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Y9 FLASHCARDS > 9F Chemistry > Flashcards

9F Chemistry Flashcards

1
Q

At what temperaure does liquid nitrogen boil?

A

-196ºC

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2
Q

How is a ‘trashcano’ formed?

A

A plastic bottle of liquid nitrogen is put at the bottom of a dustbin filled with water. Due to its very low boiling point (-196ºC) the nitrogen quickly turns into a gas. As a result, the pressure in the bottle increases until it gives away, forming an explosion

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3
Q

What was the ‘trashcano’ explosion caused by? What can this change also cause

A
  • This explosion is caused by a physical change
  • This is because no new subtances are made
  • Physical changes can also cause natural explosions, such as in volcanoes and geysers
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4
Q

By what type of reaction was the Buncefield fuel depot explosion in 2005 caused by?

A

This explosion was caused by a chemical reaction.
- New substances were formed as the petrol vapour suddenly ignited and produced large amounts of hot carbon dioxide gas and water vapour

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5
Q

What happens in a chemical reaction?

Give an example? And the word equation?

A
  • Atoms in the reactants are rearranged to form new products with different properties
  • Eg: hydrogen reacts with oxygen to form water. Hydrogen and oxygen are gases but water is a liquid at room temperature
  • WORD EQUATION: hydrogen + oxygen -> water
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6
Q

What does the particle theory explain?

A

The particle theory explains how the forces of particles hitting the walls of a container cause pressure in gases

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7
Q

How is gas pressure increased?

A
  • increasing the number of gas particles (so more particles hit a surface)
  • decreasing the size of the container (so particles hit a surface more often)
  • increasing the temperature (so the particles move faster and hit more often, with more force)
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8
Q

Name one of the most reactive metals, what does it do?

A

Caesium is one of he most reactive metals, and will react violently with water (explosion)

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9
Q

What is the reactivity series?

A

The reacticity series is a list of metals in order of reactivity, the one at the top being the most reactive

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10
Q

Name the reacticity list in order starting from the most reactive?

A
  1. potassium. 9. Tin
  2. Sodium. 10. Lead
  3. Lithium. 11. Copper
  4. Calcium. 12. Mercury
  5. Magnesium. 13. Silver
  6. Aluminium. 14. Gold
  7. Zinc. 15. Platinum
  8. iron
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11
Q

What do you do in order to know where to place a meral in the reactivity series?

A

We look at how vigorously it reacts with water, acids and oxygen

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12
Q

How do you know how reactive a metal is when it reacts with acids and water?

A

The reactions can produce bubbles of hydrogen gas, and the more bubbles formed it is more reactive

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13
Q

What happens with metals that react with water?

Write the equation?

A

The metals that react with water form a metal hydroxide and hydrogen
- metal + water -> metal hydroxide + hydrogen

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14
Q

What happens with metals that react with dilute acids?

Write the equation

A

They form a slat and hydrogen

- metal + acid -> salt + hydrogen

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15
Q

What do the salts formed depend on?

A

They depend on which acid is used.

  • Chlorides are formed from hydrochloric acid.
  • Sulfates are formed from sulfuric acid
  • Nitrates are formed from nitric acid
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16
Q

What do metals that react with oxygen form?

Name the reaction

A

They form metal oxides

  • metal + oxygen -> metal oxide
  • This is an oxidation reaction as the metal has gaied oxygen
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17
Q

What happens to iron and steel when they are in contact of….?

A

Iron and steel slowly react when they are in contact with air and water. They form brown flakes that gradually crumble and break away. Eventualy all the metal corrodes away.

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18
Q

How can rusting be prevented?

A
  • Rusting can be prevented by using a physical barrier on the metal, such as paint or oil, to keep out the air and water. This is relatively cheap but is not suitable in all situations
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19
Q

Name another way to prevent rusting, that is more expensive and is normally used in the sea?

A

Sacrificial protection is the key name for this, and it consists of attaching blocks of a more reactive metal, such as zinc or magnesium, to the iron or steel. Because of this, the more reactive metal reacts with the water and oxygen instead of the iron. This is normally used for items in contact with the sea because salt speeds up rusting

20
Q

What do most chemical reacctions that cause explosions need?

A

They need oxygen, which can come from the air but explosives usually have an oxidiser or oxidising agent mixed with them

21
Q

What does the oxidising agent do during the reaction?

A

During the reaction, this substance releases oxygen, because the more oxygen there is, the quicker the reaction is

  • Diferent oxidisers relase different amounts of oxygen
22
Q

What is potassium nitrate?

A

KNO3, is the oxidisind agent that is mixed with powdered charcoal to make gunpower.
Then the potassium nitrate releases oxygen, which reacts with the carbon in the charcoal to form carbon dioxide.
The carbon is therefore oxidised by the potassium nitrate

23
Q

Name another way in which exlxplosives react more quickly?Why?

A

They also react more quickly if the solid fuel is broken down into tiny pieces. Chemical reactions take place on the surface of a solid.
Small pieces of a solid have a larger surfac area than one large piece therefore there will be more particles exposed at the surface and more reactions can take place

24
Q

What is the law of conservation of energy?

A

Energy cannot be created or destroyed, only transferred

25
Q

What is an exothermic reaction? Give examples were this happens?

A

An exothermic reaction is a reaction in which energy stored in the reactants is transfered to the surroundings.
The addition of energy causes the temperature to increase in the sorroundings.
Examples of exothermic reactions are combustion and neutralisation

26
Q

What is an endothermic reaction? Give an example?

