Worksheet for identifying variables in scientific experiments.

Problem Overview:

The task involves identifying and highlighting variables in three different experimental scenarios. The goal is to distinguish between independent variables, dependent variables, and controlled variables.

#### Definitions:
1. Independent Variable: The variable that is manipulated or changed by the experimenter.
2. Dependent Variable: The variable that is measured or observed; it depends on the independent variable.
3. Controlled Variables: Factors that are kept constant throughout the experiment to ensure that any changes in the dependent variable are due to the independent variable.

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Scenario 1: Nicholas's Experiment

Description:
Nicholas planted five carrot seeds in each of three different milk cartons filled with the same soil. He placed one carton outside in the sun, one on a counter in classroom light, and one inside a dark closet. He watered each carton daily and measured plant growth after 15 days.

#### Step-by-Step Analysis:
1. Independent Variable: The factor that Nicholas changed was the location of the cartons (outside in the sun, on the counter in classroom light, and inside a dark closet). This is the variable he manipulated to observe its effect on plant growth.
- Highlight in pink: "one on the counter in the classroom light, one on the counter in the classroom light, and one inside a dark closet."

2. Dependent Variable: The outcome that Nicholas measured was the height of the plants after 15 days. This is what changed in response to the independent variable.
- Highlight in yellow: "measured how tall each plant grew."

3. Controlled Variables: Factors that were kept constant include:
- The number of seeds in each carton (five seeds).
- The type and amount of soil in each carton.
- The amount of water given to each carton (25 mL daily).
- The duration of the experiment (15 days).
- Highlight in green: "five carrot seeds," "same level with the same kind of soil," "25 ml of water each day at 11 am," "watered all three cartons every day for fifteen days."

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Scenario 2: Stacy's Experiment

Description:
Stacy chose 2 fat-free chips, baked chips, and regular potato chips of the same size. She crushed them, placed them on brown paper bags, waited 30 minutes, and measured the widest part of the grease stain for each chip.

#### Step-by-Step Analysis:
1. Independent Variable: The factor Stacy changed was the type of chips (fat-free, baked, and regular potato chips). This is the variable she manipulated to observe its effect on the grease stain.
- Highlight in pink: "2 fat free chips, baked chips, and regular potato chips."

2. Dependent Variable: The outcome Stacy measured was the widest part of the grease stain for each chip. This is what changed in response to the independent variable.
- Highlight in yellow: "measure the widest part of the grease stain for each chip."

3. Controlled Variables: Factors that were kept constant include:
- The size of the chips (all chips were the same size).
- The method of crushing the chips.
- The type of paper bag used (brown paper bags).
- The waiting time before measuring (30 minutes).
- Highlight in green: "all about the same size," "then she crushed them each on a brown paper bag and waited 30 minutes."

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Scenario 3: Lawrence's Experiment

Description:
Lawrence chose three identical paper cups and poked a small hole in the bottom of each. He filled each cup with the same level of water but used different materials (soil, sand, pebbles) in each cup. He then poured 1 cup of water into each cup and measured the amount of water drained from each cup after holding it over a tray for one minute.

#### Step-by-Step Analysis:
1. Independent Variable: The factor Lawrence changed was the type of material in each cup (soil, sand, pebbles). This is the variable he manipulated to observe its effect on water drainage.
- Highlight in pink: "different material - soil, sand, or pebbles."

2. Dependent Variable: The outcome Lawrence measured was the amount of water drained from each cup. This is what changed in response to the independent variable.
- Highlight in yellow: "measured the amount of water that drained into the tray from each cup."

3. Controlled Variables: Factors that were kept constant include:
- The size and type of paper cups.
- The size of the holes in the bottom of each cup.
- The amount of water poured into each cup (1 cup).
- The duration of the experiment (1 minute).
- Highlight in green: "three identical paper cups," "poked a similar hole in the bottom of each cup," "filled each cup to the same level," "poured 1 cup of water into each cup at a time and held it over the tray for one minute."

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Final Answer:

For each scenario, the variables are highlighted as follows:

1. Nicholas's Experiment:
- Independent Variable (pink): "one on the counter in the classroom light, one on the counter in the classroom light, and one inside a dark closet."
- Dependent Variable (yellow): "measured how tall each plant grew."
- Controlled Variables (green): "five carrot seeds," "same level with the same kind of soil," "25 ml of water each day at 11 am," "watered all three cartons every day for fifteen days."

2. Stacy's Experiment:
- Independent Variable (pink): "2 fat free chips, baked chips, and regular potato chips."
- Dependent Variable (yellow): "measure the widest part of the grease stain for each chip."
- Controlled Variables (green): "all about the same size," "then she crushed them each on a brown paper bag and waited 30 minutes."

3. Lawrence's Experiment:
- Independent Variable (pink): "different material - soil, sand, or pebbles."
- Dependent Variable (yellow): "measured the amount of water that drained into the tray from each cup."
- Controlled Variables (green): "three identical paper cups," "poked a similar hole in the bottom of each cup," "filled each cup to the same level," "poured 1 cup of water into each cup at a time and held it over the tray for one minute."

Boxed Final Answer:
\boxed{
\text{See detailed explanations above for highlighting the variables in each scenario.}
}