Chemistry Flashcards
what is an isotope?
different atomic forms of the same element, which have the SAME number of protons but a DIFFERENT umber of neutrons
properties of ionic compounds?
- high melting and boiling points
- when melted or dissolved they can conduct electricity
what is the charge of an ion which has gained an electron?
what is the charge of an ion which has lost an electron?
negative
postitive
properties of simple molecular substances?
- low melting and boiling points
- gases or liquids at room temperature
- dont conduct electricity
properties if giant covalent bonds?
- very high melting and boiling points
- dont conduct electricity(apart from graphite)
properties of a diamond and graphite?
diamond- four covalently bonded carbon atoms. very hard.
graphite- 3 covalently bonded carbon atoms rather than 4. this makes graphite slippery and good conductor of electricity cause it has a de localised electron.
properties of metallic structures?
- hard, malleable
- delocalised electron so it can conduct heat and electricity
what holds the metallic structure together?
the electrons and the positive ions have a strong electrostatic attraction.
why are alloys harder than pure metals?
the different sized atoms means that the layers are distorted therefore do not slide over each other and are therefore harder.
what is nitinol and why is it used in medicine?
nitinol is a “smart material” that can remember a shape it used to be. it is used in braces as the mouth warms up the nitinol tries to go back to the ‘remembered shape’ and pulls the teeth with it.
how big is nano particle?
contains roughly a few hundred atoms
give 3 examples of nanoscience?
1) nanotubes can be used in building materials
2) they can be absorbed by the body better therefore can deliever drugs to the right cells quicker
3) used in sun cream as they do the right job yet dont leave white marks on the skin.
what is a thermosetting polymer?
they have crosslinks. these hold the chains together in a solid structure, therefore these will not soften when heated. they are hard, rigid and strong.
what is a thermosoftening polymer?
the do not have crosslinks between the chains, they can melt very easily and therefore soften when heated. (remould)
what is low density polythene?
made by heating ethene to bout 200 degrees under a HIGH pressure. is flexible and used in bags and bottles
what is high density polythene?
made at a lower temperature and LOWER pressure its more rigid and used in drainpipes and water tanks
what is the relative atomic mass?
how heavy the different atoms are. (usually the same as the mass number)
what is the relative formula mass?
in a compound, is the relative atomic mass of all the atoms ADDED TOGETHER.
what is a mole?
the relative formula mass of a substance in grams
how do you figure out how many moles?
NUMBER OF MOLES= mass in g(of element or compound) DIVIDED BY the relative formula mass (of element or ompound)
