Biology Unit 10: Energy Flows in Ecosystems

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Unit 10 Energy Flows in Ecosystems

1. State that the Sun is the principal source of energy input to biological systems.

2. Define the terms: 

• food chain as a chart showing the flow of energy (food) from one organism to the next beginning with a producer (e.g. mahogany tree → caterpillar → song bird → hawk), 

• food web as a network of interconnected food chains showing the energy flow through part of an ecosystem, 

• producer as an organism that makes its own organic nutrients, usually using energy from sunlight, through photosynthesis, 

• consumer as an organism that gets its energy by feeding on other organisms, 

• herbivore as an animal that gets its energy by eating plants, 

• carnivore as an animal that gets its energy by eating other animals.

3. Describe energy losses between trophic levels.

As you go up a trophic level, energy is lost. For example, we have this chain:

mahogany tree → caterpillar → song bird → hawk

The mahogany tree gets the biggest amount of energy from the Sun. When the chain reaches the hawk, the hawk gets a very small amount of energy from the song bird. This is because energy is lost throughout the chain due to heat loss. Only about 10% of energy gets passed on to the next species in the chain. 

4. Define the terms: 

• decomposer as an organism that gets its energy from dead or waste organic matter, 

• ecosystem as a unit containing all of the organisms and their environment, interacting together, in a given area, e.g. decomposing log or a lake, 

• trophic level as the position of an organism in a food chain or food web.

5. Explain why food chains usually have fewer than five trophic levels.

As said above, only 10% of energy gets passed on from each species in the chain. If the chain were to continue, eventually there would be no energy to pass on. This is why food chains have a limit of around five trophic levels.

6. Describe the carbon cycle.

The carbon cycle is the cycle of which carbon travels around the Earth's atmosphere.

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7. Discuss the effects of the combustion of fossil fuels and the cutting down of forests on the oxygen and carbon dioxide concentrations in the atmosphere.

Combustion of fuels results in carbon dioxide and nitrous oxides being released into the atmosphere. These contribute to overall global warming. Deforestation increases the amount of carbon dioxide in the atmosphere; this is because there are no more trees to use carbon dioxide for photosynthesis. 

Biology Unit 11: Human Influences on the Ecosystem

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Unit 11 Human Influences on the Ecosystem

1. List the undesirable effects of deforestation (to include extinction, loss of soil, flooding, carbon dioxide build up).

• Trees serve has habitats for animals; if they are cut down animals lose their homes and become more vulnerable to predators. The species will die out because they don't have a place to live

• Without trees, land is vulnerable to weather conditions that cause erosion

• Flooding will become easier because the land has no barriers that stop the water

• Trees use carbon dioxide in photosynthesis, and without trees the carbon dioxide levels in the atmosphere will rise

2. Describe the undesirable effects of overuse of fertilisers (to include eutrophication of lakes and rivers).

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3. Describe the undesirable effects of pollution to include: 

• water pollution by sewage and chemical waste, 

• air pollution by greenhouse gases (carbon dioxide and methane) contributing to global warming.

If chemical waste and rubbish flow into our seas, this basically makes the water unclean and makes it difficult for aquatic life to survive.

Carbon dioxide and methane are both greenhouse gases; greenhouse gases are the gases that absorb heat and reflect it back into the atmosphere, causing the world temperature to increase. This is bad for the environment as heat will cause ice at the Poles to melt, raising average sea levels.

4. Discuss the causes and effects on the environment of acid rain, and the measures that might be taken to reduce its incidence.

When sulphur dioxide and nitrogen oxides are released into the atmosphere, they mix with oxygen, water, and other chemicals. This causes acid rain. 

To reduce buildup that leads to acid rain, the burning of fossil fuels should be reduced. This is because combusting fossil fuels release both sulphur dioxide and nitric oxides. 

5. Explain how increases in greenhouse gases (carbon dioxide and methane) are thought to cause global warming.

This is similar to second point of point 3.

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6. Describe the need for conservation of: 

• species and their habitats, 

• natural resources (limited to water and non-renewable materials including fossil fuels).

Species need to me conserved because all specie are part of the food chain. If the food chain is disrupted, all species of the food chain will be affected, including humans. Their habitats must also be conserved to ensure they are able to survive.

