1 - 1 - Principles of Chemistry Flashcards
1
Q
How are the particles arranged in a solid?
A
- Strong forces of attraction between particles which folds them close together in fixed positions in a lattice arrangement
- The particles don’t move from their position, keep a definite shape and volume
- The particles vibrate in position
- The hotter they become the more they vibrate
2
Q
How are the particles arranged in a liquid?
A
- Weaker force of attraction between particles
- Randomly free to move past each other but still stay close together
- Have a definite volume but no definite shape
- Particles are constantly moving in a random motion
3
Q
How are the particles arranged in a gas?
A
- Very weak forces of attraction
- Far apart and move freely but in straight lines
- No definite shape or volume and will fill any container
- Constantly move in a random motion
- ## When temperature increases the pressure increases
4
Q
What is melting?
A
Solid to liquid
5
Q
What is evaporating?
A
Liquid to gas
6
Q
What is condensing?
A
Gas to liquid
7
Q
What is freezing?
A
Liquid to solid
8
Q
What is subliming?
A
Solid to gas
9
Q
Describe an experiment to show diffusion in water
A
- Potassium manganite (VII) in water
- The bright purple colour will slowly diffuse
10
Q
Describe an experiment to show diffusion in water
A
- Potassium manganite (VII) in water
- The bright purple colour will slowly diffuse out
- The solution can be diluted further by adding more water
11
Q
Describe an experiment to show the random motion of particles in air
A
- Fill half a gas jar with bromine gas (brown) and the other half with air separating it with a glass plate
- If you remove the glass plate the bromine gas will slowly diffuse through the air
- The random motion means that the bromine will eventually diffuse right through the air
12
Q
Describe an experiment to show gas diffusion
A
- Aqueous ammonia (NH3) gives off ammonia gas
- HCl gives off hydrogen chloride gas
- Soak two
13
Q
Describe an experiment to show gas diffusion
A
- Aqueous ammonia (NH3) gives off ammonia gas
- HCl gives off hydrogen chloride gas
- Soak two pieces of cotton wool in the liquids and put in a sealed glass tube
- A ring of ammonia will form almost in the middle just slightly closer to the HCl
- This is because the particles of ammonia are smaller and lighter so will diffuse more quickly
14
Q
Nucleus
A
- Middle of the atom
- Contains protons and neutrons
- Has a positive charge because of the protons
- Almost the whole mass of the atom is concentrated in the nucleus
- Very small
- Relative mass of 1
15
Q
Electrons
A
- Move around the nucleus in energy levels called shells
- Negatively charged
- Tiny but cover a lot of space
- Virtually no mass (1/2000)
- Number of electrons = number of neutrons
16
Q
Electrons
A
- Move around the nucleus in energy levels called shells
- Negatively charged
- Tiny but cover a lot of space
- Virtually no mass (1/2000)
- Number of electrons = number of neutrons
- If electrons are added or removed the atom becomes charged and is an ion
17
Q
Atomic number
A
- How many protons there are
- The smaller number
- Atoms of the same element will have the same number of protons
18
Q
Mass Number
A
The number of protons and neutrons
19
Q
What are molecules?
A
- Groups of atoms
- Can be made from one element of different elements
- Held together by covalent bonds
20
Q
What are elements?
A
One type of atom only
21
Q
What are compounds?
A
- A substance that is made of two or more different elements which are chemically bonded together
- Difficult to separate
- The properties of a compound are often totally different from the properties of the elements
22
Q
What are elements?
A
One type of atom only
e.g. oxygen
23
Q
What are compounds?
A
- A substance that is made of two or more different elements which are chemically bonded together
- Difficult to separate
- The properties of a compound are often totally different from the properties of the elements
- e.g. carbon dioxide
24
Q
What are mixtures?
A
- No chemical bond between different parts of a mixture and can be separated through distillation
- Properties of a mixture are just the properties of the separate parts
- e.g. air
25
When is filtration used?
