Hands-on Activity: Element, Mixture, Compound
Educational Standards :
Learning Objectives (Return to Contents)
After this activity, students should be able to:
Materials List (Return to Contents)
To share with the entire class:
Introduction/Motivation (Return to Contents)
Everybody is completely surrounded by matter. To better understand this matter - how it affects you, how you affect this and how it can be manipulated for the benefit of the society, it is important to build a basic understanding of the types and properties of matter. The diversity of the matter in the world and in the universe is astounding. If we are to understand this diversity, we must start with a way of organizing and describing matter.
All matter is made up of elements which are fundamental substances that cannot be broken down by chemical means. Element is a substance that can not be further reduced as to simpler substances by ordinary processes.
A compound is a pure substance composed of two or more different atoms chemically bonded to one another. That means that it can not be separated into its constituents by mechanical or physical means and only can be destroyed by chemical means.
A mixture is a material containing two or more elements or compounds that are in close contact and are mixed in any proportion. For example, air, sea water, crude oil, etc. The constituents of a mixture can be separated by physical means like filtration, evaporation, sublimation and magnetic separation. The constituents of a mixture retain their original set of properties. The mixtures can be classified to homogeneous and heterogeneous mixtures. A homogeneous mixture has the same uniform appearance and composition throughout its mass. For example, sugar or salt dissolved in water, alcohol in water, etc. A heterogeneous mixture consists of visibly different substances or phases. The three phases or states of matter are gas, liquid, and solid. A heterogeneous mixture does not have a uniform composition throughout its mass.
New materials have been among the greatest achievements of every age and they have been central to the growth, prosperity, security, and quality of life of humans since the beginning of history. It is always new materials that open the door to new technologies, whether they are in civil, chemical, construction, nuclear, aeronautical, agricultural, mechanical, biomedical or electrical engineering.
The study of metal alloys which are mixture of different metals is a significant part of materials science and material engineering. Of all the metallic alloys in use today, the alloys of iron (steel, stainless steel, cast iron, tool steel, alloy steels) make up the largest proportion both by quantity and commercial value. Iron alloyed with various proportions of carbon gives low, mid and high carbon steels. For the steels, the hardness and tensile strength of the steel is directly related to the amount of carbon present, with increasing carbon levels also leading to lower ductility and toughness. The addition of silicon and graphitization will produce cast. The addition of chromium, nickel and molybdenum to carbon steels (more than 10%) gives us stainless steels.
Other significant metallic alloys are those of aluminium, titanium, copper and magnesium. Copper alloys have been known for a long time (since the Bronze Age), while the alloys of the other three metals have been relatively recently developed. The alloys of aluminium, titanium and magnesium are also known and valued for their high strength-to-weight ratios and, in the case of magnesium, their ability to provide electromagnetic shielding. These materials are ideal for situations where high strength-to-weight ratios are more important than bulk cost, such as in the aerospace industry and certain automotive engineering applications.
Other than metals, polymers and ceramics are also an important part of materials science. Polymers are the raw materials (the resins) used to make what we commonly call plastics. Plastics are really the final product, created after one or more polymers or additives have been added to a resin during processing, which is then shaped into a final form.
Another application in industry is the making of composite materials. Composite materials are structured materials composed of two or more macroscopic phases. Applications range from structural elements such as steel-reinforced concrete, to the thermally insulative tiles which play a key and integral role in NASA's Space Shuttle thermal protection system which is used to protect the surface of the shuttle from the heat of re-entry into the Earth's atmosphere. One example is Reinforced Carbon-Carbon (RCC), The light gray material which withstands reentry temperatures up to 1510 °C (2750 °F) and protects the Space Shuttle's wing leading edges and nose cap. RCC is a laminated composite material made from graphite rayon cloth and impregnated with a phenolic resin.
Other examples can be seen in the "plastic" casings of television sets, cell-phones and so on. These plastic casings are usually a composite material.
Vocabulary/Definitions (Return to Contents)
Procedure (Return to Contents)
Before the Activity
Before the class start set up 9 plastic dishes of bolts, nuts and washers as below and put them on a table (Show the dish numbers by a marker):
Put all of these dishes on one table for later use. Let's call it table B. And put the rest of the material on another table (table A).
With the Students
In the beginning of the activity make the students into groups of four and ask each group to go through table A and compare and contrast the different items on the table and make a list of their discussion. Ask the students to discuss their list. (Some of them may categorize the material as element, mixture and compounds).
Here the different types of matter can be explained on the board and after that discuss all the materials on table A again to separate them to classes of elements, mixtures (homogeneous and heterogeneous) and compound. Now the sets of washers, bolts and nuts can be used to better convey and review the concept of element, mixtures and compound. Explain to the students that if they think each washer, bolt and nut as an individual atom then the contents of dishes 1, 2 and 3 are elements because they are all the same atom and that can not be further reduced as to simpler substances. The contents of dishes 4, 5 and 6 are compound because they show one substance composed of two or more different atoms chemically bonded to one another and the contents of dishes 7, 8 and 9 are mixtures because they are materials containing two or more elements or compounds and are mixed in any proportion.
Safety Issues (Return to Contents)
No safety issue is required.
Investigating Questions (Return to Contents)
Assessment (Return to Contents)
Assessment is made at discretion of instructor.
ContributorsParnia Mohammadi, Roberto Dimaliwat
Supporting Program (Return to Contents)National Science Foundation GK-12 and Research Experience for Teachers (RET) Programs, University of Houston
Last Modified: March 10, 2014