Alevel Marine science textbook

The kinetic particle theory describes all matter as a collection of particles that are in constant, random motion, with the amount of movement determined by the energy the particles possess.

The state of matter may change as energy is transferred away from or to the molecules, affecting their movement and arrangement.

When liquid water cools down, the movement of the water molecules slows, and they arrange in a regular structure called a lattice, resulting in the formation of solid ice.

When ice is heated, the water molecules gain energy, vibrate faster, and the forces holding them together start to break, allowing the molecules to flow and take the shape of their container, forming liquid water.

Evaporation occurs when water molecules at the surface gain enough energy to escape the forces attracting them to other molecules, allowing them to turn into water vapor, especially as the surface water warms up.

Atoms are made of three subatomic particles: protons (positively charged), neutrons (neutral), and electrons (negatively charged).

An atom consists of a nucleus at its center, made up of protons and neutrons. Electrons move around the nucleus in orbits called shells. The first shell can hold two electrons, while the next two shells can hold up to eight electrons each. Atoms are most stable when their outermost shell is full.

An element is made of atoms that have a specific number of protons, known as the atomic number. This atomic number never varies and is used to identify the characteristics of elements.

A compound is a substance formed when individual atoms bond together in a specific ratio. For example, a water molecule is a compound made of two hydrogen atoms bonded to one oxygen atom, represented as a 2[H]:1[O] ratio.

Emergent properties are new characteristics that a compound develops through bonding, which can be very different from the properties of the individual elements that make it up. For instance, hydrogen and oxygen are gases at room temperature, but when combined to form water, it becomes a liquid at room temperature.

A covalent bond forms when two atoms share a pair of electrons. This type of bonding occurs mainly in non-metal elements and compounds formed between non-metals, resulting in complete outer shells for both atoms involved in the bond.

Compounds with covalent bonds can exist as solids, liquids, or gases at room temperature and normal atmospheric pressure. For example, water, which contains two covalent bonds between oxygen and hydrogen atoms, is a prevalent covalent compound on Earth.

Covalent bonds are formed when atoms share one or more pairs of electrons, creating strong chemical bonds between them.

Covalent bonds in glucose store a lot of energy, making glucose a useful molecule for holding chemical energy in ecosystems.

Ionic bonds form when a sodium ion loses an electron, becoming positively charged, and a chloride ion gains that electron, becoming negatively charged. The electrostatic attraction between these oppositely charged ions creates the ionic bond.

When an atom gains an electron, it becomes negatively charged (anion). When it loses an electron, it becomes positively charged (cation) due to the imbalance between protons and electrons.

Sodium loses an electron to become a sodium ion (Na+), while chloride gains an electron to become a chloride ion (Cl-). This transfer of electrons results in the formation of positive and negative ions that are attracted to each other, creating an ionic bond.

The three-dimensional ionic lattice structure allows for a stable arrangement of ions, maximizing the electrostatic attraction between the positively charged sodium ions and negatively charged chloride ions. This structure contributes to the properties of ionic compounds, such as high melting and boiling points.

Common salts found in the ocean include sodium chloride (NaCl), calcium carbonate (CaCO3), and magnesium sulfate (MgSO4). These salts are formed through ionic bonds between their respective ions.

A hydrogen bond is a weaker bond that occurs between molecules containing a hydrogen atom bonded to an atom of oxygen, nitrogen, or fluorine. In water, two hydrogen atoms are covalently bonded to an oxygen atom, resulting in unequal sharing of electrons. This creates a partial positive charge on the hydrogen atoms and a partial negative charge on the oxygen atom, leading to the formation of hydrogen bonds between water molecules.

Hydrogen bonds significantly impact the properties of water by:

1. Solvent capabilities: Water's polarity allows it to dissolve many ionic and covalent substances, making it a universal solvent.
2. Density: Hydrogen bonds cause water to expand when it freezes, making ice less dense than liquid water.
3. Specific heat capacity: The high number of hydrogen bonds gives water a high specific heat capacity, allowing it to moderate temperature changes effectively.

