Book 2 - The Building Blocks Of Chemistry Flashcards
(96 cards)
1
Q
What did John Dalton conclude:
A
- Every element is made of its own distinctive atoms of a particular mass
- Other chemicals are made from atoms that have joined together in some way.
2
Q
What do elements form when they react?
A
They form compounds
3
Q
How do elements form compounds?
A
Elements react by gaining, losing or sharing electrons.
4
Q
How do the elements in group 1 bond with the elements in group 7?
A
The group 1 element loses an electron to become stable. This electron is given to the group 7 element which also becomes stable.
5
Q
What charge does a group 1 ion have?
A
Positive
6
Q
What elements react in ionic bonding ?
A
Metal with a non-metal
7
Q
How are ionic compounds held together?
A
Strong forces of attraction between the oppositely charged ions.
8
Q
Which groups’ elements form ions?
A
1,2,6,7
9
Q
How are charged particles arranged as a result of ionic bonding?
A
Giant ionic structures
10
Q
Why are the ions in a giant lattice structure held together so strongly?
A
The force exerted by an ion on the other ions is equal in all directions (attraction between them)
11
Q
How are atoms in ionic bonds represented?
A
Dot and cross diagrams
12
Q
What does the formula of an ionic compound show?
A
The ratio of ions present.
13
Q
What is the overall charge of an ionic compound?
A
Zero
14
Q
When are brackets needed in a formula?
A
When there is more than one type of atom in the ion being multiplied.
15
Q
How are covalent bonds formed?
A
When atoms share pairs of electrons.
16
Q
What type of substances have covalent bonds?
A
Simple molecules (atoms joined by covalent bonds)or giant covalent structures
17
Q
What types of elements use covalent bonding?
A
Non-metals
18
Q
Give four examples of giant covalent structures?
A
- Diamond
- Graphite
- Silica
- Buckminsterfullerene
19
Q
How are atoms in metals arranged?
A
They are closely packed together and arranged regular layers.
20
Q
How are atoms in metals held together?
A
Metallic bonding is positively charged metal ions held together by electrons in the most outermost shell of each atom. The delocalised electrons can move throughout the lattice.
21
Q
What purpose do delocalised electrons play in metallic bonding?
A
Strong electrostatic attraction between the negatively charged electrons and positively charged ions bond the metal ions.
22
Q
What are the properties of ionic substances?
A
High melting and boiling points because the electrostatic forces of attraction between the positive and negative ions is very strong to hold the giant ionic lattice structure together. Therefore, it takes a lot of energy to melt or boil an ionic compound.
23
Q
Do ionic substances conduct electricity?
A
In a solid state, they cannot because the ions are not free to move in a solid state. But they do conduct in molten state and in aqueous solutions since the ions are free to move and carry charge to the electrodes.
24
Q
What are ionic bonds?
A
The electrostatic forces of attraction between oppositely charged ions.
25
What do covalent bonds form between?
Non-metals
26
What are simple molecules?
These contain only a few atoms held together by strong covalent bonds. An example is carbon dioxide (CO2), the molecules of which contain one atom of carbon bonded with two atoms of oxygen.
27
What are the properties of simple molecular substances?
Low melting and boiling points - This is because the weak intermolecular forces break down easily.
Non-conductive - Substances with a simple molecular structure do not conduct electricity. This is because they do not have any free electrons or an overall electric charge.
28
What do giant covalent structures contain lots of?
Non-metal atoms
29
How are the atoms usually arranged in giant covalent structures?
The atoms are usually arranged into giant regular lattices - extremely strong structures because of the many bonds involved.
30
What are the properties of giant covalent structures?
Very high melting points - Substances with giant covalent structures have very high melting points, because a lot of strong covalent bonds must be broken.
Variable conductivity - Some giant covalent structures conduct electricity as they have free electrons whereas other giant covalent structures do not conduct electricity as they have no free electrons.
31
What are the structure of metals?
The metal atoms are packed close together in a regular metallic structure. The outer shell electrons are lost from each atom and become free to move throughout the metal. This leaves a giant structure (lattice) of positive metal ions surrounded by delocalised electrons.
