a Copper is an element which is a pure substance b A chocolatechip cookie does not have a uniform composition which makes it a heterogeneous mixture c The gases oxygen and nitrogen have a uniform composition in nitrox which makes it ID: 547013
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Slide1
Solutiona. Copper is an element, which is a pure substance.b. A chocolate-chip cookie does not have a uniform composition, which makes it a heterogeneous mixture.c. The gases oxygen and nitrogen have a uniform composition in nitrox, which makes it a homogeneous mixture.Study Check 3.1A salad dressing is prepared with oil, vinegar, and chunks of blue cheese. Is this a homogeneous or heterogeneous mixture?Answerheterogeneous
Classify each of the following as a pure substance (element or compound) or a mixture (homogeneous or heterogeneous):a. copper in copper wireb. a chocolate-chip cookiec. nitrox, a combination of oxygen and nitrogen used to fill scuba tanks
Sample Problem
3.1 Classifying MixturesSlide2
Solutiona. A physical change occurs when the gold ingot changes shape.b. A chemical change occurs when gasoline burns and forms different substances with new properties.c. A physical change occurs when the size of the garlic pieces changes.Study Check 3.2Classify each of the following as a physical or chemical change:a. Water freezes on a pond.b. Gas bubbles form when baking powder is placed in vinegar.c. A log is cut for firewood.
Answera. physical change b. chemical change c. physical changeClassify each of the following as a physical or chemical change:a. A gold ingot is hammered to form gold leaf.
b. Gasoline burns in air.c. Garlic is chopped into small pieces.
Sample Problem
3.2 Physical and Chemical ChangesSlide3
SolutionStep 1 State the given and needed quantities.Step 2 Write a temperature equation.Step 3 Substitute in the known values and calculate the new temperature.
TF = 38 + 32 = 70. °F Answer to the ones place In the equation, the values of 1.8 and 32 are exact numbers, which do not affect the number of SFs used in the answer.
Sample Problem 3.3 Converting from Degrees Celsius
to Degrees Fahrenheit
The typical temperature in a hospital room is set at 21
°
C
.
What is that temperature
in degrees
Fahrenheit?Slide4
Study Check 3.3In 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?Answer12 °F
Continued
Sample Problem 3.3
Converting from Degrees Celsius
to Degrees FahrenheitSlide5
SolutionStep 1 State the given and needed quantities.Step 2 Write a temperature equation.Step 3
Substitute in the known values and calculate the new temperature.
Sample Problem 3.4
Converting from Degrees Fahrenheit to Degrees Celsius
In a type of cancer treatment called
thermotherapy
, temperatures as high as 113
°
F
are
used to
destroy cancer cells or make them more sensitive to radiation. What is that temperature
in degrees
Celsius?Slide6
Study Check 3.4A child has a temperature of 103.6 °F. What is this temperature on a Celsius thermometer?Answer39.8 °C
Continued
Sample Problem 3.4
Converting from Degrees Fahrenheit to Degrees CelsiusSlide7
SolutionStep 1 State the given and needed quantities.Step 2 Write a plan to convert the given unit to the needed unit. Step 3 State the equalities and conversion factors.
A defibrillator gives a high-energy-shock output of 360 J. What is this quantity of energy in calories?
Sample Problem
3.5 Energy Units
Slide8
Step 4 Set up the problem to calculate the needed quantity. Sample Problem 3.5
Energy Units
Continued
Study
Check
3.5
When 1.0 g of glucose is metabolized in the body, it produces 3.8 kcal. How
many kilojoules
are produced
?
Answer
16 kJSlide9
SolutionStep 1 State the given and needed quantities.Step 2 Use the energy value for each food type and calculate the kcal rounded off to the tens place. Using the energy values for carbohydrate, fat, and protein (see Table 3.7), we can calculate the energy for each type of food.
The Nutrition Facts label for crackers states that 1 serving contains 19 g of carbohydrate, 4 g of fat, and 2 g of protein. What is the energy from each food type and the total energy, in kilocalories, for one serving of crackers? Round off the kilocalories for
each food type to the tens place.
Sample Problem 3.6 Energy Content for a Food Using Nutrition Facts
Slide10
Step 3 Add the energy for each food type to give the total energy from the food. Total energy = 80 kcal + 40 kcal + 10 kcal = 130 kcal
Sample Problem 3.6 Energy Content for a Food Using Nutrition Facts
Continued
Study
Check
3.6
a.
Using
the nutrition values for one serving of crackers in Sample Problem
3.6, calculate
the energy, in kilojoules, for each food type. Round off the kilojoules
for each
food type to the tens place.
b.
What
is the total energy, in kilojoules, for one serving of crackers?
