Welcome to this experimental science test. We hope that you will find it interesting and worthwhile. Carefully read through these directions and the directions on the next page before you begin to work.

You may be part of a group for the first part of this exercise. Each group should carry out the experiment and collect the data together, but each student must record the data in his or her own booklet. Be sure to record the data exactly as you observe them. After the data have been collected, each student should answer the questions independently.

After you have finished your experiment and have recorded all of the data, you will be asked to answer some questions about the experiment and the data you recorded. Your answers must be written in this test booklet in the space provided. Make sure that you understand each question before you begin to write. At any time while you are writing your answers, you may look back at the directions for the experiment and the data you collected. Be sure that your answers are written as clearly and neatly as possible.

Before you turn the page, read the list of materials given below and check to make sure that your group has everything listed.

Materials in the Kit 500 ml beaker thermometer 10 ml graduated cylinder test tube brush dropper bottle of Solution A dropper bottle of Solution B tongs plastic measuring cup plastic gloves hot and cold tap water paper towels clock ruler goggles lab aprons pen or pencil

Effect of Temperature on Reaction Rate

Chemicals are made up of atom or groups of atoms, called molecules. When chemicals are mixed, the atoms or molecules may chemically react with each other to form new chemicals. The reaction rate, the time it takes a given number of the atoms or molecules to react, depends partly on their average speed. The average speed depends upon temperature.

Your task is to investigate the relationship between the temperature of a mixture of chemicals and its reaction rate.

Read all directions before beginning these experiments. WEAR YOUR GLOVES, GOGGLES, AND APRONS WHENEVER YOU HANDLE CHEMICALS OR HOT WATER. DO NOT GET THE REAGENTS ON YOUR CLOTHES OR SKIN. IF YOU GET ANY OF THE REAGENTS ON YOUR CLOTHES OR SKIN, WASH IT OFF IMMEDIATELY WITH LOTS OF WATER AND NOTIFY YOUR TEACHER. CLEAN UP ANY SPILLS IMMEDIATELY.

1. Wash the graduated cylinder and the thermometer in tap water and dry them with paper towels.

2. Allow water to run from the hot tap until the water is very warm. Using the plastic measuring cup, add 200 ml of water from the hot tap to the 500 ml beaker.

3. Stand the graduated cylinder in the beaker of water.

4. Make sure the bottles containing Solutions A and B are tightly closed. Using the tongs, carefully place the bottles of Solutions A and B in the beaker of hot water, next to the graduated cylinder. The bottles should be in the hot water.

5. Place the thermometer inside the graduated cylinder.

6. Wait 3 minutes.

7. Use the tongs to remove Solutions A and B from the beaker. While stirring with the thermometer, immediately add exactly 4 ml each of Solution A and Solution B to the graduated cylinder and record the start time to the nearest second. Continue to stir the mixture with the thermometer and observe the mixture's color. (Note: Stir gently so that the thermometer is not broken.) As soon as the mixture begins to turn yellow, record the temperature of the mixture and the end time (to the nearest second) in Table 1 on the next page.

8. Immediately pour the mixture in the waste disposal bucket or down the drain and flush the sink with running tap water. Thoroughly wash and dry the thermometer and the graduated cylinder.

9. Repeat Steps 2-8, substituting for the hot water the following mixtures of hot and cold tap water (the proportions do not have to be exact):

150 ml hot water and 50 ml cold water

100 ml hot water and 100 ml cold water

10. To find the elapsed time, subtract the start time from the end time. Express your answer in seconds and record it in Table 1. Show your calculations in the space below Table 1.

Laboratory Data

Table 1

Amount of hot water (ml)	Amount of cold water (ml)	Start time (hrs:mins:sec)	End time hrs:mins:sec)	Elapsed time (sec)	Temperature (°C)
200	0
150	50
100	100

Observations/Notes/Calculations:

Questions

Please answer the following questions by yourself.

1. On the sheet of graph paper below, plot the temperature (degrees Celsius, or °C) of the mixture versus the time (seconds, or sec) when the mixture began to turn yellow. Draw a smooth line that passes near (but not necessarily through) all the data points.

2. On the basis of your conclusion in Question 1, explain how the relationship between temperature and reaction rate is used in everyday life. Give an example to support your explanation.