Biology Unit 7.1: Nervous Control in Humans

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Unit 7.1 Nervous Control in Humans

1. Describe the human nervous system in terms of the central nervous system (brain and spinal cord as areas of coordination) and the peripheral nervous system which together serve to coordinate and regulate body functions.

The human nervous system serves to detect and respond to stimuli. It is split into two parts: the central nervous system (CNS), and the peripheral nervous system (PNS).

The CNS consists of the brain and spinal cord. The spinal cord is a long tubular bundle of nervous tissue and support tissue that runs through a tunnel in the backbone so it is protected; the skull protects the brain. The CNS gives instructions to the other parts of the body to perform certain jobs.

The PNS functions to detect stimuli and send impulses to the brain regarding the detected stimuli. It is made up of receptors and nerves that help carry the impulses. The receptors detect the stimuli in the environment. There are many receptors in the human body that detect different stimuli, such as light, touch, sound, temperature, and chemicals. The opposite of receptors is effectors: made up of muscle and glands, they respond to the stimuli. 

2. Describe the structure and function of the eye, including accommodation and pupil reflex.

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Functions

• iris: widens and narrows to control the amount of light entering the eye

• suspensory ligaments: loosens and tightens to adjust the thickness of the lens

• choroid: middle layer that surrounds the eye, contains blood vessels

• sclera: outer, protective layer of the eye

• retina: inner section of the eye, sensitive to light, where the fovea is located, contains rods and cones

• fovea: a light sensitive section, the sharpest part of vision

Accommodation is the widening and narrowing of the lens so the light rays can hit the retina at the right spot in order to see things. The light rays need to be refracted to be directed to the fovea, and this process makes sure the light is focused. The lens adjusts by changing shape to focus on the light.

On near objects	On far objects
Ciliary muscles contract	Ciliary muscles relax
Suspensory ligaments relax	Suspensory ligaments contract
Lens thickens and becomes more convex and elastc	Lens stretches so it is thinner and less convex
Gives lens refractory power	Decreases refractory power

The pupil reflex is an automatic reflex that allows the pupil to increase in size in dim lighting to let as much light as possible enter the eye. When it decreases, it is to protect the retina so that it does not get damaged by too much light.

3. Identify motor (effector), relay (connector) and sensory neurones from diagrams.

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These are the three types of neurones, labelled with their different parts.

4. Describe a simple reflex arc in terms of sensory, relay and motor neurones, and a reflex action as a means of automatically and rapidly integrating and coordinating stimuli with responses.

Reflexes are fast, automatic and can't be learnt. They exist to ensure a good chance of survival. Reflex actions include blinking (stimulated by bright light), knee jerking (stimulated by the force applied to the knee), and yawning (stimulated by high carbon dioxide levels). 

The reflex arc is the process of from sensing the stimuli to reacting to it:

receptor --> sensory --> relay --> motor --> effector

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Chemistry Unit 5: Electricity and Chemistry

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Unit 5. Electricity and Chemistry

1. State that electrolysis is the chemical effect of electricity on ionic compounds, causing them to break up into simpler substances, usually elements.

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From the diagram, you can see that the electrolyte (solution) is made up of negative and positive ions; these are called anions and cations, respectively. Through electrolysis, we can use electricity to separate and obtain the anions and cations. The electrolyte is a compound that can conduct electricity for the process to happen. 

2. Use the terms electrode, electrolyte, anode and cathode.

Electrode: the conducting material which passes an electrical current (carbon is commonly used)

Electrolyte: the solution being broken down

Anode: the positive electrode, attracts anions

Cathode: the negative electrode, attracts cations

3. Describe electrolysis in terms of the ions present and the reactions at the electrodes.

The ionic compound will only be able to be broken down if they are in liquid form, as in a liquid the ions can move freely. To obtain a liquid, water can be added to the compound to dissolve it. This way, the anions are free to be attracted to the anode and the cations to the cathode. 

4. Describe the electrode products, using inert electrodes, in the electrolysis of: 

• molten lead(II) bromide, 

• aqueous copper chloride, 

• dilute sulphuric acid.

Molten lead (II) bromide --> lead 2+ ion (to cathode) + bromine 1- ion (to anode)

Aqueous copper chloride --> copper 1+ ion (to cathode) + chlorine 2-  ion (to anode)

Dilute sulphuric acid --> hydrogen (to cathode) + sulphur (to anode)

5. State and use the general principle that metals or hydrogen are formed at the negative electrode (cathode), and that non-metals (other than hydrogen) are formed at the positive electrode (anode).

