Embedded Files
Use the search feature to find content (and happiness!)
Pure Substances
Pure Substances
A pure substance is one with a uniform and definite composition. Pure substances can be divided into two groups: elements and compounds:
A pure substance is one with a uniform and definite composition. Pure substances can be divided into two groups: elements and compounds:
Elements
Elements
Elements - only contain one kind of atom. Some examples of elements include hydrogen, sodium, carbon, and sulfur.
Elements are the simplest forms of matter which cannot be decomposed into simpler substances by any chemical or physical means.
Elements are classified on the Periodic Table of Elements. There are 90 kinds of naturally-occurring elements and they are the building blocks for all other substances.
Elements can combine with one another to form compounds.
Compounds
Compounds
Compounds are substances composed of two or more elements that are chemically combined.
Water, for example, is a compound because it is composed of only H20 molecules. Each molecule of water is a chemical combination of two hydrogen atoms and one oxygen atom.
Compounds like water can be separated into simpler substances only by chemical means.
Water can be broken down into its component elements of hydrogen and oxygen with a process called electrolysis.
Mixtures
Mixtures
Mixtures are simply a heterogeneous or homogeneous physical combination of two or more substances. Mixtures can be separated based solely on physical properties, or by undergoing physical changes.
The melting of ice, the freezing of water, the evaporation of water, or the bending of a piece of metal are all physical changes that do not change the identity of the substance.
For instance, the formula for water is always H20 no matter what state the water is in. Physical separation techniques-such as filtration, evaporation, or distillation, are ways to separate a mixture into its component parts.
Imagine making a mixture of sugar in water. The sugar can be recovered by evaporating or boiling off the water; then the water can be recovered by condensation. The sugar has the same properties before mixing and after separation. The same is true of the water.
Therefore, properties of each component part before mixing and after separation will not be changed by undergoing the physical separation. The sugar is not changed. It is still sweet.
Homogeneous Mixtures
Homogeneous Mixtures
Solutions
Solutions
A homogeneous mixture, also called a solution, is a mixture that has a completely uniform composition; it is the same throughout. The components of this type of mixture are evenly distributed throughout the sample.
Air, salty water, and brass are examples of solutions.
Brass is a solid solution and is a mixture of copper and zinc.
Air is a gaseous solution consisting of a mixture of nitrogen gas as well as other gases like oxygen and carbon dioxide.
Colloids
Colloids
A colloid is another type of homogeneous mixture that is thick and gooey.
Gels, glue, molasses, honey, fog, and Jell-O are examples of colloids.
Heterogeneous Mixtures
Heterogeneous Mixtures
Suspensions
Suspensions
A suspension is a special type of heterogeneous mixture where particles are suspended in a solution.
Italian salad dressing is a suspension. Muddy water and dusty air are also suspensions.
In suspensions, particles are dispersed throughout a fluid but they tend to settle out over time.
Heterogeneous
Heterogeneous
🍪A heterogeneous mixture is one that is not uniform in composition. You can see different parts.
If one portion of the heterogeneous mixture were to be sampled, its composition would be different from the composition of another portion.
A chocolate chip cookie is a heterogeneous mixture because the numbers of chips vary throughout the cookie; every bite will have a different number of chips! 🍪
Soil, containing bits of decayed material along with sand, silt, and/or clay, is also a heterogeneous mixture.
Separating Mixtures
Separating Mixtures
Mixtures are simply a heterogeneous or homogeneous physical combination of two or more substances. Mixtures can be separated based solely on physical properties, or by undergoing physical changes.
The melting of ice, the freezing of water, the evaporation of water, or the bending of a piece of metal are all physical changes that do not change the identity of the substance. For instance, the formula for water is always H20 no matter what state the water is in.
Physical separation techniques-such as filtration, evaporation, or distillation, are ways to separate a mixture into its component parts. The properties of each component part before mixing and after separation will not be changed by undergoing the physical separation.
For example, imagine making a mixture of sugar in water. The sugar can be recovered by evaporating or boiling off the water; then the water can be recovered by condensation. The sugar has the same properties before mixing and after separation. The same is true of the water.
Report abuse