A: Mix and Flow of Matter, section 3: density, temperature, and buoyancy

Question 1

Define viscosity

Answer 1

The state of being thick, sticky, and semifluid in consistency, due to internal friction.

Question 2

Will the flow rate be faster if the substance is more viscous?

Answer 2

No. More viscous means it is thicker so more viscous would make the substance thick and slow to pour.

Question 3

What determines the viscosity of a substance?

Answer 3

The question is asking: what determines if the substance will be thick or thin?

The internal resistance or friction between the particles determines the viscosity.

Question 4

What factor has an effect on viscosity?

Answer 4

Temperature

Viscosity will decrease with increased temperature because as particles move more quickly, they interact for shorter time (shorter interactions) reducing internal friction or stress and therefore decreasing viscosity.

Question 5

How can viscosity be measured?

Answer 5

Using the ramp test, you can measure viscosity.

Ramping the temperature during a flow test is a fast test method to determine the temperature dependence of a material’s viscosity. In a flow temperature ramp, the temperature is varied continuously and the instantaneous viscosity is recorded.

Question 6

What is density?

Answer 6

The amount of matter in a given volume

Question 7

What density of a substance depend on?

Answer 7

It depends on the particles of a substance and whether the substance is a solid liquid or gas

Question 8

What is the formula for density?

Answer 8

Density (d) = mass (m) / volume (v)

density is mass divided by volume

Question 9

Why can ships float?

Answer 9

Ships contain a large quantity of air and the average density of the ship is lighter than the density of water

Question 10

Under what conditions could density remain constant?

Answer 10

Density does not change as long as the temperature, pressure, and material stays the same.

Side-note:
Density is NOT constant when the temperature changes, but for liquids and solids it doesn’t change very much with temperature or pressure. Liquids and solids expand only slightly with increasing temperature, and they compress only slightly with increasing pressure, so their densities are approximately constant under most ordinary conditions.

Question 11

Why does the density change as you heat a substance?

Answer 11

As energy is added, the particles move quickly and farther apart, thus increasing the volume. The density increases because mass remains constant but the volume increases

Question 12

What is a force?

Answer 12

It is a push or pull of an object, and is measured in Newtons (N).

E.g. buoyant force, normal force, gravitational force

Question 13

What is buoyancy?

Answer 13

It is the tendency of a substance to float.

This is a force that keep a boat above water instead of sinking if the boat is designed correctly.

The boat doesn’t keep rising though since there is an opposing force of gravity pushing it towards the center of the Earth.

Question 14

Why do buoyant objects float?

Answer 14

They take up space in a fluid, pushing some of it away of displacing it causing them to float, because the fluid pushes back against the force of gravity

Question 15

What is the buoyant force?

Answer 15

The buoyant force pushes objects away from the center of the Earth (up).

Question 16

What is a flow rate?

Answer 16

How quickly a fluid can flow

Question 17

What is a plimsoll line?

Answer 17

It shows how heavily a ship can be loaded in different weather conditions

Question 18

How do hot air balloons work?

Answer 18

As the air inside the balloon is heated, the balloon becomes less dense than the surrounding air. The buoyant force of the air will push the hot air balloon upwards, until the buoyant force equals the force of gravity. At that point the balloon will remain at the same altitude (distance from the surface of the Earth).

Question 19

What is the unit used for mass in the density equation?

Answer 19

grams (g)

This can take the metric prefixes such as kilograms kg when measuring mass in general. Density is measured mostly in grams per volume rather than kg per volume, but make sure to always show your units.

Question 20

What is the unit used for volume in the density equation?

Answer 20

cm3 centimeters cubed

Question 21

What are the units used for density?

Answer 21

g/cm3

3 should be superscript as in centimeters cubed

Question 22

What is pressure measured in?

Answer 22

Pascals

Question 23

What is the formula for pressure?

Answer 23

Pressure (P)= force (N)/ area (m2)

2 should be subscript as in meters squared

Pressure is measured in Pascals which is equivalent to Newton per meter squared

Question 24

How does drinking out of a straw work?

Answer 24

When we suck on the straw that lessens the pressure on the outside in the water or fluid and increases the pressure on the inside of the straw

Question 25

What does Pascal’s Law state?

Answer 25

An enclosed fluid transmits pressure in all directions equally

Question 26

What is a pneumatic device?

Answer 26

It is a pressure system that uses air instead of water

Question 27

What is a hydraulic device?

Answer 27

It is a pressure system that uses water instead of air