Lec2

Question 1

Intramolecular forces are :

Answer 1

forces that hold atoms together within a molecule.
Or
forces that exist between molecules.

Question 2

Types of chemical bonds:

Answer 2

1-ionic bond
2-covalent bond
3-metallic bond

Question 3

ionic bonds (chemical bond) function is?

Answer 3

-Transfer of electrons between a non metal & a metal
-Observed in formation of salts, example NaCl

Question 4

Covalent bond (chemical) function is?

Answer 4

-Sharing of electrons between two non metals
-Observed in organic compounds , example CH4

Question 5

__________ bond Observed in organic compounds , example CH4

Answer 5

covalent

Question 6

___________ bond Observed in formation of salts, example NaCl

Answer 6

Ionic bonds

Question 7

Metallic bond (chemical) is form from?

Answer 7

Metallic electrons are generally delocalized ; the result is a large number of free electrons around positive nuclei , sometimes called an electron sea.

Question 8

The attractions between molecules are not nearly as strong as the intramolecular attractions (bonds)
T/F

Answer 8

T

Question 9

Many physical properties reflect intermolecular forces, like _____________, ____________, _________, ________________, and ________________.

Answer 9

boiling points, melting points, viscosity لزوجة , surface
tension التوتر السطحي, and capillary action.

Question 10

Types of forces:

Answer 10

1-Binding Forces
A-Cohesion ;sim
B-Adhesion ;diff
2-Repulsive Forces
3-attractive forces

Question 11

Types of binding forces:

Answer 11

1-Cohesion – similar molecules
2-Adhesion – different molecules

Question 12

Repulsive forces mechanism (function)?

Answer 12

prevent molecules from annihilating(destroy) each other

Question 13

Attractive forces ex:

Answer 13

Van der Waals , Hydrogen bond

Question 14

When molecules interact, both ___________ and __________ forces operate.

Answer 14

Repulsive
Attractive

Question 15

When the molecules are brought so close that the outer charge clouds touch, they __________.

Answer 15

Repel each other

Question 16

______________ are necessary for molecules to cohere( bind ), whereas ____________ act to prevent the molecules from interpenetrating and annihilating ( destroy)each other.

Answer 16

Attractive forces
Repulsive forces

Question 17

van der Waals forces ??

Answer 17

1-Dispersion forces (or london dispersion forces)
2- dipole-dipole forces

referred to collectively as van der Waals forces.

Question 18

Types of Intermolecular Force (Weakest to strongest forces):

Answer 18

1-dispersion forces (or london dispersion forces)
2- dipole-dipole forces
3-hydrogen bonding ( a special dipole-diploe force )
4- ion-dipole forces

Question 19

_______________is the weakest intermolecular force

Answer 19

The London dispersion force

Question 20

____________ are the attractive forces that cause nonpolar substances to condense to liquids and to freeze into solids when the temperature is lowered sufficiently.

Answer 20

London forces

Question 21

Dispersion forces: The tendency of an electron cloud to distort is called its ____________.

Answer 21

Polarizability

Question 22

Dipole-Dipole interactions result when…..

Answer 22

when two dipolar molecules interact with each other through space, the negative portion of one attracted to positive portion of second polar molecule.

Question 23

The dipole–dipole interactions experienced when H is bonded to N, O, or F are unusually strong.
We call these interactions ____________.

Answer 23

hydrogen bonds

Question 24

Ion-dipole intreraction occurs between ___________and___________.

Answer 24

charged ion
Molecule that has a dipole

Question 25

The strength of these forces(ion-dipole forces) is what makes it possible for ionic substances to dissolve in _______solvents.

Answer 25

Polar

Question 26

These bonds ( van der waal forces ) can occur between __________ or ________ molecules.

Answer 26

Nonpolar Polar

Question 27

van der Waals bonds are extremely dependent on the _____________________________________, and are significant only when the electron clouds of the molecules are just touching.

Answer 27

distance of separation between molecules,

Question 28

Gases have lower _________ than other states of matter, such as solids and liquids

Answer 28

Lower

Question 29

An ideal gas is defined as

Answer 29

one in which all collisions between atoms or molecules are perfectly elastic and in which there are no intermolecular attractive forces

Question 30

Specifically, an ideal gas ...(properties)

Answer 30

1 . Obeys all of the gas laws under all conditions. 2 . Does not condense into a liquid when cooled. 3 . Shows perfectly straight lines when its V and T & P and T relationships are plotted on a graph. We assume that gases are ideal to simplify our calculations.

Question 31

A real gas is defined as

Answer 31

gas that at all standard pressure and temperature conditions does not obey gas laws.

Question 32

_________________those in which the atoms, ions, or molecules that make up the solid exist in a regular, well-defined arrangement.

Answer 32

Crystalline solids

Question 33

The smallest repeating pattern of crystalline solids is known as the ___________.

Answer 33

Unit cell

Question 34

The structural of crystalline solids ,such as ice, sodium chloride , and menthol are arranged in ________________________.

Answer 34

affixed geometric Patterns or lattice.

Question 35

Crystalline solids show ________________, passing rather sharply from the solid to the liquid state.

Answer 35

definite melting points

Question 36

_________________ are composed of positively charged ions in a field of freely moving electrons, some times called the ____________.

Answer 36

Metallic crystals Electron gas

Question 37

Metals are good conductors of electricity because of…….

Answer 37

the free movement of the electrons in the lattice

Question 38

.Metals may be soft or hard and have low or high melting point T/F

Answer 38

T

Question 39

The main types of crystalline solids are:

Answer 39

1- ionic solids 2- metallic solids 3- covalent network solids 4- molecular solids

Question 40

the phenomenon in which a solid chemical compound exists in ____________________, such as carbon and sulfure

Answer 40

more than one crystalline form

Question 41

Polymorphic forms of a drug substance can have different chemical and physical properties. T/F

Answer 41

T

Question 42

Liquid crystals that are formed by temperature change ("partial melting" of the solid phase) are called _________________.

Answer 42

thermo tropic liquid crystals

Question 43

Properties of liquid crystals:

Answer 43

1.Are mobile 2.Show consistent color changes 3.Sensitive to electric field 4.Solublization of water-insoluble material 5-Highly viscous in nature.