Natural resources must be conserved because the Earth has only a limited amount. If all resources were to be used up, there would be none left for future generations. While fossil fuels can be produced again, it would take millions of years, and humanity doesn't have that much time to wait!

Chemistry Unit 1: The Particle Nature of Matter

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Unit 1 The Particle Nature of Matter

1. Demonstrate understanding of the terms atom and molecule.

An atom is a particle that makes up an element. It consists of a nucleus - containing protons and neutrons - and electrons.

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A molecule is also a particle that makes up an element. Atoms make up molecules, so their definitions are similar. 

For example, this water molecule consists of two hydrogen atoms and one oxygen atoms. 

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Biology Unit 4.1: Nutrients

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Unit 4.1 Nutrients

1. List the chemical elements that make up:
• carbohydrates,
• fats,
• proteins.

Carbohydrates: starch, glucose
Fats: glycerol and fatty acids
Proteins: long chains of amino acids

2. Define nutrition as taking in of nutrients which are organic substances and mineral ions, containing raw materials or energy for growth and tissue repair, absorbing and assimilating them.

3. Describe the structure of large molecules made from smaller basic units, i.e.
• simple sugars to starch and glycogen,
• amino acids to proteins,
• fatty acids and glycerol to fats and oils.

This is basically point 1, but it goes into a bit more detail on structure.

4. Describe tests for:
• starch (iodine solution),
• reducing sugars (Benedict’s solution),
• protein (biuret test),
• fats (ethanol).

Iodine: tests for starch, blue-black if present, brown if not
Benedict's solution: tests for glucose, brick red if present, blue if not
Biuret test: tests for protein, purple if present, blue if not
Ethanol: tests for fats, will emulsify if present, won't if not

5. List the principal sources of, and describe the importance of:
• carbohydrates,
• fats,
• proteins,
• vitamins (C and D only),
• mineral salts (calcium and iron only),
• fibre (roughage),
• water.

Carbohydrates provide our bodies with energy. They can be found in food products such as rice, noodles, bread and potatoes. Fats also provide our bodies with energy, and they help our bodies absorb a multitude of vitamins. They can be found in plants and fish, such as lentil beans and salmon. Proteins come from meat, fish and eggs; they help our bodies with processes of growth and repair.

Vitamin C can be found in citrus fruits and is used for maintaining healthy skin and absorbing iron. A vitamin C deficiency is called scurvy. Vitamin D comes from oily fish, and it helps to absorb calcium and maintain strong bones. A deficiency in vitamin D is rickets.

Calcium comes from milk, and it helps maintain the strength and health of bones. A person would have weak bones without the intake of calcium. Iron can be found in red meats, and is used to produce haemoglobin. Anaemia is a vitamin D deficiency.

Fibre is used to prevent constipation, by adding bulk to faeces. It can be found in wholegrain foods, fruits and vegetables, and nuts.

Water makes up 70% of the human body. It has many important roles, such as transporting nutrients around the body and regulating body temperature. If a person doesn't intake enough water, they will become dehydrated.

6. Describe the use of microorganisms in the manufacture of yoghurt.

1. Milk is heated to be pasteurised
2. After the milk has cooled, bacteria called Lactobacillus bacteria is added. This breaks down lactose in milk to form lactic acid.
Lactic acid lowers the pH of the yoghurt so it doesn't go off, and denatures milk proteins, which gives yoghurt its sharp taste.

7. Describe the deficiency symptoms for:
• vitamins (C and D only),
• mineral salts (calcium and iron only).

Refer to point 5!

Chemistry Unit 11: Air and Water

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Unit 11 Air and Water

1. Describe a chemical test for water.

There are two ways in which you can go about. The first is using anhydrous copper sulphate; in the presence of water, the anhydrous copper sulphate turns from white to blue. Alternatively, you could use anhydrous cobalt chloride; in the presence of water, the anhydrous cobalt chloride turns from blue to pink. 

2. Describe and explain, in outline, the purification of the water supply by filtration and chlorination.

Filtration is used to separate insoluble substances from the water. Afterwards, the water is chlorinated to get rid of bacteria that couldn't be removed through filtration.

