Chm1020C - Chapter 2

Front 1

If a pure substance is not an element, it is a ________ ________.

Back 1

chemical compound

Front 2

A _______ ________ is a pure substance composed of atoms of one or more elements combined in fixed ratios.

Back 2

chemical compound

Front 3

Some examples of chemical compounds include:

Back 3

• water (hydrogen and oxygen)
• table sugar (carbon, hydrogen and oxygen)

Front 4

True or False? Once elements are combined to form compounds, the original, characteristic properties of the elements are replaced by the characteristic properties of the compounds.

Back 4

True. Consider the difference between table sugar, a white crystalline substance that is soluble in water, and its constituent elements: carbon, which is usually a black powder and is not water soluble; hydrogen, the lightest gas known; and oxygen, the atmospheric gas needed for respiration.

Front 5

A(n) ____ _________ is something with a uniform and fixed composition at the nanoscopic level. It can be recognized by the unchanging nature of its properties.

Back 5

pure substance

Front 6

A(n) _______ is a pure substance composed of only one kind of atom.

Back 6

element

Front 7

A(n) ____ is the smallest particle of an element, and different elements have different atoms

Back 7

atom

Front 8

______ is anything that has mass and occupies volume.

Back 8

matter

Front 9

The four states of matter are ______, _______, _____, and _______.

Back 9

solids, liquids, gases, plasma

Front 10

A(n) _____ is matter that retains its shape and volume, regardless of the container in which it is placed.

Back 10

solid

Front 11

A(n) ______ is matter that retains its volume, but not its shape.

Back 11

liquid

Front 12

A(n) _____ is matter that does not retain its shape or volume.

Back 12

gas

Front 13

Samples of matter large enough to be seen, felt, and handled—and thus large enough for ordinary laboratory experiments—are called ___________ samples.

Back 13

macroscopic

Front 14

___________ samples are so small that they have to be viewed with the aid of a microscope.

Back 14

microscopic

Front 15

The structure of matter that really interests chemists, however, is at the __________ level, i.e., in the range of 0.0000000001 m.

Back 15

nanoscopic

Front 16

Most samples of matter as they occur in nature are not pure substances, but ________.

Back 16

mixtures

Front 17

A _____________ mixture has a nonuniform composition that is clearly visible and uneven, as in chocolate chip cookies or the different kinds of crystals in many rocks.

Back 17

heterogeneous

Front 18

____________ mixtures are uniform in composition and are referred to as solutions.

Back 18

homogeneous

Front 19

A homogeneous mixture that may be in the solid, liquid, or gaseous state is called a(n) _________.

Back 19

solution

Front 20

Some examples of solutions are:

Back 20

• Clean air (gas), which consists mostly of nitrogen and oxygen.
• Freshly brewed tea (liquid).
• Some brass alloys (solid), which are homogeneous mixtures of the elements copper and zinc.
  

Front 21

When any mixture is separated into its components, the components are said to be ________.

Back 21

purified

Front 22

Some examples of elements include:

Back 22

• mercury
• helium
• uranium

Front 23

Heterogeneous samples of matter are all ________ and can be physically separated into various kinds of homogeneous matter.

Back 23

mixtures

Front 24

Homogeneous matter can be either a ____ ________ or a _______. If it is a _______, it is described as a solution and has the same composition throughout.

Back 24

pure substance, mixture, mixture

Front 25

If the homogeneous matter is a pure substance, it has a fixed composition and must be either a(n) ________ or a ________.

Back 25

element, compound

Front 26

Once elements have combined into compounds, only ________ _________ can separate them.

Back 26

chemical reactions

Front 27

About __ of the elements on the periodic table are not found anywhere in nature but have only been produced artificially in laboratories, usually in extremely small quantities.

Back 27

18

Front 28

What are the two distinguishing properties of metals?

Back 28

• They conduct electric current.
• They have a shiny appearance.
  

Front 29

True or False? The familiar nonmetals include all of the elemental gases, and carbon, sulfur, phosphorus, and iodine, which are solids

Back 29

True.

Front 30

Seven nonmetals exist under everyday conditions as two-atom molecules, known as ________ __________.

Back 30

diatomic molecules

(hydrogen, oxygen, nitrogen, fluorine, iodine, chlorine, bromine)

Front 31

A(n) _______ ________ is a written combination of element symbols that represents the atoms combined in a chemical compound. The symbols represent the elements, and the subscripts indicate the relative numbers of atoms of each kind.

