Chapter 3

Question 1

Classify each of the following as a pure substance (element or compound) or a mixture (homogeneous or heterogeneous):

copper in wire

a chocolate-chip cookie

nitrox, a combination of oxygen and nitrogen used to fill scuba tanks

Answer 1

Copper is an element, which is a pure substance.

A chocolate-chip cookie does not have a uniform composition, which makes it a heterogeneous mixture.

The gases oxygen and nitrogen have a uniform composition in nitrox, which makes it a homogeneous mixture.

Question 2

A salad dressing is prepared with oil, vinegar, and chunks of blue cheese. Is this a homogeneous or heterogeneous mixture?

A mouthwash used to reduce plaque and clean gums and teeth contains several ingredients, such as menthol, alcohol, hydrogen peroxide, and a flavoring. Is this a homogeneous or heterogeneous mixture?

Answer 2

heterogeneous mixture

homogeneous mixture

Question 3

3.1 Classify each of the following pure substances as an element or a compound:

a silicon (Si) chip

hydrogen peroxide (H2O2)

oxygen gas (O2)

rust (Fe2O3)

methane (CH4) in natural gas

Answer 3

element

compound

element

compound

compound

Question 4

3.3 Classify each of the following as a pure substance or a mixture:

baking soda (NaHCO3)

a blueberry muffin

ice (H2O)

zinc (Zn)

trimix (oxygen, nitrogen, and helium) in a scuba tank

Answer 4

pure substance

mixture

pure substance

pure substance

mixture

Question 5

3.5 A dietitian includes one of the following mixtures in the lunch menu. Classify each of the following as homogeneous or heterogeneous:

vegetable soup

tea

fruit salad

tea with ice and lemon slices

Answer 5

heterogeneous

homogeneous

heterogeneous

heterogeneous

Question 6

Classify each of the following as a physical or chemical change:

A gold ingot is hammered to form gold leaf.

Gasoline burns in air.

Garlic is chopped into small pieces.

Milk left in a warm room turns sour.

Answer 6

A physical change occurs when the gold ingot changes shape.

A chemical change occurs when gasoline burns and forms different substances with new properties.

A physical change occurs when the size of the garlic pieces changes.

A chemical change occurs when milk turns sour and forms new substances.

Question 7

Classify each of the following as a physical or chemical change:

Water freezes on a pond.

Gas bubbles form when baking powder is placed in vinegar.

A log is cut for firewood.

Butter melts in a warm room.

Answer 7

physical change

chemical change

physical change

physical change

Question 8

3.7 Indicate whether each of the following describes a gas, a liquid, or a solid:

The breathing mixture in a scuba tank has no definite ­volume or shape.

The neon atoms in a lighting display do not interact with each other.

The particles in an ice cube are held in a rigid structure.

Answer 8

gas

gas

solid

Question 9

3.11 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°C.

A puzzle is cut into 1000 pieces.

Cheese is grated.

Answer 9

physical

chemical

physical

physical

physical

Question 10

3.13 Describe each of the following properties for the element ­fluorine as physical or chemical:

is highly reactive

is a gas at room temperature

has a pale, yellow color

will explode in the presence of hydrogen

has a melting point of −220°C

Answer 10

chemical

physical

physical

chemical

physical

Question 11

In the process of making ice cream, rock salt is added to crushed ice to chill the ice cream mixture. If the temperature drops to −11°C, what is it in degrees Fahrenheit?

A hot tub reaches a temperature of 40.6 °C. What is that temperature in degrees Fahrenheit?

Answer 11

12 °F

105 °F

Question 12

A child has a temperature of 103.6 °F. What is this temperature on a Celsius thermometer?

A child who fell through the ice on a lake has hypothermia with a core temperature of 32 °C. What is this temperature in degrees Fahrenheit?

Answer 12

39.8 °C

90. °F

Question 13

3.15 Your friend who is visiting from Canada just took her temperature. When she reads 99.8 °F, she becomes concerned that she is quite ill. How would you explain this temperature to your friend?