3. State some of the uses of water in industry and in the home.

Home: cooking, cleaning, washing

Industry: cooling, planting in agriculture

4. Describe the separation of oxygen and nitrogen from liquid air by fractional distillation.

Like crude oil, liquid air can be separated in a fractionating column. Liquid air is pumped into the bottom of the column and it is heated. Nitrogen gas evaporates from the air and is collected at the top of the column, while liquid oxygen is collected from the bottom. 

5. Describe the composition of clean air as being a mixture of 78% nitrogen, 21% oxygen and small quantities of noble gases, water vapour and carbon dioxide. 

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6. State the common air pollutants as carbon monoxide, sulphur dioxide and oxides of nitrogen, and describe their sources.

Carbon monoxide, sulphur dioxide and nitrogen oxides are what make air dirty. Carbon monoxide comes from the incomplete burning of fuels, so any machinery that burns a fuel could release carbon monoxide. Additionally, burning cigarettes also produce carbon monoxide. Sulphur dioxide and nitrogen oxides both come from burning fossil fuels.

7. Explain the presence of oxides of nitrogen in car exhausts and their catalytic removal.

Oxides of nitrogen are formed in car engines due to heat and pressure. They are poisonous and harmful to humans, so catalytic converters are put into engines. Nitrogen oxide is reduced, meaning that it loses oxygen, so it breaks down into separate nitrogen and oxygen gases. In addition, carbon monoxide is oxidised, meaning it gains oxygen, so it becomes carbon dioxide. 

8. Explain why the proportion of carbon dioxide in the atmosphere is increasing, and why this is important.

Carbon dioxide levels are rising due to excessive human activity, such as factory production and deforestation. This is important because CO2 is one of the gases that contribute to the greenhouse effect, therefore resulting in global warming. Global warming is the general increase of temperature, and this has a great effect on our environment. 

9. State the adverse effect of common air pollutants on buildings and on health.

Air pollutants affect the materials used to build buildings; they cause the materials to become discoloured, brittle, and prone to deterioration. Pollutants also have negative effects on health, including eye, throat and nose irritation, breathing problems, and cancer. 

10. Describe the formation of carbon dioxide: 

• as a product of complete combustion of carbon-containing substances, 

• as a product of respiration, 

• as a product of the reaction between an acid and a carbonate, 

• as a product of thermal decomposition.

When anything containing carbon burns, the carbon reacts with oxygen, gets oxidised, and becomes carbon dioxide. Carbon dioxide is a product of respiration, from the equation glucose + oxygen --> carbon dioxide and water. Similarly, when an acid and carbonate react together, a product of the reaction is carbon dioxide (the other is water). Carbon dioxide is also produced from thermal decomposition. Take the decomposition of calcium carbonate for instance: when calcium carbonate is heated, it breaks down into calcium oxide and carbon dioxide. 

11. Describe the essential conditions for the manufacture of ammonia by the Haber process including the sources of the hydrogen and nitrogen, i.e. hydrocarbons or steam and air.

The Haber process is a process that manufacture ammonia. Nitrogen from the atmosphere and hydrogen, formed through the reacted of methane and steam, are reacted together to form ammonia; this is a reversible reaction.

nitrogen + hydrogen <--> ammonia

N + 3H <--> NH3

The amount of ammonia produced at a time is quite low - about 15%. To produce a higher yield, the following conditions are needed:

• low temperature

• high pressure

• catalyst of iron to speed up the reaction 

This is an important process because ammonia is used in the manufacture of fertilisers used in agriculture. Fertilisers speed up the growth of plants and gives them additional nutrients, so that they grow quickly and healthily. 

12. Describe the rusting of iron in terms of a reaction involving air and water, and simple methods of rust prevention, including paint and other coatings to exclude oxygen.

Iron rusts when it comes into contact with both air and water. Water reacts with the iron over time and the oxygen in the air oxidises the iron. Combined, this forms a layer of rust. 

There are several ways to prevent rust from forming. One would be to simply use a coat of paint; this acts as a barrier to prevent contact with water and air. Another way would be to galvanise the iron, which is to coat the iron in zinc. Similar to paint, the zinc acts as a barrier. Lastly, sacrificial protection can be used. A block of zinc is placed next to the iron, so that any water and air present reacts with the zinc, rather than the iron. 

