Chapter 3 - Matter and energy

Question 1

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

a) a silicon (Si) chip
b) hydrogen peroxide (H2 O2)
c) oxygen gas (O2)
d) rust (Fe2 O2)
e) Methane CH4 (natural gas)

Answer 1

a) a silicon (Si) chip {ELEMENT}
b) hydrogen peroxide (H2 O2) {__COMPOUND__}
c) oxygen gas (O2) {ELEMENT}
d) rest (Fe2 O2) {__COMPOUND__}
e) Methane (natural gas) {__COMPOUND__}

Pure substances are made up of one type of atom or molecule. Elements are composed of only one type of atom and have one chemical symbol in their formulas, whereas compounds consist of atoms of two or more elements chemically bonded together and have multiple element symbols in their chemical formulas.

Question 2

Classify each of the following as a homogenous or heterogeneous mixture.

a) Herbal tea
b) Hot fudge sundae
c) vegetable oil

Answer 2

a) Herbal tea {__HOMOGENOUS__}
b) Hot fudge sundae {__HETEROGENOUS__}
c) vegetable oil {__HOMOGENOUS__}

Question 3

Classify each of the following as an element, a compound, or a mixture.

a) Acetic acid (CH3COOH) in apple cider vinegar
b) an oil spill in the ocean
c) xenon gas in lights

Answer 3

a) Acetic acid (CH3COOH) in apple cider vinegar {__compound __}
b) an oil spill in the ocean {__ mixture __}
c) xenon gas in lights {__element __}

All attempts used; correct answer displayed
You sorted 1 out of 3 items incorrectly. Recall that an element contains only one single type of atom, as found in the periodic table, while a compound is made up of two or more atoms. A mixture contains two or more different substances, such as a mixture of compounds or atoms. If the substance is a single species that contains two or more elements that you can look up in the periodic table, it is a compound.
The element xenon has the chemical formula Xe and can be found on the periodic table. Elements are the simplest type of a pure substance. The oil and water in the ocean spill are not chemically bonded together and can be physically separated, using a filter. Therefore, they form a mixture. The atoms of carbon, hydrogen, and oxygen in acetic acid are chemically bonded together to form the compound acetic acid.

No, vinegar is not a compound. A compound is formed when two separate and different materials (element, molecule, or even another compound) form a bond to each other.

Oil is a complex mixture of molecular compounds. A molecule is the smallest unit of a substance that retains the substance’s characteristics. Molecules, in turn, are composed of atoms.

Xenon (Xe), chemical element, a heavy and extremely rare gas of Group 18 (noble gases) of the periodic table. It was the first noble gas found to form true chemical compounds. More than 4.5 times heavier than air, xenon is colourless, odourless, and tasteless.

Question 4

Iron rusting is a Physical or Chemical change?

Answer 4

Chemical change

Question 5

Grinding coffee beans is Physical or Chemical change?

Answer 5

Physical change

Question 6

digesting a cheeseburger
baking a cake
burning coal
converting water to hydrogen and oxygen
are all examples of a Physical or Chemical change?

Answer 6

Chemical change

Question 7

The physical state(s) present when a substance is melting is (are)

Answer 7

Solid + liquid

Question 8

When a solid is converted directly to a gas, the change of state is called

Answer 8

sublimation

Question 9

What is 68 ∘F in degrees Celsius?

Answer 9

Using the equation that relates a Fahrenheit temperature and its corresponding Celsius temperature, 32 is subtracted from 68 ∘C . Then that result is divided by 1.8.

TC=(TF−32)/1.8
TC=68∘C/1.8
TC=20.∘C

Question 10

What is 68 ∘F in kelvins?

Answer 10

After converting the Fahrenheit temperature to Celsius, as done in Part A, the equation that relates a Celsius temperature and its corresponding Kelvin temperature is used:

TK=TC+273
=20.∘C+273
=293 K

Question 11

Using the energy values for foods (see the table), determine each of the following (round off the answers in kilocalories or kilojoules to the tens place):

Food Type kcal/g kJ/g
Carbohydrate 4 17
Fat 9 38
Protein 4 17

the total kilojoules for one cup of orange juice that contains 27 g of carbohydrate, no fat, and 2 g of protein
Express your answer to two significant figures and include the appropriate units.

