关于我们 About US 投稿/Contribute

首页> 培训>A-Level>考题> 正文

A-Level化学-物质Substances and Their Structure

新东方 2016-03-16 16:58

  Revision: Substances and their Structure and Properties

  Carbon

  Diamond

  Structure - Each carbon atom is covalently bonded to another 4 carbon atoms which forms up a tetrahedral shape which repeats itself throughout the macromolecule.

  Melting point - The Melting point of diamond is 3820 degrees Kelvin which is extremely high and this is because of the multiple strong covalent bonds throughout the molecule. Density - The density of diamond is 3.52g/cm3

  Electrical conductivity - Diamond does not conduct electricity.

  Graphite

  Structure - Each carbon atom is covalently bonded to another 3 carbon atoms which forms up different planes which are joined by weak intramolecular forces. There is a "sea" of delocalized electrons between the layers.

  Melting point - The Melting point of graphite is 3652 degrees kelvin which is extremely high and this is because of the multiple strong covalent bonds throughout the molecule.

  Density - The density of graphite is 2.09g/cm3

  Electrical conductivity - Graphite is a very good electrical conductor because of the sea of delocalized electrons.

  Ice

  Structure - Each Ice molecule forms up a regular hexagonal lattice out of water molecules which bond to each other through hydrogen bonding between a hydrogen and a lone pair of electrons on an oxygen. Ice can form up 9 other structural forms at different temperatures and pressures. At normal pressures it can also form up a structure similar to diamond.

  Melting point - The Melting point of Ice is 273 degrees kelvin which is low because the hydrogen bonds are weak.

  Density - The density of Ice is 0.93g/cm3, which is less than water's 1.00g/cm3. This means ice floats.

  Electrical conductivity - Ice does not conduct electricity.

  Sodium Chloride

  Structure - Sodium chloride forms crystals with cubic symmetry. In these, the larger chloride ions, shown to the left as yellow spheres, are arranged in a cubic close-packing, while the smaller sodium ions, shown to the left as blue spheres, fill the octahedral gaps between them. Each ion is surrounded by six of the other kind. This same basic structure is known as the halite structure. It is held together with an ionic bond and electrostatic forces.

  Melting point - The Melting point of NaCl is 1074 degrees kelvin due to the strong electrostatic forces.

  Density - The density of graphite is 2.16g/cm3

  Electrical conductivity - Sodium chloride only conducts electricity in the molten or aqueous state where the ions are free to move.

  Iodine

  Structure - Each Iodine atom bonds covalently to another to form an I2 molecule. These I2 molecules then bond to each other through weak inter-molecular bonds. In solid iodine the molecules are arranged in waves as shown right.

  Melting point - The Melting point of Iodine is 386 degrees Kelvin.

  Density - The density of Iodine is 4.94 g/cm3.

  Electrical conductivity - Iodine does not conduct electricity.

  Polythene

  Structure - Polythene is a giant covalent structure formed from polymerization of ethene. This forms up very long chains which then lay down into two regions, amorphous regions (A) and crystalline regions (B) The amount of each type of region varies and causes different properties.

  Melting point - The Melting point of polythene is ~388-408 degrees kelvin.

  Density - The density of Polythene is 0.91-0.97g/cm3.

  Electrical conductivity - Polythene does not conduct electricity.

分享到:
相关文章 A-Level化学
推荐

智囊分享

A-level经济学专业词汇解析

提到A-level经济学,可能很多小伙伴两眼热泪吧,尤其是想到那些常用的专业词汇的时候吧,不仅难记忆,就是理解都不是那...
A-Level作为英国高中课程大概有20门的热门课程。在申请的选课这一环节中,大部分家长和学生在选择课程的时候都很迷茫。...
很多同学咨询想去英国留学,是初中毕业后直接就读A-level课程好呢?还是到高二年级就读比较好呢?下面,主页君就这个问...
  今天兆龙留学为大家分享的是已经在英国就读GCES第一年的学生如何申请英国的A-LEVEl。一起来看看吧。   1、申请时间
  A-Level中文对于中国学生来说,自然是英国顶尖大学不怎么待见的科目。如果想要上最top的英国大学,数学、物理、经...
推荐给好友


邮箱格式错误

发表成功

您的评论将在编辑审核后发表,感谢您的参与

登录继续邮箱格式错误

没有账号? 快速注册忘记密码?

其它账号登陆:

需编辑审核