The term 'opposites attract' applies here: cathodes (-) attract cations (+), while anodes (+) attract anions (-). To help you with this, think about this trick:

Cations = pussytive --> positive

Even for me, this tip is weird, but in it's own weird way it works!

Metals and hydrogen are positive, so they are the cations in the equation. If the metal is more reactive than hydrogen on the reactivity scale, it will get replaced by hydrogen and hydrogen will be formed at the cathode. The less reactive substance will be formed at the cathode.

For example, in aqueous sodium chloride there is sodium (Na+) and hydrogen (H+). Hydrogen takes sodium's place in the reaction --> 2H+ + 2e- = H2 

This is called a reduction as the negatively charged ions in the circuit are attracted to the positive cations, therefore reducing the cation to neutral. 

Non-metals are negative, so they are the equation's anions. They attract the positive ions from the circuit and also become neutral; this is called oxidisation. 

6. Relate the products of electrolysis to the electrolyte and electrodes used, exemplified by the specific examples in the Core together with aqueous copper(II) sulphate using carbon electrodes and using copper electrodes (as used in the refining of copper).

Electrolysis can also be used to purify metals. When doing so, instead of using carbon rods as electrodes we use the metal we want to purify. 

Let's say we want to purify copper. We take a rod of impure copper as our anode, and pure copper as our cathode. The solution used is aqueous copper sulphate. When the circuit is switched on, copper ions are attracted to the anode as they are cations (all metals are cations!). The impurities of the anode become sludge and the anode decreases in size, while the cathode gains copper ions and increases in size. 

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7. Describe the electroplating of metals, using laboratory apparatus.

Electroplating a metal is to coat a metal with another metal. We do this because maybe the metal being coated is highly reactive and we want to protect them. Metals commonly used to for electroplating are tin, silver, copper and chromium. 

To electroplate, the cathode is the object to be plated and the anode is the metal you want to plate with. The electrolyte is a salt solution of the same metal as the anode. When the circuit is switched on, the anode ions are attracted to the cathode, wearing away the anode. The concentration of the solution stays the same because no ions are being taken from it. 

Say you want to coat a brass key in copper. With alligator clips that are connected to wires, you attach a rod or wire of copper as your anode and the key as your cathode. The wires will be connected to the power supply accordingly. In a beaker of copper sulphate, the anode and cathode are placed into the electrolyte and the circuit is switched on. With this lab equipment, this is a simple process of electroplating. 

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8. Predict the products of the electrolysis of a specified binary compound in the molten state, or in aqueous solution.

Let's use sodium chloride.

At the anode: 2Cl --> Cl2 + 2e-

At the cathode: Na+ + e- --> Na

9. Describe, in outline, the chemistry of the manufacture of 

• aluminium from pure aluminium oxide in molten cryolite, 

• chlorine, hydrogen and sodium hydroxide from concentrated aqueous sodium chloride.

Aluminium: aluminium ore, bauxite, is purified to obtain a white powder; this white powder is aluminium oxide. Aluminium can be extracted from aluminium oxide through electrolysis.

Chlorine, hydrogen and sodium: sodium chloride (brine) is used as a electrolyte for electrolysis, and chlorine, hydrogen and sodium can be obtained from there. 

Physics Unit 1: Motion

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Unit 1 Motion

1. Define speed and calculate speed from total distance / total time.

Speed is the rate of how fast something travels, measured by how far it has travelled in how much time. The equation we use to calculate speed is:

speed = distance / time

2. Distinguish between speed and velocity. 

While speed only measures how fast something travels, velocity measures how fast something travels in a given direction. 

3. Plot and interpret a speed/time graph and a distance/time graph.

First up is a distance/time graph:

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The blue line and first third of the red line represent a steady speed as they go up in straight lines without and changes. The second third of the red line shows that the object is stationary; you can tell because they have not changed their distance but time is passing. The last third of the red line shows the object returning to its start. 

Now a speed/time graph:

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The blue line and first third of the red line show constant acceleration. The second third of the red line shows constant speed, as the speed is not changing but time is passing. The last third of the red line shows constant deceleration, because the object's speed is decreasing. 

4. Recognise from the shape of a speed/time graph when a body is 

• at rest, 

• moving with constant speed, 

• moving with changing speed.

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5. Recognise linear motion for which the acceleration is constant and calculate the acceleration.

