MYP Integrated Sciences Study Guide: Food Chemistry, Physics, and Environment

Food Chemistry and Microbiology

Definition of Food Chemistry: Food chemistry is the branch of science concerned with the nature of food, its properties, and how it is processed and absorbed by the body. It involves the study of components such as water, proteins, fats, vitamins, and carbohydrates.
Main Functions of Molecular Components in Food:
- Proteins: Used for muscle growth and repair.
- Carbohydrates: Provide short-term energy.
- Fats: Provide long-term energy stores.
- Other Noted Functions/Items:
  - Used to transport oxygen around the body (e.g., hemoglobin, a protein).
  - Needed for healthy bones (e.g., minerals like calcium).
  - Needed for a healthy digestive system (e.g., fiber).
Water Content and Food Spoilage:
- Water provides a place for bacterial growth. When bacteria grow on food, it causes the food to spoil.
- The percentage of water in food is an indicator of how long food can be stored safely before spoiling.
- Data Comparison:
  - Watermelon: $92 \%$ water.
  - Pineapple: $95 \%$ water.
  - Cucumber: $96 \%$ water.
- Conclusion: Among watermelon, pineapple, and cucumber, the watermelon would contain the lowest number of bacteria when stored in the same conditions because it has the lowest water percentage ( $92 \%$ ).
Food Poisoning Prevention:
- Food poisoning is an illness caused by eating contaminated food, often by bacteria such as Salmonella or Escherichia coli (E. coli).
- Precautions and Justifications:
  - Suggestion 1: Cooking food to the correct internal temperature.
  - Justification 1: High heat kills harmful bacteria, making the food safe for consumption.
  - Suggestion 2: Avoiding cross-contamination (e.g., using different cutting boards for raw meat and vegetables).
  - Justification 2: This prevents the transfer of bacteria from raw products to foods that will not be cooked further.
Chemical Processes in Bread Preparation:
- Fermentation: A chemical process that occurs in the absence of oxygen (anaerobic respiration).
- Word Equation: $\text{glucose} \rightarrow \text{ethanol} + \text{carbon dioxide}$
- Balanced Chemical Equation: $1 C_6H_{12}O_6 \rightarrow 2 C_2H_5OH + 2 CO_2$
- The Role of Yeast: Yeast undergoes fermentation, releasing carbon dioxide gas as a byproduct. This gas becomes trapped in the dough, forming bubbles that cause the dough to rise and create a light, airy texture.

Sustainable Transportation and Physics

E-Bikes as a Sustainable Alternative: Governments are exploring electric bicycles (e-bikes) as environmentally friendly transport solutions to replace fossil fuel vehicles and improve public health.
Forces Acting on a Moving E-Bike:
- Applied Force: The force generated by the motor or the rider's pedaling.
- Friction: Between the tires and the road surface.
- Air Resistance: Opposing the forward motion as the bike moves through the air.
- Weight: The downward force due to gravity acting on the bike and rider.
- Normal Reaction: The upward force from the road supporting the bike.
Battery Capacity and Range:
- Range: The distance a bike can travel before the battery runs out. Affected by battery capacity, frame material, terrain, and pedaling effort.
- Formula for Capacity: $\text{capacity} = \text{voltage} \times \text{ampere-hours}$
- Battery Comparison Data:
  - Battery 1: Voltage = $50\,V$ , Ampere-hours = $15\,Ah$ , Capacity = $750\,Wh$ .
  - Battery 2: Voltage = $30\,V$ , Ampere-hours = $20\,Ah$ .
  - Calculation for Battery 2: $30\,V \times 20\,Ah = 600\,Wh$ .
Terrain and Energy Consumption:
- Flat terrain: $4\,Wh$ per mile.
- Mountainous terrain: $30\,Wh$ per mile.
- Scenario: An e-bike with $750\,Wh$ capacity travels $300\,km$ on flat terrain.
- Calculation (Mountainous Range):
  - Distance in miles = $\frac{750\,Wh}{30\,Wh/\text{mile}} = 25\,\text{miles}$ .
  - Conversion ( $1\,\text{mile} = 1.6\,km$ ): $25\,\text{miles} \times 1.6\,km/\text{mile} = 40\,km$ .
Materials and Chemistry:
- Common e-bike materials: Aluminium, Magnesium alloy, Carbon fiber.
- Magnesium (Mg): Found in Group 2 of the periodic table.
- Electronic Configurations:
  - Aluminium (Al): $(2, 8, 3)$ .
  - Carbon (C): $(2, 4)$ .
Health Implications: Cycling increases heart rate, leading to improved blood flow. Daily cycling improves long-term health by strengthening the cardiovascular system and reducing the risk of chronic diseases.

Light, Color, and Plant Growth

The Electromagnetic (EM) Spectrum:
- Visible light is the portion detectable by the human eye.
- Order of Regions (Increasing Wavelength): Gamma rays, X-rays, Ultraviolet, Visible light, Infrared, Microwaves, Radio waves.
- Colors of Visible Light: Blue and violet have shorter wavelengths ( $400\text{--}500\,nm$ ), while red has longer wavelengths ( $\approx 700\,nm$ ).
Experiment: Influence of Light Color on Plant Height:
- Independent Variable: Color of light (Red, Green, Blue).
- Dependent Variable: Height of the plant ( $cm$ ).
- Control Variables: Light intensity, duration of exposure, amount of water provided, type of soil, and initial plant size.
- Plant Height Data (Day 0 to Day 14):

