C1 Flashcards
Why did it take more than 50 years for Wegener’s ideas to be accepted?
it was difficult to work out how whole continents could move: it was not until the 1960s that enough evidence was discovered to support the theory fully.
What are the errors that occur with this experiment?
Note that there is some air in the tube with the copper turnings. The oxygen in this air will also react with the hot copper, causing a small error in the final volume recorded. It is also important to let the apparatus cool down at the end of the experiment, otherwise the final reading will be too high.
How is nitrogen and oxygen separated?
by fractional distillation of liquid air
What was the aim of the Miller-Urey experiment?
Stanley Miller and Harold Urey carried out some experiments in 1952 and published their results in 1953. The aim was to see if substances now made by living things could be formed in the conditions thought to have existed on the early Earth.
How do volcanoes form?
Magma (molten rock) is less dense than the crust. It can rise to the surface through weaknesses in the crust, forming a volcano.
What happened during the Miller-Urey experiment?
The two scientists sealed a mixture of water, ammonia, methane and hydrogen in a sterile flask. The mixture was heated to evaporate water to produce water vapour. Electric sparks were passed through the mixture of water vapour and gases, simulating lightning. After a week, contents were analysed. Amino acids, the building blocks for proteins, were found.
How would you perform the experiment to measure the percentage of oxygen in the air?
Gas syringes are used to measure the volume of gas in the experiment. The starting volume of air is often 100 cm3 to make the analysis of the results easy, but it could be any convenient volume. You take away the volume at the end from the volume at the start to get the volume of oxygen and then work out the percentage.
What is a continental drift?
The Earth’s crust and upper part of the mantle are broken into large pieces called tectonic plates. These are constantly moving at a few centimetres each year. Over millions of years the movement allows whole continents to shift thousands of kilometres apart.
Why did the level of carbon dioxide go down?
Photosynthesis by plants and algae used carbon dioxide from the atmosphere.
dissolving in the oceans
the production of sedimentary rocks such as limestone
the production of fossil fuels from the remains of dead plants and animals
Why do people choose to live near volcanoes?
The land there is very fertile.
How do you liquify the air?
Air is filtered to remove dust, and then cooled in stages until it reaches –200°C. At this temperature it is a liquid. We say that the air has been liquefied.
Here’s what happens as the air liquefies
water vapour condenses, and is removed using absorbent filters
carbon dioxide freezes at –79ºC, and is removed
oxygen liquefies at –183ºC
nitrogen liquefies at –196ºC.
The liquid nitrogen and oxygen are then separated by fractional distillation.
What are the uses of nitrogen and oxygen?
liquid nitrogen is used to freeze food
food is packaged in gaseous nitrogen to increase its shelf life
oil tankers are flushed with gaseous nitrogen to reduce the chance of explosion
oxygen is used in the manufacture of steel and in medicine.
What theory did the Miller-Urey experiment support?
The Miller-Urey experiment supported the theory of a ‘primordial soup’, the idea that complex chemicals needed for living things to develop could be produced naturally on the early Earth.
Before Wegener, what was the theory as to why the Earth had mountains?
it was thought that mountains formed because the Earth was cooling down, and in doing so contracted. This was believed to form wrinkles, or mountains, in the Earth’s crust.
How does fractional distillation separate the liquid air?
The liquefied air is passed into the bottom of a fractionating column. Just as in the columns used to separate oil fractions, the column is warmer at the bottom than it is at the top.The liquid nitrogen boils at the bottom of the column. Gaseous nitrogen rises to the top, where it is piped off and stored. Liquid oxygen collects at the bottom of the column. The boiling point of argon - the noble gas that forms 0.9 percent of the air - is close to the boiling point of oxygen, so a second fractionating column is often used to separate the argon from the oxygen.
How can you measure the percentage of oxygen in the air?
by passing a known volume of air over hot copper and measuring the decrease in volume as the oxygen reacts with it. Here are the equations for this reaction:
copper + oxygen → copper oxide
What happens when tectonic plates meet?
