# Grade 8 Fluids (Density,Â viscosity, Buoyancy, Hydraulics, Pneumatics)

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Fluids exist in different colors, weight, and viscosity. All throughout this week, we discussed the density, viscosity, buoyancy, hydraulics, and pneumatics. How much did you understand these subtopics? If you believe you understood much then all you have to do is take up this grade 8 tests and see if you need more study hours to properly understand the topics. All the best!

• 1.

### In what states of matter can you find fluids?

• A.

Solids, gases and liquids

• B.

Gases and solids

• C.

Gases and liquids

• D.

Liquids and solids

C. Gases and liquids
Explanation
Fluids can be found in both gases and liquids. Gases, such as air, are considered fluids because they have the ability to flow and take the shape of their container. Liquids, on the other hand, also have the ability to flow and take the shape of their container, making them fluids as well. Solids, however, do not have the ability to flow and therefore cannot be classified as fluids.

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• 2.

### An important characteristic of fluids is that they can flow.  Fluids can do this because...

• A.

Particles in fluids are slippery

• B.

Particles in fluids can move around each other

• C.

Particles in fluids have a coating

B. Particles in fluids can move around each other
Explanation
Fluids can flow because particles in fluids can move around each other. Unlike solids, where particles are tightly packed and fixed in position, the particles in fluids have more freedom to move. This allows fluids to take the shape of their container and flow easily. The ability of particles in fluids to move around each other is what enables fluids to exhibit properties such as viscosity and fluidity.

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• 3.

### Gases are more compressible than liquids because...

• A.

The particles in gas are more attracted to each other

• B.

The particles in gas are smaller

• C.

The particles in gas are farther apart

C. The particles in gas are farther apart
Explanation
Gases are more compressible than liquids because the particles in a gas are farther apart. In a gas, the particles have more space between them compared to the particles in a liquid. This allows for more flexibility in rearranging the particles and compressing the gas. In contrast, the particles in a liquid are closer together, which limits their ability to be compressed. Therefore, the greater distance between gas particles makes gases more compressible than liquids.

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• 4.

### Water is ________________ oil.

• A.

Denser than

• B.

Less dense than

• C.

Has the same density as

A. Denser than
Explanation
Water is denser than oil because water molecules are closely packed together, resulting in a higher mass per unit volume compared to oil. This higher density causes water to sink when mixed with oil, as oil molecules are less tightly packed and have a lower mass per unit volume.

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• 5.

### The particles in water are ____________ oil

• A.

Farther apart than in

• B.

The same as in

• C.

Closer together than in

C. Closer together than in
Explanation
The correct answer is "closer together than in". This is because water molecules are held together by hydrogen bonds, which result in a relatively high density of particles in water compared to oil. As a result, the particles in water are closer together than in oil.

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• 6.

### Viscosity is caused by the ...

• A.

Thickness of a fluid

• B.

The attraction between the particles in a fluid

• C.

The spaces between the particles in a fluids

B. The attraction between the particles in a fluid
Explanation
Viscosity is caused by the attraction between particles in a fluid. If attraction is strong, it's harder for the particles to flow past each other, so it flows slower. Thickness is a way to describe viscosity, but is more a result and not the cause. The spaces between the particles is not always an indicator of how viscous a fluid will be. For example, oil is more viscous than water. But, it is less dense.

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• 7.

### If an object with  a density of 2g/mL, is placed in a water tank and displaces 10mL of water, what is the mass of the object?

• A.

20g

• B.

5g

• C.

15g

A. 20g
Explanation
The mass of the object can be calculated using the formula:
Mass=Density×Volume
In this case, the density of the object is given as 2 g/mL and the volume it displaces is 10 mL
Substitute these values into the formula:
Mass=2 g/mL×10 mL
Mass=20 g
Therefore, the mass of the object is 20 g.

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• 8.

### If 2 objects with the same mass are placed into water tanks... -object A displaces 10mL of water -object B displaces 15mL of water Which object is denser?

• A.

Object A

• B.

Object B

A. Object A
Explanation
Given that both objects have the same mass but displace different volumes of water:
Object A displaces 10 mL of water
Object B displaces 15 mL of water
The volume of water displaced by an object is directly related to the volume of the object itself when immersed in water. Therefore:
The volume of Object A is 10 mL
The volume of Object B is 15 mL
Since density is inversely proportional to volume (given the same mass), the object with the smaller volume (Object A) has a higher density. Thus, Object A is denser than Object B.

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• 9.

### Hydraulics and pneumatics are very similar.  How are they different?

• A.

Hydraulics uses water, pneumatics uses a gas

• B.

Hydraulics uses a liquid, pneumatics uses a gas

• C.

Hydraulics uses a gas, pneumatics uses a liquid

• D.

Hydraulics uses a liquid, pneumatics uses a solid

B. Hydraulics uses a liquid, pneumatics uses a gas
Explanation
Hydraulics and pneumatics are both methods of transmitting power using fluid pressure, but they differ in the type of fluid used. Hydraulics uses a liquid, typically oil or water, to transmit power and generate force. On the other hand, pneumatics uses a gas, usually compressed air, to transmit power and create motion. This difference in fluid type affects the performance, applications, and characteristics of both systems.

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• 10.

### Because of the way the particles are, ____________________(hydraulics, pneumatics) is more efficent.

hydraulics
Hydraulics
Explanation
Because of the way the particles are, hydraulics is more efficient.

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• 11.

### Which would be easier?

• A.

Holding a heavy object up on land

• B.

Holding a heavy object in water

• C.

They're both the same, it depends on the arm

B. Holding a heavy object in water
Explanation
Holding a heavy object in water would be easier because water provides buoyancy, which counteracts the force of gravity. This buoyant force reduces the effective weight of the object, making it feel lighter and easier to hold. In contrast, holding a heavy object up on land requires exerting more force against gravity without any buoyant support. Therefore, holding a heavy object in water would be less physically demanding.

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• 12.

### I want to make an ice cream sunde.  I can't get the caramel sauce out of the bottle.  What could I try to make the caramel sauce come out of the bottle easier?

• A.

Heat up the bottle

• B.

Put the bottle in the fridge

• C.

Shake the bottle with more force

A. Heat up the bottle
Explanation
Heating up the bottle can help to make the caramel sauce come out easier because heat causes substances to expand. By heating up the bottle, the caramel sauce inside will become less viscous and flow more easily, making it easier to pour out of the bottle.

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• Current Version
• May 15, 2024
Quiz Edited by
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• Dec 08, 2009
Quiz Created by
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