 kg
(g) 324 mg
As an instructor is preparing for an experiment, he requires 225 g phosphoric acid. The only container readily available is a 150-mL Erlenmeyer flask. Is it large enough to contain the acid, whose density is 1.83 g/mL?
- Answer
-
Yes, the acid's volume is 123 mL.
Calculate the density of aluminum if 27.6 cm3 has a mass of 74.6 g.
- Answer
-
2.70 g/cm3
Calculate these masses.
(a) What is the mass of 6.00 cm3 of mercury, density = 13.5939 g/cm3?
(b) What is the mass of 25.0 mL octane, density = 0.702 g/cm3?
- Answer
-
(a) 81.6 g; (b) 17.6 g
Calculate these volumes.
(a) What is the volume of 25 g iodine, density = 4.93 g/cm3?
(b) What is the volume of 3.28 g gaseous hydrogen, density = 0.089 g/L?
- Answer
-
(a) 5.1 mL; (b) 37 L
Contributors and Attributions
Paul Flowers (University of North Carolina - Pembroke), Klaus Theopold (University of Delaware) and Richard Langley (Stephen F. Austin State University) with contributing authors. Textbook content produced by OpenStax College is licensed under a Creative Commons Attribution License 4.0 license. Download for free at http://cnx.org/contents/85abf193-2bd...a7ac8df6@9.110).