Answer 11

carb=17kJ/g
fat=9
27g x 17kJ/g = 459kJ
2g x 17kJ=34kJ

459kJ+34kJ= 493kJ

2 sig figs = 49x10 to the 1 kJ or 490kJ

Question 12

Using the energy values for foods (see the table), determine each of the following (round off the answers in kilocalories or kilojoules to the tens place):

Food Type kcal/g kJ/g
Carbohydrate 4 17
Fat 9 38
Protein 4 17

the grams of carbohydrate in one apple if the apple has no fat and no protein and provides 67 kcal of energy
Express your answer to two significant figures and include the appropriate units.

Answer 12

so you can use dimensional analysis,

you need a value in grams, and you have “kcal/g” and “kcal”.

You need to cancel out “kcal” and have “g” at the top (numerator).

kcalkcal/g=kcalkcal∗g=g

so divide the energy by the values given in the table.

Mass of apple =67kcal4kcal/g=16.75 g

2 sigs= 17g

Question 13

Using the energy values for foods (see the table), determine each of the following (round off the answers in kilocalories or kilojoules to the tens place):

Food Type kcal/g kJ/g
Carbohydrate 4 17
Fat 9 38
Protein 4 17

the kilocalories in one tablespoon of vegetable oil, which contains 15 g of fat and no carbohydrate or protein

Answer 13

140kcal

Question 14

Using the energy values for foods (see the table), determine each of the following (round off the answers in kilocalories or kilojoules to the tens place):

Food Type kcal/g kJ/g
Carbohydrate 4 17
Fat 9 38
Protein 4 17

the grams of fat in one avocado that has 385 kcal, 15 g of carbohydrate, and 1 g of protein

Answer 14

36g

Question 15

What is 53 ∘F in degrees Celsius?

Answer 15

Using the equation that relates a Fahrenheit temperature and its corresponding Celsius temperature, 32 is subtracted from 53 ∘C . Then that result is divided by 1.8.

Tc=(TF−32)1.8
=53∘C1.8
=12∘C

Question 16

What is 53 ∘F in kelvins?

Answer 16

After converting the Fahrenheit temperature to Celsius, as done in Part A, the equation that relates a Celsius temperature and its corresponding Kelvin temperature is used:

TK =TC+273
=12∘C+273
=285K

Question 17

Using the energy values for foods (see the table), determine each of the following (round off the answers in kilocalories or kilojoules to the tens place):

Food Type kcal/g kJ/g
Carbohydrate 4 17
Fat 9 38
Protein 4 17

the total kilojoules for one cup of orange juice that contains 28 g of carbohydrate, no fat, and 3 g of protein

Answer 17

carb=17kJ/g
fat=9
28g x 17kJ/g = 476kJ
3g x 17kJ=51kJ

476kJ+51kJ= 527kJ

2 sig figs = 530 kJ

Question 18

Using the energy values for foods (see the table), determine each of the following (round off the answers in kilocalories or kilojoules to the tens place):

Food Type kcal/g kJ/g
Carbohydrate 4 17
Fat 9 38
Protein 4 17

the grams of carbohydrate in one apple if the apple has no fat and no protein and provides 61 kcal of energy

Answer 18

so you can use dimensional analysis,

you need a value in grams, and you have “kcal/g” and “kcal”.

You need to cancel out “kcal” and have “g” at the top (numerator).

kcalkcal/g=kcalkcal∗g=g

so divide the energy by the values given in the table.

