Data & Evidence
A cube has a mass of 200 g and a volume of 100 mL. Will it sink or float in water? Explain.
Density = 2 g/mL → sinks (greater than water)
What is the independent variable when testing which materials conduct electricity?
Type of material
A circuit doesn’t work. The battery is dead. What type of error is this?
Equipment error
Identify the energy transformation: battery → wire → bulb
Chemical → electrical → light + heat
Why must a circuit be closed?
To allow continuous flow of electrons
A material floats AND conducts electricity. What can you infer?
Low density but conductive (possible composite or hollow metal)
A student records:
Object A: floats halfway
Object B: sinks slowly
Object C: floats completely
Rank them from greatest to least density.
B > A > C
Design a test to determine if an unknown material is a thermal insulator.
Expose to heat, measure temperature change over time
A student forgets to record volume but still calculates density. What’s the issue?
Missing data → invalid conclusion
Why does a flashlight get warm after being on for a long time?
Energy lost as heat during transformation
If you replace a metal wire with plastic, what happens and why?
Circuit stops; plastic is an insulator
Why are metals used in wires but rubber used as coating?
Conductors inside, insulators outside for safety
Two substances dissolve in water at different rates. What variable must be controlled to make this a fair comparison?
Temperature, amount of solute, stirring, volume of water (any valid control)
A student wants to compare solubility of sugar and salt. Identify a flaw:
They use different amounts of water.
Uncontrolled variable → invalid comparison
In a density test, air bubbles stick to the object. How does this affect results?
Makes object seem less dense (more buoyant)
Compare energy transformations in a flashlight vs a battery-powered fan.
Flashlight → light; fan → motion; both include heat loss
A bulb is dim. List TWO possible causes.
Weak battery, high resistance, poor connections
You must design a boat that carries weight without sinking. What properties matter most?
Density, volume, shape (displacement)
A material conducts electricity but not heat well. What does this tell you about its properties?
Conductivity can differ by type; electrical ≠ thermal conductivity
Create a procedure to test relative density using only water, a scale, and a graduated cylinder.
Measure mass, measure volume via displacement, calculate density, and compare
A student says: “This object is heavier, so it will sink.” Why is this reasoning flawed?
Mass alone doesn’t determine sinking; density does
A device converts electrical energy into motion AND sound. What might it be and why?
Motorized device (fan, toy); motion creates vibrations → sound
Compare series vs parallel circuits in terms of energy transfer (conceptual, not vocabulary-heavy).
Series: shared energy; Parallel: multiple pathways, more consistent output
A device fails: it doesn’t light OR move. Analyze both matter AND energy causes.
Material issue (insulator), circuit break, energy not transferring
A student claims: “If it floats, it has no mass.” Use evidence to refute this.
Floating depends on density, not the absence of mass; floating objects still have measurable mass
Design an investigation to compare BOTH electrical conductivity AND thermal conductivity of the same materials.
Two controlled tests, same materials; measure current flow vs heat transfer
Identify TWO possible sources of error in this investigation:
Water temperature can affect density and solubility, while object shape can affect drag and displacement observations.
Trace ALL energy transformations in a system where a battery powers a buzzer and light simultaneously.
Chemical → electrical → sound + light + heat
A student adds more bulbs to a circuit and notices dimming. Explain using energy transfer reasoning.
Energy is distributed across more loads → less energy per bulb
Claim: Copper wire coated with plastic is the best material for creating a safe and efficient electrical circuit system.
Claim: Copper wire coated with plastic is the best material for creating a safe and efficient electrical circuit system.
Reasoning: Copper is a strong conductor that allows electrical energy to flow easily through a circuit. The plastic coating acts as an insulator, helping protect users from electric shock and preventing electrical energy from escaping the wire.
Evidence: In the investigation, copper allowed the bulb to light brightly, showing that electricity flowed efficiently. The plastic coating also prevented direct contact with the metal wire, making the circuit safer to use.