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Lec 1-4.pdf Flashcards
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Lec 1-4.pdf Flashcards
Lec 1-4.pdf Flashcards
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1
Question
What did the Greek philosopher Democritus propose around 460 BC?
Answer
Democritus proposed that all matter was composed of invisible particles called 'atomos' meaning 'uncuttable', which is the origin of the name 'atoms'.
2
Question
What is formed when two or more atoms come together?
Answer
Two or more atoms can form an electrically neutral entity called a molecule.
3
Question
What results from the attraction between atoms and molecules?
Answer
Attraction between atoms and between molecules results in materials we can see and touch.
4
Question
What is the basic unit of water?
Answer
The basic unit of water is a molecule made of two hydrogen atoms and one oxygen atom.
5
Question
What happens when a molecule attains high kinetic energy?
Answer
If each molecule attains a kinetic energy that is higher than the attraction between these molecules, they appear in vapor form.
6
Question
What is the transformation between vapor, liquid, and solid called?
Answer
The transformation between vapor, liquid, and solid is called the change of state.
7
Question
What energy is required to change a solid to a liquid state?
Answer
A change from the solid to the liquid state will require additional energy, known as the latent heat of fusion.
8
Question
What is the temperature at which a change from solid to liquid occurs known as?
Answer
The temperature at which this change occurs is known as the melting temperature or fusion temperature.
9
Question
What is needed when water boils to transform the liquid to vapor?
Answer
When water boils, energy is needed to transform the liquid to vapor, and this quantity of energy is known as the heat of vaporization.
10
Question
What process allows some solids to change directly to vapor?
Answer
Some solids can change directly to vapor by a process called sublimation, as seen in dry ice.
11
Question
What are primary bonds dependent on?
Answer
The formation of primary bonds depends on the atomic structures and their tendency to assume a stable configuration.
12
Question
What are primary bonds also called?
Answer
Primary bonds are also called chemical bonds.
13
Question
What are the three different types of primary bonds?
Answer
The three different types of primary bonds are ionic, covalent, and metallic.
14
Question
What is the classic example of ionic bonding?
Answer
The classic example of ionic bonding is the bond between Na and Cl of sodium chloride.
15
Question
Where does ionic bonding exist in dentistry?
Answer
In dentistry, ionic bonding exists in some dental materials such as in gypsum.
16
Question
What are covalent bonds?
Answer
In many chemical compounds, two valence electrons are shared by adjacent atoms, creating covalent bonds.
17
Question
How are atoms held together in covalent bonding?
Answer
By virtue of sharing electrons, the two atoms are held together by covalent bonds to form a molecule that is sufficiently stable and electrically neutral.
18
Question
Where does covalent bonding occur?
Answer
Covalent bonding occurs in many organic compounds such as in dental resins that form the backbones structure of hydrocarbon chains.
19
Question
What characterizes metallic bonds?
Answer
The outer shell valence electrons can be removed easily from metallic atoms and form positive ions.
20
Question
What is described as an electron cloud or gas in metals?
Answer
The free valence electrons can move about in the metallic space lattice to form what is sometimes described as an electron cloud or gas.
21
Question
What properties do free electrons give metals?
Answer
The free electrons give the metal its characteristically high thermal and electrical conductivity.
22
Question
What ability do metallic bonds provide to metals?
Answer
Metallic bonds are also responsible for the ability of metals to deform plastically.
23
Question
What are secondary bonds?
Answer
Secondary bonds do not share electrons, instead charge variations among atomic groups of the molecule induce pole forces that attract adjacent molecules or parts of a large molecule.
24
Question
What are Van der Waals forces?
Answer
Van der Waals forces of attraction arise from dipole attractions.
25
Question
What is a hydrogen bond?
Answer
A hydrogen bond is a special case of dipole attraction of polar compounds.
26
Question
What did Robert Hooke explain in 1665?
Answer
In 1665, Robert Hooke explained crystal shapes in terms of the packing of their component parts.
27
Question
What is a crystal formation characterized by?
Answer
Crystals form a regularly spaced configuration known as a crystal lattice.
28
Question
What is the simplest and most regular lattice?
Answer
The simplest and most regular lattice is cubic, characterized by axes that are all of equal length and meet at 90 degree angles.
29
Question
What is a vacancy in a lattice structure?
Answer
Each missing atom site is called a vacancy.
30
Question
What is a typical non-crystalline solid made of SiO2?
Answer
Glass is a typical non-crystalline solid of SiO2 because its atoms tend to be arranged in non-repeating units.