Where tectonic plates meet, the Earth’s crust becomes unstable as the plates push against each other, or ride under or over each other. Earthquakes and volcanic eruptions happen at the boundaries between plates, and the crust may ‘crumple’ to form mountain ranges.
Why did the level of oxygen in the atmosphere increase?
The appearance of plants and algae caused the production of oxygen, which is why the proportion of oxygen went up due to photosynthesis.
What are the three main layers of the earth (starting from the outermost) and what are their properties?
crust (relatively thin and rocky)
mantle (has the properties of a solid, but can flow very slowly)
core (made from liquid nickel and iron, consists of a solid inner core and a liquid outer core)
What are the two main gases in the atmosphere?
The two main gases are both elements and account for about 99 percent of the gases in the atmosphere. They are:
78 percent nitrogen (a relatively unreactive gas)
21 percent oxygen (the gas that allows animals and plants to respire and for fuels to burn)
The remaining gases, such as carbon dioxide, water vapour and noble gases such as argon, are found in much smaller proportions.
What are the differences between oceanic and continental plates?
Oceanic plates are denser than continental plates. They are pushed down underneath continental plates if they meet.
What was the earlier atmosphere like on earth?
Its early atmosphere was probably formed from the gases given out by volcanoes. It is believed that there was intense volcanic activity for the first billion years of the Earth’s existence. The early atmosphere was probably mostly carbon dioxide with little or no oxygen. There were smaller proportions of water vapour, ammonia and methane. As the Earth cooled down, most of the water vapour condensed and formed the oceans.
Venus and Mars today and similarities to earth?
It is thought that the atmospheres of Mars and Venus today, which contain mostly carbon dioxide, are similar to the early atmosphere of the Earth.
What did Wegener theorise?
Wegener suggested that mountains were formed when the edge of a drifting continent collided with another, causing it to crumple and fold.
Why do tectonic plates move?
The plates move because of convection currents in the Earth’s mantle. These are driven by the heat produced by the natural decay of radioactive elements in the Earth.
What are the two main types of tectonic plates?
Oceanic plates occur under the oceans.
Continental plates form the land.
Why do we know the theory before Wegener is false?
If the idea was correct, however, mountains would be spread evenly over the Earth’s surface. We know this is not the case.
Who proposed the theory of plate tectonics and continental drift
a German scientist, Alfred Wegener
How are unsaturated vegetable fats hardened?
reacting them with hydrogen, a reaction called hydrogenation.
During hydrogenation, vegetable oils are reacted with hydrogen gas at about 60ºC. A nickel catalyst is used to speed up the reaction. The double bonds are converted to single bonds in the reaction. In this way unsaturated fats can be made into saturated fats – they are hardened.
How are vegetable oils extracted?
The plant material is crushed and pressed to squeeze the oil out. Olive oil is obtained this way. Sometimes the oil is more difficult to extract and has to be dissolved in a solvent. Once the oil is dissolved, the solvent is removed by distillation, and impurities such as water are also removed, to leave pure vegetable oil. Sunflower oil is obtained in this way.
What are the properties of saturated vegetable oils?
The fatty acids in some vegetable oils are saturated: they only have single bonds between their carbon atoms. Saturated oils tend to be solid at room temperature, and are sometimes called vegetable fats instead of vegetable oils.
How do emulsifiers work?
Emulsifier molecules have two different ends:
a hydrophilic end - ‘water-loving’ - that forms chemical bonds with water but not with oils
a hydrophobic end - ‘water-hating’ - that forms chemical bonds with oils but not with water.The hydrophilic ‘head’ dissolves in the water and the hydrophobic ‘tail’ dissolves in the oil. In this way, the water and oil droplets become unable to separate out.
What are vegetable oils?
Vegetable oils are natural oils found in seeds, nuts and some fruit. These oils can be extracted.
