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Scientific Inquiry and Skills - Identifying Variables (Independent, Dependent, Control)

Grade 6IB

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Independent Variable (IV): The factor that is intentionally changed or manipulated by the scientist in an experiment. It is the 'cause' in a cause-and-effect relationship and is typically plotted on the xx-axis.

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Dependent Variable (DV): The factor that is observed, measured, or recorded as a result of the changes made to the independent variable. It is the 'effect' and is typically plotted on the yy-axis.

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Controlled Variables (CV): These are the factors that are kept constant throughout the experiment to ensure a fair test. If these are not controlled, they may influence the results, making the experiment invalid.

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Fair Test: A scientific investigation where only the independent variable is changed, and all other variables are kept the same to ensure that the DVDV is only affected by the IVIV.

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Hypothesis Formulation: A scientific prediction often expressed in the format: 'If the IndependentVariableIndependent Variable is [increased/decreased], then the DependentVariableDependent Variable will [increase/decrease/change] because...'

📐Formulae

y=f(x)y = f(x) where yy is the Dependent Variable and xx is the Independent Variable.

ΔIV→ΔDV\Delta IV \rightarrow \Delta DV (A change in the Independent Variable leads to a change in the Dependent Variable).

Validity∝Control of Variables\text{Validity} \propto \text{Control of Variables}

💡Examples

Problem 1:

A student wants to investigate how the temperature of water affects the time it takes for 5g5g of sugar to dissolve. Identify the variables.

Solution:

Independent Variable: Temperature of the H2OH_2O; Dependent Variable: Time taken for sugar to dissolve (seconds); Controlled Variables: Mass of sugar (5g5g), volume of H2OH_2O, and the stirring speed.

Explanation:

The scientist changes the temperature (IV) to see how it impacts the speed of dissolving (DV), while keeping everything else the same (CV) to ensure the results are reliable.

Problem 2:

An experiment measures the volume of O2O_2 gas produced by a plant when placed at different distances from a light source.

Solution:

Independent Variable: Distance from the light source (cmcm); Dependent Variable: Volume of O2O_2 produced (mLmL); Controlled Variables: Type of plant, concentration of CO2CO_2 in the water, and the duration of the experiment.

Explanation:

Distance is the factor being manipulated to observe the change in oxygen production, which indicates the rate of photosynthesis.

Problem 3:

Identify the variables in a study testing if the mass of a ball affects the distance it travels when rolled down a ramp.

Solution:

Independent Variable: Mass of the ball (gg); Dependent Variable: Distance traveled (mm); Controlled Variables: Height of the ramp, angle of the ramp, and the surface material of the floor.

Explanation:

To isolate the effect of mass, the physical properties of the ramp and floor must remain identical for every trial.