Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Science 2 > Chemistry 5 > Flashcards

Chemistry 5 Flashcards

0
Q

How are compounds formed ?

A

When two or more elements are chemically combined. It is difficult to separate this into the original elements

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
1
Q

How do you work out the amount of neutrons an element has ?

A

Mass number - atomic number

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is an isotope ?

A

Different atomic forms of the same element, which have the SAME number of PROTONS but a DIFFERENT number of NEUTRONS

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Why do isotopes have to have the same number of protons ?

A

Because otherwise they are different elements altogether

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Name 2 examples of popular isotopes

A

Carbon-12 and Carbon-14

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the difference between carbon-12 and Carbon-14 ?

A

Carbon-14 has two more neutrons

a mass number of 14

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Describe ionic bonding

A

When atoms lose or gain electrons to form charged particles called ions. They are strongly attracted to each other because opposite charges attract

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

When elements lose their electrons they become ions, which means …

A

They react easily and quickly with an ion that has an opposite charge

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What structure do ionic compounds have ?

A

Regular lattice structures

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Describe an ionic compounds structure

A

It is a closely packed regular lattice arrangement. There are very strong forces of electrostatic attraction caused by the opposite charges attracting

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Why do ionic compounds have high melting and boiling points ?

A

A large amount of energy is needed to overcome the high attraction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

When ionic compounds melt, what can they do ?

A

Carry electric current

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What happens when ions are added to water ?

A

They dissolve and the ions separate leaving them free to move

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What groups of the periodic table are most likely to form ions ?

A

1&2 and 6&7

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What do ionic compounds contain ?

A

A positively charged part and a negatively charged point

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the overall charge of every compound ?

A

Zero

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How can you work out the formula of an ionic compound ?

A

Look at the charges of each components and remember that when added together they must equal 0

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is covalent bonding ? Why is it done ?

A

When atoms share electrons in their outer shells. It means both atoms have full outer shells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Substances with covalent bonds can either be …..

A

Simple molecules or giant covalent structures

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Describe simple molecules

A
  • form very strong covalent bonds

* the forces of attraction between molecules are weak (intermolecular)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Why are simple molecular substances easy to break down ?

A

Their weak intermolecular forces can be broken down easily

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Give three examples of simple molecular substances

A
  • Chlorine
  • Oxygen
  • Water
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Give three examples of giant covalent structures

A
  • Diamond
  • silicon dioxide (silica)
  • Graphite
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Are giant covalent structures similar to giant ionic structures ?

A

Yes, except there are no charge ions. The atoms are bonded by very strong covalent bonds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Do giant covalent structures conduct electricity ?

A

No, not even when molten. However graphite is an exception to the rule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Describe a diamonds formation and features

A

Each carbon atom has four covalent bonds forming a very rigid structure. It makes it the hardest natural substance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What is silica comprised of ?

A

Silicon and oxygen, this is what sand is made of

27
Q

How does a pencil work ?

A

Each carbon atom in graphite only forms three covalent bonds. The layers of graphite can slide over each other and therefore rubbed onto paper

28
Q

Why is graphite the only non-metal to conduct heat and electricity ?

A

Each carbon atom has a delocalised free electron which carries the heat or electricity through the material

29
Q

What are free electrons ?

A

They come from the outer shell of every metal atom. They are free o move throughout the structure.

30
Q

Why are metals relatively strong ?

A

They have strong electrostatic attraction between the positive metal ions and the negative free electrons

31
Q

Why can metals be bent and shaped ?

A

Their regular structure means layers can slide over each other

32
Q

What is an alloy ?

A

A mixture of two or more metals

33
Q

Why are alloys harder ?

A

Different elements have different sized atoms, so when mixed the levels are distorted and they cannot be slid over each other

34
Q

What is an example of a good new material ?

A

Nitinol - A shape memory alloy

35
Q

What is nitinol ?

A

It is an alloy of nickel and titanium that can be bent like rubber when cool. When twisted too much it stays bent, however when heated it returns to a remembered shape

36
Q

Give 2 uses for shape memory alloys an explain them

A
  • Glasses Frames - if accidentally bent thy can be popped back into shape with hot water
  • Dental Braces - when the mouth warms it tries to return to a remembered shape, pulling the teeth in
37
Q

1nm = how many m

A

1nm = 0.000,000,001m

38
Q

How small is a nanoparticle ?

A

1-100 nanometers across

39
Q

How many atoms does a nano particle contain ?

A

Roughly a few hundred

40
Q

What is a fullerene ?

A

Molecules of carbon shaped like hollow balls or closed tubes. The carbon atoms are arrange in hexagonal rings

41
Q

Fullerenes form nanotubes which are tiny hollow carbon tubes. Give an example how this can be used

A

They can be used to reinforce tennis racket strings as their covalent bonds are very strong

42
Q

What determines the properties of plastics ?

A

Forces between molecules

43
Q

Describe weak forces between molecules

A

Individual tangled chains of polymers held together by weak intermolecular forces, free to slide over each other

44
Q

Describe strong forces between molecules

A

They have strong intermolecular forces, with cross links that hold the chains firmly together

45
Q

What are termosoftening plastics ?

A

Polymers that don’t have cross links which can easily be overcome and therefore melted. They can be melted and reshaped as many times as you want

46
Q

What are thermosetting plastics ?

A

They have cross links which form a solid structure that won’t soften when heated

47
Q

What plastic is used for bags and bottles ?

A

Low density polymers

48
Q

What plastic is used for drainpipes and water tanks ?

A

High density polymers

49
Q

What does Ar stand for ?

A

Relative atomic mass

50
Q

What is relative atomic mass ?

A

A way of saying how heavy different atoms are

51
Q

Where do you find an elements relative atomic mass ?

A

The top number for each element on the periodic table

52
Q

What does Mr stand for ?

A

Relative formula mass

53
Q

What does relative formula mass tell you ?

A

The mass of the whole compound

54
Q

How do you calculate Mr ?

A

Add up all of the atomic masses in the formula

55
Q

One mole of a substance =

A

It’s Mr in grams

56
Q

What is the formula for number of moles ?

A

No. of moles =

Mass in grams divided by Mr

57
Q

What does the empirical formula do ?

A

To find the formula of a compound in its simplest form

58
Q

There are three important steps to calculating masses in reactions, what are they ?

A
  1. Write out the balanced equation
  2. Work out Mr for the bits you need
  3. Divide by the two you know and then multiply by the other
59
Q

What does percentage yield compare ?

A

Actual yield and predicted yield

60
Q

What does percentage yield tell us ?

A

How successful the experiment was by comparing how much you actually made compared to what you predicted

61
Q

What is the formula for percentage yield ?

A

Percentage yield =

Actual yield divided by predicted yield multiplied by 100

62
Q

True or False - yields are always less than 100%

A

True

63
Q

Why do we find percentage yield ?

A

It is done to find the most sustainable ways to get as much yield as possible

64
Q

What is paper chromatography ?

A

A way of separating artificial colours using paper

65
Q

Why are machines better than chromatography ?

A

Very sensitive, very fast, very accurate

66
Q

How can gas chromatography identify substances ?

A

The gas is sent through a column at different speeds which separates them, a detector measures their ‘retention time’ (time to exit column) and measures it on a graph

Science 2 (7 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions