Substances Summary

Substunces Summary

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• https://www.youtube.com/watch?v=OpWFUqPPtWE (Einbetten)

Elements

• Elements are substances that are made up of just one type of atom. Each element has a unique set of characteristics that scientists refer to as its properties. Elements can be classified into metallic and non-metallic elements. All metallic elements -:
• shiny
• solid at room temperatures(apart from mercury)
• good conductors of heat and electricitymalleable(bent and hammered into sheets)
• ductile(stretched into wires
• Non -metallic elements-:
• dull(not shiny)
• do not conduct heat or electricity)
• Break or crumble when you bend them(brittle)
• solid or gases at room temperature(apart from bromine)
• There are 118 elements, but only 91(92) occur naturally.
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• Bildunterschrift: metallic elements

Atoms

• The way atoms are arranged in Elements determines many of the physical properties of an element. Monatomic elemets are rare, with only 6 of the 92 naturally occurring elements being monatomic.
• These are -: Helium, Neon, Argon, Krypton, Xenon and Radon.
• Molecules are cluster of two or more atoms bonded together. In a molecular element, all the molecules are identical with the same shape, size, number and types of atoms.
• The atoms in metals don't form molecules, but instead form large grid-like structures known as crystal lattices. In metal lattices, the atoms are only weakly joined to each other. As a result, metals can be bent into wires.
• In non-metallic lattices, the atoms are strongly bonded to each other. This makes them hard and brittle.
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• Bildunterschrift: An atom

Compounds

• Compounds are made up of more than one type of atom. Compounds have properties that are usually very different from the properties of elements.
• Each molecule is made by combining different numbers of the same elements, oxygen hydrogen etc. Scientists represent the molecules of compounds in a similar way to the molecules of an element. H2O indicates that there are 2 hydrogen atoms for every oxygen atom.
• Compounds can also form crystal lattices. In these lattices, the atoms are strongly bonded to each other so they tend to be very hard solids at room temperatures. In a lattice of sodium chloride, sodium and chloride atoms form a grid-like structure with one sodium atom for every chlorine atom.
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• Bildunterschrift: Water Molecule H2O

Resources

• Compounds
• A closer look at atoms
• Elements and Atoms
• Physical and chemical changes
• Understanding physical change
• Substance Change
• 1_Elements
• Compounds