A useful starting point is to show elements and compounds being formed see table. Ask students to think about what is present at the start and end of each reaction. And sodium chloride has very different properties to elemental sodium. Similarly, iron is magnetic but iron sulfide is not. Compare and contrast this with the uncombined iron you can extract from breakfast cereal. A useful starting point is to show elements and compounds being formed.
Sodium and chlorine reaction. Dehydration of sucrose creates a carbon tower. Sucrose contains carbon, hydrogen and oxygen atoms. Which element can you observe at the end of the reaction? Iron and sulfur reaction. Two elements reacting together to form a compound, with observably different properties to the original elements. Extracting iron from breakfast cereal.
The iron was extracted using a magnet. Would this have been possible if it had reacted to form a compound with the cereal? A solid—solid reaction between lead nitrate and potassium iodide. Precipitation of lead iodide golden rain.
Practical activities allow students to make observations macroscopic. They need to be able to explain observations using ideas about atoms, elements and compounds sub-microscopic and chemical symbols symbolic.
Explicitly discuss these three levels of representing chemistry macroscopic, sub-microscopic and symbolic , which are known as the Johnstone triplet , and how they link together. This helps students build detailed understanding. Explicitly discuss these three levels of representing chemistry macroscopic, sub-microscopic and symbolic , which are known as the Johnstone triplet rsc. Molecular modelling kits can help students learn how to represent molecules and distinguish between elements and compounds.
Save budget and switch commercial modelling kits for things like marshmallows and cocktail sticks. Build example models of different substances, elements and compounds, then give your students a range to try for themselves.
Limit the number of marshmallow colours to two to reduce the number of things students need to think about related to cognitive load. This helps focus them on the underlying concepts. Limit the number of marshmallow colours to two to reduce the number of things students need to think about related to cognitive load: rsc. Present a range of diagrammatic representations of elements and molecules, and ask your students to identify which are elements and which are compounds.
Model your own thinking to students, demonstrating how you approach each task and use your knowledge. Download a worksheet that asks students to build representations of molecules using white and pink marshmallows word , pdf or ppt , and teacher notes word , pdf.
Download a worksheet from the Education in Chemistry website for students to build representations of molecules using white and pink marshmallows, with teacher notes: rsc. Story-telling enlivens the knowledge students need, and the discovery of the elements provides rich pickings.
Ask students to think about why these ideas may have developed. Most elements on Earth bond with other elements to form chemical compounds, such as sodium Na and Chloride Cl , which combine to form table salt NaCl.
Water is another example of a chemical compound. The two or more component elements of a compound can be separated through chemical reactions. Chemical compounds have a unique and defined structure, which consists of a fixed ratio of atoms held together in a defined spatial arrangement by chemical bonds. Chemical compounds can be:. Pure chemical elements are not considered chemical compounds, even if they consist of diatomic or polyatomic molecules molecules that contain only multiple atoms of a single element, such as H 2 or S 8.
Boundless vets and curates high-quality, openly licensed content from around the Internet. This particular resource used the following sources:. Skip to main content. Introduction to Chemistry. Search for:. Elements and Compounds. Learning Objective Differentiate between elements and compounds and explore separation techniques.
Key Points Elements are the simplest complete chemical substances. Each element corresponds to a single entry on the periodic table. Alchemists like Joseph Louis Proust, Dalton and Berthollet and their studies on various compounds have given modern chemistry the current definition of compound. Every chemical substance is identified by its unique numerical identifier — the CAS chemical abstracts service number. Hence every chemical compound and element has a CAS number.
This makes database searches for elements and compounds more convenient. Share this comparison:. If you read this far, you should follow us:. Diffen LLC, n. Compound vs. Comparison chart Compound versus Element comparison chart Compound Element Definition A compound contains atoms of different elements chemically combined together in a fixed ratio.
An element is a pure chemical substance made of same type of atom. Composition Compounds contain different elements in a fixed ratio arranged in a defined manner through chemical bonds. They contain only one type of molecule. Elements that compose the compound are chemically combined. Elements contain only one type of atom.
Each atom has the same atomic number i. Elements cannot be broken down into simpler substances by chemical reactions. Representation A compound is represented using its chemical formula that represents the symbols of its constituent elements and the number of atoms of each element in one molecule of the compound. An element is represented using symbols. Types A huge, virtually limitless, number of chemical compounds can be created.
Compounds are classified into molecular compounds, ionic compounds, intermetallic compounds and complexes. There are about elements that have been observed. Can be classified as metal, non-metal or metalloid.
Differences in Properties Elements are distinguished by their name, symbol, atomic number, melting point, boiling point, density and ionization energies. Atomic number — the atomic number is denoted by the letter Z and is the number of protons present in the nucleus of the atom of element.
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