Topic 1-Atomic Structure And The Periodic Table Flashcards
What is an isotope?
Different forms of the same element which have the same number of protons but a different number of neutrons.
What is relative atomic mass?
An average mass taking into account the different masses and amounts of all the isotopes that make up the element.
What is a compound?
Substances formed from two or more elements.
How are compounds held together?
They are held together by chemical bonds.
How are bonds made?
Giving away, taking or sharing electrons.
What does a compound made of metals and non metals consist of?
Ions.
What happens to the metal in the compound?
It loses electrons to form positive ions.
What happens to non metals in a compounds?
They gain electrons to form negative ions.
What is ionic bonding?
The opposite charges of the ions mean they are strongly attracted to each other.
What is covalent bonding?
Where each atom shares an electron with another atom.
What is a mixture?
Two or more elements or compounds mixed together.
What is different between a mixture and a compound?
There is no chemical bond between the different parts of a mixture.
Describe how you separate substances using chromotography?
Draw a lime near the bottom of a sheet of filter paper using pencil.
Add a spot of ink to the line and place the sheet in a beaker of solvent.
The solvent depends on what is being tested as some compounds dissolve well in water however sometimes ethanol is needed.
Make sure the ink isnt touching the solvent.
The solvent seeps up the paper carrying the ink with it.
Each different dye will move up the paper at a different rate so the dyes will separate out. Each dye will form a spot in a different place.
If any of the dyes are insoluable in the solvent you used it will stay on the baseline.
When the solvent has reached near the top and take the paper out the beaker and leave it to dry.
The end drued result is a chromatogram.
Whag does filtration do?
Separates insoluable solids from a liquid. Also used in purification to get rid of solid impurities in a reaction mixture.
What is used in filtration?
Filter paper is folded into the cone shape and the solid is left in the filter paper.
Describe the process of evaporation?
Pour the solution into an evaporating dish.
Slowly heat the solution and the solvent will evaporate and the solution will get more concentrated. Crystals will start to form.
Keep heating the dish until you have dry crystals.
What can you only ise evaporation for?
Only if the salt doesnt break down when it is being heated.
Desribe the process of crystallisation?
Pour the solution into an evaporating dish and gently heat the solution. Some of the solvent will evaporate and the solution will get more concentrated.
When you see the crystals start to form remove the dish from the heat and leave the solution to cool.
The salt should start to form crystals as it becomes insoluable in the cold, highly concentrated solution.
Filter the crystals out the solution and leave them in a warm place to dry.
Desribe the crystallisation and filtration practical to separate rock salt?
Grind the mixture to make sure the salt crystals are small so they will dissolve easily.
Put the mixture in the water and stir. The salt will dissolve but the sand wont.
Filter the solution. The grains of sand wont fit through the holes of the filter paper so they collect on the paper instead. The salt passes through the filter paper as it is part of the solution.
Evaporate the water from the salt so it forms dry crystals.
What is rock salt?
A mixture of salt and sand.
Why does salt and sands physical properties allow them to be separated?
They are both compounds but salt dissolves in water and sand doesnt.
Describe simple distillation?
Simple distillation is used to separate a liquid from a solution.
The solution is heated. The part of the solution that has the lowest boiling point evaporates first.
The vapour is then cooled, condensed and is then collected.
The rest of the solution is left in the flask.
What mixture can you use distillation to separate?
You can use it to get pure water from seawater.
The water evaporates and condenses and eventually you will be left with just left with salt in the flask.
What is the problem with simple distillation?
It can only separate things with very different boiling points.
If the temperature goes higher than the boiling point of the substance and goes to the higher boiling point the mixtures will mix again.