Atomic structure Flashcards
How many different types of elements are there?
118
How much oxygen makes up the earths atmosphere
21%
What is a compound
A compound is a chemical substance made up of 2 or more elements that are chemically joined together
Key features of a chemical reaction
- compounds are broken or formed
- at least 1 new substance is created
-measurable energy change
-no atoms are created or destroyed
What is a reactant
-the chemicals that are reacting with each other
what is a product
the chemicals being made
why do equations need to be balanced
because atoms cannot be created or destroyed
name the different types of chemical equations
symbol equations and word equations
what are mixtures
consists of two or more elements or compounds not
chemically combined together
name all separation techniques
evaporation
filtration
chromotography
fractional distillation
simple distillation
what does chromotography do
separates components from a mixture
what does filtration do
Filtration separates mixtures that contain insoluble (can’t dissolve) solids and liquids (which are soluble).
how does filtration work
Filtration is performed by pouring the mixture through filter paper:
The insoluble solid is trapped by the filter paper.
The liquid runs through the filter paper and is collected below.
what does fractional distillation do
separates alot of liquids with different boiling points
what does simple distillation do
separates a solid from a liquid whilst keeping the liquid
what is the radius of an atom
0.1 nanometres
what is the radius of a nucleus
1x10^-14 m
features of the nucleus
- in the middle of the atom
- contains protons and neutrons
- overall positive charge because of the protons
- where most of the atoms mass is concentrated
features of electrons
- move around the nucleus in electron shells
- negatively charged and tiny, but cover a lot of space
- the volume of their orbits determine the size of the atom
- have basically no mass–
where is the mass number
at the top
wheres the atomic number
at the bottom of the element
what is an element
a substance that consists of atoms with the same atomic number
what are isotopes
different forms of the same element, which have the same number of protons but different number of neutrons
what is the relative atomic mass
the average mass, taking into account the different masses and abundances of all the isotopes that make up the element
equation for relative atomic mass
sum of ( isotope abundance x isotope mass number) / sum of abundances of all the isotopes
when would you know whether to use evaporation or crystalisation
use evaporation if the salt doesnt decompose, if it does, use crystalisation
how does crystalisation work
- pour the solution into an evaporating basin
- heat the solution, it will get more concentrated#
- once some of the solvent has evaporated, or once crystals have began to form, remove the dish from the heat and allow it to cool
- the salt should start to form crystals as it becomes insoluble in the cold, highly concentrated solution
- filter the crystals out of the solution, and leave them in a warm place to dry
how to separate rock salt
- salt dissolves in water, but sand doesnt, so first
1. Grind the mixture to make sure the salt crystals are small, so will dissolve easily
2. Put the mixture into water and stir, the salt will dissolve but the sand wont
3. filter the mixture, the grains of sand wont fit through the tiny holes in the filter paper, so they collect on the paper instead. The salt passes through the filter paper as its part of the solution
4. Evaporate the water from the salt so that it forms dry crystals
simple distillation apparatus
- we place our solution in a flask with the liquid and dissolved solid
- this flask is connected to a continuous glass tube
- the glass tube is surrounded by a jacket called a condenser
- cold water from the tap continuously runs through the condenser
- after running through the condenser, the water simply goes down the sink
in simple distillation, cold water from the tap continuously runs down the condenser, what does this do?
it keeps the internal glass tube cold
how does simple distillation work
- start by heating your solution with a bunsen burner
- as we heat the liquid, it begins to evaporate, turning into vapour
- the vapour rises up the glass tube
- the vapour then passes into the condenser
- the vapour then condenses back into a liquid as it passes through the condenser
- we are left with crystals of the solid in the flask, and liquid collected in a beaker
fractional distillation apparatus
- the flask containing our liquids with different boiling points is connected to a long column containing glass beads called the fractionating column
- thermometer at the top of the fractionating column
- condenser and beaker under it
how does fractional distillation work with two liquids
- gently heat the mixture
- both liquids will start to evaporate, but the one with a lower boiling point will evaporate more easily
- we have a mixture of two different vapours making their way to the fractionating column
- when they reach the fractionating column, they condense and drip back into the flask, where they evaporate again
- this repeated evporation and condensation increases the amount of the chemical with a lower boiling point in the fractionating column
- the vapours pass along the condenser and turn into a liquid, but the liquid still contains both chemicals
- at one point, the thermometer reaches the temp of boiling point of the chemical with the lower boiling point, and it stops rising, and its mostly the chemical passing through the condenser so we can collect it
- the thermometer temp begins to rise again, but then its mostly the chemical with the higher boiling point, so we can collect that
how do we know when were collecting a pure sample of a chemical in fractional distillation
the thermometer’s temperature remains constant
