Experiment 4A (Coagulation of Latex):
Aim: To study the coagulation process in latex and how to prevent coagulation.
Problem statement: Does acid cause latex to coagulate and alkali prevent latex from coagulating?
Hypothesis: The presence of acid in latex causes latex to coagulate, while the presence of alkali prevents the coagulation of latex.
Variables:
(a) Manipulated variable : Ethanoic acid, CH3COOH and ammonia, NH3 solution.
(b) Responding variable : Coagulation of latex.
(c) Fixed variable : Volume of latex.
Materials: Latex, 1.0 mol dm−3 of ethanoic acid, CH3COOH and 1.0 mol dm−3 of ammonia, NH3 solution.
Apparatus: Beaker, measuring cylinder, glass rod and dropper.
Procedure:
1. Label the beakers A, B and C respectively.
2. Measure 20 cm3 of latex using a measuring cylinder and pour it into each beaker.
3. Measure 2 cm3 of ethanoic acid, CH3COOH using a measuring cylinder and pour the acid into beaker A while stirring continuously with a glass rod.
4. Step 3 is repeated by replacing ethanoic acid, CH3COOH with ammonia, NH3 solution for beaker B, while beaker C acts as a control.
5. The observation is recorded.
Observation: Construct a suitable table to record your observation.
Discussion:
1. Which substance causes latex to coagulate and which substance prevents latex from coagulating?
2. Explain your observation of beaker C.
3. What substance can be used to replace ethanoic acid, CH3COOH and ammonia, NH3 solution?
Conclusion:
Can the hypothesis be accepted? What is the conclusion of this experiment?
Answer:
1. Ethanoic acid causes latex to coagulate, while ammonia solution prevents latex from coagulation.
2. Latex in beaker C coagulate after being left for a while. Bacteria in the air enter the latex and secrete lactic acid that causes latex to colagulate.
3. Methanoic acid and barium hydroxide solution.
Aim: To study the coagulation process in latex and how to prevent coagulation.
Problem statement: Does acid cause latex to coagulate and alkali prevent latex from coagulating?
Hypothesis: The presence of acid in latex causes latex to coagulate, while the presence of alkali prevents the coagulation of latex.
Variables:
(a) Manipulated variable : Ethanoic acid, CH3COOH and ammonia, NH3 solution.
(b) Responding variable : Coagulation of latex.
(c) Fixed variable : Volume of latex.
Materials: Latex, 1.0 mol dm−3 of ethanoic acid, CH3COOH and 1.0 mol dm−3 of ammonia, NH3 solution.
Apparatus: Beaker, measuring cylinder, glass rod and dropper.
Procedure:
1. Label the beakers A, B and C respectively.
2. Measure 20 cm3 of latex using a measuring cylinder and pour it into each beaker.
3. Measure 2 cm3 of ethanoic acid, CH3COOH using a measuring cylinder and pour the acid into beaker A while stirring continuously with a glass rod.
4. Step 3 is repeated by replacing ethanoic acid, CH3COOH with ammonia, NH3 solution for beaker B, while beaker C acts as a control.
5. The observation is recorded.
Observation: Construct a suitable table to record your observation.
Discussion:
1. Which substance causes latex to coagulate and which substance prevents latex from coagulating?
2. Explain your observation of beaker C.
3. What substance can be used to replace ethanoic acid, CH3COOH and ammonia, NH3 solution?
Conclusion:
Can the hypothesis be accepted? What is the conclusion of this experiment?
Answer:
1. Ethanoic acid causes latex to coagulate, while ammonia solution prevents latex from coagulation.
2. Latex in beaker C coagulate after being left for a while. Bacteria in the air enter the latex and secrete lactic acid that causes latex to colagulate.
3. Methanoic acid and barium hydroxide solution.