L13 Centrifuge and separating funnel Notes PDF

Separation techniques Separation techniques Can you name the ones we have learnt about so far?  Separation techniques So far we have learnt about: Sieving Decanting Magnets Filtration Evaporation (and crystallization) Distillation Chromatography Floatation Plastic will float...

Separation techniques Separation techniques Can you name the ones we have learnt about so far?  Separation techniques So far we have learnt about: Sieving Decanting Magnets Filtration Evaporation (and crystallization) Distillation Chromatography Floatation Plastic will float on water and can be scooped out with a net Separating funnel When one liquid does not mix with another liquid (they are immiscible) but floats on top of it, a separating funnel can be used to separate the two liquids. Oil floats on water. This mixture can be separated using a separating funnel. Separating funnel A separating funnel is another piece of equipment used to separate mixtures. It separates two immiscible liquids of different densities. The less dense liquid floats on top.  Oil and coloured water in a separating funnel. Oil is less dense than water so forms a layer on top. You can open the tap and let out the lower layer of water (the more dense liquid) into a beaker Then use a different beaker to collect the oil afterwards Separating funnel Separating funnel Oil and water (Immiscible liquids- they do not mix) If you shake them, they will form a temporary emulsion. After about 5 min they will separate. Separating funnel Centrifuge Centrifuge Centrifuge with tubes Centrifuge A centrifuge is a machine that creates a rotational force. It is used to separate a mixture containing particles of different densities. Centrifuging blood If you just want to give a patient the plasma  After spinning the mixture in a centrifuge a pellet is formed from the more dense particles, which are forced to the bottom of the tube. The remaining solution on top is called the supernatant  The supernatant from the first spin at low speed can be removed off the top with a pipette and placed into a new centrifuge tube. This can be spun at a faster speed to further separate the particles remaining in the mixture if they have different densities  Separation of a mixture by centrifuging There are 4 different substances in this mixture which all have different densities. At low spin speeds the largest particle will form a pellet. Each time the supernatant is spun again the next largest particle will form the pellet Mixture of flour and red water Look at the pellet Raw Milk  Before the invention of centrifugal separators, separation was performed by letting milk sit in a container until the cream floated to the top and could be skimmed off by hand. The cream and milk are being separated based on density.  A variant container-separator had a nozzle at the bottom which was opened to allow the milk to drain out of the bottom. A window in the side, near the nozzle at the bottom, allowed the operator to observe when the milk was drained. This is like the use of a separating funnel.  Centrifuging milk The centrifugal separator made it possible to separate cream from milk faster and more easily, without having to let the milk sit for a time, and risk it turning sour. The original centrifugal separators were hand-cranked. Separating funnel and centrifuge notes 1. Describe and explain how to separate a mixture of oil and water with a separating funnel. Sketch and label a diagram to support your answer. 2. How does a centrifuge work to separate mixtures? 3. What would happen if you put freshly collected blood in a centrifuge and why? 4. What would happen if you put freshly collected milk in a centrifuge and why? 5. Draw a sketch of a centrifuge tube after a mixture has been centrifuged in it, label the pellet and the supernatant.