Properties of Chalk and Baking Soda Copy

Teacher Goals

• Observe physical changes of chalk when mixed with water and hydrochloric acid.

• Examine changes in the crystal form from the mixtures of chalk with water and hydrochloric acid.

• Infer if the reactions are chemical changes.

Required Resources

• • 3 glass slides per group
  • 1 hand lens per group
  • grease pencil or crayon
  • hot plate
  • test tube holder
  • toothpick
  • chemical scoop or wooden splint
  • 1 piece of chalk per group
  • baking soda
  • distilled water in plastic bottle or dropper
  • 3M hydrochloric acid (HCl)
  • paper toweling
  • Data and observation table
  • To be filled out as experiment is being conducted.

• Use these forms and rubrics for the activity Properties of Chalk and Baking Soda.

  • Analysis and Conclusions
  • Data and Observations

Steps

1. Hypothesis

   Based on your knowlege of substances, hypothesize whether or not a physical change in a substance always signals that a chemical change has occurred.

2. Label slide

   Obtain 2 glass slides and with a grease pencil or crayon draw a line dividing the slides into two halves. Mark one side of each slide "water" and the other side "hydrochloric acid (HCl)" (figure A).

3. Adding chalk

   Using the third slide, scrape equal quantities of chalk (calcium carbonate) onto each side of one of the labeled slides (Figure B).

4. Examine structure

   Examine the crystal structure of chalk with the hand lens. Record the appearance in the data table.

5. Add water

   Add 10 drops of water to the powdered chalk on the side marked "water." Stir the water and chalk together with a toothpick. Record any physical changes in the data table.

6. Add hydrochloric acid

   Add 10 drops of hydrochloric acid to the powdered chalk on the side marked "hydrochloric acid." Stir the hydrochloric acid and chalk together with a different toothpick. Record in the data table any physical changes that you observe. 

7. Evaporate liquid

   Carefully place the slide on a hot plate set on low heat to evaporate the liquid.

8. Remove slide

   When all the liquid has been evaporated, remove the slide using test tube holders. Allow the slide to cool by placing it on a pad of paper towels.

9. Observe crystal structure

   Using the hand lens, observe the crystal structure of the two solids on the slide and record their appearance in the data table.

10. Repeat steps with baking soda

    Using the second labeled slide, repeat steps 2-9 with baking soda. Use a chemical scoop or wooden splint to place the baking soda on the slide.

11. Record data

    Complete the data forms below.

Teacher Notes

• Read all directions before having students complete the experiments. Print the rubric prior to starting the experiment.

• Younger students should not handle the hydrochloric acid. Older students should be given the precautions before handling. Supervision should be maintained at all times