Day	Red Light ( $700\,nm$ )	Green Light ( $550\,nm$ )	Blue Light ( $400\,nm$ )
0	$0.0\,cm$	$0.0\,cm$	$0.0\,cm$
1	$0.3\,cm$	$0.5\,cm$	$0.2\,cm$
2	$0.9\,cm$	$1.7\,cm$	$1.5\,cm$
3	$1.5\,cm$	$2.3\,cm$	$2.2\,cm$
4	$2.8\,cm$	$2.5\,cm$	$3.0\,cm$
5	$4.1\,cm$	$3.0\,cm$	$3.8\,cm$
6	$5.3\,cm$	$3.9\,cm$	$4.2\,cm$
7	$6.4\,cm$	$4.9\,cm$	$5.0\,cm$
8	$8.0\,cm$	$5.6\,cm$	$6.3\,cm$
9	$9.3\,cm$	$7.0\,cm$	$8.1\,cm$
10	$11.0\,cm$	$8.3\,cm$	$10.2\,cm$
11	$12.8\,cm$	$9.3\,cm$	$11.4\,cm$
14	$14.0\,cm$	$9.9\,cm$	$12.8\,cm$

Average Height Increase Calculation (Green Light):
- Total increase over 14 days = $9.9\,cm$ .
- Average = $\frac{9.9\,cm}{14\,\text{days}} \approx 0.7\,cm/\text{day}$ .
Qualitative Observations:
- Red Light: Tall, thin stems; perhaps specialized for reaching light.
- Green Light: Shorter, potentially less healthy appearance due to reflection of green light.
- Blue Light: Sturdy stems and darker green leaves.
Discussion on healthiest Plant: While the red light plant grew tallest, the blue light plant might be considered "healthiest" based on qualitative factors like leaf density or stem strength.
Scientific Improvement: Using a white light control group allows the student to compare specific wavelengths against a natural full spectrum to see if individual colors are more or less effective than sunlight.

Optical Density and Refraction

Definition of Refraction: The change of direction of light at a boundary due to a difference in optical density.
Investigation 1: Glass Block:
- Data (Incidence $i$ vs. Refraction $r$ ):
  - $15^{\circ} \rightarrow 10^{\circ}$
  - $30^{\circ} \rightarrow 20^{\circ}$
  - $45^{\circ} \rightarrow 28^{\circ}$
  - $60^{\circ} \rightarrow 35^{\circ}$
  - $75^{\circ} \rightarrow 39^{\circ}$
- Prediction: When light travels from a less optically dense material to a more optically dense material, the light is refracted towards the normal.
Investigation 2: Water (Refraction Cup):
- Data (Incidence $i$ vs. Refraction $r$ ):
  - $0^{\circ} \rightarrow 0^{\circ}$
  - $15^{\circ} \rightarrow 11^{\circ}$
  - $30^{\circ} \rightarrow 22^{\circ}$
  - $45^{\circ} \rightarrow 32^{\circ}$
  - $60^{\circ} \rightarrow 41^{\circ}$
  - $75^{\circ} \rightarrow 47^{\circ}$
Comparison of Glass and Water: Light is refracted more in glass than in water ( $10^{\circ}$ vs $11^{\circ}$ at $15^{\circ}$ incidence; $28^{\circ}$ vs $32^{\circ}$ at $45^{\circ}$ incidence). This supports the prediction that glass has a higher optical density than water.
Liquids Ordered by Optical Density (Highest to Lowest):
1. Cinnamon oil
2. Vegetable oil
3. Liquid coolant
4. Ethanol
5. Methanol
Identity of Liquid Similar to Water: Liquid coolant (based on data matching the refraction indices of water).

Experimental Design: Salt Concentration and Refraction

Research Question: How does the mass of salt dissolved in water affect the angle of refraction of light?
Variables:
- Independent: Mass of salt ( $g$ ) added to a fixed volume of water.
- Dependent: Angle of refraction ( $^{\circ}$ ) measured at a constant angle of incidence.
- Control: Volume of water, temperature of water, angle of incidence ( $45^{\circ}$ ), type of light source.
Method Highlights:
- Equipment: Refraction cup, ray box, protractor, salt, electronic balance, water, stirring rod.
- Measurement: Use a balance to measure salt in increments (e.g., $5\,g$ , $10\,g$ , $15\,g$ ). Dissolve fully, then shine a light ray through the cup at a fixed angle; read the refraction angle from the bottom of the cup.
- Safety: Ensure electrical equipment (ray box) stays away from water; clean up spills immediately to prevent slipping.

Energy and Natural Resources

Classification of Energy Sources:
- Renewable: The Sun (Solar), Wind, Tides.
- Non-renewable: Coal, Oil, Natural gas.
Comparison: Coal-Fired Power Station vs. Windmill:
- Similarities: Both use a generator to convert kinetic energy into electricity; both use power cables and wires to transport electricity to the grid.
- Differences: Coal requires burning fuel (chemical to thermal energy) and creates pollution/ $CO_2$ ; a windmill uses wind energy (kinetic) directly to spin blades/turbines, producing no emissions during operation.
Extraction of Natural Resources: Extraction can affect local communities through:
- Effect 1: Environmental degradation (loss of biodiversity or local water contamination).
- Effect 2: Economic shifts (creation of jobs but also potential for "boom and bust" cycles or displacement of local populations).

Community Pollution Solutions

City A: Education and Recycling:
- Focused on public education and visible community recycling bins for plastics. Waste is trucked to a recycling plant.
- Benefit: Increases awareness and changes long-term behavior.
- Limitation: Depends on voluntary public cooperation.
City B: Engineering and Waste Capture:
- Uses nets on pipe outlets to catch waste before it reaches water bodies. Organic waste is used for biomass energy.
- Benefit: Directly prevents pollution even if the public is negligent; generates energy.
- Limitation: High maintenance cost to empty nets; mechanical failure risks.
Global Implications: Plastic waste in aquatic ecosystems leads to ingestion by marine life, microplastic entry into the food chain, and physical destruction of habitats like coral reefs.