9 A group of atoms held together by sharing electrons (covalent bonds) Molecule:A group of atoms held together by sharing electrons (covalent bonds)Compound:A substance containing more than one element.
11 CompoundsPure substance composed of two or more different elements joined by chemical bonds.Made of elements in a specific ratiothat is always the sameHas a chemical formulaCan only be separated bychemical means, not physicallyH2ONaClCO2
12 What are each of these? Atom, Element, Molecule, or Compound
13 Single Chemical Formula: All pure substances can be represented by aSingle Chemical Formula:H2OIf it’s really a pure substance, you should only need to write ONE chemical formula to describe it’s composition.
14 All molecules can be represented by a Chemical Formula:H2Osubscript
15 Chemical Formulas show how many atoms of each element are in one molecule: # of Carbon atoms# of atoms total# of elementsChemical FormulaO212H2O23C3H8O3123C6H12O4Cl4236
16 How many atoms of each element are present in one molecule of: (NH4)2SO3(NH4)2SO3(NH4)2SO3(NH4)2SO3N…………….H……………S…………….O……………2813281328132813
17 Pure Substances: Pure Substances: Pure Substances: Pure Substances: Are made of only one compound or one element.Can be represented by one chemical formula.Examples:SaltSaltSaltSaltSaltSaltCopperCopperCopperCopperWaterWaterWaterH2ONaClCu
19 Pure Substances: Pure Substances: Pure Substances: Pure Substances: Are made of only one compound or one element.Can be represented by one chemical formula.Examples:SaltSaltSaltSaltSaltSaltCopperCopperCopperCopperWaterWaterWaterH2ONaClCu
20 Heterogeneous Mixture: Homogenous MixtureAn even mixture; particles are blended evenly throughout the mixture.(= “solutions”)Heterogeneous Mixture:An uneven mixture;particles are unevenly distributed.
21 MixturesA combination of two or more pure substances that are not chemically combined.substances held together by physical forces, not chemicalNo chemical change takes placeEach item retains its propertiesin the mixtureThey can be separated physicallyChem4kids.com
23 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.