Name ___________________________ Block _________ Date _________

 

 

 

Chem Catalyst:

One of the questions that came up after our last lab was, “Does the amount of calcium chloride in the water change how warm the water gets in station D?”  I liked this question (mostly because it makes a great lab to explain how to design an experiment). 

HYPOTHESIS: Do you think the amount of calcium chloride (CaCl₂) will affect the final temperature?

RATIONALE: Explain why you answered the question the way you did.

 

 

Materials

50 ml beaker or plastic cup

Thermometer

Scoop or plastic spoon

6 scoops of calcium chloride

water

Clock

Graduated cylinder

Procedure

1. Place 40ml of water in a beaker.

2. Make a data table to record your data.

3. Record the initial temperature of the water (⁰C).

4. Measure 1 spoonful of calcium chloride (CaCl₂) into your beaker and stir for 2 min.
5. Record the temperature (⁰C) of the water at the end of 2 minutes.

6. Calculate the temperature change of the water.

7. Repeat the experiment with 0, 2, 3 spoons of calcium chloride.
8. Record data on the class data table.

 

 

 

Data: The effect of calcium chloride on water

 

Amount of chemical (scoops)	Change in temperature (°C)						Median change in (o C)
	Trials (Each group is one trial)						temperature
	1             2		3             4		5            6
0
1
2
3

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Lab. Questions:

1) Graph the data from this lab.  Remember that the dependent variable goes on the Y axis. Please label each axis and give the graph a title.

 

 

 

 

2) Is your hypothesis supported by the data in this lab?  Explain.

 

 

General science questions.

1) Do you have more confidence in one measurement or the median?  Explain why?

 

 

 

 

2) We call anything that changed a variable.  What varied or changed in this experiment? 

 

 

 

 

3) What did we purposely change?  We call this the “independent variable” because we are free and independent to change any variable we want and we chose that one.

 

 

 

 

4) What did we measure?  We call this the “dependent variable” because its change is dependent on our independent variable.

 

 

 

 

 

5) What things could have changed, but we tried to keep the constant?  We label these as “extraneous variables.”

 

 

 

 

6) The trial that is used to test if the equipment or procedure will affect your results is called the control group.  The control group will not have the independent variable present.  Which of our trials is the control for this experiment?

 

 

 

 

 

 

7) Use the answers to the previous questions to fill in the following table.

 

 

 

 

 

Analysis

1.   Did your results qualitatively match the accepted hypotheses, theories, or laws? You will need to ask me what the expected hypothesis is for this lab.  Explain.

 

 

 

 

 

2.   Look at your procedure and expectations.  Describe at least two sources of experimental error. 

 

 

 

 

 

3. What would you do differently to achieve better results (if I gave you the chance)?

 

 

 

 

 

 

 

4. What questions do you have that could lead to future experiments? Remember the guidelines for good questions from last lab.

 

 

 

 

 

 

 

     5. What experiments would you do to answer those questions?  Draw an experimental design         diagram to develop those experiments.

 

 

 

 

Name ___________________________ Block _________ Date _________

Homework

For each of the following experiments, draw an experimental design diagram and fill in all the blanks with the correct ideas from the experiment.  They are not necessarily chemical experiments, but that is fine for this assignment.

 

1. Ten seeds were planted in each of 5 pots that contained 500g of potting soil.  The pots were given the following amounts of distilled water each day for 40 days: Pot 1 = 50ml, Pot 2: 100ml, Pot 3: 150ml, Pot 4: 200ml, and Pot 5: 250ml.  Because pot 3 was the recommended amount of water, it will be used as the control.  The height of each plant was measured at the end of the experiment.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2. Gloria wanted to find out if the color of food would affect whether kindergarten children would select it for lunch.  She put food coloring into 4 identical bowls of mashed potatoes.  The colors were red, green, yellow, and blue.  Each child chose a scoop of potatoes of the color of their choice.  Gloria watched 100 students and recorded the number of students choosing each color.

 

 

 

 

 

 Homework/  Review

1. Classify the data collected in today’s lab as an observation or inference.  Explain.

 

 

 

 

2. Classify the data in today’s lab as qualitative or quantitative.  Explain.

 

 

 

 

Please classify the following as observation or inference AND qualitative or quantitative.

 

3. It is cold in here.

 

4. The sky is blue.

 

5. My dog is dreaming.

 

6. The asphalt is 100⁰C.

 

7. I have 10 fingers.

 

8. The molecules in my body are moving 10 times faster than those in the table.

 

 

 

 

Please list the steps of the  scientific method.

 

Scientific Method Notes

 

 

Scientific method:

          Observe

          Question

          Hypothesis

          Experiment

          Conclusion

 

Experimental design.

1.     Independent Variable (also called “you change it” variable and “manipulated” variable is the part of an experiment that you purposefully change.

2.     Dependent Variable (also called the “it changed” variable or “responding” variable is the one you measure.

3.     Extraneous variables – everything else that can change but we try to keep them constant.

4. We must perform enough trials so that a mistake in one sample will not mess up our results.  (For our purposes, 3-6 usually works well.)

 

Example of experimental design – my graduate studies with toads.