32
What are delocalised electrons?
Delocalised electrons are electrons that de associated themselves from their individual atom.
33
What do group 2 and 3 metals form when they lose an electron to become stable?
2+ and 3+
34
What do non-metal atoms groups 5 and 6 become when they gain an extra electrons?
3- and 2-
35
What can non-metals not form on their own?
Ionic compounds
36
What are the four types of models/diagrams?
- Molecular models
- Electron energy level diagrams
- Dot and cross
- Structural formulae
37
What do molecular models help us to picture?
They help us to visualise the shape of the molecule.
38
What do electron energy level diagram show us?
How covalent bonds are formed.
39
What do dot and cross diagrams show us?
Used to represent covalent bonds.
40
What do structural formula show us?
The bonds between atoms
41
Which types of substances have low boiling points?
Substances made of simple molecules.
42
Why do some substances have low boiling points?
The intermolecular forces between simple molecules are weak.
43
What is an intermolecular force?
A weak force between simple molecules.
44
Why is graphite soft and slippery?
- It contains layers of covalently bonded carbon atoms.
- There are no covalent bonds between the layers.
- The layers can slide over each other.
45
Why can graphite conduct electricity?
There are delocalised electrons along the layers.
46
What are fullerenes?
Large cage like structures based on hexagonal rings of carbon atoms.
47
Why does graphite have delocalised electrons?
Each carbon only forms three covalent bonds out of a possible four leaving a spare electron.
48
Give two possible uses of fullerenes.
- Delivering drugs to a specific part of the body.
| - Catalysts and lubricant
49
Why is it possible to bend and shape metals?
The layers of atoms and ions in a giant metallic structure can slide over each other.
50
Explain how nano technology can be used to treat cancer.
- Nano gold particles can be injected and absorbed by tumours.
- Tumours have thin leaky blood vessels allowing the gold nano particles to enter without going into healthy cells.
- A laser heats the Gold which heats the tumour cells but not surrounding cells.
51
Give two disadvantages of using nanotechnology in medicine.
- They have a large surface surface area meaning a spark could trigger an explosion.
- Nanoparticles could enter the bloodstream causing damage.
52
Why do metals allow electricity and heat to pass through?
Delocalised electrons allow electricity and heat to pass through more easily.
53
What are shape memory alloys?
An alloy that if deformed, can return to its original shape on heating.
54
Why are alloys harder than pure metals?
They are different sized atoms making it more difficult for the layers to slide.
55
What do the properties of polymers depend on?
- The monomers used to make it.
| - The conditions of the reaction.
56
How is Low Density Polyethene formed?
Ethene reacts under very high pressure and a trace of oxygen.
57
How is High Density Polyethene (HDPE) formed?
Using a catalyst at 60 degrees Celsius and slightly raised pressure.
58
What is a thermosoftening polymer?
A polymer that softens when heated and is made up of individual polymer chains tangled together. Can be reshaped and recycled.
59
What are thermosetting polymers?
Polymers which don't melt when heated and have strong covalent bonds forming cross links between polymer chains. Cannot be reshaped or recycled.
60
What is nanoscience?
The study of small particles between 1 and 100 nanometers in size.
61
Give six possible uses of nano technology in the future?
- Self cleaning glass
- Modern sun cream
- Cosmetics that are absorbed deeper into your skin
- Cancer treatment
- Nano-tech electronics
- Nanotechnology military suits.
62
Some atoms are ions, meaning they are charged, why is this?
They contain different numbers of protons and electrons.
63
What is a nanometre (nm)?
Is one millionth of a millimetre
64
Different Nanoparticles have very different properties from the same materials in bulk. Give examples for their differences.
- May be different colour
- May have different strength
- May react differently
- May have different electrical/thermal conductivity
65
What are the concerns about the Nanoparticles?
There are concerns about the effects of Nanoparticles on people. Given that the Nanoparticles have different properties to the bulk material, it is possible some Nanoparticles may be toxic even if the bulk material is not. For example, Nanoparticles are normally more reactive than the bulk material and can pass through the skin and cell membranes. Further research is needed to find out the effects.