Water is called the universal solvent because its partial charges allow it to interact with and dissolve a wide variety of substances, including ionic compounds and many covalent substances like glucose and atmospheric gases. This property is crucial for biological processes and chemical reactions in nature.

Ice is unique because it is less dense than liquid water due to the hydrogen bonds forming a crystal lattice structure when water freezes. This property is important because it allows ice to float on water, providing insulation for aquatic life during cold temperatures and affecting the climate and ecosystems.

The specific heat capacity of water is high due to the extensive hydrogen bonding between water molecules. This allows water to absorb and store large amounts of heat without significant temperature changes, acting as a temperature buffer and helping to moderate the planet's climate.

Coastlines help create mild climates by influencing temperature through the thermal properties of water, which can absorb and release heat more slowly than land.

• Elements are pure substances that cannot be broken down into simpler substances.
• Compounds are substances formed when two or more elements chemically bond together in fixed proportions.

The number of covalent bonds an atom can form is determined by its valence electrons. Atoms tend to form bonds to achieve a full outer shell, typically following the octet rule.

• Covalent Bonds: Share electrons (think 'co' for cooperation).
• Ionic Bonds: Transfer electrons (think 'I' for 'I give you my electron').
• Hydrogen Bonds: Weak attractions between polar molecules (think 'H' for 'Hold hands gently').

Solubility refers to the extent to which a solute, like sodium chloride, can dissolve in a solvent, such as water. Sodium chloride dissolves easily in water due to the polarity of water molecules, which interact with the ionic bonds of sodium and chloride ions, breaking them apart and allowing the ions to disperse in the solution.

As the temperature of seawater rises, the rate of dissolution of salts increases. This is because warmer water causes individual water molecules to move faster, which helps mix the ions into the water and facilitates the breaking of ionic bonds, allowing for greater solubility of salts.

Salinity is a measure of the concentration of dissolved salts in seawater, typically expressed in parts per thousand (ppt). It is determined by measuring the total dissolved solids (TDS) left after evaporating a known volume of seawater, with the average salinity of the open ocean being 35 ppt.

Variations in salinity at different locations in the ocean can be caused by the water cycle, particularly through processes like precipitation (rain or snow), which can lower the salinity in specific areas.

Fresh water runoff decreases the salinity of ocean water by diluting the salt content. This occurs when rainwater flows over land and eventually reaches the ocean, introducing fresh water into the saline environment.

Evaporation increases salinity levels because it removes water from the solution, leaving the salts behind. This can lead to salinity levels higher than 35 ppt in areas with high evaporation rates and limited fresh-water inflow.

A hypersaline environment is one where the salinity is significantly higher than that of typical seawater, often exceeding 35 ppt. An example is Don Juan Pond in Antarctica, which has a salinity of 440 ppt due to extreme evaporation and low precipitation.

Increased salinity lowers the freezing point of water, meaning that saltwater can remain liquid at temperatures where pure water would freeze. This property is crucial for marine organisms that thrive in icy environments.

The equipment needed includes a temperature probe or digital thermometers and 4 medium test tubes marked with different salinity concentrations (0.5 moldm-3, 1.0 moldm-3, 1.5 moldm-3, and 2 moldm-3).

Distilled water is used to ensure that no additional impurities or ions from tap water affect the results of the experiment, providing a controlled environment for accurate measurements.

It is predicted that as sodium chloride is added to water, the freezing point of the solution will decrease, meaning the solution will freeze at a lower temperature than pure water.

The ice bath is used to maintain a low temperature environment for the test tubes, allowing for the observation of the freezing point of the sodium chloride solutions as they cool down.

The solvent is water, and the solute is sodium chloride (NaCl).

