Print this chapterPrint this chapter

Lesson 10 Endothermic and Exothermic Reactions

  Conclusion

Visual observations can readily indicate the occurrence of a chemical reaction.



B10.5 A pink substance is formed when two clear, colourless liquids are mixed.
The most important piece of evidence that indicates a chemical reaction occurred is the formation of a new substance with unique properties. Some of those properties may be a different colour, state, odour, or temperature. Sometimes, you need to look at several pieces of evidence to accurately conclude whether or not a chemical reaction has occurred.

In the next lesson, you will look at how to identify the types of chemical reactions that can occur.

  Virtual Lab

Chemical Changes @ Explore Learning


Background Information:

Please work through this lab to observe evidence of chemical reactions.

Please note: if you scroll down while in the Gizmo you will see a list of questions. You DO NOT need to complete these questions. You are able to complete them for extra practice if you would like.


  1. Click on the play icon to open the virtual lab or go to the Online Resources for Print Students section in your online course.
  2. For “Reactant 1” select “Sodium.”
  3. For “Reactant 2” select “Water.”
  4. Select “Gas collection.” Then select “Label reactants,” “Show chemical equation,” and “Show balanced equation” (which appears after “Show chemical equation” is selected).
  5. Drag the thermometer on top of the Erlenmeyer flask.
  6. Record the appearance of the reactants. Record the initial mass. Record the initial temperature.
  7. Click on the play icon.
  8. Record your observations of any changes to the appearance of the substances. If you want to watch the reaction again, click the replay button.
  9. Record the final mass and the final temperature.
  10. Select “Glowing splint” and drag it to the top of the test tube.
  11. Record your observations.
  12. Click on the procedure 2 tab to continue.

    Observation
    appearance of reactant 1
    grey solid
    appearance of reactant 2
    clear, colourless liquid
    initial mass (g)
    2 417.0
    initial temperature (°C)
    observation of reaction
    Bubbles are produced.
    Grey solid disappears.
    final mass (g)
    2 417.0
    final temperature (°C)
    diagnostic test (glowing splint) result
    A pop is heard. Glowing split causes small explosion.
  1. For “Reactant 1” select “Hydrogen peroxide.”
  2. For “Reactant 2” select “Potassium iodide.”
  3. Select “Gas collection.” Then select “Label reactants,” “Show chemical equation,” and “Show balanced equation.”
  4. Drag the thermometer on top of the Erlenmeyer flask.
  5. Record the appearance of the reactants. Record the initial mass. Record the initial temperature.
  6. Click on the play icon.
  7. Record your observations of any changes to the appearance of the substances. If you want to watch the reaction again, click the replay button.
  8. Record the final mass and the final temperature.
  9. Select “Glowing splint” and drag it to the top of the test tube.
  10. Record your observations.
  11. Click on the procedure 3 tab to continue.

    Observation
    appearance of reactant 1
    clear, colourless liquid
    appearance of reactant 2
    clear, yellow liquid
    initial mass (g)
    2 401.6
    initial temperature (°C)
    observation of reaction
    Solution colour changes to brown then back to yellow.
    Bubbles are produced.
    final mass (g)
    2 401.6
    final temperature (°C)
    diagnostic test (glowing splint) result
    Glowing splint ignites.
  1. For “Reactant 1” select “Silver nitrate.”
  2. For “Reactant 2” select “Hydrochloric acid.”
  3. Select “Normal setup.” Then select “Label reactants,” “Show chemical equation,” and “Show balanced equation.”
  4. Record the appearance of the reactants. Record the initial mass.
  5. Click on the play icon.
  6. Record your observations of any changes to the appearance of the substances. If you want to watch the reaction again, click the replay button.
  7. Record the final mass.
  8. Click on the procedure 4 tab to continue.

    Observation
    appearance of reactant 1
    clear, colourless liquid
    appearance of reactant 2
    clear, colourless liquid
    initial mass (g)
    360.0
    observation of reaction
    White precipitate forms.
    final mass (g)
    360.0

  1. For “Reactant 1” select “Silver nitrate.”
  2. For “Reactant 2” select “Copper.”
  3. Select “Normal setup.” Then select “Label reactants,” “Show chemical equation,” and “Show balanced equation.”
  4. Record the appearance of the reactants. Record the initial mass.
  5. Click on the play icon.
  6. Drag the magnifier over top of the Erlenmeyer flask.
  7. Record your observations of any changes to the appearance of the substances. If you want to watch the reaction again, click the replay button.
  8. Record the final mass.
  9. Click on the procedure 5 tab to continue.

    Observation
    appearance of reactant 1
    clear, colourless liquid
    appearance of reactant 2
    copper-coloured coil
    initial mass (g)
    observation of reaction
    Solution turns blue.
    White crystals form.
    final mass (g)
  1. For “Reactant 1” select “Sodium.”
  2. For “Reactant 2” select “Chorine.”
  3. Select “Closed system.” Then select “Label reactants,” “Show chemical equation,” and “Show balanced equation.”
  4. Record the appearance of the reactants. Record the initial mass.
  5. Click on the play icon.
  6. Drag the magnifier over top of the Erlenmeyer flask.
  7. Record your observations of any changes to the appearance of the substances. If you want to watch the reaction again, click the replay button.
  8. Record the final mass.
  9. Click on the procedure 6 tab to continue.

    Observation
    appearance of reactant 1
    grey solid
    appearance of reactant 2
    yellow gas
    initial mass (g)
    1 351.1
    observation of reaction
    Flames form.
    A white crystal forms.
    final mass (g)
    1 351.1
  1. For “Reactant 1” select “Ammonium nitrate.”
  2. For “Reactant 2” select “Potassium hydroxide.”
  3. Select “Gas collection.” Then select “Label reactants,” “Show chemical equation,” and “Show balanced equation.”
  4. Drag the thermometer on top of the Erlenmeyer flask.
  5. Drag Phenol red on top of the Erlenmeyer flask.
  6. Record the appearance of the reactants. Record the initial mass. Record the initial temperature. Record the initial pH.
  7. Click the play icon.
  8. Record your observations of any changes to the appearance of the substances. If you want to watch the reaction again, click the replay button.
  9. Record the final mass and the final temperature.
  10. Select “Glowing splint” and drag it to the top of the test tube.
  11. Record your observations.
  12. Drag the nose onto the test tube.
  13. Record your observations.

    Observation
    appearance of reactant 1
    white powder
    appearance of reactant 2
    clear, colourless liquid
    initial mass (g)
    2 867.0
    initial temperature (°C)
    phenol red results
    pink colour—basic
    observation of reaction
    Bubbles are formed.
    final phenol red results
    yellow colour—neutral
    final mass (g)
    2 867.0
    final temperature (°C)
    glowing splint test
    Splint is extinguished.
    odour
    There is a strong smell of ammonia.