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Classifying Matter: Elements, Compounds, and Mixtures. By Liz LaRosa www.middleschoolscience.com 2009. Chemistry:. Matter:. The study of matter and its changes. Anything that has mass and volume. Pure Substances. A sample of matter that has definite chemical and physical properties.
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Classifying Matter:Elements, Compounds, and Mixtures By Liz LaRosa www.middleschoolscience.com 2009
Chemistry: Matter: The study of matter and its changes Anything that has mass and volume
Pure Substances • A sample of matter that has definite chemical and physical properties. Atoms Elements Compounds Molecules
Elements • pure substance that cannot be separated into simpler substance by physical or chemical means.
Kinetic Molecular Theory Matter is made of tiny particles called atoms, which combine to form molecules.
Molecule: Compound: A group of atoms held together by sharing electrons (covalent bonds) A substance containing more than one element.
Four different molecules: • Which are compounds?
Compounds Pure substance composed of two or more different elements joined by chemical bonds. • Made of elements in a specific ratio that is always the same • Has a chemical formula • Can only be separated by chemical means, not physically H2O NaCl CO2
Single Chemical Formula: • All pure substances can be represented by a H2O If it’s really a pure substance, you should only need to write ONE chemical formula to describe it’s composition.
Chemical Formula: • All molecules can be represented by a H2O subscript
Chemical Formula # of elements # of atoms total # of Carbon atoms Chemical Formulas show how many atoms of each element are in one molecule: O2 1 2 0 H2O 2 3 0 C3H8O 3 12 3 C6H12O4Cl 4 23 6
How many atoms of each element are present in one molecule of: How many atoms of each element are present in one molecule of: How many atoms of each element are present in one molecule of: (NH4)2SO3 (NH4)2SO3 (NH4)2SO3 (NH4)2SO3 N……………. H…………… S……………. O…………… 2 8 1 3 2 8 1 3 2 8 1 3 2 8 1 3
Pure Substances: Pure Substances: Pure Substances: Pure Substances: Pure Substances: Pure Substances: Pure Substances: Pure Substances: Examples: Are made of only one compound or one element. Can be represented by one chemical formula. Salt Salt Salt Salt Salt Salt Copper Copper Copper Copper Water Water Water H2O NaCl Cu
Pure Substances: Pure Substances: Pure Substances: Pure Substances: Pure Substances: Pure Substances: Pure Substances: Pure Substances: Examples: Are made of only one compound or one element. Can be represented by one chemical formula. Salt Salt Salt Salt Salt Salt Copper Copper Copper Copper Water Water Water H2O NaCl Cu
Homogenous Mixture An even mixture; particles are blended evenly throughout the mixture. (= “solutions”) Heterogeneous Mixture: An uneven mixture; particles are unevenly distributed.
Mixtures • A combination of two or more pure substances that are not chemically combined. • substances held together by physical forces, not chemical • No chemical change takes place • Each item retains its properties in the mixture • They can be separated physically Chem4kids.com
Mixtures vs. Compounds http://www.bbc.co.uk/schools/ks3bitesize/science/chemistry/elements_com_mix_6.shtml
Can you identify the following? You will be shown a series of photos. Tell if each photo represents an item composed of an element, compound, or mixture. Review: • An element contains just one type of atom. • A compound contains two or more different atoms joined together. • A mixture contains two or more different substances that are only physically joined together, not chemically. • A mixture can contain both elements and compounds.
Element, Compound, or Mixture? Copper Cu
Element, Compound, or Mixture? Jelly Beans
Element, Compound, or Mixture? Jelly Beans
Element, Compound, or Mixture? Table Sugar
Element, Compound, or Mixture? Table Sugar C12H22O11
Element, Compound, or Mixture? Diamond
Element, Compound, or Mixture? Diamond C
Element, Compound, or Mixture? NaCl Salt
Element, Compound, or Mixture? Neon Gas
Element, Compound, or Mixture? Ne Neon Gas
Element, Compound, or Mixture? Pure Water
Element, Compound, or Mixture? Pure Water H2O
Element, Compound, or Mixture? Aluminum
Element, Compound, or Mixture? Aluminum Al
Element, Compound, or Mixture? Lemonade
Element, Compound, or Mixture? Lemonade
Element, Compound, or Mixture? Silver Ag