The solubility increases with the addition of more sodium chloride; 11.6 g will dissolve more than 2.9 g, indicating a higher concentration of solute in the solution.

As the concentration of sodium chloride increases, the freezing point of the solution decreases, indicating a colligative property effect.

The freezing point would be significantly lower than that of pure water, but the exact value would depend on the specific freezing point depression calculation for sodium chloride.

The experiment could be extended by testing different solutes, varying temperatures, or altering the pressure to observe their effects on the freezing point.

The mixing of ocean layers is significant for nutrient distribution and maintaining uniform temperature and salinity, which are crucial for marine life.

The pH scale measures the concentration of hydrogen ions in water, which is crucial for the survival of aquatic organisms; it indicates whether a solution is acidic, neutral, or alkaline.

A pH value below 7.0 indicates that the solution is acidic.

The logarithmic nature of the pH scale means that a decrease of 0.1 in pH corresponds to a 25% increase in acidity, rather than a linear 1% increase.

Monitoring pH levels in aquatic environments is important because changes in pH can significantly affect the survival and reproduction of sensitive organisms.

Distilled water is pure and free from impurities, which prevents contamination of equipment. It also has a neutral pH, making it ideal for calibration without affecting the pH readings of other solutions.

Vinegar, being an acidic solution, can be used to test the effects of acidity on various substances, while baking soda, a basic substance, can be used to test the effects of alkalinity. Together, they help demonstrate the pH scale and its impact on chemical reactions.

Marine organisms such as coral reefs, shellfish (like oysters and clams), and plankton are at the greatest risk due to their reliance on calcium carbonate for their shells and skeletons. Ocean acidification reduces the availability of carbonate ions, making it difficult for these organisms to maintain their structures.

Cold water can dissolve more gas than warm water. As water temperature increases, the movement of water molecules speeds up, causing dissolved gas molecules to evaporate more quickly. This results in lower gas solubility in warmer water.

As the concentration of a particular gas in the atmosphere increases, the concentration of that gas in seawater also rises, maintaining a state of equilibrium. Turbulence and wave action help facilitate this gas exchange.

Different methods may yield varying results due to factors such as:

1. Measurement precision: Variability in the sensitivity of indicators or probes.
2. Sample handling: Contamination or differences in sample size and conditions.
3. Indicator limitations: Some indicators may not accurately reflect pH in certain ranges.

The pH is expected to decrease (become more acidic) when vinegar (an acid) is added to baking soda (a base) due to the neutralization reaction that occurs between the acid and base.

As temperature increases, the concentration of dissolved oxygen decreases. For example:

When atmospheric pressure increases, the concentration of gases in the atmosphere increases, pushing more gas molecules to dissolve in seawater. Conversely, when atmospheric pressure decreases, more dissolved gas molecules escape into the atmosphere, reducing their concentration in seawater.

As depth increases in the ocean, water pressure increases, which enhances the ability of gases to dissolve in water and remain dissolved. This means that deeper waters generally have a higher concentration of dissolved gases compared to shallower waters.

Gases are more soluble in water with lower salinity because fewer solutes allow more water molecules to interact with gas molecules. For instance, fresh water from rivers has higher levels of dissolved gases compared to saltwater in the open ocean, leading to higher oxygen levels in estuaries than in the ocean.

Dissolved oxygen is crucial for the survival of marine organisms as it is used for respiration. The concentration of DO varies with temperature, salinity, and pressure, generally decreasing with increasing temperature and salinity. The highest concentrations of DO are found in the surface layer of the ocean, where factors like water motion and photosynthesis contribute to supersaturation levels.

The photic zone is the upper layer of the ocean where light penetrates, allowing photosynthesis to occur. This zone is crucial for producers as it enables them to generate oxygen as a by-product, which increases the concentration of dissolved oxygen in the surface layer.

