Amelia chapter one

Law of conservation of mass

Total mass remains constant throughout a chemical change 

Ex: burning of paper. The mass doesn’t change, the paper just changes into a different substance.

Solids, liquids, gasses

Solid: matter characterized by rigidity

Liquid: a relatively incompressible fluid

Gas: easily compressible fluid 

Physical property

A characteristic that can be observed for a material without changing its chemical identity.

ex: physical state (solid, liquid, gas), melting point, color 

Chemical property

A characteristic of a material involving its chemical change 

ex: iron’s ability to react with oxygen to produce rust, zinc’s ability to react with hydrochloric acid to produce hydrogen gas, heat of combustion

Physical change

A change in the former matter but not it’s chemical identity 

ex: chromatography, freezing water, dissolving salt in water 

Chemical change

A change in which one or more kinds of matter are transformed into new matter

ex: rusting of iron, leaves changing color,explosion of fireworks 

Substance

Kind of matter which cannot be separated into other kinds of matter 

ex: sodium chloride 

Pure substance/chemical substance

A material that is homogeneous and has constant properties throughout

ex: sugar, salt, oxygen gas 

Impure substances

Substances that contain traces of other materials in it, heterogeneous 

ex: soil 

Element

A substance that cannot be decomposed by any chemical reaction into simpler substances

ex: sulfur, mercury, iodine 

Compound

A substance composed of two or more elements chemically combined 

ex: sodium chloride, hydrogen peroxide, salt 

Mixture

A material that can be separated by physical means into two or more substances 

ex: sodium chloride in water 

Homogeneous mixture

A mixture that is uniform in its properties throughout given samples 

ex: salt water, air 

Heterogeneous mixture

A mixture that consists of physically distinct parts, each with different properties 

ex: beach stand, stew, 

Intensive property

A physical property of a system which does not depend on the system’s size or amount of material

ex: viscosity, melting point, temperature

Extensive property

A property of a system which depends on the amount of matter present

ex: volume, mass

Chromatography

A group of similar separation techniques. Depends on how fast a substance moves, in a stream of liquid or gas, past a stationary phase.

Three kinds: paper, column, gas

 

Paper: Mostly dealing with pigments. The color samples are drawn/put onto the paper which is bathed in water. Slowly as the methanol/water creeps up the paper, the dyes in the sample are separated.

Column: A solution is poured into a column containing powdered chalk. Liquid is then poured into the column, causing the substances to separate into bands. The substances continue to separate further.

Gas: A stationary material is packed into a column. As the gas moves through the mixture, substances of the gas are attracted differently to the stationary material, thus separating.

 

Paper chromatography can be used in the lab when trying to decipher the different pigments that make up a single color. ex: m;m lab

 

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