Why are emulsions useful?
Emulsions are thicker (more viscous) than the oil or water they contain. This makes them useful in foods such as salad dressings and ice cream. Emulsions are also used in cosmetics and paints.
Which is healthier, unsaturated fats or saturated fats?
Unsaturated fats are thought to be a healthier option in the diet than saturated fats.
What do emulsifiers do?
Emulsifiers are substances that stabilise emulsions, stopping them separating out.
What are the advantages of vegetable oils in cooking?
Vegetable oils have higher boiling points than water. This means that foods can be cooked or fried at higher temperatures than they can be cooked or boiled in water. Food cooked in vegetable oils:
cook faster than if they were boiled have different flavours than if they were boiled.
What happens if you mix oil and water together?
If oil and water are shaken together, tiny droplets of one liquid spread through the other liquid, forming a mixture called an emulsion. However, if an emulsion is left to stand eventually the oil and water will separate.
What are the two categories of unsaturated oils?
monounsaturated fats have one double bond in each fatty acid
polyunsaturated fats have many double bonds.
What are the disadvantages of vegetable oils in cooking?
However, vegetable oils are a source of energy in the diet. Food cooked in vegetable oils releases more energy when it is eaten than food cooked in water. This can have an impact on our health. For example, people who eat a lot of fried food may become overweight.
What are the properties of unsaturated vegetable oils?
The fatty acids in some vegetable oils are unsaturated: they have double bonds between some of their carbon atoms. Unsaturated oils tend to be liquid at room temperature, and are useful for frying food.
How can you test for unsaturated vegetable oils?
Using the bromine water test. Bromine water can also be used to determine the amount of unsaturation of a vegetable oil. The more unsaturated a vegetable oil is, the more bromine water it can decolourise.
What are the two main types of emulsions?
oil droplets in water (milk, ice cream, salad cream, mayonnaise)
water droplets in oil (margarine, butter, skin cream, moisturising lotion).
Alkenes are unsaturated hyrdocarbons. What does this mean?
They contain a double covalent bond, which is shown as two lines between two of the carbon atoms. The presence of this double bond allows alkenes to react in ways that alkanes cannot. They can react with oxygen in the air, so they could be used as fuels. But they are more useful than that: they can be used to make ethanol and polymers (plastics) - two crucial products in today’s world.
Why can alkenes act as monomers?
Alkenes can act as monomers because they are unsaturated (they have a double bond):
ethene can polymerise to form poly(ethene), also called polythene propene can polymerise to form poly(propene), also called polypropylene.
What is polypropene used for?
crates and ropes
How does cracking work?
Fractions containing large hydrocarbon molecules are heated to vaporise them. They are then either:
passed over a hot catalyst, or
mixed with steam and heated to a very high temperature.
These processes break chemical bonds in the molecules, causing thermal decomposition reactions. Cracking produces smaller alkanes and alkenes (another type of hydrocarbon).
What is polythene used for?
plastic bags and bottles
What is polychloroethene used for?
water pipes and insulation on electricity cables
Why are fuels from oil mixtures containing large hydrocarbon molecules inefficient?
they do not flow easily and are difficult to ignite. Crude oil often contains too many large hydrocarbon molecules and not enough small hydrocarbon molecules to meet demand.
What are the advantages and disadvantages of recycling polymers?
Many polymers can be recycled. This reduces the disposal problems and the amount of crude oil used. But the different polymers must be separated from each other first, and this can be difficult and expensive to do.
What is the advantage and disadvantage of fermentation?
Produces carbon dioxide, but Unlike ethene, sugar from plant material is a renewable resource.
How is ethanol produced from fermentation?
Sugar from plant material is converted into ethanol and carbon dioxide by fermentation. The enzymes found in single-celled fungi (yeast) are the natural catalysts that can make this process happen.