Back 31

chemical formula

(H2O, is two hydrogen atoms and one oxygen atom)

Front 32

Sometimes a line or lines are drawn between symbols to indicate which atoms are connected in molecules. Formulas that show the connections in this way are known as _________ formulas, whereas formulas that give just one symbol for each element present are called ________ formulas.

Back 32

structural, molecular

Front 33

Methane and the many millions of compounds that contain carbon combined with hydrogen—and often also with nitrogen, oxygen, phosphorus, or sulfur—are known as _______ __________.

Back 33

organic compounds

Front 34

Compounds not based on carbon are referred to as _________ __________.

Back 34

inorganic compounds

Front 35

Which of the following represent elements and which represent compounds?

1. KI
2. Co
3. Ag
4. No
5. Cl2

Back 35

The chemical symbols in (1) and (4) represent compounds—the second letter in an element symbol is never a capital letter; (2) and (3) represent the elements cobalt and silver; and (5) represents the element chlorine, which exists as diatomic molecules.

Front 36

A ________ ________ is a process in which one or more pure substances are transformed into one or more different pure substances.

Back 36

chemical reaction

Front 37

A representation of a chemical reaction by the formulas of reactants and products is called a _______ _________.

Back 37

chemical equation

Front 38

A chemical equation in which the total number of atoms of each kind is the same in reactants and products is known as a __________ chemical equation.

Back 38

balanced

Front 39

A(n) ________ is a substance that undergoes chemical change.

Back 39

reactant

Front 40

A(n) _______ is a substance produced as a result of chemical change.

Back 40

product

Front 41

A property that can be observed without changing the identity of a substance is known as a(n) ________ _______.

Back 41

physical property (boiling point, melting point, color, odor, volume, density)

Front 42

The measurement of mass per unit of volume is called ________.

Back 42

density

(d = m/v)

Front 43

Processes that result in changes of identity of a substance are known as ________ ________.

Back 43

chemical changes

Front 44

A(n) ________ ________ is observable in chemical reactions and changes in the identity of one or more reactants.

Back 44

chemical property (reactivity, flammability, oxidation states, chemical stability)

Front 45

A(n) ________ ________ produces a new arrangement of atoms. The number and kinds of atoms in the reactants and products remain the same, but the reactants and products are different substances that can be recognized by their different properties.

Back 45

chemical reaction

Front 46

Some physical changes and almost all chemical reactions are accompanied by changes in ______.

Back 46

energy

Front 47

_____ is the ability to cause change or, in the formal terms of physics, to do work.

Back 47

energy

Front 48

Energy in storage, waiting to be used, is __________ ______.

Back 48

potential energy

Front 49

Energy in use, rather than in storage, is _______ ______, the energy associated with motion.

Back 49

kinetic energy

Front 50

The word _________ describes information that is numerical.

Back 50

quantitative

Front 51

The word __________ describes information that is not numerical.

Back 51

qualitative

Front 52

Converting a quantity expressed in one set of units to another is known as _____ _________.

Back 52

unit conversion

Front 53

An _______ a way of expressing one quantity using two different units

Back 53

equality

(12 eggs = 1 dozen eggs)

Front 54

A(n) __________ ______ is a ratio in which the numerator refers to the same quantity as the denominator.

Back 54

conversion factor

Front 55

Would it be possible for two pure substances to have exactly the same set of properties? Give reasons for your answer.

Back 55

No, they would be the same substance.

Front 56

Nitroglycerine, the chemical compound that led to Alfred Nobel’s fortune, is also used for the treatment of heart conditions. What does this illustrate about the versatility of many chemical compounds? Are the risks and benefits associated with the use of nitroglycerin as an explosive the same as for using it to treat angina, a heart condition?

Back 56

This fact illustrates that one chemical can have many different uses depending on its quantity. The benefits of using a small amount of nitroglycerin in treating angina outweigh the risks, while when used in larger quantities, the risks can be reversed, such as when it is used as an explosive.

Front 57

Chemical changes can be both useful and destructive to humanity’s purposes. Cite a few examples of each kind of change from your own experience. Also give evidence from observation that each is indeed a chemical change and not a physical change.