Mass of apple =61kcal4kcal/g=15.25 g
2sigs=15g

Question 19

Using the energy values for foods (see the table), determine each of the following (round off the answers in kilocalories or kilojoules to the tens place):

Food Type kcal/g kJ/g
Carbohydrate 4 17
Fat 9 38
Protein 4 17

the kilocalories in one tablespoon of vegetable oil, which contains 19 g of fat and no carbohydrate or protein

Answer 19

170kcal

Question 20

Using the energy values for foods (see the table), determine each of the following (round off the answers in kilocalories or kilojoules to the tens place):

Food Type kcal/g kJ/g
Carbohydrate 4 17
Fat 9 38
Protein 4 17

the grams of fat in one avocado that has 455 kcal, 17 g of carbohydrate, and 4 g of protein

Answer 20

15x4 carb=60
1x4 protein=4

455-64=391
391/9 fat=43.4
round to the nearest tenths = 41g

Correct answer is shown. Your answer 40g was either rounded differently or used a different number of significant figures than required for this part.

41g

Question 21

Classify each of the following as an element, a compound, or a mixture.

a) xenon gas in lights
b) sodium hypochlorite (NaOCl) in bleach
c) a salad dressing in oil and vinegar

Answer 21

a) xenon gas in lights -element
b) sodium hypochlorite (NaOCl) in bleach- compound
c) a salad dressing in oil and vinegar - mixture

Question 22

Matter

Answer 22

• is the material that makes up all things

* is anything that has mass and occupies space

Question 23

Matter is classified according to its composition:

Answer 23

Pure substance

Mixtures

Question 24

Pure substances

Answer 24

have a fixed or definite composition.

Question 25

Mixtures

Answer 25

contain two or more different substances that are physically mixed but not chemically combined.
•two or more substances in different proportions •substances that can be separated by physical methods

Question 26

A pure substance is classified as -

Answer 26

Elements

Compounds

Question 27

Elements

Answer 27

are pure substances that contain only one type of material, such as
•copper, Cu
•lead, Pb
•aluminum, Al

The element copper consists of copper atoms.

Question 28

Compound

Answer 28

A compound contains two or more elements in a definite ratio, such as  
•  hydrogen peroxide (H2O2)
•  table salt (NaCl)
•  sugar (C12H22O11)
•  water (H2O)

Question 29

Homogeneous Mixtures

Answer 29

In a homogeneous mixture,
•the composition is uniform throughout
•the different parts of the mixture are not visible
Familiar examples of homogeneous mixtures are air, which contains oxygen and nitrogen gases, and seawater, a solution
of salt and water.

These are called solutions such as sugar solution
Brass is a homogeneous mixture of copper and zinc atoms.

Question 30

Heterogeneous Mixtures

Answer 30

In a heterogeneous mixture,
•the composition varies from one part of the mixture to another
•the different parts of the mixture are visible

these are called suspension and colloid such as soap

Question 31

Identify each of the following as a pure substance or a mixture:
A.  pasta and tomato sauce 
B.  aluminum foil
C.  helium 
D.  air

Answer 31

A. pasta and tomato sauce - mixture
B. aluminum foil - pure substance
C. helium - pure substance
D. air - mixture

Question 32

Identify each of the following as a homogeneous or heterogeneous mixture:
A.  hot fudge sundae
B.  shampoo
C.  sugar water
D.  peach pie

Answer 32

A. hot fudge sundae - heterogeneous mixture
B. shampoo - homogeneous mixture
C. sugar water - homogeneous mixture
D. peach pie - heterogeneous mixture

Question 33

Physical Change

Answer 33

A physical change occurs in a substance if there is
•a change in the state
•a change in the physical shape
•no change in the identity and composition of the substance

Question 34

Chemical Change

Answer 34

During a chemical change, a new substance forms that has
•a new composition
•new chemical properties
•new physical properties

Sugar caramelizing at a high temperature is an example of a chemical change.

Question 35

Classify each of the following changes as physical or chemical:
A.  burning a candle
B.  ice melting on the street
C.  toasting a marshmallow
D.  cutting a pizza
E.  iron rusting in an old car

Answer 35

A. burning a candle - chemical
B. ice melting on the street - physical
C. toasting a marshmallow - chemical
D. cutting a pizza - physical
E. iron rusting in an old car - chemical

Question 36

Temperature

Answer 36

Temperature
•is a measure of how hot or cold an object is compared to another object
•indicates the heat flow from the object with a higher temperature to the object with a lower temperature
•is measured using a thermometer
•A comparison of the Fahrenheit, Celsius, and Kelvin temperature scales

Question 37

Celsius to Fahrenheit Conversion

Answer 37

Multiply the °C temperature by 1.8. Add 32 to this number. This is the answer in °F.

