Unit 2: States Of Matter Flashcards Preview

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Flashcards in Unit 2: States Of Matter Deck (23):


An air-like, fluid state of matter air-like fluid substance which expands freely to fill any space available, irrespective of its quantity. Due to this, temperature and pressure determine its volume.

Properties include:
- Indefinite volume, resulting in temperature and pressure determining its volume
- Takes shape of its container
- Low density
-Possesses high thermal energy, resulting in high molecular vibration

[For example: oxygen, vapor]



A substance that flows freely but is of constant volume, meaning it has definite volume but not shape.

[For example: oil]



A gas-like state of matter consisting of positively charged ions, free electrons, and neutral particles.

Properties include:
- Unlike gases, good conductors of electrical currents. -
Most commonly occurring state of matter.

[For example: the sun, fire, lightning]



Matter with definite volume and definite shape.

Properties include:
- Rigid
- Tightly packed molecules
- Possess little thermal energy, resulting in very little molecular vibration



The degree of degree of consistency measured by the quantity of mass per unit volume (or compactness).


Endothermic Reaction

A process that absorbs heat, such as melting or evaporation.

[For example: sublimation, evaporation]


Exothermic Reaction

A process that releases heat.

[For example, deposition, condensation.]



The process by which water vapor changes from gas to liquid. Molecules slow down when condensation occurs. The energy they give up is released as heat.



The process by which water changes to water vapor. Evaporation absorbs heat to increase the speed of the molecules.


How does pressure affect phase change?

The points where phase changes occur depend on pressure as well as temperature. When pressure is lower, it's easier for molecules to break away from each other. When pressure is higher, molecules have a difficult time separating.


How does temperature affect phase change?

Temperature is a measurement of the average kinetic energy of the molecules within a substance. Kinetic energy is the energy of motion and can be measured as the movement of molecules within an object. Examining the impact of different temperatures on kinetic energy identifies its effects on the various states of matter.


Kinetic Energy

The energy of motion, can be measured as the movement of molecules within an object.


How does temperature affect phase change?

Examining the impact of different temperatures on kinetic energy identifies its effects on the various states of matter.

As temperature rises, the kinetic energy of the molecules within matter begin to vibrate, which decreases the attraction of these molecules.



The continuous physical force exerted on or against an object by something in contact with it.


Kinetic Theory of Matter

The Kinetic Theory of Matter states that matter is composed of a large number of small particles—individual atoms or molecules—that are in constant motion.


Law of Conservation of Energy

The law of Conservation of Energy states that the total energy of an isolated system remains constant, it is said to be conserved over time. This law means that energy can neither be created nor destroyed; rather, it can only be transformed from one form to another.


Melting Point

The temperature threshold at which the vibration of molecules becomes sufficient enough to cause a solid to change to liquid.

The melting point, in turn, also identifies the temperature at which the liquid will change back to the solid, so it is also the freezing point.


Freezing Point

Also known as the melting point, this is the temperature at which a liquid will change back into a solid.


Boyle's Law

Boyle's Law states that, 'for a fixed amount of an ideal gas kept at a fixed temperature, pressure and volume are inversely proportional'.

In layman's terms: Boyle's Law is a gas law, stating that the pressure and volume of a gas have an inverse, or opposite, relationship when temperature is held constant.


Boiling Point

In a liquid, molecules are not as tightly compressed as in a solid, and they can move around. As the temperature -- and thus the kinetic energy -- of a liquid increases, the molecules begin to vibrate more rapidly. They then reach a threshold at which their energy becomes so great that the molecules escape into the atmosphere, and the liquid becomes a gas. This temperature threshold is called the boiling point if the change is from liquid to gas as the temperature increases.


Condensation Point/Dew Point

Also known as the boiling point, this is the temperature threshold at which a gas will change into a liquid.


Entropy (S)

Hard: Entropy is a thermodynamic quantity representing the unavailability of a system's thermal energy for conversion into mechanical work, often interpreted as the degree of disorder or randomness in the system.

Easy: Entropy is a measure of the random activity in a system. The entropy of a system depends on your observations at one moment. How the system gets to that point doesn't matter at all. If it took a billion years and a million different reactions doesn't matter. Here and now is all that matters in entropy measurements.

When we say random, we mean energy that can't be used for any work. It's wild and untamed. Scientists use the formula (delta)S = (delta)Q /(delta)T. "S" is the entropy value, "Q" is the measure of heat, and "T" is the temperature of the system measured in Kelvin degrees. When we use the symbol delta, it stands for the change. Delta T would be the change in temperature (the original temperature subtracted from the final).


Enthalpy (H)

Enthalpy is a measurement of energy (specifically heat, or thermal, energy). It is the thermodynamic quantity equivalent to the internal energy (U) of a system plus the product of pressure (P) and volume (V). It is represented by the formula H = U + PV.