Variables in Heat Transfer - Middle School Physical Science
Card 1 of 25
Which variable should you identify when changing how hot or cold the surroundings are?
Which variable should you identify when changing how hot or cold the surroundings are?
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Ambient (surrounding) temperature, $T_{amb}$. The temperature difference with surroundings affects heat transfer rate.
Ambient (surrounding) temperature, $T_{amb}$. The temperature difference with surroundings affects heat transfer rate.
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Which variable should you identify when changing the thickness of an insulating layer?
Which variable should you identify when changing the thickness of an insulating layer?
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Thickness of material, $d$. Thicker insulation reduces the rate of heat transfer.
Thickness of material, $d$. Thicker insulation reduces the rate of heat transfer.
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Which variable should you identify when changing how well two objects touch each other?
Which variable should you identify when changing how well two objects touch each other?
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Contact area between objects, $A$. Larger contact area allows more heat to flow between objects.
Contact area between objects, $A$. Larger contact area allows more heat to flow between objects.
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Which variable should you identify when comparing heating by conduction, convection, or radiation?
Which variable should you identify when comparing heating by conduction, convection, or radiation?
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Mode of heat transfer. Each mode transfers thermal energy through different mechanisms.
Mode of heat transfer. Each mode transfers thermal energy through different mechanisms.
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What formula links power, time, and thermal energy transferred in many lab setups?
What formula links power, time, and thermal energy transferred in many lab setups?
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$Q = Pt$. Power times time gives total energy transferred in many heating experiments.
$Q = Pt$. Power times time gives total energy transferred in many heating experiments.
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Which variable should you identify when the heater setting or burner output is changed?
Which variable should you identify when the heater setting or burner output is changed?
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Power (rate of energy transfer), $P$. Higher power settings transfer energy faster to the substance.
Power (rate of energy transfer), $P$. Higher power settings transfer energy faster to the substance.
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Which control variable should be kept the same to compare $\Delta T$ fairly between trials?
Which control variable should be kept the same to compare $\Delta T$ fairly between trials?
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Initial temperature, $T_i$. Starting all samples at the same temperature ensures fair comparison.
Initial temperature, $T_i$. Starting all samples at the same temperature ensures fair comparison.
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Identify the independent variable: You vary the mass and measure $\Delta T$ after heating.
Identify the independent variable: You vary the mass and measure $\Delta T$ after heating.
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Mass, $m$. You're changing mass to see its effect on temperature change.
Mass, $m$. You're changing mass to see its effect on temperature change.
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Identify the dependent variable: You vary heating time and record the temperature outcome.
Identify the dependent variable: You vary heating time and record the temperature outcome.
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Temperature change, $\Delta T$. Temperature change is what you measure as the outcome.
Temperature change, $\Delta T$. Temperature change is what you measure as the outcome.
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Which variable should be controlled: You compare materials but want a fair test of $c$?
Which variable should be controlled: You compare materials but want a fair test of $c$?
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Keep $m$ and $Q$ (or $P$ and $t$) the same. Equal mass and energy input isolates the effect of specific heat.
Keep $m$ and $Q$ (or $P$ and $t$) the same. Equal mass and energy input isolates the effect of specific heat.
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Identify the missing variable to record: You measure $T_i$ and $T_f$ to find $\Delta T$.
Identify the missing variable to record: You measure $T_i$ and $T_f$ to find $\Delta T$.
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Final temperature, $T_f$. You need both temperatures to calculate the change.
Final temperature, $T_f$. You need both temperatures to calculate the change.
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Which variable should be held constant when testing the effect of surface area on cooling rate?
Which variable should be held constant when testing the effect of surface area on cooling rate?
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Type of material (and starting $T_i$). Keeping these constant isolates surface area as the only variable.
Type of material (and starting $T_i$). Keeping these constant isolates surface area as the only variable.
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Which variable should you identify if you change how much material is being heated or cooled?