Answer 13

In the United States, we still use the Fahrenheit temperature scale. In °F, normal body temperature is 98.6. On the Celsius scale, her temperature would be 37.7 °C, a mild fever.

Question 14

3.17 Calculate the unknown temperature in each of the following:

37.0°C=___°F

65.3°F=___°C

−27°C=___K

62°C=___K

114°F=___°C

Answer 14

98.6 °F

18.5 °C

246 K

335 K

46 °C

Question 15

3.19 A patient with hyperthermia has a temperature of 106 °F. What does this read on a Celsius thermometer?

Because high fevers can cause convulsions in children, the doctor needs to be called if the child’s temperature goes over 40.0 °C. Should the doctor be called if a child has a temperature of 103 °F?

Answer 15

41 °C

No. The temperature is equivalent to 39 °C.

Question 16

When 1.0 g of glucose is metabolized in the body, it produces 3900 cal. How many joules are produced?

A swimmer expends 855 kcal during practice. How many kilojoules did the swimmer expend?

Answer 16

16 000 J

3580 kJ or 3.58×10^3 kJ

Question 17

3.21 Discuss the changes in the potential and kinetic energy of a roller-coaster ride as the roller-coaster car climbs to the top and goes down the other side.

Answer 17

When the roller-coaster car is at the top of the ramp, it has its maximum potential energy. As it descends, potential energy changes to kinetic energy. At the bottom, all the energy is kinetic.

Question 18

3.23 Indicate whether each of the following statements describes potential or kinetic energy:

water at the top of a waterfall

kicking a ball

the energy in a lump of coal

a skier at the top of a hill

Answer 18

potential

kinetic

potential

potential

Question 19

3.25 Convert each of the following energy units:

3500 cal to kcal

415 J to cal

28 cal to J

4.5 kJ to cal

Answer 19

3.5 kcal

99.2 cal

120 J

1100 cal

Question 20

3.27 The energy needed to keep a 75-watt light bulb burning for 1.0h is 270 kJ. Calculate the energy required to keep the light bulb burning for 3.0 h in each of the following energy units:

joules

kilocalories

Answer 20

8.1x10^5 J

190 kcal

Question 21

3.29 Calculate the kilocalories for each of the following:

one stalk of celery that produces 125 kJ when burned in a calorimeter

a waffle that produces 870. kJ when burned in a calorimeter

Answer 21

29.9 kcal

208 kcal

Question 22

3.31 Using the energy values for foods, determine each of the following (round off the answer for each food type to the tens place):

the total kilojoules for one cup of orange juice that contains 26 g of carbohydrate, no fat, and 2 g of protein

the grams of carbohydrate in one apple if the apple has no fat and no protein and provides 72 kcal of energy

the kilocalories in one tablespoon of vegetable oil, which contains 14 g of fat and no carbohydrate or protein

the grams of fat in one avocado that has 410 kcal, 13 g of carbohydrate, and 5 g of protein

Answer 22

470 kJ

18 g

130 kcal

38 g

Question 23

3.33 For dinner, Charles had one cup of clam chowder, which contains 16 g of carbohydrate, 12 g of fat, and 9 g of protein. How much energy, in kilocalories and kilojoules, is in the clam chowder? (Round off the answer for each food type to the tens place.)

Answer 23

210 kcal, 880 kJ

Question 24

3.35 A patient receives 3.2 L of intravenous (IV) glucose solution. If 100. mL of the solution contains 5.0 g of glucose (carbohydrate), how many kilocalories did the patient obtain from the glucose solution?

Answer 24

640 kcal

Question 25

3.37 If the same amount of heat is supplied to samples of 10.0 g each of aluminum, iron, and copper, all at 15.0 °C, which sample would reach the highest temperature (see Table 3.11)?

Answer 25

Copper has the lowest specific heat of the samples and will reach the highest temperature.