66
Why do Nanoparticles of a substance have different properties to the bulk material?
The main reason why Nanoparticles have different properties from large pieces of the same material is that Nanoparticles have a much larger surface area to volume ratio. This means that a much higher fraction of atoms are on the surface.
67
What is the relative charge of a proton?
+1
68
What is the relative charge of a neutron?
0 (neutral)
69
What is the relative charge of an electron?
-1
70
What is the relative mass of a proton and neutron?
1
71
What is the relative mass of an electron?
0.0005
72
Why do different atoms have different masses?
They contain different numbers of subatomic particles.
73
What is the mass number?
Number of protons + number of neutrons
74
What is the atomic number?
The number of protons and electrons. (SEPARATELY) E.g Atomic number 11 means there are 11 protons and 11 electrons
75
How do you work out the number of neutron?
Mass number - Atomic number
76
What is an isotope?
Are atoms of the same element with different mass numbers. In other words, they are atoms with the same protons but different neutrons.
77
What is relative atomic mass (Ar)?
The average mass of the atoms in an element (their individual mass numbers will differ because of the existence of isotopes)
78
If you have 35Cl and 37 Cl what is their relative atomic mass?
35 + 37/2 = 36 (Ar)
79
What is the relative formula mass (Mr)?
Is the sum of the relative atomic masses (Ar) of all the atoms shown in the formula. E.g H2O contains two hydrogen atoms (Ar=1) and one oxygen atom (Ar =16) and so has a relative formula mass of 18.
80
How to work out the percentage by mass of an element in a compound?
100X relative mass of all the atoms of that element/Mr
81
What is the triangle used to work out moles, mass (g) and Mr?
Mass/Mr x Moles
82
In a reaction the reactants rearrange to form the products, so the mass should be the same. List 3 reasons why you do not get as much product as you might expect?
1-When you carry out a reaction, chemicals are lost among the way.
2-Sometimes other reactions can take place as well as the reaction you want.
3-Some reaction are reversible and the products can turn back into their reactants.
83
How do you work out the percentage yield?
Mass of products obtained/maximum theoretical mass of product x100
84
What is empirical formula?
The simplest whole number ratio of atoms or ions of each element in a substance.
85
What is the empirical formula of Silica dioxide Sio2?
1:2
86
What is the molecular formula?
The chemical formula showing the different elements and the number of atoms of each element in a molecule.
87
What is paper chromatography?
An analytical technique that separates compounds by their relative speeds in a solvent as it spreads through paper.
88
What is a pigment?
A solid, coloured substance.
89
Explain how artificial colourings in food can be analysed?
A sample of the colour from the food is placed on a piece of the chromatography paper along with samples of known dyes, then a solvent is added. The solvent soaks up the paper, taking the dyes with it. The more soluble a colouring is the further up the paper it travels.
90
What is a gas chromatography?
A method that separates chemicals in a very small sample. It can be used to separate fragments of DNA to make a DNA profile.
91
How does a gas chromatography work?
The sample is injected into the machine and is vaporised. The sample passes through a long column packed with a solid that is wound into a coil. An inert (unreactive) gas, such as nitrogen, is passed through the column to move the sample through. Different substances in the mixture travel through the column at different speeds. This means they reach the end of the column at different times and so are separated.
92
What is a retention time?
The time taken for a substance to reach the detector at the end of the gas chromatography column.
93
What is a mass spectroscopy?
An analytical technique that involves breaking molecules into charged fragments and measuring their mass/charge ratios. Also known as mass spectrometry.
94
How does a mass spectroscopy work?
It does this by measuring the mass of the particles in the substance.
95
Give three advantages of using instrumental analysis?
- They are highly accurate and sensitive.
- They are quicker
- They enable very small samples to be analysed.
96
Give three disadvantages of using instrumental analysis.
- It is usually very expensive
- It takes special training to use.
- It gives results that can only be interpreted by comparison with known substance data.