C66H12O6 → 2C2H5OH + 2CO2
What do the properties of polymers depend on?
the chemicals they are made from, and the conditions in which they are made.
What is the disadvantage and advantage of using steam and ethene to make ethanol?
he process is continuous – as long as ethene and steam are fed into one end of the reaction vessel, ethanol will be produced. These features make it an efficient process, but there is a problem. Ethene is made from crude oil, which is a non-renewable resource.
How do you test for unsaturation?
Bromine water is a dilute solution of bromine, normally orange-brown in colour. It becomes colourless when shaken with an alkene (unsaturated), but its colour remains the same when it is shaken with alkanes (saturated).
What does cracking do?
Cracking allows large hydrocarbon molecules to be broken down into smaller, more useful hydrocarbon molecules.
What is the chemical formula of glucose?
C6H12O6 (little numbers)
How can we produce biodegradable plastics?
it’s possible to include substances such as cornstarch that cause the polymer to break down more quickly. Carrier bags and refuse bags made from such degradable polymers are available now.
What is the difference between high density poly(ethene) and low density poly(ethene)
: LDPE, low-density poly(ethene), is weaker than HDPE, high-density poly(ethene), and becomes softer at lower temperatures.
Drawing displayed formulas of polymers (keep revising this)?
Polymer molecules are very large compared with most other molecules, so the idea of a repeating unit is used when drawing a displayed formula. When drawing one, starting with the monomer:
change the double bond in the monomer to a single bond in the repeating unit add a bond to each end of the repeating unit.
What are the advantages and disadvantages of polymers being unreactive?
they are suitable for storing food and chemicals safely. Unfortunately, this property makes it difficult to dispose of polymers. They can cause litter and are usually sent to landfill sites.
What are alkenes?
The alkenes are a family of hydrocarbons that share the same general formula:
CnH2n
The general formula means that the number of hydrogen atoms in an alkene is double the number of carbon atoms.
what are polymers?
Polymers are very large molecules made when many smaller molecules join together, end-to-end. The smaller molecules are called monomers.
What are some of the uses of modern polymers?
new packaging materials
waterproof coatings for fabrics (such as for outdoor clothing)
fillings for teeth
dressings for cuts
hydrogels (for example for soft contact lenses and disposable nappy liners)
smart materials (for example shape memory polymers for shrink-wrap packaging).
How can you make ethanol from steam and ethene?
Ethanol can be made by reacting ethene (from cracking crude oil fractions) with steam. A catalyst of phosphoric acid is used to ensure a fast reaction.
ethene + steam → ethanol
What are the ethical issues of biofuels?
Food that could be used to feed people is being used on fuel
could lead to food shortages
more land is taken up
increase the price of food
Why does complete combustion happen?
Fuels burn when they react with oxygen in the air. If there is plenty of air, complete combustion happens.
What happens as you go up the fractionating column?
Hydrocarbon with smaller molecules condense at the top, which have the properties of:
lower boiling points
lower viscosity (they flow more easily)
higher flammability (they ignite more easily).
Which makes them better fuels.
How is bioethanol made and how can it be used?
Bioethanol is made by fermenting sugars from sugar cane, wheat and other plants. It cannot be used on its own unless the engine is modified. However, modern petrol engines can use petrol containing up to 10 percent ethanol without needing any modifications, and most petrol sold in the UK contains ethanol.
Name the first four alkanes and their molecular formula:
methane CH4 (small 4) ethane C2H6 (small numbers) propane C3H8 (small numbers) butane C4H10 (small numbers)
What are the environmental issues of biofuels?
Biodiesel naturally contains little sulfur. For example, it may be said that they are carbon neutral – the amount of carbon dioxide released when they are used is the same as the amount absorbed by the plants as they grew. If so, this would reduce the production of this greenhouse gas. However, while biofuels produce less carbon dioxide overall, they are not carbon neutral. This is because fossil fuels are used in their production, for example in making fertilisers for the growing plants.