Which variable should you identify if you change how much material is being heated or cooled?
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Mass of the substance, $m$. More mass requires more energy for the same temperature change.
Mass of the substance, $m$. More mass requires more energy for the same temperature change.
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What is the relationship between thermal energy, mass, specific heat, and temperature change?
What is the relationship between thermal energy, mass, specific heat, and temperature change?
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$Q = mc\Delta T$. Shows how thermal energy depends on mass, specific heat, and temperature change.
$Q = mc\Delta T$. Shows how thermal energy depends on mass, specific heat, and temperature change.
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What property of a material explains why equal heating can produce different $\Delta T$ values?
What property of a material explains why equal heating can produce different $\Delta T$ values?
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Specific heat capacity, $c$. Materials with high $c$ need more energy per degree of temperature change.
Specific heat capacity, $c$. Materials with high $c$ need more energy per degree of temperature change.
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Which variable must be identified when comparing temperature changes of different substances?
Which variable must be identified when comparing temperature changes of different substances?
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Type of substance (material). Different materials heat up at different rates due to their properties.
Type of substance (material). Different materials heat up at different rates due to their properties.
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Which variable is commonly manipulated to change the amount of thermal energy transferred?
Which variable is commonly manipulated to change the amount of thermal energy transferred?
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Heating time, $t$. Longer heating transfers more thermal energy to the substance.
Heating time, $t$. Longer heating transfers more thermal energy to the substance.
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What is the formula for temperature change used as a measured outcome?
What is the formula for temperature change used as a measured outcome?
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$\Delta T = T_f - T_i$. Subtract initial from final temperature to find the change.
$\Delta T = T_f - T_i$. Subtract initial from final temperature to find the change.
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What is the dependent variable in a temperature-change investigation?
What is the dependent variable in a temperature-change investigation?
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Temperature change, $\Delta T$. It's what you measure to see how thermal energy affects the system.
Temperature change, $\Delta T$. It's what you measure to see how thermal energy affects the system.
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Identify the best controlled variable to reduce heat loss effects when comparing two trials in the same room.
Identify the best controlled variable to reduce heat loss effects when comparing two trials in the same room.
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Same container and insulation conditions. Minimizes differences in heat loss between trials.
Same container and insulation conditions. Minimizes differences in heat loss between trials.
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What environmental variable should be controlled because it affects heat transfer to or from the surroundings?
What environmental variable should be controlled because it affects heat transfer to or from the surroundings?
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Ambient (room) temperature. Temperature difference drives heat transfer to/from surroundings.
Ambient (room) temperature. Temperature difference drives heat transfer to/from surroundings.
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What surface-related variable should be controlled because it affects heat transfer to air or water?
What surface-related variable should be controlled because it affects heat transfer to air or water?
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Exposed surface area. Larger areas transfer heat faster to surroundings.
Exposed surface area. Larger areas transfer heat faster to surroundings.
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Which variable should be controlled to compare conduction through different solids fairly?
Which variable should be controlled to compare conduction through different solids fairly?
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Thickness (same length of material). Same thickness ensures fair comparison of conduction rates.
Thickness (same length of material). Same thickness ensures fair comparison of conduction rates.
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Identify the dependent variable when investigating how insulation thickness affects cooling.
Identify the dependent variable when investigating how insulation thickness affects cooling.
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Rate of temperature change, $\frac{\Delta T}{\Delta t}$. Measures how fast temperature drops per unit time.
Rate of temperature change, $\frac{\Delta T}{\Delta t}$. Measures how fast temperature drops per unit time.
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What variable should be held constant when comparing cooling curves for different liquids in identical cups?
What variable should be held constant when comparing cooling curves for different liquids in identical cups?
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Initial temperature, $T_i$. Same starting temperature ensures fair cooling comparison.
Initial temperature, $T_i$. Same starting temperature ensures fair cooling comparison.
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