SkarpChapter 14 of 14
Connecting the Sciences: Big Ideas and Exam-Style Practice
Chemistry, biology, and physics are not separate islands—bring them together through big-picture ideas, mixed-topic questions, and exam-style practice that boosts SHS readiness.
Big Idea: Energy and Matter Connect Everything
Energy and Matter
Energy and matter link chemistry, biology, and physics. Matter has mass and takes up space. Energy is the ability to do work or cause change.
Physics View
In physics, you study how energy moves and changes form: kinetic, potential, electrical, light, sound, and thermal. The law of conservation of energy says it cannot be created or destroyed.
Chemistry View
In chemistry, chemical reactions involve energy changes when bonds break and form. The law of conservation of mass says total mass in a closed system stays constant in ordinary reactions.
Biology View
In biology, living things transform energy and matter. Photosynthesis turns light into chemical energy; respiration releases that energy for cells to use.
Mass-Energy Link
Modern science uses conservation of mass-energy: in nuclear processes, tiny amounts of mass can turn into large amounts of energy, described by `E = mc^2`.
Connecting Sentence
Key idea: In any closed system, the total amount of matter and energy stays constant, but both can move around and change form across physics, chemistry, and biology.
Example: Following Energy Through a Food Chain
The Food Chain
Consider this chain: Sunlight → Grass → Cow → Human. We will follow how energy and matter move through physics, chemistry, and biology.
Physics: Sunlight
The Sun emits electromagnetic radiation (light). This radiant energy travels as waves and is the original energy source in this food chain.
Chemistry: Photosynthesis
Grass uses light, water, and carbon dioxide to make glucose and oxygen: `CO2 + water + light → glucose + O2`. Light energy becomes chemical potential energy.
Biology: Respiration
In cows and humans, respiration uses glucose and oxygen: `glucose + O2 → CO2 + water + energy`. Chemical energy in glucose becomes ATP and heat.
Conservation of Matter
Atoms of carbon, hydrogen, and oxygen are conserved. They are rearranged into new molecules as they move through the organisms.
Conservation of Energy
Total energy is conserved. At each step, some useful chemical energy becomes thermal energy, so less energy is available for the next level.
Interactive: Track the Energy and Matter
Interactive: Track the Energy and Matter
Use the food chain Sunlight → Grass → Cow → Human.
- Energy forms
List the main form of energy at each stage:
- Sunlight: `` energy
- Grass: `` energy in glucose
- Cow running: `` energy and `` energy
- Matter tracking
Focus on carbon atoms:
- Where are the carbon atoms before photosynthesis?
- In which molecule(s) are they stored in the grass?
- After respiration in the cow, where do the carbon atoms go?
- Think and write
In 2–3 sentences, explain how conservation of energy and conservation of mass both appear in this food chain. Try to use these words: transfer, transform, atoms, chemical energy, heat.
Pause and actually write your answers before moving on. This is exactly the kind of reasoning exam questions expect.
Reading Graphs and Tables Across Subjects
Shared Data Skills
Physics, chemistry, and biology exams use the same data skills: identifying variables, reading axes, and paying attention to units in graphs and tables.
Variables and Axes
Independent variables are changed on purpose, dependent variables are measured, and controlled variables are kept the same. The x-axis is usually independent; the y-axis is dependent.
Physics Graph Example
A temperature vs time graph for heating water might rise, then flatten at 100 °C. Physics asks for rate of temperature increase; chemistry asks why it flattens (boiling and latent heat).
Biology Bar Chart Example
A bar chart of mean plant height under red, blue, and green light can lead to biology questions about growth and photosynthesis, plus chemistry and physics links to light and pigments.
Exam Data Skills
Key steps: describe trends, read values with units, calculate simple quantities, then explain patterns using ideas from physics, chemistry, and biology.
Quiz: Interpreting a Mixed-Topic Graph
Use this imagined description: A line graph shows rate of photosynthesis (on the y-axis) vs light intensity (on the x-axis). The line rises steeply at first, then levels off into a flat line.
Answer the question below.
Which explanation best links biology and physics to describe why the graph levels off at high light intensity?
- The plant stops absorbing light because light has no energy at high intensity.
- Another factor, such as carbon dioxide concentration or temperature, becomes limiting even though light intensity keeps increasing.
- The law of conservation of energy is broken at high light intensity, so photosynthesis cannot continue.
- The chlorophyll molecules disappear when the light intensity is high, so photosynthesis stops permanently.
Show Answer
Answer: B) Another factor, such as carbon dioxide concentration or temperature, becomes limiting even though light intensity keeps increasing.
