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Abi Science 2017 > Particles Of Which Substances Are Made > Flashcards

Particles Of Which Substances Are Made Flashcards

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1
Q

What kind of structure does an ionic substance form?

A

An ionic crystal lattice

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2
Q

What is an ionic crystal lattice?

A

A giant 3D structure consisting of billions of ions

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3
Q

What kind of force holds an ionic crystal lattice together?

A

Electrostatic force

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4
Q

What is an electrostatic force?

A

The force of attraction between negative and positive ions

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5
Q

What is the magnitude of an electrostatic force?

A

It is very strong

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6
Q

What phase are ionic compounds at room temperature?

A

Solids

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7
Q

What kind of melting point does an ionic compound have?

A

High

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8
Q

Why do ionic compounds have high melting points?

A

It takes a lot of energy to overcome the electrostatic forces holding the solid together

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9
Q

Can ionic compounds conduct electricity?

A

Not in solid form

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10
Q

Why can’t a solid ionic compound conduct electricity?

A

The ions are not free to move

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11
Q

When can ionic compounds conduct electricity?

A

When they are molten

When they are dissolved

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12
Q

Why can ionic compounds conduct electricity when molten or dissolved?

A

The ions are now free to move around and act as charge carriers

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13
Q

What is an electrolyte?

A

A solution that has dissolved ions in it

i.e a solution that can conduct electricity

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14
Q

What is dissociation?

A

When the lattice of an ionic compound is broken up

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15
Q

Why are solid ionic compounds brittle?

A

They break easily

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16
Q

Why do solid ionic compounds break easily?

A

When pressure is put on them
The layers of ions move
Like charged ions line up
The electrostatic repulsion break the crystal

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17
Q

What two kinds of structures can covalent substances form?

A

Covalent molecular structures

Covalent network structures

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18
Q

What are covalent molecular structures?

A

Structures made out of covalent molecules

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19
Q

What are intramolecular forces?

A

The force of attraction existing within a covalent molecule

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20
Q

What is the general magnitude of intramolecular forces?

A

Strong

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21
Q

What is a polar molecule?

A

A molecule consisting of atoms, where one atom has a greater electronegativity than the other
The bonding pair is more strongly attracted to that atom

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22
Q

What is a non-polar molecule?

A

A molecule consisting of atoms, where the atoms have an equal electronegativity
The bonding pair is perfectly shared between them

23
Q

What does a polar covalent bond cause?

A

The more electronegative atom will be more negatively charged
The other atom will have a slightly positive charge

24
Q

What are intermolecular forces?

A

The forces existing between covalent molecules

These forces hold the crystal lattice of covalent molecular structures together

25
Q

What is the general magnitude of intermolecular forces?

A

Weak

26
Q

Why are covalent molecular structures easy to break apart and have low melting points?

A

The intermolecular forces are weak and easy to break

27
Q

What is the general melting point of a covalent molecular structure?

A

Low

28
Q

Why does water have a greater density than ice?

A

The intermolecular forces present in the solid phase result in an open tetrahedral structure, which takes up more space

29
Q

Why does ice float on water?

A

Its density is less than that of water

30
Q

Do covalent molecular structures conduct electricity?

A

No

31
Q

What are covalent network structures?

A

Substances consisting of non-metal atoms covalently bonded to non-metal atoms

32
Q

What kind of melting points do covalent network structures have?

A

Extremely high

33
Q

What is an example of a covalent network structure?

A

Carbon

34
Q

What does it mean when a substance has an allotrope?

A

It has more than one crystalline form

35
Q

What is an example of an allotrope?

A

Carbon

It can form both diamond and graphite

36
Q

Why is diamond such a hard substance?

A

Each carbon atom is bonded to four other carbon atoms

37
Q

What is the melting point of diamond?

A

3500° C

38
Q

How does graphite differ from diamond? (On a molecular level)

A

In graphite, the carbon atoms are only bonded to three other carbon atoms
This causes the structure of graphite to occur in layers

39
Q

Why is graphite so much softer than diamond?

A

The bonds between the layers of carbon atoms are very weak

They can easily slide over one another

40
Q

Why can graphite conduct electricity?

A

The fourth valence electron of graphite is free to move around

41
Q

What are the properties of covalent network structures?

A

Extremely high melting points
Solid at room temperature
Hard (except graphite)
Do not conduct electricity (except graphite)

42
Q

What is the lattice of a metal like?

A

Regularly spaced positive ions held together by the force of attraction between these positive ions and the ‘sea’ of negative electrons

43
Q

What are the properties of metallic substances?

A

Conductors of both heat and electricity
Malleable and ductile
High density
Have lustre

44
Q

Why are metallic substances malleable and ductile?

A

The force of attraction existing in its lattice still exists under these conditions

45
Q

Why do metallic substances have a high density?

A

The atoms are packed closely together

46
Q

Why do metals have lustre?

A

The loosely bound electrons reflect all frequencies of light

This causes a photoelectric effect (shine of a metal)

47
Q

What is an example of an ionic compound?

A

Sodium chloride

NaCl

48
Q

What are three examples of a covalent molecular structure?

A

Dry ice (CO2(s))
Iodine (s)
Ice (H2O(s))

49
Q

What are the main differences between a covalent network and a covalent molecular structure?

A

Covalent network: atoms covalently bonded

Covalent molecular: molecules with intermolecular forces holding them together

50
Q

What kind of particles exist in a metallic crystal lattice?

A

Positive metal ions

51
Q

What force holds a metallic crystal lattice together?

A

Metallic bond

52
Q

What is a metallic bond?

A

The force existing between the ions and the delocalised electrons

53
Q

Give two examples of a metallic crystal lattice?

A

Sodium (Na)

Silver (Ag)

Abi Science 2017 (18 decks)

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