A

An endothermic reaction is a reaction that transfers energy from the sorroundings to the reactants.
Thermal decomposition is an example of an endothermic reaction

27
Q

What do many exothermic reactions need to start them off?

A

MAny endothermic reactions need energy to start them off

28
Q

Why do people use methane as a fuel for exothermic reactions?

A

As methane is a hydrocarbon, during its process of burning the hydrogen and carbon atoms are both oxidised. A lot of energy is transferred to the surroundings during the reaction.

29
Q

What does a mixture of methane and oxygen need to start the reaction, give and example, and why does it need it

A

A mixture of methane and oxygen doesn’t burn without some energy to start the reaction
Eg: from a flame or a spark
This input of energy is needed to break some bonds in the reactants to separate some atoms.
After this the reaction can then start: atoms are rearranged, new bonds are formed and energy is transfered

30
Q

What do some reactions, such as thermal decomposition need.

A

They are endothermic and need a continuous input of energy to keep them going

31
Q

What can we predict with the reactivity series? Give an example?

A

We can use the reacticity series to predict wether a chemical reaction will take place. Each metal will react with compounds of the metals below it in the series.
Eg: aluminium is more reactive than iron. It reacts with iron oxide and takes the place of the iron:
aluminium + iron oxide -> aluminium oxide + water

32
Q

Aluminium + iron oxide -> aluminium oxide + iron, what is th name for this type of reaction?

A

This is a displacement reaction as the aluminium has displaced the iron.

33
Q

What does a displacement reaction need in order to start?

A

This reaction needs an initial input of energy by lighting a fuse. During the reaction, aluminium forms strong bonds with oxygen and a large amount of energy is transferred to the surroundings. The temperature increases so much that the iron is formed as a molten liquid.

34
Q

What does the thermite reaction consist off?

A

The same reaction, known as thermite reaction, is used on a larger scale to join two sections of railway track. The molten iron runs onto the gap in the rail. As it cools it solidifies and welds the sections of the rail together

35
Q

Where do displacement reactions also take place?

A

They aso take place in solutions. Eg: when a piece of zinc is dipped into copper sulfate solution, a coating of copper forms on the surface of the zinc. Some of the zinc takes the place of the copper and forms zinc sulfate solution. If the reaction is left for long enough, the solution will turn colourless as only zinc sulfate solution will be left

36
Q

What way do displacement reactions work?

A

Displacement reactions only work one way. Copeer cannot displace zinc from zinc sulfate solution because copper is less reactive than zinc

37
Q

What happens with platinum?

A

It is so unreactive that it doesn’t cause problems if put into the body.

38
Q

How is gold found?

A

Platinum, like gold it occurs uncombined in its native state in the Earth’s crust

39
Q

What happens to other metals that are more reactive than gold an platinum?

A

Other metals are more reactive and occur as compounds, including oxides, carbonates and chlorides.

40
Q

What is an ore? What happens with reactive metals?

A

An ore is a rock that contains enough of a metal or metal compound to be worth mining. Reactive metals need to be chemically extracted from their ores

41
Q

How does iron occur? How is the oxygen removed? What is the word equation?

A

Iron occurs as iron oxide in the ore haematite.
The oxygen is removed by heating the iron oxide with carbon. Carbon is more reactive than iron so it displaces iron from iron oxide

Iron oxide + carbon -> iron + carbon dioxide

42
Q

What happens to the carbon during this reaction (with iron oxide)?
Where does this reaction take place?
Why is limestone added?

A

The carbon is oxidised by the iron oxide. At the same time, the iron oxide is reduced to iron as it has lost oxygen.

  • Carbon is a reducing agent because it has removed the oxygen from the iron oxide.
  • This reation takes place in a blast furnace.
  • Limestone is added to remove the impurities, which are extracted as ‘slag’
43
Q

How does aluminium occur as?

What happens to carbon?

A

Aluminium occurs as aluminium oxide in an ore called bauxite. As carbon is not reactive enough to displace aluminium from aluminium oxide, therefore a more powerful method is needed

44
Q

What is the name for the method for extracting metals that have a greater reactivity than carbon?
How does it work?

A

Electrolysis is used to extract the reactive metals from their ores. This involves passing electricity through a molten metal compound.
- the electricity transfers energy to the compound and splits it up to obtain the metal
Eg: (for aluminium, word equation for electrolysis)
- aluminium oxide -> aluminium + oxygen

45
Q

Why can’t iron be extracted using electrolysis?

What is electrolysis only used for?

A

Actually, iron could also be extracted by using electrolysis but it is too expensive.
A lot of electricity would be needed to heat the iron oxide to keep it molten, and the process of electrolysis also requires vas amounts of electricity.
Electrolysis is only used to extract the very reactive metals that cannot be obtained by heating their oxides with carbon.

46
Q

For how much time have different types of metals been known?

A

Metals that occur in the native state and those that can be extracted by heating their oxides with carbon have been known for a long time (3000 BCE)

On the other hand, metals that can only be extracted from their ores by electrolysis have been obtained much recently

47
Q

Name the first 20 elements of the periodic table?

A

1) H = Hydrogen 11) Na = Sodium
2) He = Helium 12) Mg = Magnesium
3) Li = Lithium 13) Al = Aluminium
4) Be = Beryllium 14) Si = Silicon
5) B = Boron 15) P = Phosphorus
6) C = Carbon 16) S = Sulfur
7) N = Nitrogen 17) Cl = Chlorine
8) O = Oxygen 18) Ar = Argon
9) F = Fluorine 19) K = Potassium
10) Ne = Neon 20) Ca = Calcium

Y9 FLASHCARDS (10 decks)

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