AQA A Level Chemistry复习笔记1.6.1 Bond Energy
Bond Energy During a reaction, enthalpy changes take place because bonds are being broken and formed Energy (in the form of heat) is needed to overcome attractive forces between atoms Bond breaking...
Bond Energy During a reaction, enthalpy changes take place because bonds are being broken and formed Energy (in the form of heat) is needed to overcome attractive forces between atoms Bond breaking...
Electron Pairs The valence shell electron pair repulsion theory (VSEPR) predicts the shape and bond angles of molecules Electrons are negatively charged and will repel other electrons when close to...
State Changes Changes of state are physical changes that are reversible These changes do not change the chemical properties or chemical makeup of the substances involved Vaporization includes evapo...
Mole & Avogadro Constant The Avogadro constant (NA or L) is the number of particles equivalent to the relative atomic mass or molecular mass of a substance The Avogadro constant applies to atom...
Relative Masses Atomic Mass Unit The mass of a single atom is so small that it is impossible to weigh it directly Atomic masses are therefore defined in terms of a standard atom which is called the...
Structure of an Atom All matter is composed of atoms, which are the smallest parts of an element that can take place in chemical reactions Atoms are mostly made up of empty space around a very smal...
Recombinant DNA Technology Recombinant DNA The genetic code is universal, meaning that almost every organism uses the same four nitrogenous bases – A, T, C & G. There are a few exceptions The g...
Genome Sequencing Projects A genome contains all of the genes within an organism Advances in technology have allowed scientists to map and sequence the genes within an organism's genome Genome sequ...
Totipotent Cells A stem cell is a cell that can divide (by mitosis) an unlimited number of times Each new cell that is produced when a stem cell divides has the potential to remain a stem cell or t...
Gene Mutations A gene mutation is a change in the sequence of base pairs in a DNA molecule that may result in an altered polypeptide Mutations occur continuously and spontaneously Errors in the DNA...
The Definition of a Community Species do not exist by themselves in their own isolated environment, they interact with other species forming communities A community can be defined as: Multiple popu...
ISEF 国际科学与工程大奖赛(Regeneron ISEF)是全球最大规模、最高等级、也是唯一面向9-12年级(即初三至高三)中学生的科学学术活动,每年在美国的不同城市举行。 学术活动学科包括了所有自然科学和部分社会科...
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