Lesson Plan

• Describe the colour changes of anhydrous cobalt(II) chloride and copper(II) sulfate when water is present.
• Explain the hydration reactions that cause the observed colour shifts.
• Demonstrate the correct, safe procedure for performing the water‑detection test.
• Interpret observed colour changes to determine the presence or absence of water.
• Identify common errors and outline strategies to avoid them.

• Anhydrous cobalt(II) chloride (solid)
• Anhydrous copper(II) sulfate (solid)
• Test tubes or small glass containers (minimum 3)
• Droppers
• Distilled water (control)
• Safety goggles and protective gloves
• Waste‑disposal container

Begin with a quick question: “What happens to hygroscopic salts when they encounter moisture?” Students recall prior knowledge of hydrate formation, then the teacher outlines today’s success criteria – students will correctly perform and interpret two colour‑change tests for water.

1. Do‑Now (5'): Students list familiar hygroscopic salts and predict colour changes.
2. Mini‑lecture (10'): Explain the principle behind the colour change, show the hydration equations, and discuss safety.
3. Teacher Demonstration (10'): Perform the test with cobalt(II) chloride, copper(II) sulfate, and a control tube; students note observations.
4. Guided Practice (15'): In pairs, students repeat the procedure with an unknown sample, record results, and compare with the control.
5. Check for Understanding (5'): Quick oral quiz – “What colour indicates water presence for each reagent?”
6. Safety & Error Review (5'): Discuss common mistakes (moist reagents, insufficient sample) and how to avoid them.

Summarise that both reagents give a rapid visual cue for water through colour change. Students complete an exit ticket describing one observation and its interpretation. For homework, they research another qualitative test for water and prepare a short summary.