Question 26

3.39 Use the heat equation to calculate the energy for each of the ­following (see Table 3.11): calories to heat 8.5 g of water from 15 °C to 36 °C joules lost when 25 g of water cools from 86 °C to 61 °C kilocalories to heat 150 g of water from 15 °C to 77 °C kilojoules to heat 175 g of copper from 28 °C to 188 °C

Answer 26

180 cal 2600 J 9.3 kcal 10.8 kJ

Question 27

3.41 Use the heat equation to calculate the energy, in joules and ­calories, for each of the following (see Table 3.11): to heat 25.0 g of water from 12.5 °C to 25.7 °C to heat 38.0 g of copper from 122 °C to 246 °C lost when 15.0 g of ethanol, C2H6O, cools from 60.5 °C to −42.0°C lost when 125 g of iron cools from 118 °C to 55 °C

Answer 27

1380 J, 330. cal 1810 J, 434 cal 3780 J, 904 cal 3600 J, 850 cal

Question 28

When steam from a pan of boiling water reaches a cool window, it condenses. How much heat, in kilojoules, is released when 25.0 g of steam condenses at 100 °C? Ice bags are used by sports trainers to treat muscle injuries. If 260. g of ice is placed in an ice bag, how much heat, in kilojoules, will be released when all the ice melts at 0 °C?

Answer 28

56.5 kJ 86.8 kJ

Question 29

How many kilojoules are released when 75.0 g of steam at 100 °C condenses, cools to 0 °C, and freezes at 0 °C? (Hint: The solution will require three energy calculations.) How many kilocalories are needed to convert 18 g of ice at 0 °C to steam at 100 °C? (Hint: The solution will require three energy calculations.)

Answer 29

226 kJ 13 kcal

Question 30

3.43 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. Coffee is freeze-dried. Water on the street turns to ice during a cold wintry night. Ice crystals form on a package of frozen corn.

Answer 30

melting sublimation freezing deposition

Question 31

3.45 Calculate the heat change at 0 °C for each of the following, and indicate whether heat was absorbed/released: calories to melt 65 g of ice joules to melt 17.0 g of ice kilocalories to freeze 225 g of water kilojoules to freeze 50.0 g of water

Answer 31

5200 cal absorbed 5680 J absorbed 18 kcal released 16.7 kJ released

Question 32

3.47 Identify each of the following changes of state as evaporation, boiling, or condensation: The water vapor in the clouds changes to rain. Wet clothes dry on a clothesline. Lava flows into the ocean and steam forms. After a hot shower, your bathroom mirror is covered with water.

Answer 32

condensation evaporation boiling condensation

Question 33

3.49 Calculate the heat change at 100 °C for each of the following, and indicate whether heat was absorbed/released: calories to vaporize 10.0 g of water joules to vaporize 5.00 g of water kilocalories to condense 8.0 kg of steam kilojoules to condense 175 g of steam

Answer 33

5400 cal absorbed 11 300 J absorbed 4300 kcal released 396 kJ released

Question 34

3.51 Draw a heating curve for a sample of ice that is heated from −20°C to 150 °C. Indicate the segment of the graph that ­corresponds to each of the following: solid melting liquid boiling gas

Answer 34

See teal sticky note!

Question 35

3.53 Using the values for the heat of fusion, specific heat of water, and/or heat of vaporization, calculate the amount of heat energy in each of the following: joules needed to melt 50.0 g of ice at 0 °C and to warm the liquid to 65.0 °C kilocalories released when 15.0 g of steam condenses at 100 °C and the liquid cools to 0 °C kilojoules needed to melt 24.0 g of ice at 0 °C, warm the ­liquid to 100 °C, and change it to steam at 100 °C

Answer 35

30 300 J 9.6 kcal 72.2 kJ

Question 36

3.55 A patient arrives in the emergency room with a burn caused by steam. Calculate the heat, in kilocalories, that is released when 18.0 g of steam at 100 °C hits the skin, condenses, and cools to body temperature of 37.0 °C.

