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MasteringChemistry CHM1033 CH.2

Chapter 2 questions and answers
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The blue spheres below represent atoms. What state of matter is depicted in each bin?
[tightly packed and hardly moving = solid]
[moving around fast and freely = gas]
[slightly moving but not much = liquid]
Classify each type of matter as an element, a compound, a heterogeneous mixture, or a homogeneous mixture.
[element = silver, calcium, silicon]
[compound = sulfur trioxide, toluene, sugar]
[heterogeneous mixture = soil, orange juice with pulp]
[homogeneous mixture = hot tea, air, salt water]
Classify each of the following pure substances as an element or a compound.

a silicon (Si) chip
oxygen (O2)
hydrogen peroxide (H2O2)
rust (Fe2O3)
methane (CH4) in natural gas
[element = a silicon chip, oxygen]
[compound = hydrogen peroxide, rust, methane in natural gas]
Classify each of the following mixtures as
homogeneous or heterogeneous.

vegetable soup
tea
tea with ice and a lemon slices
seawater
fruit salad
[homogeneous = tea, seawater]
[heterogeneous = vegetable soup, tea with ice and a lemon slice, fruit salad]
Classify each of the changes as a physical change or a chemical change.
[physical change = snow melting, tearing aluminum foil, slicing and apple, carving plastic]
[chemical change = rusting of iron (Fe), burning toast, bleaching skin, frying a fish]
Classify each of the properties as a physical property or a chemical property.
[physical property = the color of copper wire, the smell of vinegar, the luster of silver jewelry, the melting point of butter]
[chemical property = the flammability of ether, the reactivity of copper with oxygen, the explosiveness of fireworks]
What type of change, physical or chemical, takes place in each of the following?

Water vapor condenses to form rain.
Cesium metal reacts explosively with water.
Gold melts at 1064 degrees Celsius.
A puzzle is cut into 1000 pieces.
Sugar dissolves in water.
[physical change = water vapor condenses to form rain, gold melts at 1064 degrees Celsius, sugar dissolves in water, a puzzle is cut into 1000 pieces]
[chemical change = cesium reacts explosively with water]
Describe each of the following as a physical or chemical property.

Chromium is a steel-gray solid.
Hydrogen reacts readily with oxygen.
Nitrogen freezes at -210 degrees Celsius.
Milk will sour when left in a warm room.
[physical property = chromium is a steel-gray solid, nitrogen freezes and -210 degrees Celsius]
[chemical property = milk will sour when left in a warm room, hydrogen reacts readily with oxygen]
Convert 22.0 ∘C to degrees Fahrenheit.
71.6
Becky is going to take her dog for walk in the park, but before she leaves, she watches the weather report. According to the weather report, it is 74.0 ∘F outside. What is the outside temperature in kelvins?
296.5
Arrange the following in order of decreasing temperature.
146 degrees Celsius, 351 Kelvin, 95 degrees Celsius, 25 degrees Celsius, 58 degrees Fahrenheit, 273 Kelvin
Solve the following temperature conversions:
39.0∘C = 102∘F
Solve the following temperature conversions:
62.3∘F = 16.8∘C
Solve the following temperature conversions:
-23∘C = 250K
Solve the following temperature conversions:
65∘C = 340K
Solve the following temperature conversions:
127∘F = 52.8∘C
Duncan takes a break from studying and goes to the gym to swim laps. If swimming burns 7.35×10^5cal per hour, how many kilojoules does swimming burn in that same amount of time?

In other words, convert 7.35×10^5cal to kilojoules.
3080
Duncan knows that it takes 36400cal of energy to heat a pint of water from room temperature to boiling. However, Duncan has prepared ramen noodles so many times he does not need to measure the water carefully. If he happens to heat 0.850pint of room-temperature water, how many kilojoules of heat energy will have been absorbed by the water at the moment it begins to boil?
129
The following table lists the specific heat capacities of select substances:
Substance Specific heat capacity[J/(g⋅∘C)]
silver 0.235
copper 0.385
iron 0.449
aluminum 0.903
ethanol 2.42
water 4.184

Water (3090g) is heated until it just begins to boil. If the water absorbs 5.61×10^5J of heat in the process, what was the initial temperature of the water?
56.6∘C
The following table lists the specific heat capacities of select substances:
Substance Specific heat capacity[J/(g⋅∘C)]
silver 0.235
copper 0.385
iron 0.449
aluminum 0.903
ethanol 2.42
water 4.184

