L1 - Elements, Compounds & Mixtures Flashcards
1
Q
Define matter.
A
Anything that has mass.
2
Q
All objects are made of ________.
A
Matter
3
Q
What are the 3 states of matter?
A
- Solid
- Liquid
- Gas
4
Q
Describe the composition of mixtures.
A
Variable
5
Q
Describe the composition of pure substances.
A
Constant
6
Q
What are the 2 possible types of mixtures?
A
- Heterogeneous Mixtures
- Homogeneous Mixtures
7
Q
What are the 2 possible types of pure substances?
A
- Elements
- Compounds
8
Q
State the process by which you go from a solid to a liquid.
A
Melting
9
Q
State the process by which you go from a liquid to a gas.
A
Vaporisation
10
Q
State the process by which you go from a liquid to a solid.
A
Freezing
11
Q
State the process by which you go from a gas to a liquid.
A
Condensation
12
Q
State the process by which you go from a solid to a gas.
A
Sublimation
13
Q
State the process by which you go from a gas to a solid.
A
Deposition
14
Q
State the process by which you go from steam to water.
A
Condensing / Liquefying
15
Q
State the process by which you go from water to ice.
A
Freezing / Solidifying
16
Q
State the process by which you go from ice to water.
A
Melting / Fusing
17
Q
State the process by which you go from water to steam.
A
Evaporating / Boiling
18
Q
Describe electrical conductivity.
A
Ability to transmit electricity.
19
Q
Describe heat conductivity.
A
Ability to transmit heat.
20
Q
Describe density.
A
Mass to volume ratio.
21
Q
Describe melting point.
A
Temperature at which a solid becomes a liquid.
22
Q
Describe boiling point.
A
Temperature at which a liquid becomes a gas.
23
Q
Describe refractive index.
A
How light passing through a material is bent.
24
Q
Describe malleability.
A
Ability to be shaped by hammering.
25
Describe ductility.
Ability to be shaped by pulling into a wire.
26
What are intensive properties?
Properties that do not depend on the amount of matter present (and can be used to identify substances).
27
What are extensive properties?
Properties that depend on the amount of matter present.
28
Name 5 intensive properties.
- Boiling Point
- Colour
- Temperature
- Luster
- Hardness
29
Name 5 extensive properties.
- Volume
- Mass
- Size
- Weight
- Length
30
How can physical properties be observed?
By examining a sample of pure substance.
31
How do physical properties arise?
Arise from molecular structure and strength of intermolecular interactions.
32
How can chemical properties be observed?
By observing the course of a chemical reaction.
33
How do chemical properties arise?
Arise from the distribution of electrons around the atom's nucleus; particularly the outer (valence) electrons.
34
What is a pure substance?
A substance with a fixed set of chemical and physical properties, which cannot be separated by a physical process.
35
What is a mixture?
A physical blend of two or more substances, with variable composition.
36
Mixtures can be separated into __________.
Components
37
How can mixtures be separated into components?
By a physical process.
38
Pure substances can only be changed in identity and properties by ________ _______.
Chemical methods
39
Define element.
The simplest form of matter that has a unique set of properties.
A substance which cannot be split up into two or more simple substances by chemical means.
40
Define compound.
A substance that contains two or more elements chemically combined (bonded) in a fixed proportion.
41
Define molecule.
A group of two or more atoms that are joined together.
42
What 2 things can elements exist as?
- Atoms
| - Molecules
43
Compounds are made of _________.
Molecules
44
What is the key observation of Dalton's Atomic Theory?
Elements combine in fixed ratios.
45
Describe Dalton's Atomic Theory.
- All matter is composed of atoms
- Different elements have different types of atoms (can be characterised by atomic weight, all atoms of the same element are identical)
- Atoms cannot be made or destroyed
- Compounds are composed of two or more atoms chemically combined in fixed proportions
- Chemical reactions rearrange the atoms, changing ratios of chemical combination, and thus the identity of compounds
46
What mistakes did Dalton make in his Atomic Theory?