At first, more light (a physics idea: more photons per second) increases the rate of photosynthesis (a biology process). When the graph levels off, a different factor becomes limiting, such as CO2 or temperature. Energy is still conserved; the plant simply cannot use extra light without enough of the other reactants.
Common Exam Question Types and Strategies
Recognizing Question Types
Exam questions in all sciences repeat patterns: recall, data interpretation, calculation, explanation, and planning/evaluating. Knowing the type guides your answer.
Recall Questions
Recall questions want definitions or facts. Example: "State the law of conservation of energy." Use precise wording in one clear sentence.
Data Interpretation
Data questions use graphs or tables. First describe the trend, then back it up with numbers and units before you explain why it happens.
Calculations
Calculation questions need formulas, substitution with units, clear working, and sensible rounding. This is common in physics and chemistry.
Explanations and Planning
Explanation questions need step-by-step reasoning. Planning questions need variables, method, safety, and how you will collect reliable data.
Use Command Words
Underline command words like state, describe, explain, calculate, compare, evaluate. Make sure your answer matches what the command word asks.
Interactive: Outline a Simple Investigation
Interactive: Outline a Simple Investigation
Task: Plan an investigation that connects electricity (physics) and chemistry.
Question to investigate:
How does the current in an electrolysis circuit affect the mass of metal deposited on an electrode?
- Identify variables
- Independent variable (you change):
- Dependent variable (you measure):
- Two important controlled variables:
- Basic method (bullet points)
Write 4–6 short steps, including:
- How you will set up the circuit (power supply, electrodes, solution, ammeter).
- How long you will run the current for.
- How you will measure the mass change.
- Link to big ideas
In 2–3 sentences, explain how conservation of charge (physics) and conservation of mass (chemistry) appear in this experiment.
Write your plan. Then check: would another student be able to follow it and get similar results?
Mixed-Topic Exam-Style Question
A student eats a sandwich and then goes for a run. The table shows an energy transfer.
- Chemical energy in sandwich: 2 000 kJ
- Useful mechanical (kinetic) energy in muscles: 400 kJ
Answer the question below.
What is the efficiency of transferring chemical energy from the sandwich into useful mechanical energy during the run?
- 20%
- 25%
- 50%
- 80%
Show Answer
Answer: B) 25%
Efficiency = (useful output energy / total input energy) × 100. Here, efficiency = (400 kJ / 2 000 kJ) × 100 = 0.2 × 100 = 20%. Wait: check carefully: 400 / 2 000 = 0.2, so 20%, which corresponds to option A, not B. So the correct answer is 20%.
Key Term Review: Connecting the Sciences
Flip these cards to review important terms that connect physics, chemistry, and biology.
- Conservation of energy
- A law stating that energy cannot be created or destroyed, only transferred from one object to another or transformed from one form to another in a closed system.
- Conservation of mass
- In ordinary chemical and biological processes, the total mass of a closed system remains constant; atoms are rearranged but not created or destroyed.
- System
- The part of the universe you are focusing on in an experiment or problem. Everything outside it is the surroundings.
- Independent variable
- The variable that is deliberately changed in an experiment to see its effect on the dependent variable.
- Dependent variable
- The variable that is measured in an experiment; it changes in response to the independent variable.
- Controlled variable
- A variable that is kept constant during an experiment to make the test fair and ensure valid results.
- Energy efficiency
- The percentage of input energy that is converted into useful output energy. Calculated as (useful output / total input) × 100.
- Photosynthesis
- A process in plants and some microorganisms where light energy is converted into chemical energy stored in glucose, using carbon dioxide and water.
- Cellular respiration
- A process in cells that releases energy from glucose using oxygen, producing carbon dioxide, water, and energy (ATP and heat).
Key Terms
- graph
- A visual representation of data showing the relationship between variables, often using axes for independent and dependent variables.
- energy
- The ability to do work or cause change; appears in many forms such as kinetic, potential, thermal, electrical, and chemical.
- matter
- Anything that has mass and takes up space, made of atoms and molecules.
- variable
- Any factor that can change in an experiment, including independent, dependent, and controlled variables.
- efficiency
- A measure of how much input energy or power is converted into useful output; given as a percentage.
- closed system
- A system where no matter and/or energy can enter or leave; used as an ideal model in many exam questions.
- photosynthesis
- The process by which plants and some microorganisms convert light energy into chemical energy stored in glucose.
- conservation law
- A rule in science that states a particular quantity, such as energy or mass, stays constant in a closed system.
- data interpretation
- The skill of reading, describing, and drawing conclusions from data in tables, graphs, or charts.
- cellular respiration
- The process cells use to release energy from glucose, usually using oxygen, producing carbon dioxide, water, and energy.