An unknown substance has a mass of 16.9g . When the substance absorbs 1.521×10^2J of heat, the temperature of the substance is raised from 25.0 ∘C to 45.0 ∘C . What is the most likely identity of the substance?
iron
Substances A and B are the same mass and at the same initial temperature. When they are heated, the final temperature of A is 55 ∘C higher than the temperature of B. What does this tell you about the specific heats of A and B?
The specific heat of A must be less than the specific heat of B
The following table lists the specific heats of some common substances:
Substance Specific heat [J/(g⋅∘C)]
aluminum (Al) 0.897
copper (Cu) 0.385
cast iron 0.460
gold (Au) 0.129
silver (Ag) 0.235
sodium chloride (NaCl) 0.864
stainless steel 0.500
water (H2O) 4.184

Rank the following species according to the decreasing energy needed to raise the temperature of 10.0 g of the substance by 25.0 ∘C.
water, sodium chloride, cast iron, copper, silver
The following table lists the specific heats of some common substances:
Substance Specific heat [J/(g⋅∘C)]
aluminum (Al) 0.897
copper (Cu) 0.385
cast iron 0.460
gold (Au) 0.129
silver (Ag) 0.235
sodium chloride (NaCl) 0.864
stainless steel 0.500
water (H2O) 4.184

If you pour equal amounts of scalding hot water into different metallic cups of equal temperature, which cup will heat up the most? Rank the cups from hottest to coldest.
500-g silver cup, 500-g aluminum cup, 750-g aluminum cup
Calculate the energy in joules and calories required to heat 27.0g water from 14.0∘C to 28.7∘C
1660
Calculate the energy in joules and calories required to heat 27.0g water from 14.0∘C to 28.7∘C
397
Calculate the energy in joules and calories required to heat 38.0g copper (Cu) from 132∘C to 256∘C
1810
Calculate the energy in joules and calories required to heat 38.0g copper (Cu) from 132∘C to 256∘C
434
Calculate the energy in joules and calories lost when 30.0g ethanol, C2H5OH, cools from 62.5∘C to -46.0∘C
8010
Calculate the energy in joules and calories lost when 30.0g ethanol, C2H5OH, cools from 62.5∘C to -46.0∘C
1910
Calculate the energy in joules and calories lost when 162g iron, Fe, cools from 168∘C to 45∘C
2150
One cup of clam chowder contains 9g of protein, 11g of fat, and 15g of carbohydrate.

How many kilocalories are in the clam chowder? (Round the final answers to the nearest tens place.)
200 kcal
One cup of clam chowder contains 9g of protein, 11g of fat, and 15g of carbohydrate.

How many kilojoules are in the clam chowder? (Round the final answers to the nearest tens place.)
820 kJ
A high-protein diet contains 70g of carbohydrate, 160g of protein, and 4.9g of fat.

How many kilocalories does this diet provide? (Round the final answers to the nearest tens place.)
960 kcal
A high-protein diet contains 70g of carbohydrate, 160g of protein, and 4.9g of fat.

How many kilojoules does this diet provide? (Round the final answers to the nearest tens place.)
4000 kJ
Using the following data, calculate the kilocalories for each food burned in a calorimeter:

one stalk of celery that heats 550g of water from 25.0∘C to 36.0∘C.
6.05 kcal
Using the following data, calculate the kilocalories for each food burned in a calorimeter:

a waffle that heats 4930g of water from 20.8∘C to 67.4∘C.
230 kcal
Drag the appropriate labels to their respective targets.
[bottom to top = solid, melting of the solid, liquid, boiling of the liquid, gas]
Rank from highest to lowest. To rank items as equivalent, overlap them.
the average kinetic energy of the molecules after point d, the average kinetic energy of the molecules from point b to point c, the average kinetic energy of the molecules before point a
Classify the following phase changes as processes that require the input of energy, or as processes that have a net output of energy.
[output of energy = freezing, deposition, condensing]
[input of energy = vaporizing, subliming, melting]
Identify each of the following changes of state as melting, freezing, sublimation, or deposition:

The solid structure of a substance breaks down as liquid forms.
melting
Identify each of the following changes of state as melting, freezing, sublimation, or deposition:

Coffee is freeze-dried.
sublimation
Identify each of the following changes of state as melting, freezing, sublimation, or deposition:

Water on the street turns to ice during a cold wintry night.
freezing
Identify each of the following changes of state as melting, freezing, sublimation, or deposition:

Ice crystals form on a package of frozen corn.
deposition
Calculate the heat in calories needed to condense 19.0g of steam at 100∘C.
1.03×10^4
Indicate whether heat was absorbed or released in situation above.
released
Calculate the heat in joules needed to condense 7.10g of steam at 100∘C.
1.60×10^4
Indicate whether heat was absorbed or released in situation above.
released
Calculate the heat in kilocalories needed to vaporize 44g of water at 100∘C.
24
Indicate whether heat was absorbed or released in situation above.
absorbed
Calculate the heat in kilojoules needed to vaporize 4.00kg of water at 100∘C.
9040
Indicate whether heat was absorbed or released in situation above.
absorbed
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