Science Study Guide

Assignments Covered

• CW Experimental Variables
• CW Photosynthesis: Energy and Mass
• CW Introduction to Food Chains and Webs

Experimental Variables

Key Definitions

• Independent Variable: The factor changed during the experiment.
• Control Variables: Factors kept constant to measure the effect of the independent variable.
• Dependent Variable: The factor measured or tested; the results of the experiment.

Practice Problems

1. Marcus's Plant Growth Experiment:

   • Independent Variable: Amount of sunlight (2h, 6h, 12h).
   • Dependent Variable: Height of the plants after two weeks.
   • Control Variables: Type of plant, amount of water, type of soil, size of pots.
   • Repetition: Repeat 3 times for consistent results.

2. Alicia's Chemical Reaction Experiment:

   • Independent Variable: Vinegar concentrations (10%, 25%, 50%).
   • Dependent Variable: Reaction time.
   • Control Variables: Amount of baking soda, amount of vinegar, room temperature.
   • Repetition: Repeat 3 times for consistent results.

3. Ethan's Music Experiment:

   • Independent Variable: Music genres (classical, rock, pop).
   • Dependent Variable: Change in heart rate.
   • Control Variables: Volume of music, listening duration, time of day.
   • Repetition: Repeat 3 times for consistent results.

Photosynthesis: Energy and Mass

Key Concepts

• Equation Interpretation: Coefficient (big number) × Subscript (small number) = Number of atoms.
• If missing: Coefficient = 1, Subscript = 1.

Practice Equations

1. Equation: 2H₂ + O₂ → 2H₂O

   • Left Side: Hydrogen: 4, Oxygen: 2
   • Right Side: Hydrogen: 4, Oxygen: 2

2. Equation: N₂ + 3H₂ → 2NH₃

   • Left Side: Nitrogen: 2, Hydrogen: 6
   • Right Side: Nitrogen: 2, Hydrogen: 6

3. Equation: 2Na + Cl₂ → 2NaCl

   • Left Side: Sodium (Na): 2, Chlorine (Cl): 2
   • Right Side: Sodium (Na): 2, Chlorine (Cl): 2

Food Chains and Webs

Key Definitions

• Producer: Makes food using sunlight (e.g., plants).
• Primary Consumers: Eat producers (e.g., deer, rabbits).
• Secondary Consumers: Eat primary consumers.
• Tertiary Consumers: Eat secondary consumers.
• Decomposers: Break down dead matter (e.g., bacteria, fungi).

Examples and Questions

1. Role of Organisms

   • Producers make their food (e.g., trees).
   • Primary consumers eat producers (e.g., rabbits).
   • Decomposers break down dead things.

2. Food Web Dynamics

   • Base: Producers.
   • Effect of Removal: Entire ecosystem can be affected.
   • Missing Components: The sun and decomposers.

Additional Concept

• KCALS: Measurement for energy.

Conclusion

• Understand and identify variables in experiments.
• Interpret chemical equations in photosynthesis.
• Comprehend the structure and dynamics of food chains and webs.

For further practice, explore the Food Chain Game on Sheppard Software.