Shawn910018的部落格

 Experiment date: 2013/10/25

First Experiment

1. Principle:

     Freezing is a process of crystallization. So if there are no condensation nuclei, it will be hard to freeze. In this way, we can make pure water colder than 0 degree, and still won’t turn into ice. This is called “supercooling.”

     When a liquid is in supercooling status, if you shake it, then the molecular will hit each other. They will become little crystals and can be condensation nuclei. Then, other moleculars can attach it and freeze together.

What’s more. You can also do it by changing it’s pressure. This Experiment is based on this way.

1. Safety and Waste Disposal:

The ice with salt can make the temperature become lower than 0 degree. Don’t put your finger in the plastic bowl with these things for too long.

1. Procedure:

(1)Prepare a battle of soda, some ice, a plastic bowl, and a bag of salt.

(2) Put ice and salt into the plastic bowl with the Proportion of 3:1.(It can be lower than 0 degree.)

(3) Put the battle of soda on half of the ice and salt, and put another half on it.

(4)Wait for an hour.

(5) Take away the ice on the battle and take it out. (IMPORTANT: Don’t shake the soda.)

(6) Open the battle slowly, let the CO₂ come out. Then show every one it is still liquid.

(7) Lock the battle and shake it. It will freeze.

Second Experiment

1. Principle:

This experiment’s principle have two part. First is crosslinking. And second is ferrimagnetism. When we put Na₂B₄O₇^.10H₂O into the water, it will Dissociation. Polyvinyl acetate, or PVAc is (C4H6O2)_n. When it mix with Na₂B₄O₇^.10H₂O in water, it will be many H-bond between PVAc. And this is crosslinking.

Second, every molecular’s Magnetic field is pointing the different direction, with different strength. This means the whole part of the molecular is having a Magnetic field. And this is ferrimagnetism. So it will be able to be Attract by a magent.

1. Chemicals and their Properties:

polyvinyl acetate: d:86.09 g/mol Often use in glue.

Fe₃O₄: 231.533 g/mol d:5.11 g/cm³~5.18 g/cm³ mp:1538 °C~1590 °C

Na₂B₄O₇^.10H₂O: 381.37 g/mol d: 1.73 g/cm³ mp: 741 °C bp: 1575 °C

1. Safety and Waste Disposal:

Na₂B₄O₇^.10H₂O is a thing that is toxic. Wash your hand clearly after finish the experiment.

1. Procedure:

(1)   Weigh out 50g of polyvinyl acetate and 10g of Fe₃O_4.

(2)   Put it into a Container and stir them. Make sure you stir it enough.

(3)   Pour Na₂B₄O₇^.10H₂O with water in. 1mL for once. Then stir it quickly.

(4)   Stop when you pull it up by your stick. (near 20mL)

(5)   Take it out and Knead it until it’s glossy.