lab

Using Effervescent Tablets to Explore the Scientific Method

The purpose of this lab is to learn and reinforce the standard steps used in science- The Scientific Method.

Explaining the steps of the scientific method
· Observe and Question: Just as early scientists such as Ptolemy and Copernicus observed phenomena and asked why and how things happen, scientists today begin the process of experimentation in the same way.
· Conduct research. It is impossible to form a clear and testable hypothesis without an understanding of what is already known about a question or observation. In science, before a hypothesis can be formed, research must be done. Scientific journals and other scientific writings can provide explanations, details, and background information so that a reasonable hypothesis can be formed.
· Form a hypothesis. A hypothesis is a statement, that is clear and concise. It is testable and can be supported or refuted. The language in a hypothesis should be objective, not subjective. For example, in the figure above the hypothesis is “The amount of sunlight a plant receives affects the growth of the plant”. Both “amount of sunlight” and “growth” can be measured. This hypothesis can be tested, and conclusions easily made. The hypothesis “South-facing windows are better for plants” is not clear or testable. “South-facing window” can have many interpretations, as does “better”.
· Experiment. A well-designed experiment has several features:
. A Control: a groups of test subjects that is set aside and not manipulated. This group serves as a basis for comparison. In the figure above, five plants are set aside and receive the ‘normal’ amount of daily sunlight in the window.
. Clear Variables: Two main types of variables in a study are DEPENDENT variables and INDEPENDENT variables. Dependent variables are also called Response variables. In a study, the dependent variable is the one that responds to changes in the Independent variable (a.k.a. the test variable). Data is typically recording the dependent variable. The Independent variable is the one that is manipulated or changed in order to see an effect in the response variable. In the example above, the dependent variable is GROWTH while the independent variable is the amount of sunlight.
. Standard conditions: In a study, the only variable that should change across subjects is the Independent Variable. All other potential variables or conditions should be kept the same. In the example above, the seed type, pots, water, and nutrients are all things that could potentially affect the Dependent Variable, and so these must all be carefully controlled or standardized.
· Analyze data and form conclusions. Data is collected, summarized, and often graphed to show relationships or trends.
. There are two types of data: QUANTITATIVE and QUALITATIVE. Quantitative data is data that is measured (often with an instrument of some kind), recorded as numbers, and objective (i.e. no room for interpretation). Qualitative data is data that is described rather than measured, recorded as words not numbers, and can be subjective because it is often impressions or observations. For example, plant growth could be recorded in two ways. Quantitatively, you could snip off each plant at the soil level and measure the weight on a scale. Quantitatively, you could record the size of the plant as ‘small, medium, or large’. Quantitative data is often summarized and graphed.
. Usually, the independent variable is shown on the x-axis while the dependent variable is shown on the y-axis.

. Once the data is summarized and graphed, you may be able to make a conclusion. This step revisits the original hypothesis, for example “The amount of daily sunlight a plant receives affects the growth of the plant”. The results may support or refute your hypothesis. If the results refute your original hypothesis or if the data is inconclusive, you may retest your original hypothesis or revise it and then test this new hypothesis. The process may become a continuous loop of testing and revising hypotheses.
· Report results. In scientific studies, results and conclusions are shared, often in peer-reviewed journals or publications. This allows others to critique the work, and to repeat it in order to test the hypothesis. This continual process of testing and retesting hypotheses improves our understanding of the natural world and how it works.

The Scientific Method is DEDUCTIVE rather than INDUCTIVE. In deductive reasoning, specific results are predicted from a general premise. Hypothesis testing uses deduction. In Inductive reasoning, a general conclusion is drawn from a number of observations.

Deductive

Inductive

· All living things are made of cells.
· Bacteria are living things.
· Bacteria are made of cells.

· Bacteria are made of cells.
· Fungi are made of cells.
· Plants are made of cells
· Animals are made of cells.
· All living things are made of cells.

Using Effervescent Tablets to Explore the Scientific Method

Learning Objectives:

· Follow the steps of the scientific method to test a hypothesis
· Accurately collect, summarize, and analyze data
· Create a graph and use it to make conclusions

We will be using the steps of the Scientific Method to test a basic chemical property: Endothermic vs. Exothermic reactions.

