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Chemistry > C2 > Flashcards

C2 Flashcards

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1
Q

What is a compound?

A

A compound is a substance made from two or more chemically joined elements.

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2
Q

What is the overall charge on an ionic compound?

A

The overall charge on an ionic compound is zero.

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3
Q

What is the bond when two atoms share a pair of electrons?

A

Covalent bonding.

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4
Q

Describe the structure in a diamond.

A

In a diamond, each carbon atom forms with four covalent bonds with its neighbours.

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5
Q

What do we call the structure of a substance held together by a network of covalent bonds?

A

Giant covalent structures

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6
Q

Why do metals form crystals?

A

Metals form crystals because the atoms in metals are built up later by layer in a regular pattern.

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7
Q

Which electrons do metal atoms use to form metallic bonds?

A

The sea of free delocalised electrons.

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8
Q

How are metals in metals arranged?

A

Atoms in metals are closely packed together in regular layers.

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9
Q

Why do ionic compounds have high melting and boiling points?

A

There are many strong electrostatic forces of attraction to break.

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10
Q

Why does making a substance molten or in solution make it easier to conduct electricity?

A

The ions are free to move and can carry electrical charge.

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11
Q

Why do covalent bonds have low melting points?

A

Covalent bonds have low melting points because although the covalent bonds are strong, the intermolecular forces are weak.

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12
Q

Why don’t simple molecular substances conduct electricity?

A

There is no overall charge on the simple molecules, so their molecules cannot carry electrical charge.

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13
Q

Name four properties of giant covalent bonds.

A

They are very hard, have high melting and boiling points and are insoluble in water.

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14
Q

Why is graphite soft?

A

Graphite is soft because the carbon atoms are only bonded to three other carbon atoms, and there are no covalent bonds between the layers, so they can slide past each other easily.

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15
Q

Why does graphite conduct electricity?

A

Graphite conducts electricity because instead of being bonded to four other atoms, the carbon atoms bond to three other carbon atoms, so there is one delocalised electron.

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16
Q

What are fullerenes?

A

Fullerenes are large, carbon molecules containing cage-like structures.

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17
Q

What are shape memory alloys?

A

Shape memory alloys are alloys that can be shaped and return to their original shape when heated.

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18
Q

How can we make polymers?

A

We can make polymers from chemicals made from crude oil.

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19
Q

What do the properties of a polymer depend on?

A

The monomers used to make it and the condition the reaction takes place in.

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20
Q

What is nanoscience?

A

Nanoscience is the science of very tiny things.

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21
Q

Give an example of a use of nanoscience.

A

Nanoparticles in face creams can be absorbed deeper into the skin.

22
Q

What is an element?

A

An element is a substance consisting of atoms with the same number of protons.

23
Q

What are isotopes?

A

Isotopes are atoms of the same element with different numbers of neutrons.

24
Q

What is a mole?

A

A mole is the amount of pure substance containing the same number of chemical units.

25
Q

Why are instrumental methods are good for detecting and identifying substances?

A

They are:
• Fast
• Accurate
• Sensitive

26
Q

Why will the yield of a product always be less than expected?

A
  • Some reactants remain unreacted
  • Product may be lost when transferred
  • Reactants may form other products
27
Q

What is the definition of activation energy?

A

The least amount of energy needed for a chemical reaction to occur.

28
Q

What is the definition of an endothermic reaction?

A

Reactions that transfer energy from the surroundings to the reacting chemicals.

29
Q

What is an exothermic reaction?

A

A reaction that transfers energy from the reacting chemicals to their surroundings.

30
Q

Why is the rate of reaction important in industry?

A

Rate are wanted to be carried out as safely, quickly and cheaply as possible.

31
Q

How do you measure the rate of a reaction?

A

Measure:
• The decreasing mass of mixture
• The increasing volume of gas given
• The decreasing light through a solution

32
Q

What things affect the rate of reactions?

A
  • Temperature
  • Pressure
  • Surface area
  • Catalysts
33
Q

What is the collision theory?

A

The theory in which one atom must collide with another with the correct activation energy in order to reach.

34
Q

What is the definition of an explosion?

A

A very fast reaction which releases a large volume of gaseous product

35
Q

Why does the temperature increase re rate of reaction?

A

• The particles collide more often
- There are more chances for them to react

• The particles have more energy when they collide
- A higher number of collisions take place with particles with the correct activation energy

36
Q

Why does increasing the pressure increase the rate of reaction?

A

• Increases the frequency of collisions

37
Q

Why does increasing the concentration of reactants increase the rate of reaction?

A
  • More particles of the reactant in the SAME SPACE
  • More crowded, more likely to collide
  • Frequent collisions = faster reaction
38
Q

How do catalysts speed up the rate of a reaction?

A

They lower the activation energy.

39
Q

Why does the industry use catalysts?

A
  • Cheaper to use a catalyst than to pay for extra energy

* Lower temperatures help to save non-renewable sources

40
Q

Give an example of an exothermic reaction.

A

When methane burns, it becomes oxidised and releases energy.

41
Q

Give and example of an endothermic reaction.

A

Thermal decomposition of calcium carbonate which forms calcium oxide and carbon dioxide.

42
Q

Give one use of an exothermic reaction in the industry.

A

Reusable hand warmers:
• Crystallisation of supersaturated solution is used

Disposable hand warmers:
• Oxidisation of iron to release energy

43
Q

Give a use of an endothermic reaction in industry.

A

Chemical cold packs:
• Contain ammonium nitrate and water
• Ammonium nitrate dissolves, takes away heat from surroundings
• Reduce pain and swelling

44
Q

What is the definition of gas pressure?

A

The force that the gas exerts on the walls of its container.

45
Q

What is the definition of concentration?

A

A measure of the number of particles of the solute in the solvent.

46
Q

What are the benefits of chemical energy?

A

Chemical energy is:
• Efficient
• The easiest to store and utilise
• Readily available and easy to find

47
Q

What are the disadvantages of chemical energy?

A

Chemical energy:
• Can destroy living cells
• Is bad for our health/environment

48
Q

Why is carbon dioxide always a gas?

A
  • It has simple, small molecules
  • Weak intermolecular forces
  • Small amount of energy needed to overcome
49
Q

Why are compounds like methane gas at room temperature?

A

They are made of small molecules or covalent bonds that act only between the atoms within a molecule.

50
Q

Describe the process of gas chromatography.

A
  • Sample vaporised and passed through a column.
  • The chemicals are carried through the column at different speeds.
  • A detector detects the different chemicals and shows them as a peak on a chart.

Chemistry (3 decks)

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