Friday, September 9, 2016

Physical Properties of Matter

physical property is any attribute, quality, or characteristic of a material that can be observed or measured without changing the composition of the substances in the material. There are many different properties that can be observed. The following are some examples.

Viscosity is the tendency of a liquid to keep from flowing—its resistance to flowing.

the degree to which something is thick, sticky, and semifluid in consistency, due to internal friction.

a quantity expressing the magnitude of internal friction, as measured by the force per unit area resisting a flow in which parallel layers unit distance apart have unit speed relative to one another.

One way to think about viscosity is to consider how "thick" a liquid is. Syrup is MORE viscous than water is.

The viscosity of a liquid usually decreases as its temperature goes up.

Conductivity is used to express how well a material allows heat or electricity to flow.

the degree to which a specified material conducts electricity, calculated as the ratio of the current density in the material to the electric field that causes the flow of current. It is the reciprocal of the resistivity.

(also thermal conductivity)the rate at which heat passes through a specified material, expressed as the amount of heat that flows per unit time through a unit area with a temperature gradient of one degree per unit distance.

Materials that have high conductivity, such as metals, are called conductors.

Malleability is the ability of a solid to be hammered without shattering.

(of a metal or other material) able to be hammered or pressed permanently out of shape without breaking or cracking.

Most metals malleable to a greater degree than are other things, like ice or glass.

Hardness of a material relates to the degree to which its surface can be penetrated. For an object to scratch another object, it must be made of a material that has more hardness then the other.

a measure of how resistant solid matter is to various kinds of permanent shape change when a compressive force is applied.

Melting and Boiling Points
The melting point is the temperature at which a substance changes from solid to liquid. This same temperature is also the point at which the substance changes from a liquid to solid (freezing point).

The boiling point is the temperature at which a substance changes from a liquid to a gas. At this same temperature, gases condense into a liquid (condensation point).

Density is the ratio of a substance's mass to its volume and can be expressed mathematically as D=M/V. Density results from the number of protons, neutrons, and electrons in the atoms that make up the substances and how closely they are arranged to each other either in the substance.

The physical properties of a material can be used to help identify it. A sample can be compared to known quantities to determine if the sample is made from them. For example, if an unknown metal has a density of 10.5 g/cm, it might be silver. If the other properties of the unknown match other known properties of silver, then the conclusion that the sample is sliver might be well-founded.

Separating Mixtures

Some physical properties can be used to separate mixtures. For example, a strong magnet could extract iron shavings from sand.

Other processes can be used with fluids.

Filtration is a process that uses a porous material to separate substances based on the size of their molecules.

A sample of the substance is poured through a filter and the filtrate comes out. Large particles of a suspension will be deposited on the filter paper as a residue.

a liquid that has passed through a filter

Evaporation is a process that will remove a liquid from a solution leaving behind the solid.

If a solutions is exposed to a temperature that is above the boiling point of the solvent, the solvent will turn to gas and leave the solute behind.

Evaporation is (one example) useful for separating a mixture of a solid and a liquid. 

Distillation is a process that separates the substances in a solution based on their boiling points.

If a solutions is exposed to a temperature that is above the boiling point of the solvent, the solvent will turn to gas and leave the solute behind. 
 Distillation can separate a mixture of two liquids that have different boiling points such as alcohol and water.

Centrifugal Separation
A centrifuge can be used to separate a suspension into layers based on the density of the particles. Samples are exposed to strong centrifugal forces which causes the most dense particles to separate from the less dense particles.

Some physical properties can be changed. For example, hardness and viscosity will change when a substance goes from a solid to a liquid. Some changes are reversible. Others are not. Freezing and melting both can be reversed. Scratching or changing the shape (flattening) are not directly reversible.


Definitions and content from:
New Oxford American Dictionary
Physical Science Concepts in Action, Pearson