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5 Indicators of a Chemical Change

5 Indicators of a Chemical Change. From this lesson you will be able to determine if a chemical change has taken place. What is a Chemical Change?. It is a change that occurs when a substance changes composition by forming one or more new substances.

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5 Indicators of a Chemical Change

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  1. 5 Indicators of a Chemical Change From this lesson you will be able to determine if a chemical change has taken place

  2. What is a Chemical Change? • It is a change that occurs when a substance changes composition by forming one or more new substances. • The new substances/products that are formed have a different chemical formula from the original substances/reactants at the beginning.

  3. 5 Indicators of a Chemical Change • Take a look at the video of Hydrochloric Acid (HCl) reacting with Magnesium (Mg) strips. What do you observethat indicates a chemical change is taking place. Hydrochloric Acid + Magnesium http://www.youtube.com/watch?v=cpy_Zh-8sKA Hydrogen from Hydrochloric acid and Magnesium ribbon BANG… http://youtu.be/afxwDTz_JTk

  4. What did you observe? Bubbles Mg + 2HCl MgCl2 + H2 Production of Gasis an indicator of a Chemical Change. This reaction is very similar to the reactions that take place in the digestive track when Hydrochloric Acid (HCl) in your stomachaids in the digestive process. Digestion is a chemical change.

  5. 5 Indicators of a Chemical Change • Take a look at the video of a Magnesium (Mg) strip reacting with Oxygen (O2) while burning. What do you observethat indicates a chemical change is taking place? Burning Magnesium http://youtu.be/84v8yRPwo5A

  6. What did you observe? Light 2Mg + O2 2MgO Formation of Lightis an indicator of a Chemical Change. This is the same reaction that is used to make fireworks and sparklers.

  7. 5 Indicators of a Chemical Change • Take a look at the video of two clear liquids, Lead II Nitrate Pb(NO3)2 reacting with Potassium Iodide (KI). What do you observe that indicates a chemical change is taking place? Reaction of LEAD NITRATE & POTASSIUM IODIDE solutionshttp://www.youtube.com/watch?v=DITY2rXYU-I Double Displacement Lead Nitrate and Potassium Iodide http://www.youtube.com/watch? v=X2mB-q2NQXY

  8. What did you observe? Yellow Color Change and a Precipitate (insoluble solid) Pb(NO3)2 + 2KI PbI2 + 2KNO3 Permanent Color Change and Formation of a Precipitateare two indicators of a Chemical Change. Reactions like these are used in water treatment plants to form precipitates that help remove calcium, magnesium, iron, and manganese ions from the water.

  9. 5 Indicators of a Chemical Change • Take a look at the video of two solids, Barium Hydroxide Octahydrate reacting with Ammonium Thiocyanate. What do you observe that indicates a chemical change is taking place? http://youtu.be/MyAzjSdc3Fc

  10. What did you observe? A Temperature Change Ba(OH)2.8H2O + 2 NH4SCN --> Ba(SCN)2 + 10 H2O + 2 NH3 Temperature Changeis an indicator of a Chemical Change. Endothermic Reactions = absorb heat and feel cold Exothermic Reactions = release heat and feel hot

  11. Let’s Review The 5 Indicators of a Chemical Change are… 1. Production of Gas 2. Production of Light 3. Permanent Color Change 4. Formation of a Precipitate 5. Temperature Change

  12. Test Your Knowledge • Go to the Live Chem website below: • http://www.chem.ox.ac.uk/vrchemistry/LiveChem/transitionmetals_content.html • While in the Virtual Chemistry Lab, perform the following 5 experiments and record whether they demonstrate a chemical change. Then choose 5 other experimental mixes of your ownand record whether they demonstrate a chemical change. Use the 5 Indicators of a Chemical Change to support your findings for all 10 experiments conducted. • Click on the next slide for the Lab Write-up.

  13. 5 Indicators of a Chemical Change Lab Purpose: The purpose of this lab experiment is to determine whether a chemical change has taken place using the 5 indicators of a chemical change. Safety Equipment Necessary: If you were performing these experiments in the laboratory, what safety measures would you need to take to ensure your safety and the safety of others around you? Data Table:

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