Back 57

One example is the combustion of gasoline to propel vehicles. This reaction is a chemical change because the liquid gasoline is converted to heat and gases. Another constructive example is the burning of coal to heat water into steam, which is then used to turn a turbine and produce electricity. The combustion of coal results in a flame and in other gases. The above two examples are examples of chemical changes because the products have a different chemical formula than reactants; another way to look at this reaction is that it is not reversible. On the other hand, a destructive reaction is the use of ammonia nitrate to construct bombs for devastation. This compound is a solid but, when mixed with the correct reactants, will produce a flame and a rapid expansion of gases that makes the explosion. The products formed in this reaction are definitely different than the starting materials.

Front 58

What is the state (solid, liquid, gas) in which each of the following elements is commonly encountered?

1. tin
2. bromine
3. dysprosium
4. xenon
5. samarium
6. lithium
7. mercury
8. iodine
   

Back 58

1. tin: solid
   
2. bromine: liquid
   
3. dysprosium: solid
   
4. xenon: gas
5. samarium: solid
6. lithium: solid
7. mercury: liquid
8. iodine: solid
   

Front 59

True or False? An element is the smallest part of a compound that may still be identified as the compound.

Back 59

False, a molecule is the smallest part of a compound.

Front 60

True or False? An atom is the smallest part of a compound that may still be identified as the compound.

Back 60

False, a molecule is the smallest part of a compound.

Front 61

You have a mixture of sand and salt . How would you separate these two substances? When you have them as separate substances, how can you prove which is which?

Back 61

A mixture of sand and salt can be separated by adding water to the mixture. The salt will dissolve in the water while the sand will not and will settle to the bottom. Filtration of the solution will result in the capture of sand on the filter paper while the dissolved salt will pass through the funnel (filtrate). The sand can be identified because it is not soluble in water and can be recovered by filtering. The salt can be recovered from the filtrate by evaporating the water.

Front 62

Atrazine is a selective herbicide that has the molecular formula ‍. This compound is used for season-long weed control in corn, sorghum, and certain other crops. What elements are present in atrazine?

Back 62

Atrazine, C8H14N5Cl ‍, contains the elements carbon, hydrogen, nitrogen, and chlorine.

Front 63

Which of the following statements is true of a balanced chemical equation?

1. The total number of molecules of reactants has to be the same as the total number of product molecules.
2. The total number of atoms in the reactant molecules doesn’t have to equal the total number of atoms in the product molecules.
3. The identity of the atoms in the reactants has to be the same as the identity of the atoms in the products.
4. The physical state of the reactants has to be the same as the physical state of the products.
   

Back 63

The identity of the atoms in the reactants has to be the same as the products. The number of atoms on each side of the equation must also be equal.

Front 64

Given the following sentence, write a chemical equation using chemical symbols that convey the same information: “One nitrogen molecule reacts with three hydrogen molecules to produce two ammonia molecules, each containing one nitrogen and three hydrogen atoms.”

Back 64

N2 + 3 H2 -> 2 NH3

Front 65

Name four kinds of energy.

Back 65

1. Electrical energy can be generated by chemical reactions used in alkaline batteries and car batteries.
2. Heat energy can be generated by chemical reactions involving combustion or burning of gasoline.
3. Light energy can be generated by chemical reactions used by fireflies or in glow sticks.
4. Mechanical energy can by generated by using water behind a dam to turn a turbine or the alternator on a car using the belt of the engine.
   

Front 66

Prove that each of the following equations in question is balanced.

1. 2 Na(s) + Cl2(g) --> 2 NaCl(s)
2. N2(g) + 3 Cl2(g) --> 2 NCl3(g) [named as nitrogen trichloride]
3. CO2(g) + H2O(l) --> H2CO3(aq) [carbonic acid]
4. 2 H2O2(aq) [hydrogen peroxide] --> O2(g) + 2 H2O(l)

Back 66

1. On the left side of the arrow, “2 Na” means 2 Na atoms; one Cl2 molecule contains 2 Cl atoms. On the right side 2 NaCl units contain 2 Na atoms and 2 Cl atoms.
2. On the left one N2 -molecule contains 2 N atoms and 3 Cl2 molecules contain 6 Cl atoms. On the right 2 NCl3 molecules contain a total of 2 N atoms and 6 Cl atoms.
3. On the left there are 1 C atom, 2 H atoms, and 2+1 = 3 O atoms. On the right there are 1 C atom, 2 H atoms, and 3 O atoms.
4. On the left there are 4 H atoms and 4 O atoms in 2 molecules of H2O2 . On the right there are 4 H atoms in the 2 molecules of water; there are also 2 O atoms in the 2 water molecules and 2 more O atoms in the O2 molecule for a total of 4 O atoms.