Chemistry 8 Lesson 14: Exercise 3
1. Summary of theory
1.1. Experiment purpose
– Perform dissolution and heating of potassium permanganate (potassium permanganate)
– Perform the reaction with calcium hydroxide (clear lime water).
– Practice skills in using tools and chemicals to successfully and safely conduct experiments
1.2. Some safety rules in the laboratory
– Experiments are only allowed in the presence of teachers in the laboratory.
– Read the instructions carefully and think before doing the experiment.
– Always be aware of where to put safety equipment.
– Must wear a lab coat.
– Must wear safety glasses.
– You have to tie your hair up.
– Clean the laboratory table before starting an experiment.
– Never taste laboratory chemicals. Do not eat or drink in the laboratory.
– Do not look down the test tube.
– If chemical spills or accidents occur, notify the teacher immediately.
– Wash skin when in contact with chemicals.
– If chemicals get into eyes, wash eyes immediately.
– Dispose of laboratory waste in the right place as instructed.
1.3. Laboratory instruments, chemicals
a. Laboratory instruments
– Test tubes, alcohol lamps, wooden clamps, fireflies, etc.
– Test tubes, suction meters, wooden clamps, …
– Calcium hydroxide solution, sodium carbonate solution.
– Potassium permanganate (purple medicine)
1.4. Experimental steps
a. Experiment 1: Dissolving and heating potassium permanganate
– Take an amount (about 0.5 g) of potassium permanganate and divide it into 3 parts.
– Put a part in the water contained in the test tube (1), shake to dissolve (hold the test tube lightly on the palm of your hand).
– Put 2 parts in test tube 2 and heat. Put a firefly that still has red embers in it to try, if you see that it is burning, continue to cook. When the firestick does not ignite, stop heating and let the test tube cool. Then add water, shake until dissolved.
Observe the color of the solution in 2 test tubes.
b. Experiment 2: Carry out the reaction with calcium hydroxide (clear lime water)
a) Use your breath to blow into a test tube containing calcium hydroxide. Observe comments.
b) Pour the sodium hydroxide solution into the water test tube and the clear lime water test tube. Observe comments.
2. Experimental results
2.1. Experiment 1: Dissolving and heating potassium permanganate
+ Test tube 1: Potassium permanganate is completely soluble in water, forming a purple solution
+ Test tube 2: Potassium permanganate is partially soluble in water. Solution color is lighter than test tube 1.
+ Test tube 1: Potassium permanganate is completely soluble in water, forming a purple solution is a physical phenomenon. Solids dissolve in water to form solutions
+ Test tube 2:
- Place 2 portions in test tube 2 and heat. Put a firefly that still has red embers in it to try, if you see that it is burning, continue to cook. Firesticks ignite due to the reaction that produces oxygen, which is the gas that sustains life and combustion.
- Let the test tube cool before adding water to avoid the temperature difference causing the glass tube to crack, break, and spill dangerous chemicals.
- Then add water, shake until dissolved. Realized that only partially soluble in water, the color of the solution is lighter than the test tube 1. When heated, potassium permanganate, Manganese oxide and Oxygen gas are produced.
Chemical equations in words: Potassium permanganate → Potassium manganate + manganese dioxide + oxygen
2.2. Experiment 2: Carry out the reaction with calcium hydroxide (clear lime water)
Video 2: Reaction between Calcium hydroxide and carbon dioxide
Video 3: Reaction between Calcium hydroxide and sodium carbonate
a) Using your breath to blow into a test tube containing calcium hydroxide, observe that the clear lime water is cloudy.
b) When adding sodium carbonate to test tube 2 containing calcium hydroxide, it was observed that the clear lime water was cloudy.
a) Clear lime water is cloudy due to insoluble solids formed as calcium carbonate.
Chemical equation in words: Calcium hydroxide + carbon dioxide → calcium carbonate + water
b) When adding sodium carbonate to test tube 2 containing calcium hydroxide, calcium carbonate and sodium hydroxide are formed.
Chemical equation in words: Calcium hydroxide + sodium carbonate → Calcium carbonate + sodium hydroxide
Question 1: Write a word equation when sodium carbonate is added to clear lime water
State the phenomenon of writing word equations and chemical equations
a) heat iron and sulfur
b) heat the sugar
c) let the breath into the clear lime water
d) heating the potassium permanganate
e) Add sodium carbonate to clear lime water
Verse 2: Why does it foam when pouring acid on the marble floor?
After the lesson, you should know the steps and techniques to perform some experiments:
- Dissolve and heat potassium permanganate (potassium permanganate)
- Carry out the reaction with calcium hydroxide (clear lime water)