Answer 36

10.8 kcal

Question 37

3.71 Classify each of the following as an element, a compound, or a mixture: carbon in pencils carbon monoxide (CO) in automobile exhaust orange juice

Answer 37

element compound mixture

Question 38

3.73 Classify each of the following mixtures as homogeneous or heterogeneous: hot fudge sundae herbal tea vegetable oil

Answer 38

heterogeneous homogeneous homogeneous

Question 39

3.75 Identify each of the following as solid, liquid, or gas: vitamin tablets in a bottle helium in a balloon milk in a bottle the air you breathe charcoal briquettes on a barbecue

Answer 39

solid gas liquid gas solid

Question 40

3.77 Identify each of the following as a physical or chemical ­property: Gold is shiny. Gold melts at 1064 °C. Gold is a good conductor of electricity. When gold reacts with sulfur, a black sulfide compound forms.

Answer 40

physical physical physical chemical

Question 41

3.79 Identify each of the following as a physical or chemical change: A plant grows a new leaf. Chocolate is melted for a dessert. Wood is chopped for the fireplace. Wood burns in a woodstove.

Answer 41

chemical physical physical chemical

Question 42

3.81 Calculate each of the following temperatures in degrees Celsius and kelvins: The highest recorded temperature in the continental United States was 134 °F in Death Valley, California, on July 10, 1913. The lowest recorded temperature in the continental United States was −69.7°F in Rodgers Pass, Montana, on ­January 20, 1954.

Answer 42

56.7 °C, 330. K −56.5°C, 217 K

Question 43

3.83 What is −15°F in degrees Celsius and in kelvins?

Answer 43

-26 degrees C, 247 K

Question 44

3.85 A 0.50-g sample of vegetable oil is placed in a calorimeter. When the sample is burned, 18.9 kJ is given off. What is the energy value (kcal/g) for the oil?

Answer 44

9.0 kcal/g

Question 45

3.87 On a hot day, the beach sand gets hot but the water stays cool. Would you predict that the specific heat of sand is higher or lower than that of water? Explain.

Answer 45

The same amount of heat causes a greater temperature change in the sand than in the water; thus the sand must have a lower specific heat than that of water.

Question 46

3.91 The melting point of dibromomethane is −53°C and its ­boiling point is 97 °C. Sketch a heating curve for dibromomethane from −100°C to 120 °C. What is the state of dibromomethane at −75°C? What happens on the curve at −53°C? What is the state of dibromomethane at -18°C? What is the state of dibromomethane at 110 °C? At what temperature will both solid and liquid be present?

Answer 46

solid solid dibromomethane melts liquid gas -53 degrees C

Question 47

3.93 If you want to lose 1 lb of “body fat,” which is 15% water, how many kilocalories do you need to expend?

Answer 47

3500 kcal

Question 48

3.95 A hot-water bottle for a patient contains 725 g of water at 65 °C. If the water cools to body temperature (37 °C), how many kilojoules of heat could be transferred to sore ­muscles?

Answer 48

85kJ

Question 49

3.97 When a 0.66-g sample of olive oil is burned in a calorimeter, the heat released increases the temperature of 370 g of water from 22.7 °C to 38.8 °C. What is the energy value for the olive oil in kcal/g?

Answer 49

9.0 kcal/g

Question 50

3.101 An ice bag containing 275 g of ice at 0 °C was used to treat sore muscles. When the bag was removed, the ice had melted and the liquid water had a temperature of 24.0 °C. How many ­kilojoules of heat were absorbed?

Answer 50

119.5 kJ

Question 51

3.103 A 70.0-g piece of copper metal at 54.0 °C is placed in 50.0 g of water at 26.0 °C. If the final temperature of the water and metal is 29.2 °C, what is the specific heat, in J/g °C, of copper?

Answer 51

Specific heat = 0.385 J/g degrees C

Question 52

3.105 A metal is thought to be titanium or aluminum. When 4.7 g of the metal absorbs 11 J, its temperature rises by 4.5 °C.

Answer 52

0.52 J/g °C titanium