Answer
a.
carbohydrate
, 320 kJ; fat, 150 kJ; protein, 30 kJ
b.
500
kJ
Slide11
Step 1 State the given and needed quantities. Step 2 Calculate the temperature change (ΔT).
ΔT = 38.5 °C – 33.2 °C = 5.3 °C
During surgery or when a patient has suffered a cardiac arrest or stroke, lowering
the body temperature will reduce the amount of oxygen needed by the body. Some methods used to lower body temperature include cooled saline solution, cool water blankets, or cooling caps worn on the head. How many kilojoules are lost when the body temperature of a surgery patient with a blood volume of 5500 mL is cooled from 38.5 °C to 33.2 °C? (Assume that the specific heat and density of blood is the same as for water.)
Sample Problem
3.7 Calculating
Heat Loss
Slide12
Step 3 Write the heat equation and needed conversion factors. Heat = m × ΔT × SHStep 4 Substitute in the given values and calculate the heat, making sure units cancel.
Study Check 3.7How many kilocalories are lost when 560 g of water cools from 67 °C to 22 °C?Answer25 kcal
Continued
Sample Problem
3.7
Calculating Heat Loss
Slide13
SolutionStep 1 State the given and needed quantities.Step 2 Write a plan to convert the given quantity to the needed quantity.
Step 3 Write the heat conversion factor and any metric factor.
Ice bag therapy is used by sports trainers to
treat muscle injuries. If 260. g of ice are placed in an ice bag, how much heat, in joules, will be absorbed to melt all the ice at 0 °C?
Sample Problem
3.8 Heat of Fusion
Slide14
Step 4 Set up the problem and calculate the needed quantity.Study Check 3.8In a freezer, 150 g of water at 0 °C is placed in an ice cube tray. How much heat, in kilocalories, must be removed to form ice cubes at 0 °C?
Answer12 kcal
Continued
Sample Problem 3.8
Heat of Fusion
Slide15
SolutionStep 1 State the given and needed quantities.Step 2 Write a plan to convert the given quantity to the needed quantity.
Step 3 Write the heat conversion factor and any metric factor.
In a sauna, 122 g of water is converted to steam at 100
°C. How many kilojoules of heat are needed?
Sample Problem 3.9
Using Heat of Vaporization
Slide16
Step 4 Set up the problem and calculate the needed quantity.Study Check 3.9When 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?Answer56.5 kJ released
Continued
Sample Problem 3.9
Using Heat of Vaporization
Slide17
Solutiona. A temperature of 120 °C occurs on the diagonal line above the boiling (condensation) point, which indicates that water is a gas.b. A temperature of 100 °C, shown as a horizontal line, indicates that the water vapor is changing to liquid water, or condensing.c. A temperature of 40 °C occurs on the diagonal line below the boiling point but above the freezing point, which indicates that the water is in the liquid state.Study Check 3.10Using the cooling curve for water, identify the state or change of state for water as solid, liquid, gas, condensation, or freezing.a. at 0
°C b. at –20 °CAnswera. freezing b. solidUsing the cooling curve for water, identify the state or change of state for water as
solid, liquid, gas, condensation, or freezing.a. at 120
°C b. at 100 °C c. at 40 °C
Sample Problem
3.10 Using a Cooling CurveSlide18
SolutionStep 1 State the given and needed quantities.Step 2 Write a plan to convert the given quantity to the needed quantity. Total heat = kilojoules needed to melt the ice and heat the water from 0.0 °
C (freezing point) to 37.0 °CStep 3 Write the heat conversion factor and any metric factor.
Charles has increased his activity by doing more exercise. After a session of using
small weights, he has a sore arm. An ice bag is filled with 125 g of ice at 0.0 °C. The heat of fusion for ice is 334 J/g. How much heat, in kilojoules, is absorbed to melt the ice, and to raise the temperature of the water to body temperature, 37.0 °C?
Sample Problem
3.11
Combining
Heat Calculations
Slide19
Step 4 Set up the problem and calculate the needed quantity. ΔT = 37.0 °C – 0.0 °C = 37.0 °C Heat needed to change ice (solid) to water (liquid) at 0.0 °C:
Heat needed to warm water (liquid) from 0.0 °C to water (liquid) at 37.0 °C: Calculate the total heat: Melting ice at 0.0 °C 41.8 kJ Heating water (0.0 °C to 37.0 °C) 19.4 kJ Total heat needed
61.2 kJ
Continued
Sample Problem
3.11
Combining
Heat Calculations
Slide20
Study Check 3.11How 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.)Answer226 kJ
Continued
Sample Problem
3.11 Combining
Heat Calculations