By finding the gradient of the line, we can find out if the acceleration is constant. The equation for this is:

acceleration  = change in velocity / time taken

To figure out the change in velocity, you deduct the initial velocity from the final velocity. 

6. Recognise motion for which the acceleration is not constant.

When this is plotted out onto a graph, the line will not be consistent, representing non-constant acceleration.

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7. Calculate the area under a speed/time graph to work out the distance travelled for motion with constant acceleration. 

To do so, we need to find the gradient of the graph using the rise and the run. The rise is how much the steep rises from its starting position, and the run is how far it travels horizontally from its starting position. 

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For example, we take random x,y points from the graph above: 4, 20. To find the area, we calculate the area of a triangle, as the shape of the rise/run form a triangle: (4 seconds x 20 meters/second) / 2 = 40 meters. 

8. Demonstrate a qualitative understanding that acceleration is related to changing speed. 

Acceleration is the rate of which an object changes speed, so when a speed changes, we assume that the acceleration has either increased or decreased. 

Chemistry Unit 2: Experimental Techniques

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Unit 2.1 Methods of Separation and Purification

1. Describe paper chromatography.

Chromatography is used to separate two or more dissolved solids in a solution. Paper chromatography uses water to separate the solids. A line is draw on a piece of paper and the solution is dotted on that line. After labelling the dot, the piece of paper is placed into water (or another solvent), the water level meeting a place a little below the pencil line. As the water travels up the paper (this is called capillary action), it separates the solids in the solution. 

We can use chromatography to evaluate the contamination of food or water, which is part of health and safety procedures. 

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2. Interpret simple chromatograms.

The further a substance moves up the paper, the more soluble it is. 

3. Describe methods of separation and purification: filtration, crystallisation, distillation, fractional distillation.

Filtration: when you have a solid and solution, filtering the mixture can help you separate each from the other e.g. sand and water

Crystallisation: crystallisation allows you to separate a solute from a solvent. The solution is left to dry or heated up, evaporating the solvent and leaving the solute in the form of crystals e.g. salt and water

Distillation: distillation helps you obtain a pure liquid from a mixture of liquids. The mixture is heated up in a flask, and the liquid with the lower boiling point will evaporate first. The vapour is cooled in the Liebig condenser and collected in the form of a liquid e.g. ethanol and water

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Fractional distillation: this process is similar to distillation, but it is used to separate more parts in a mixture. The mixture is heated up in a flask, and attached above the flask is a column with beads. This helps to separate the different parts as they evaporate. The vapours are then cooled through the Liebig condenser and collected as liquids e.g. crude oil

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4. Understand the importance of purity in substances in everyday life, e.g. foodstuffs and drugs.

As mentioned above, checking the purity of things is important as contamination can result in health and safety issues, especially food or drugs. They can cause you to become very sick.

5. Identify substances and assess their purity from melting point and boiling point information.

Take water for example. We all know that the boiling point of water is 100°c. If the boiling point has changed, this indicates that the water is not pure. This is the same with the melting point.

6. Suggest suitable purification techniques, given information about the substances involved.

With the above methods of separation and purification, I have given some examples of what each method can be used for. 

Physics Unit 4: Simple Kinetic Molecular Model of Matter

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Unit 4.1 States of Matter

1. State the distinguishing properties of solids, liquids and gases.

Solid	Liquid	Gas
Particles are tightly packed in a regular pattern	Particles are loosely bonded with gaps between them	Particles are completely seperated
Particles vibrate together, keeping its shape and position	Particles vibrate and slide past one another	Particles are free to move
Retains a fixed volume and shape	Takes shape of its container	Takes shape of its container
Does not flow easily	Flows easily	Flows easily

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Unit 4.2 Molecular Model

1. Describe qualitatively the molecular structure of solids, liquids and gases. 

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As mentioned above, particles in solids are in fixed positions, while particles in liquids and gases are more free.

2. Relate the properties of solids, liquids and gases to the forces and distances between molecules and to the motion of the molecules.

In solids, the particles are close together because they are bonded in fixed positions. In liquids, the particles are attached together but are not as rigorously held together as particles in a solid. In gases, the molecules are completely unattached so the space between particles can be far and wide. 

3. Interpret the temperature of a gas in terms of the motion of its molecules.

When a gas is hot, its particles move quickly and collide often. This is because heat energy is given to the particles, giving them the kinetic energy to move. The hotter the gas, the faster the particles will move. 

4. Describe qualitatively the pressure of a gas in terms of the motion of its molecules.

Imagine you've got a sealed container containing gas. When the gas particles move, they hit the sides of the container; this creates pressure on the container. The pressure of the gas depends on how often and how hard the molecules are colliding with the inside of the container. 