ENDO = ‘inside’

EXO = ‘outside’

THERMIC = ‘heat’

An endothermic reaction takes place when energy is absorbed from surroundings in the form of heat, and exothermic is when energy is released from the system into the surroundings. An endothermic reaction will cool the surroundings because the reactions draw the heat energy into themselves. As heat leaves an area, the temperature will drop. Exothermic reactions, on the other hand, make the surrounding environment hotter since heat energy is released.
·
Endothermic examples:
evaporation as sweating cools a person down, melting ice
·
Exothermic examples
: fire, the reaction of mixing epoxy, the reaction used in hand-warmers

Exercise 1: Effect of tablet number on temperature

Materials

10 Alka-Seltzer® Tablets (or similar effervescent tablets)
4 Disposable Cups of the same type (plastic, Styrofoam, paper, etc)
Distilled Water
½ cup measuring cup
1 Laboratory Thermometer or Temperature Probe (found in lab kit)

Procedure

Safety: Use safety glasses or goggles when conducting this investigation. Keep solutions and tablets out of reach of children and pets. Safely dispose of all solutions down the drain immediately after procedure.

1. Place ½ cup (~120 ml) of distilled water in each of 4 cups or beakers. Stir the water in each with the thermometer and ensure that the water in each cup or beaker is at the same temperature. Record this as the temperature with 0 tablets in Data Table 1. TAKE A CLOSE-UP PHOTO OF YOUR THERMOMETER READING AT THIS STEP, TO BE INCLUDED IN THE POST LAB REVIEW
2. Place a thermometer in the water of the first container, add 1 effervescent tablet, and stir until the solution temperature remains constant.
3. Record the temperature with 1 tablet in Data Table 1.
4. Record ‘type of reaction’ in Data Table 1.
5. Place the thermometer in the next container, add 2 effervescent tablets, and stir until the solution temperature remains constant. Record temperature and ‘type of reaction’ in Data Table 1.
6. Repeat step 5 with three tables, and again with four tables. TAKE A CLOSE-UP PHOTO OF YOUR FINAL THERMOMETER READING, TO BE INCLUDED IN THE POST LAB REVIEW.
7. Prepare a graph of your data. It should be similar to the one shown below. You may use a graphing software such as Excel, or you may hand draw the graph using the graph paper provided.

8. Safely dispose of all solutions down the drain.

Exercise: Testing a new hypothesis

In this exercise, you will choose a new independent variable, formulate a new hypothesis, design a simple experiment, test it, and make conclusions. This procedure should build off of the one use in Exercise 1. Here are some examples of what you might decide to alter and retest:
· You could choose a different type of water (i.e. tap water, well water, sparkling water). **FOR SAFETY REASONS, DO NOT CHOOSE OTHER CHEMICALS TO TEST IN PLACE OF WATER.

· You could choose a different type of effervescent tablet (i.e. use the ‘Cold and Flu’ formula instead of the ‘Antacid’ formula.
· You could choose a different starting temperature (i.e. use room temperature, ice water, and hot water to see the temperature change using the same number of tablets)
· You could continue to add tablets (using 5, 6, 7, etc) to see if the trend continues or if there is a maximum number of tablets that produces an effect)
· You could break a tablet up and test ½, ¼, etc to see if the same trend occurs.
· You could choose a different type of cup (i.e. plastic vs Styrofoam vs ceramic, etc)
· You could use different amounts of water in each cup (i.e. instead of ½ cup in each, try testing ¼ vs ½ vs 1 vs 2 cups, each with the same number of tablets
Remember- you must standardize all other conditions other than your Independent variable. Your dependent variable should be the same as in Exercise 1.

Materials

Alka-Seltzer® Tablets (or similar effervescent tablets)- the number depends on YOUR test

Disposable Cups
Water
measuring cups
1 Laboratory Thermometer or Temperature Probe (found in lab kit)

Procedure

Safety: Use safety glasses or goggles when conducting this investigation. Keep solutions and tablets out of reach of children and pets. Safely dispose of all solutions down the drain immediately after procedure.

1. BEFORE you begin,
a. formulate your hypothesis and state in in Data Table 2. Remember, a hypothesis is a statement, not a question. For example, “Temperature will decrease more in tap water vs distilled water”.
b. Write out a detailed procedure in Data Table 2.
c. In Data Table 3, write in YOUR independent variable and the levels or categories you will test.
2. Conduct your procedure, collecting your temperature data and recording results in Data Table 2.
3. Prepare a graph of your data.
4. Safely dispose of all solutions down the drain.

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