Tutor profile: Ryan K.
A student has accidentally broken some glass into a beaker containing salt. Explain a method the student could carry out to separate the salt from the glass.
Salt is a soluble substance and glass is insoluble. The student can use this difference to separate the two substances using physical separating techniques. First, the student can add water to the salt/glass mixture as this will cause the salt to dissolve but the glass to remain in the saltwater solution. Once all the salt has been dissolved the student can then use filtration to separate the insoluble glass from the saltwater solution. After the glass has been removed the student can then use one of two methods to separate the salt from the saltwater solution. 1. If the student doesn't need to collect the water again then he can use crystallisation to evaporate off the water slowly to leave behind the salt crystals. When doing this he needs to be careful as if he does this step too quickly the salt crystals can become very hot and start to spit from the evaporating dish. The second method is to use distillation and in this method, he would be able to collect his original water again as well as the salt crystals that would be left behind. Filtration and crystallisation are the norms in this case but some people would prefer to collect the solvent (water) back again at the end.
A biologist has discovered a new cell inside a sample of water. He places the cell under a microscope and he can observe the cell moving around using what looks like small tails from the end of the cell. The biologist believes he has found a type of bacteria, what else would the biologist be able to observe to prove his theory correct?
If the cell is a bacteria cell then the tails at the end of the cells are flagella, long whip-like structures that help the bacteria to move around. The biologist would also be able to see a loop of chromosomal DNA that contains most of the genetic material of the bacteria. He should also be able to observe a cell wall and a slime coat on the outside of the cell which both help to protect the bacteria from its environment.
If you had two identical boxes both containers are topped with a lid. Inside one box a gas has been placed inside and in the other box, a block of solid metal has been placed. Explain, in terms of particles, why the gas exerts pressure on the lid of its container but the block of metal does not.
For pressure to occur there needs to be a collision of particles. The particles inside a gas are free to move around and contain large amounts of energy. The gas inside the box can therefore move and collide with the lid of its container causing pressure to be experienced. The block of metal is a solid, solid particles can not freely move around and therefore cannot collide with the lid of the container and so cannot produce a pressure on the lid of its container.
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