°F = (°C × 9/5) + 32

Question 38

Fahrenheit to Celsius conversion

Answer 38

°C = (°F − 32) x 5/9

Question 39

Example °C to °F Conversion

For example, to convert 26°C to °F (the temperature of a warm day):

Answer 39

°F = (°C × 9/5) + 32

°F = (26 × 9/5) + 32

°F = (46.8) + 32

°F = 78.8° F

Question 40

A person with hypothermia has a body temperature of 34.8 °C. What is that temperature in degrees Fahrenheit?

Answer 40

TF = 1.8TC + 32
TF = 1.8(34.8) + 32
TF = 62.6 + 32 = 94.6 °F
Answer to the tenths place.

Question 41

On a cold winter day, the temperature is –15 °F. What is that temperature in degrees Celsius?
A.  −85 °C
B.  −47 °C
C.  −42 °C
D.  −26 °C

Answer 41

TC = (–15 − 32) / 1.8
TC = –47 /1.8 = −26 °C
Answer is D.

Question 42

Energy

Answer 42

In countries other than the United States, energy is shown in kilojoules (kJ).
1 Cal = 1000 calories
1 Cal = 1 kcal

Question 43

A cup of whole milk contains 13 g of carbohydrate, 9.0 g of fat, and 9.0 g of protein. How many kilocalories does a cup of milk contain? (Round the final answer to the tens place.)

A. 50 kcal
B. 80 kcal
C. 170 kcal

Answer 43

13 g carbohydrate× 4 kcal/g= 52 kcal

9. 0 g fat × 9 kcal/g = 81 kcal
10. 0 g protein × 4 kcal/g = 36 kcal

Total energy = 52 kcal + 81 kcal + 36 kcal = 169 kcal
Answer is C. 170kcal

Question 44

Classify each of the following as a pure substance (element or compound) or a mixture
(homogeneous or heterogeneous):
a. copper in wire
b. a chocolate-chip cookie
c. nitrox, a combination of oxygen and nitrogen used to fill scuba tank

Answer 44

SOLUTION
a. 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

Question 45

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

Answer 45

heterogeneous mixture

Question 46

molecules

Answer 46

is the smallest piece of a compound that is still a compound.

Question 47

How to convert Celsius to Kelvin?

Answer 47

K=C+273

Question 48

40 degree Celsius to Kelvin?

Answer 48

K=C+273
K=40+273
K=313
313K

Question 49

How to convert Kelvin to Celsius?

Answer 49

C=K-273

Question 50

313K to Celsius?

Answer 50

C=K-273
C=313-273
C=40
40C

Question 51

How to convert Celsius to Fahrenheit?

Answer 51

F=1.8C+32

Question 52

12 degree Celsius to Fahrenheit?

Answer 52

F=(1.8x12)+32
F=21.6+32
F=53.6
53.6 degrees F

Question 53

50 degrees Celsius to F

Answer 53

F=(1.8x50)+32
F=90+32
F=122
122 degrees F

Question 54

How to convert Fahrenheit to Celsius?

Answer 54

F-32=1.8C

Question 55

80 degree F to Celsius

Answer 55

F-32=1.8C
80-32=1.8C
48=1.8C
48/1.8=C
26.6=C
26.6 degrees Celsius

Question 56

Difficult temp conversion:

300K to F

Answer 56

first: K to C
then C to F

K to C
300 -273=C
27=C

then C to F
F=(1.8x27)+32
F=48.6+32
F=80.6

Question 57

Convert 100 degree F to Kelvin

Answer 57

F to C then C to K
1.8C=F-32
1.8C=100-32
1.8C=68
c=68/1.8
C=37.7

K=273+37.7
K=310.7