Chemistry January 2020 PPE Flashcards
What is chromatography used for?
It is used to separate two soluble substances
What is a chromatogram?
The end result of a chromatography experiment
What is distillation?
The process of separating mixtures of liquids
How does distillation work?
The mixture is heated and because all boiling points are different, the liquid with the lowest boiling point will boil first, leaving the other/s behind.
Why can untreated water be dangerous?
Pesticides Pollutants Animal waste Dirt Lack of minerals Diseases Debris Chemicals Bacteria Microorganisms
What does filtration do?
Filters out big bits of debris. It also removes pesticides and other impurities. It uses activated carbon and sand
What does disinfection do?
Removes microorganisms using ozone gas and chlorine.
What does coagulation do?
Removes dirt and other particles suspended in water. Aluminium sulfate and lime are added to form floc which sticks the particles together and then sinks them to the bottom to be removed during filtration
Do atoms have a positive or negative charge?
Atoms have no overall charge
How many electrons are in the first shell?
2 electrons
What makes an element stable?
A full outer shell of electrons
Describe the structure of a metal
Metals are good conductors of heat and electricity. They
are strong and have a regular arrangement of atoms
What is the relationship between group 1 and group 7?
Group 1 needs to give away one electron to become stable and group 7 need to gain one electron to become stable, this makes it ideal to create ions with both groups
Give an example of a group 1 element
Hydrogen Lithium Sodium Potassium etc...
Do metals need to gain or lose electrons to become stable?
Metals need to lose electrons
Do non-metals need to gain or lose electrons to become stable?
Non-metals need to gain electrons
If an element gains and electron, is the ion positively or negatively charged?
It becomes a negatively charged ion
If an element loses an electron, is the ion positively or negatively charged?
It becomes a positively charged ion
What is covalent bonding?
When atoms share electrons to create a full outer shell for both atoms
Explain why ions are attracted to each other and for ionic compounds
When metals react with non-metals, the metal atoms lose electrons and become positively charged while non-metals become negatively charged. These oppositely charged ions are attracted together. They form electrostatic bonds which hold the compound together.
When a metal is joined to a metal is is called ___?
Metallic bonding
When a non-metal is joined to a non-metal it is called ___?
Covalent bonding
When a metal is joined to a non-metal it is called___?
Ionic bonding
Are ionic compounds conductive?
Only when in liquid state
How many electrons are in the third shell?
8 electrons
Why do ionic compounds have a high melting/boiling point?
They have strong electrostatic attraction between oppositely charged ions which makes it more difficult to break them apart
What is a negatively charged ion called?
An anion
What is a positively charged ion called?
A cation
What kind of of structure is an ionic compound?
An ionic lattice
How is an ionic lattice arranged?
In a regular arrangement
How are ions held together?
By strong electrostatic attractions
How could you separate salt from rock salt?
Place the rock salt in water, the salt will dissolve leaving the rock behind. Then filter out the rocks. After then evaporate the water which will leave the salt left
What is solubility?
How well a substance dissolves in liquid
What does soluble mean?
Substances that dissolve in liquid
What is a solvent?
The Liquid used to dissolve a substance
Name all three states of matter
Solid, liquid and gas
What makes a substance pure?
Pure means it only contains one element or compound
How do you determine whether a substance is pure?
You can boil a substance to see if it is pure
Why is air not a pure substance?
Air has oxygen, carbon dioxide and many more different elements and compounds in it
What four factors affect the rate of a reaction?
Temperature
Concentration (of particles)
Surface area
Catalysts
What two things does collision theory depend on?
- The collision frequency of reacting particles
2. Particles must collide with enough energy to be successful
Give two reasons why increasing the temperature increases the rate of a reaction
It increases the frequency of particles and also increases the energy of the collsions
What is the definition of a catalyst?
A substance that can increase the rate of a reaction without being used up or changed
How do catalysts increase the rate of a chemical reaction?
They provide an alternate reaction pathway with a lower activation energy
How do you calculate the mean rate of reaction?
Quantity of product formed / time