- To separate an insoluble solid from a liquid
| - Can be used for purification as well
26
Describe the process of crystallisation
- Pour the solution into an evaporation dish
- Slowly heat the solution
- Some solvent will evaporate and the solution will become more concentrated
- Stop heating when crystals start to form
- Remove the dish and leave in a warm place for the rest of the solvent to evaporate
- Dry the product using a drying oven or desiccator
27
Describe how to use crystallisation and filtration to separate rock salt
- Rock is a mixture of sand and salt which are both compounds
- Grind it up using a pestle and mortar
- Dissolve in a beaker and stir
- Filter
- Crystallise
- The sand doesn't dissolve so stays as grains that don't fit through the filter paper
- The salt is forms as crystals
28
Describe how to use crystallisation and filtration to separate rock salt
- Rock is a mixture of sand and salt which are both compounds
- Grind it up using a pestle and mortar
- Dissolve in a beaker and stir
- Filter
- Crystallise
- The sand doesn't dissolve so stays as grains that don't fit through the filter paper
- The salt is forms as crystals
29
Describe how to paper chromatography
- Draw a line near the bottom of a sheet of filter paper (in pencil)
- Add spots of different dyes to the line at regular intervals
- Loosely roll up the sheet and put in a beaker of water
- Make sure the dyes aren't touching the solvent
- Put a lid on the container to stop the liquid evaporating
- The solvent will seep up the paper carrying the dye with it
- Each dye will move at a different rate and form a spot
30
What is chromatography?
A method used to separate mixtures (can be on paper with dyes)
31
how does chromatography separate mixtures?
- The different dyes move at different rates
- Some will stick to the paper and others will dissolve
- The distance the dyes travel depends on the solvent and paper you use
32
How does chromatography help identify dyes?
- Make the chromatograms for the unknown substance and for some reference materials (dyes that you know)
- Compare the chromatograms to work out what dyes are in your unknown substance
- Some spots will match up with known dyes which must be in the unknown dye
33
How does chromatography help identify dyes?
- Make the chromatograms for the unknown substance and for some reference materials (dyes that you know)
- Compare the chromatograms to work out what dyes are in your unknown substance
- Some spots will match up with known dyes which must be in the unknown dye
34
What is distillation? Describe how it is used
Separates a liquid from a solution
- The solution is heated and the solution with the lowest boiling point evaporates
- The vapours is cooled, condenses and is collected
- The rest of the solution is left behind in a flask
- Simple distillation can be used to get pure water from sea water
- The problem is you can only get two things with very different boiling points
35
What is fractional distillation? Describe how it is used
- Used to separate a mixture of liquids
- Put the mixture in a flask and put a fractionating column on top then heat
- The different parts will evaporate at different rates
- The liquid with the lowest boiling point will go to the top
- Liquids with higher boiling points may start to evaporate
- The column is cooler towards the top
- When the first liquid has been collected raise the temperature to collect the next one
36
What are features of groups in the periodic table?
- Groups (down) are all elements with the same number of electrons on the outer shells
- Have similar properties
- The properties depend on the number of electrons
37
What are features of groups in the periodic table?
- Groups (down) are all elements with the same number of electrons on the outer shells
- Have similar properties
- The properties depend on the number of electrons
38
What are the electron shell rules?
- Electrons always occupy shells
- The lower energy levels are always filled first
1 - 2 electrons
2 - 8 electrons
3 - 8 electrons
- Atoms want a full shell
- The closer they are to a full shell the more reactive they are
39
What is oxidation?
When an electron loses an electron OR gains oxygen
40
What is reduction?
When an electron gains an electron OR loses oxygen
41
What is ionic bonding?
The transfer of electrons by losing or gaining electrons to form a charged particle (an ion) which are then strongly attracted to one another (due to opposite charges)
This is known as the electrostatic attraction
42
Which groups are most likely to form ions?
1 &2 (metals who lose an electron to form +ve ions), 6 & 7 (non-metals who gain an electron to form -ve ions)
43
What are cations?
Positively charged ions
44
What are anoins?
Negatively charged ions
45
What are the properties of giant ionic structures?
- 3D lattice arrangement
- The electrostatic attraction is very strong
- High melting and boiling points
- The higher the charge the stronger the bonds (so higher melting and boiling points)
46
What is covalent bonding?
- Sharing electrons to make a full outer shell
| - There is a strong attraction between the shared electrons and the nuclei of the atoms
47
What is the symbol formulae for ammonia?
NH3
48
What is the symbol formulae for ammonia?
NH3
49
Simple molecular structures
- Strong covalent bonds
- Weak forces of attraction between molecules
- Low melting and boiling points
- Most are gases and liquids at rom temperature
50
Giant covalent structures
- No charged ions
- Strong covalent bonds
- Lots of bonds so high melting and boiling points- Don't conduct electricity except when molten
- Usually insoluble in water
- Examples are diamond and graphite
51
Diamond
- Made of carbon atoms which each have four covalent bonds
- The hardest natural substance
- Used for drill tips and cutting tools
52
Graphite
- Made of carbon atoms which each make three covalent bonds, creating layers
- The layers are free to slide over each other
- Used as a lubricant
- Has free electrons so is the only non-metal which is a good conductor of electricity