5. Describe qualitatively the effect of a change of temperature on the pressure of a gas at constant volume.

You know that a high temperature = faster motion and faster motion = more pressure. Therefore, the higher the temperature of gas, the more pressure of the gas at constant volume. 

Unit 4.3 Evaporation

1. Describe evaporation in terms of the escape of more energetic molecules from the surface of a liquid.

Evaporation occurs when there are particles in a liquid that move faster, so fast that if they are near the surface they have enough energy to escape and become a gas. 

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2. Demonstrate understanding of how temperature, surface area and air flow over a surface influence evaporation.

Temperature: a higher temperatures means that the particles have more energy to escape, resulting in  a faster rate of evaporation.

Surface area: with a bigger surface area, more of the molecules are at the surface, allowing them to escape.

Air flow: air flow picks up molecules at the surface before they can become liquid again. The higher rate of air flow, the faster the evaporation. 

3. Relate evaporation to the consequent cooling.

When water evaporates, it takes some thermal energy from whatever is has been on, resulting in that thing being cooler. Faster particles escape first, so slower particles are left behind; this means the temperature is lower than before. 

Unit 4.4 Pressure Changes

1. Relate the change in volume of a gas to change in pressure applied to the gas at constant temperature and use the equation pV = constant at constant temperature.

Boyle's law states that pressure and volume are inversely proportionate when the gas is at a constant temperature. Lowering the volume will increase in a higher pressure, and vice versa. This is because if a gas has a smaller volume, there is less space for the particles to move; they hit the sides of the container more frequently, resulting in higher pressure. 

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Biology Unit 1: Characteristics of Living Organisms

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Unit 1: Characteristics of Living Organisms

1. List and describe the characteristics of living organisms.

Remember this handy-dandy acronym and you're golden!

Movement
Respiration
Sensitivity

Growth
Reproduction
Excretion
Nutrition

2. Define the terms of nutrition, excretion, respiration, sensitivity, reproduction, growth, movement.

Nutrition: taking in of nutrients which are organic substances and mineral ions, containing raw materials or energy for growth and tissue, absorbing and assimilating them.

Excretion: removal from organisms of toxic materials, the waste products of metabolism (chemical reactions in cells including respiration) and substances in excess of requirements.

Respiration: the chemical reactions that break down nutrient molecules in living cells to release energy.

Sensitivity: the ability to detect or sense changes in the environment (stimuli) and to make responses.

Reproduction: the processes that make more of the same kind of organism.

Growth: a permanent increase in size and dry mass by an increase in cell number or cell size or both.

Movement: an action by an organism or part of an organism causing a change of position or place.

Physics Unit 15.5+6+7: Safety Precautions, The Nuclear Atom, Isotopes

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Unit 15.5: Safety Precautions

1. Describe the hazards of ionising radiation to living things.

All types of radiation (alpha, beta, and gamma) can damage living cells because they can ionise. Ionising radiation breaks down molecules into ions. Chemical reactions in living cells can be affected by these ions. This can cause living cells to die, or mutate and become cancerous.

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2. Describe how radioactive materials are handled, used, and stored in a safe way to minimise the effects of these hazards. 

●You should stay away from radioactive materials, avoiding the eyes. If possible, you should be protected from them, and use appropriate equipment to handle them. For example, tongs.

● Radioactive materials are stored in containers lined with lead to make sure that it is not exposed to the environment outside.

● Film badges can detect radiation; they will turn black to measure the amount of radiation a person is exposed to. The badges should be checked regularly to make sure the person is not experiencing too much radioactivity.

● Wear goggles while dealing with radioactive materials, and wash hands after using them.

● Limit the amount of time exposed to radiation.

● Look out for the radioactive hazard symbol.




Unit 15.6: The Nuclear Atom

1. Describe the composition of the nucleus in terms of protons and neutrons.

In an atoms nucleus, you have protons and neutrons. Electrons are located on the outside of the nucleus.

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2. Use the term proton number Z.

The proton number is the number of protons you have in an atom. For example, let's take a look at oxygen.

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As seen from the diagram above, oxygen has 8 protons; the proton number can also be called the atomic number.

3. Use the term nucleon number A.

The nucleon number is the number of protons and neutrons combined. Using the diagram from above, we see that since oxygen has the proton number of 8 and the nucleon number of 16, it means that in oxygen there are 8 neutrons. The neutron number is also called the atomic mass.



