2.9.1 - Laboratory Activity : Coagulation of Latex

Laboratory Activity 2.9.1: Coagulation of Latex

Aim: To study the coagulation process of latex.
Problem statement: What is the chemical properties of ethanol?
Hypothesis: The presence of acid causes latex to coagulate.
Variable:

	»	Fixed variable : Amount of latex and the time for coagulation
	»	Manipulated variable : Addition of acid or alkali
	»	Responding variable : Coagulation of latex

Material: » Latex » Ethanoic acid » Ammonia solution » Red and blue litmus paper

Apparatus: » Glass stirring rod » Beaker » Dropper

Procedure:

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1. 100cm3 of latex is poured into three different beakers and label them respectively A, B and C. 2. 2cm3 of ethanoic acid is dropped into the beaker A using a dropper. 3. Ammonia solution is added into beaker B until the mixture became alkaline. The alkaline solution is tested with red litmus paper. 4. Beaker C is left behind as a control experiment.

Obervation:

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Beaker Observation A – latex + ethanoic acid Latex coagulates B – latex + ammonia solution Latex does not coagulate C – control experiment Latex coagulates after 1 day

Discussion:

	►	Latex consists of groups of rubber particles dispersed in water, which can only be seen through a microscope.
	►	Each group of rubber particles is surrounded by a negative charge membranes protein.
	►	The negative particles membrane will repel other negative particles which eventually will prevent all the particles to coagulate.
	►	When acid is added to latex, the positively charged ions H+ from acid will neutralise the negative charged membrane protein of rubber particle.
	►	The neutralise rubber particles will collide to cause the membrane to break. Rubber particle is released, combine with each other and cause them to coagulate.

Conclusion:

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Acid will coagulate latex meanwhile alkali will prevent coagulation of latex.

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