- Thought water was OH
| - Thought ammonia was NH
47
What does an atom consist of?
- Nucleus (Protons, Neutrons)
| - Electrons
48
What is combining power / valency?
The ability to form chemical bonds.
49
Describe the charges of the constituent of an atom.
Electrons - Negative
Neutrons - Uncharged
Protons - Positive
50
What does the atomic mass tell us?
Protons + Neutrons
51
What do the electrons in the outermost orbitals determine?
Atom's chemical and electrical properties.
52
What is the ability of an atom of one element to combine with other atoms controlled by?
The number of electrons which an atom will give, take or share to form a chemical compound.
53
What does combining power / valency relate to?
Number of electrons and spaces in the atom's electron shells.
54
Define Relative Atomic Mass.
The mass of one atom of an element divided by the mass of 1/12 of an atom of carbon-12.
55
Molecules contain atoms in _______ ___________.
Defined proportions
56
What does molecular formulae show?
The number of atoms found in one molecule of a substance.
57
Define Relative Molecular Mass.
The mass of a molecule relative to that of the carbon-12 atom, which is taken to have a mass of 12.
58
How is the relative molecular mass calculated?
It is the sum of the atomic masses.
59
Describe the phases of homogenous and heterogenous mixtures.
```
Homogenous = single phase
Heterogenous = multiple phase
```
60
What is a homogenous mixture?
A mixture with same properties throughout, and a uniform appearance.
61
What is a heterogenous mixture?
A mixture with variable properties, and a non-uniform appearance.
62
Describe colloids.
Colloids are visually homogenous but microscopically heterogenous mixtures.
63
Define solution.
A type of homogenous mixture formed when one substance dissolves in another. (Always has a substance that is dissolved and a substance that does the dissolving).
64
Define solute.
A substance that dissolves.
65
Define solvent.
A substance that does the dissolving.
66
How are mixtures separated?
Using differences in physical properties.
67
State and describe the techniques used to separate mixtures.
- Filtration: Select components by particle size (solid/liquid)
- Crystallisation: Select components by solubility (solid from solution)
- Extraction: Select components by solubility (solid/liquid from solution)
- Distillation: Select components by boiling point (liquid-liquid)
- Magnetisation: Magnetic metal from other components
68
What is chromatography used for?
Analysis of samples in the laboratory and in forensics.
69
Describe the process of Thin Layer Chromatography (TLC).
1) Spot of ink on filter paper
2) Dip in beaker of water / solvent
3) Solvent runs up paper by capillary action
4) Separates out different coloured components of ink
70
What does separation during Thin Layer Chromatography (TLC) depend on?
How strongly components of the mixture interact with the stationary phase (paper / chromatography plate) compared to how strongly they can interact with the solvent.
71
How is separation during Thin Layer Chromatography (TLC) explained?
By the different functional groups between molecules, different bonds that they can make to each other and the plate, and different forces that they can use to make intermolecular bonds to the solvent.
72
Describe bonding, interaction and movement of compounds during TLC.
- Weak bonds to plate = interact strongly wth solvent, so run further up the plate
- Strong bonds to plate = interact weakly with solvent, so do not shift very far
73
What is the height of plate reached by the sample characteristic of?
The sample's identity
74
Describe the process of High Performance Liquid Chromatography (HPLC).
1) Stationary phase tightly packed in long column
2) Solvent is pumped through column
3) Components of the mixture separate out depending on strength of interaction with column
4) Eventually, samples / mixtures run off the end and can be detected by UV-Visible Spectrophotometry
5) Signals are given off as the compound travels through the column which allows further analysis based on their mass, through Mass Spectrophotometry
6) Time taken for compound to run off column with specific solvent system can also be used for identification
75
Describe the application of HPLC in drug testing.
- Blood sample run through HPLC
- Machine is calibrated to pick up peaks (HPLC Spectrum)
- Peaks identify particular drugs in their system, based on retention time
- Can also be used to look at how drugs metabolise, are transformed, and excreted in the body
- Urine sample can also be used to see how steroids transform after excretion