Unit 15.7: Isotopes

1. Use the term isotope.

Some elements have more neutrons than others and they have various versions. These versions are called isotopes. The chemical properties are the same, but they have different masses due to the different amounts of neutrons. The number of protons, however, are the same, as a different number of protons would make it a different element.

2. Give and explain some practical uses of isotopes.

Take chlorine for an example. Its atomic mass is 37.5, because they have put the mean of the isotopes onto the Periodic Table. Isotopes are uses in medical therapy. For example, Cobalt 60 (as in 60 neutrons) is used to treat cancer and sterilise equipment.

3. Use the term nuclide and use the nuclide notation.

A nuclide is an atom or nucleus characterised by its number of protons and neutrons.

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Above is a diagram explaining nuclide notation. Nuclide notation is what you would see on the Periodic Table.

Biology Unit 5.1: Transport In Plants

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Unit 5.1: Transport In Plants

1. State the functions of xylem and phloem.

Xylem: specialised tissue in plants that transports water and inorganic ions from the root up to all the other parts of the plant

Phloem: specialised tissue in plants that transports food nutrients (e.g. glucose) from the leaves to other parts of the plant.

2. Identify the positions of xylem and phloem tissue.

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3. Identify root hair cells, as seen under the light microscope, and state their functions.

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Root hair cells are found at the end of young roots, their function is to help the plant absorb water and mineral ions from the soil via osmosis. They have large surface areas so they can maximise absorption. 

4. Relate the structure and functions of root hairs to their surface area and to water and ion uptake.

As said above, root hairs have large surface areas for absorption of water and ions. The cell membrane is semi-permeable so only minerals and water can go through, but not necessarily go back out.

5. State the pathway taken by water through root, stem and leaf (root hair, root cortex cells, xylem, mesophyll cells).

1. There is a high concentration of salts in the cell sap of the root hair, but a low concentration in the soil.
2. By osmosis, water passes into the root hair from the soil.
3. The cell sap is now diluted by the water. Next to the root hair is the cells of the cortex. Osmosis occurs through the cells until the water reaches the xylem.
4. The xylem vessel transports the water up the xylem tube from root to stem through a process called capillary action*.
*capillary action = cohesion of hydrogen bonding and adhesion to cell wall --> this pulls up everything against the force of gravity
5. The water leaves the xylem and is absorbed by the cells in the leaves.

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6. Investigate, using a suitable stain, the pathway of water through the aboveground parts of a plant.

7. Define transpiration as evaporation of water at the surfaces of the mesophyll cells followed by loss of water vapour from plant leaves, through the stomata.

So water is pulled up form the xylem, and is used for photosynthesis. Transpiration is when water evaporates from the leaves into the air. When the water has evaporated, more is needed to continue photosynthesis. The transpiration stream is the stream of water that is pulled up from the roots to the leaves, similar to how a drink is sucked up a straw.

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8. Describe how water vapour loss is related to cell surfaces, air spaces and stomata.

Water in the mesophyll cells forms a layer on the surface of the cell. The water evaporates into the air spaces between the spongey cells. A high concentration of water is in the cells, so water diffuses out of the leaf through the stomata. The water lost is replaced by water from the xylem.

9. Describe the effects of variation of temperature, humidity and light intensity on transpiration rate.

temperature: the higher the temperature, the faster the rate of transpiration
humidity: the higher the humidity, the slower the transpiration --> this is because there is a lot of moisture in the air
wind speed: transpiration increases as wind speed increases
light intensity: the more light, the faster the transpiration --> this is because the stomata open in light for photosynthesis
water supply: the less the water, the slower the transpiration --> when there is less water, the stomata close up to conserve water

10. Explain the mechanism of water uptake and movement in terms of transpiration producing a tension (‘pull’) from above, creating a water potential gradient in the xylem, drawing cohesive water molecules up the plant.

Once water enters the xylem tubes in the roots, it flows to the stem, then the leaves. This flow is called the transpiration stream. The columns of water in the xylem tubes are prevented form breaking by strong cohesive forces between the water molecules.

11. Define translocation in terms of the movement of sucrose and amino acids in phloem; from regions of production to regions of storage OR to regions of utilisation in respiration or growth.

Translocation is the movement of manufactured food through the phloem tissue. Food in manufactured in the leaves. In younger plants, food is distributed to areas of growth while in older plants, it is transported to areas for storage e.g. roots in a potato plant. In all plants, food needs to be transported to the cells for respiration.

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