The concentration of dissolved oxygen (DO) varies with latitude due to temperature differences:

• Tropical waters: Higher temperatures reduce the concentration of DO that water can dissolve.
• Polar waters: Colder temperatures allow for a higher concentration of DO to be dissolved in the water.

As depth increases in the ocean, the concentration of dissolved oxygen typically decreases until it reaches the oxygen minimum layer (around 500 m deep). Below this layer, the concentration of DO can begin to increase again due to several factors, including reduced respiration and increased solubility of oxygen at lower temperatures and higher pressures.

Organisms in the oxygen minimum zone, such as the vampire squid, have special adaptations for survival, including:

• Efficient gills: These fish can extract oxygen from water even at low levels.
• Specially adapted haemoglobin: This blood protein is effective at carrying oxygen throughout the body despite low oxygen availability.

Several factors contribute to the increase in dissolved oxygen below the oxygen minimum layer:

1. Decomposition: Falling detritus is colonized by bacteria that decompose organic matter, using up oxygen. Below the oxygen minimum layer, this process is completed, leading to less respiration.
2. Reduced respiration needs: Organisms in this area have fewer food resources, reducing their need for oxygen.
3. Temperature and pressure effects: As temperature decreases and pressure increases with depth, the solubility of oxygen increases, allowing more oxygen to remain dissolved in the water.

Seawater is considered a solution because it consists of solvent (water) and solutes (salts and other dissolved substances). To test this, you could:

1. Evaporate a sample of seawater to see if solid residues (salts) remain, confirming the presence of solutes.
2. Measure conductivity of the seawater, as dissolved ions increase conductivity, indicating a solution.
3. Use a refractometer to measure the refractive index, which changes with solute concentration.

In areas where precipitation is greater than evaporation, salinity tends to be lower due to the influx of freshwater, diluting the seawater. Conversely, in areas where evaporation exceeds precipitation, salinity is higher as the water evaporates, leaving salts behind.

The solubility of a gas, such as oxygen or carbon dioxide, directly affects its availability to marine life. Higher solubility means more gas can dissolve in seawater, making it accessible for organisms. Conversely, low solubility limits the amount of gas available, which can affect:

• Respiration in aquatic organisms that rely on dissolved oxygen.
• Photosynthesis in aquatic plants that utilize dissolved carbon dioxide.

Thus, changes in temperature, salinity, and pressure can significantly impact gas solubility and, consequently, marine ecosystems.

The formula for density is:

density (kg m-3) = mass (kg) / volume (m3)

As the temperature of seawater increases, density decreases. Warmer water tends to float near the surface, while colder, denser water sinks below it.

The thermocline is an area where the temperature abruptly changes with depth. In tropical seas, surface water can reach 25 °C or higher, while at depths of 2000 m or more, it may be around 1 °C.

The water at the bottom of the ocean does not freeze due to increased salinity, which lowers the freezing point of water. Additionally, ice is less dense than liquid water, causing it to float if it were to form.

If ice were to sink instead of float, the ocean would freeze from the bottom up, leaving marine organisms with no habitat during winter. Floating ice provides a habitat and insulation for marine life.

Ice reduces the rate of heat loss from the water beneath it, keeping the water under the ice warmer than the exposed water. This allows marine organisms to maintain a temperature better suited for their adaptations.

A pycnocline is an area of water where the density changes quickly with depth, formed due to increased pressure at greater depths pushing water molecules closer together, resulting in higher density.

As salinity increases, the density of seawater also increases, causing fresher, lower density water to float on saltier, denser water. This is observed in estuaries where fresh water sits above saltwater.

A halocline is an area where salinity changes significantly with depth. It is typically found between less saline surface waters and more saline bottom waters, often at the seabed in non-tropical oceans.

In tropical seas, high evaporation rates create a warm, salty surface layer that floats above less saline water, resulting in a steep decrease in salinity (the halocline) until about 750 meters. In non-tropical seas, lower salinities at the surface can occur due to greater precipitation, with salinity increasing with depth.