13. Describe the need for nitrogen-, phosphorus- and potassium-containing fertilisers.

Plants need nitrogen, phosphorus and potassium to grow healthily. Nitrogen helps with the production of proteins, which is a plant's food. Phosphorus helps balance out the pH of the soil, and potassium helps with the production of chloroplasts, which help the plant photosynthesise. 

14. Describe the displacement of ammonia from its salts by warming with an alkali.

When an ammonium salt is warmed with an alkali, the ammonia in the salt is displaced by ammonia gas.

Physics Unit 2.1: Mass and Weight

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Unit 2.1 Mass and Weight

1. Be able to distinguish between the mass and weight of an object.

Mass = the amount of substance in an object; measured in g/kg

Weight = a force due to gravity; measured in Newtons N

2. Demonstrate understanding that mass is a property that ‘resists’ change in motion.

If a force is applied to an object, it does not immediately reach a high speed as it takes time for it to accelerate. If the force is constant, there won't be constant acceleration. If the force is not constant, there will be a moment of acceleration, allowing the object to accelerate. 

For example, you hit a ball. You are the force that moves the ball, and it takes time for the ball to accelerate in the air. If you keep contact with the ball, it stays at a constant speed and will not move faster. If you hit it and lose contact, the ball will fly up into the air and accelerate. 

3. Know that the Earth is the source of a gravitational field. 

Anything with a mass will be pulled down to Earth by the force of weight. If the object has a big mass, a bigger force will be applied to it.

4. Describe, and use the concept of, weight as the effect of a gravitational field on a mass.

In comes the equation for weight:

weight = mass x gravity

N = g x m/s^2

Chemistry Unit 7.1: Speed of Reaction

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Unit 7.1 Speed of Reaction

1. Describe the effect of concentration, particle size, catalysis and temperature on the speeds of reactions.

Here are some factors that speed up the rate of a reaction:

• surface area: the larger the surface area, the faster the rate; this is because this increases the chance of particles colliding with each other
• concentration: a higher concentration means there are more particles in each cm^3 of space, so there are more collisions
• catalysis: a catalyst speeds up the rate of a reaction; it lowers the amount of energy needed for the reaction to take place, so it occurs more easily
• temperature: a higher temperature provides energy for articles to move more quickly, so they collide more often

2. Describe a practical method for investigating the speed of a reaction involving gas evolution.

An example to investigate this is using magnesium and hydrochloric acid to test the rate of reaction. The equation goes as follows:

magnesium + hydrochloric acid --> magnesium chloride + hydrogen

Equipment:

• conical flask

• gas syringe

• stopwatch

• hydrochloric acid

• magnesium

Using this apparatus, we can design an experiment that, for example, measures how long it takes for 20cm^3 of gas, using the volume of magnesium as our independent variable (the one you change). 

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The diagram above uses magnesium ribbons instead of powder, but that's completely fine.

3. Devise a suitable method for investigating the effect of a given variable on the speed of a reaction.

For the experiment above, time was the variable that we changed. The experiment could also be designed around other variables:

• the concentration of acid

• temperature conditions

• surface area of magnesium (chips? ribbon? powder?)

• the reaction with a catalyst and without

4. Interpret data obtained from experiments concerned with speed of reaction.

Once you have carried out the experiment and obtained data, you'll be able to come to a conclusion on what you were investigating.

5. Describe the application of the above factors to the danger of explosive combustion with fine powders (e.g. flour mills) and gases (e.g. mines).

So you know that variables affecting the rate of a reaction are temperature, concentration, and surface area. These are applicable to real life situations.

In a flour mill, flour is produced. Flour particles are very small, so they have a large surface area. If there is a lot of flour in the air, a small spark can cause an explosion between flour and oxygen.

In a coal mine, the air is filled with flammable gases. If the gases reach a certain concentration they can form an explosion with air. 

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6. Describe and explain the effects of temperature and concentration in terms of collisions between reacting particles (concept of activation energy will not be examined).

As mentioned above, a higher temperature will give particles more energy to move and collide, and a higher concentration means there are more particles in the space that will collide. 

As a reaction occurs and the reactants get used up, the concentration of the substance decreases; this is why reactions slow down as they happen over a span of time.

7. Define catalyst as an agent which increases rate but which remains unchanged.

A catalyst is a substance thats speeds up a reaction, but the catalyst itself will not be used up.