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Surface Tension Flashcards

1
Q

When a stone falls through a viscous liquid what forces act on it?

A

Weight (downwards) upthrust (upwards) and viscous force (upwards).

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2
Q

In what direction does the viscous force act?

A

Opposite to the motion of the stone.

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3
Q

What happens to the viscous force as the stone’s speed increases?

A

It increases.

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4
Q

What happens when the viscous drag balances the downward force of the weight of the stone?

A

The stone moves with constant velocity.

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5
Q

What is this constant velocity called?

A

Terminal velocity.

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6
Q

What is easier to pour: water or honey?

A

Water.

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7
Q

What does a little stone dropped into a cylinder of water do compared to when dropped into a cylinder containing engine oil?

A

It gets to the bottom faster.

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8
Q

What property causes these differences in flow?

A

Viscosity.

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9
Q

Define viscosity.

A

The internal friction between layers of a liquid or gas in motion.

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10
Q

Are liquids that pour slowly more or less viscous than those which pour faster?

A

More viscous.

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11
Q

Is very cold thick palm oil more or less viscous than very cold water?

A

More viscous.

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12
Q

What can viscosity be considered as?

A

Friction in fluids.

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13
Q

What opposes the movement of one layer of fluid over another?

A

Viscous forces.

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14
Q

What opposes the downward motion of a body in a viscous liquid?

A

The viscosity of the liquid.

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15
Q

Does a more viscous liquid oppose the movement of a stone more or less?

A

More.

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16
Q

What is observed when three tubes with fine bores but different diameters are dipped into clean water?

A

Water rises in the tubes

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17
Q

What is observed when the experiment is repeated with soap solution?

A

A similar situation is observed

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18
Q

What is observed when the tubes are dipped in mercury?

A

The mercury falls in the tubes.

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19
Q

What is the action of liquids to rise or fall in capillary tubes known as?

A

Capillarity.

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20
Q

Define capillarity or capillary action.

A

The tendency of a liquid to rise or fall in a narrow tube.

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21
Q

What is the shape of the surface of water and soap solution in a capillary tube?

A

The surface curves upwards.

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22
Q

What is the shape of the surface of mercury in a capillary tube?

A

The surface curves downwards away from the glass tube.

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23
Q

What two terms are required to explain capillarity?

A

Cohesion and adhesion.

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24
Q

Define cohesion.

A

The force of attraction between molecules of the same kind.

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25
Define adhesion.
The force of attraction between molecules of different kinds.
26
Does water spread on a clean glass surface?
Yes.
27
Is the cohesion of mercury molecules greater or less than the adhesion of mercury molecules to those of glass?
Greater.
28
What do mercury molecules form on a glass surface?
Globlets or spherical beads.
29
How are materials for umbrellas
raincoats
30
What does this treatment prevent?
Water from wetting the materials.
31
What forms across the spaces between the threads of the fabric?
A thin water-film.
32
What prevents water from seeping through?
The surface tension 'skin' on the raindrops.
33
What happens if the inside material of an umbrella or tent is touched?
The surface film is broken
34
Why is it difficult to wash an oily plate or dirty cloth with water only?
Because the oil or dirt repels the water.
35
How do soaps and detergents aid in washing?
They weaken the surface tension of water and help float away oil or dirt particles.
36
Does hot or cold water wash more effectively?
Hot water.
37
Why does hot water wash more effectively?
High temperatures decrease the surface tension of water.
38
What do detergents contain that aids in cleaning?
Chemicals that combine with dirt and oil
39
Besides soap
what else reduces surface tension?
40
What does the surface of a liquid behave like?
A stretched elastic skin.
41
Give an example illustrating the elastic skin behavior of a liquid's surface.
A drop of water forming slowly on a tap.
42
What supports the weight of the water in a drop forming on a tap?
The elastic bag or skin.
43
What can be made to float on the surface of clean water despite normally sinking?
A dry needle or razor.
44
How is a needle or razor made to float on water?
By placing it carefully on a small piece of filter paper
45
What supports the weight of the needle or razor?
Surface forces acting upwards.
46
What is the 'skin' of the water surface called?
Surface tension.
47
Define surface tension.
The force acting along the surface of a liquid
48
What is surface tension considered to be due to?
Forces of attraction between the molecules of the liquid.
49
Is there a net force on a molecule in the interior of a liquid?
No.
50
Why do liquids tend to form spherical drops?
Due to surface tension.
51
Compared to solids
how free are the molecules of liquids and gases to move?
52
What are liquids and gases collectively referred to as
and why?
53
Do fluids have a rigid shape?
No.
54
How do fluids respond to forces compared to solids?
Much differently.
55
What properties of fluids are discussed in the text?
Surface tension
56
What kind of arrangement do non-crystalline substances lack?
The regular arrangement of atoms characteristic of crystals.
57
What is another term for non-crystalline?
Amorphous.
58
In what ways are amorphous substances more like liquids than solids?
They lack a regular arrangement of atoms.
59
Give examples of amorphous substances.
Glass and plastics.
60
Do amorphous substances form crystals?
No.
61
What do amorphous solids usually consist of?
Long-chainline molecules intertwined in the liquid state.
62
How do amorphous substances behave when cooled?
Oddly.
63
At what temperature do crystalline solids solidify?
A constant temperature.
64
What does not occur in amorphous solids when the melted material cools?
Crystallization.
65
Why doesn't crystallization occur in amorphous solids?
Because the molecules cannot be untangled before they are frozen.
66
What is an amorphous solid considered to be?
A supercooled liquid.
67
What is the coordination number of each atom in a simple cubic lattice?
Six.
68
What is the coordination number?
The number of immediate neighbors each atom within the solid has.
69
What is body-centred cubic (bcc) lattice?
A structure in which
70
How many atoms are in each unit cell of a bcc lattice?
Nine.
71
How many immediate neighbors does the central atom in a bcc lattice have?
Eight.
72
What is the coordination number of each atom in a bcc lattice?
Eight.
73
Give examples of crystals with a body-centred cubic lattice structure.
Sodium and iron crystals.
74
What is face-centred cubic (fcc) lattice?
A structure with atoms at the eight corners of the cube plus one atom at the centre of each of the six faces of the cube.
75
How many atoms are in each unit cell of an fcc lattice?
14
76
How many immediate neighbors does each atom in an fcc lattice have?
12
77
What is the coordination number of each atom in an fcc lattice?
12
78
Give examples of crystals with a face-centred cubic lattice structure.
Copper
79
What is hexagonal close-packed (hcp) lattice?
A structure in which one layer of atoms is arranged in regular hexagons
80
What is the coordination number of each atom in an hcp lattice?
12
81
Give examples of crystals with a hexagonal close-packed lattice structure.
Magnesium and zinc crystals.

Physics (25 decks)

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