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# HELUS8Ch3

### Physical Science: 8th Grade: Chapter 3

Question | Answer |
---|---|

____ is the amount of mass per unit volume of a material. | Density |

The equation for density is: ____/volume | mass |

If you know any two values in the density equation, you can calculate the third value. For example, if you know an object’s mass and density, you can calculate the object’s ___. | volume |

Density depends on the ___ of which an object is made, not the size of the object. | material |

The density of a material depends on the ___ of the particles (such as atoms or molecules) that make up the material. | mass |

The more massive the particles, the ___ the density of the material. | higher |

The density of a material depends on the ___ between the particles in the material. | distance |

The farther apart the particles, the ___ the density of the material. | lower |

Because the distance between particles of a gas increases as the gas is heated, the density of a gas ___ as it is heated. | decreases |

The density of a gas changes greatly as its ___ changes. | temperature |

To measure the density of an object, you first need to measure both its mass and its ___. | volume |

The mass of an object can be measured with a ___. | balance |

To measure the mass of a substance that requires a container, subtract the mass of the ___ ___ from the total mass. | empty container |

The volume of a liquid can be measured with a ___ ___. | graduated cylinder |

A ___ ___ is a six-faced block in which all faces are rectangular. | rectangular solid |

The volume of a rectangular solid is equal to its length multiplied by its width multiplied by its ___. | height |

For an object with an irregular shape, one way to measure its volume is to place it in aliquid and measure the volume of liquid the object ___, or pushes aside. | displaces |

Once you have measured the mass and volume of an object or material, you can calculate its ___ by dividing its mass by its volume. | density |

Density is a physical property, which means that you can measure it without changing the___ of the material whose density is being measured. | composition |

A ___ is a material that can flow and has no definite shape. | fluid |

___ and gases are fluids. | Liquids |

Fluids can exert ___. | forces |

___ is the force per unit of area applied on the surface of an object. | Pressure |

Pressure depends on the area over which a force is exerted. If the area increases, thepressure ___. | decreases |

Pressure depends on the size of the force. When ___ increases, pressure also increases. | force |

The equation for pressure is P = force/_____ | area |

The SI unit of pressure is the ___, abbreviated Pa. | pascal |

A pressure of 1 Pa is equal to a force of1 N applied over an ___ of 1 m2 | area |

For any liquid in a container of any shape, the pressure depends only on the height of the ___ of liquid above the surface where you measure the pressure. | column |

The deeper underwater you go, the ___ the pressure is on you. | greater |

Pressure increases with depth because as you go deeper, the column of water above you gets ___. | taller |

In a fluid, pressure is exerted on all points on the outside of an object in a direction ___ to the surface of the object at that point. | perpendicular |

A gas, like any ___, exerts pressure on an object. | fluid |

Pressure depends on the ___ of thegas above the object. | height |

___ ___ is the force exerted per unit area by air particles. | Atmospheric pressure |

As you climb, or increase your elevation, atmospheric pressure ___. | decreases |

Atmospheric pressure at sea level is caused by a large weight of gas, but is difficult to notice because there is an equal, ___ pressure pushing out from the inside of your body. | internal |

The ___ ___ is the net upward force exerted on an object in a fluid by the surrounding fluid. | buoyant force |

In a fluid, there is no net ___ force on an object caused by pressure from the fluid. | horizontal |

Because in a fluid, pressure increases with depth, the force of the fluid pushing up on the bottom of an object is always ___ than the force of the fluid pushing down on the top of the same object. | greater |

The size of the ___ force does not depend on depth. | buoyant |

___ ___ states that the buoyant force on an object is equal to the weight of the fluid the object displaces. | Archimedes’ principle |

Whether an object sinks or floats depends on the relative size of the buoyant force on theobject and the ___ of the object. | weight |

If the buoyant force on an object is less than the object’s weight, the net force on the object is ___ and the object will accelerate downward, or sink. | downward |

When an object is ___, it is not accelerating vertically, which means that the upward (or buoyant) force and the downward forces on it are the same. | floating |

An object will float if it is less dense than the ___ around it. | fluid |

Metal boats float because they contain ___, which makes their total density less than the water around them. | air |

A ___ is an instrument that measures the density of a fluid. | hydrometer |

In a less dense fluid, a hydrometer displaces more fluid and floats ___ than in a denser fluid. | lower |

In a denser fluid, a hydrometer displaces less fluid and floats ___. | higher |

Like any fluid, air exerts ___ on things around it. | pressure |

If the buoyant force due to air pressure on an object is large enough, the object can ___ in air. | float |

Helium gas is ___ dense than nitrogen gas and oxygen gas, which are the main components of air. | less |

When a balloon is filled with helium, it is less dense than the air around it, and so the balloon ___. | floats |

Whether a hot-air balloon rises or falls can be controlled by changing the density of the ___ inside the balloon. | air |

Using a burner to heat the air in a hot-air balloon causes those air molecules to move___ ___ from each other, so that air becomes less dense than the air around theballoon. | farther apart |

When the air in a hot-air balloon ___, it becomes as dense as the air around the balloon. The total density of the hot-air balloon is then greater than the air around it, and the balloon sinks. | cools |

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jnosik