Reaction Rates: Speed It Up with Temperature!

Overview

Teach your students how temperature affects chemical reaction rates in this highly visual experiment! Students will investigate color change during the reaction of food color with bleach, and measure the reaction times using Google's Science Journal app.

NGSS Alignment

This lesson helps students prepare for these Next Generation Science Standards Performance Expectations:

• HS-PS1-5. Apply scientific principles and evidence to provide an explanation about the effects of changing the temperature or concentration of the reacting particles on the rate at which a reaction occurs.

This lesson focuses on these aspects of NGSS Three Dimensional Learning:

Science & Engineering Practices	Disciplinary Core Ideas	Crosscutting Concepts
Planning and Carrying Out Investigations. Make directional hypotheses that specify what happens to a dependent variable when an independent variable is manipulated. Asking Questions and Defining Problems. Ask questions that can be investigated within the scope of the school laboratory, research facilities, or field (e.g., outdoor environment) with available resources and, when appropriate, frame a hypothesis based on a model or theory. Analyzing and Interpreting Data Analyze data using tools, technologies, and/or models (e.g., computational, mathematical) in order to make valid and reliable scientific claims or determine an optimal design solution. Constructing Explanations and Designing Solutions. Make a quantitative and/or qualitative claim regarding the relationship between dependent and independent variables. Apply scientific ideas, principles, and/or evidence to provide an explanation of phenomena.	PS1.B: Chemical Reactions. Chemical processes, their rates, and whether or not energy is stored or released can be understood in terms of the collisions of molecules and the rearrangements of atoms into new molecules, with consequent changes in the sum of all bond energies in the set of molecules that are matched by changes in kinetic energy. PS3.A: Definitions of Energy. These relationships are better understood at the microscopic scale, at which all of the different manifestations of energy can be modeled as a combination of energy associated with the motion of particles and energy associated with the configuration (relative position of the particles). In some cases the relative position energy can be thought of as stored in fields (which mediate interactions between particles). This last concept includes radiation, a phenomenon in which energy stored in fields moves across space.	Cause and Effect. Changes in systems may have various causes that may not have equal effects. Scale, Proportion, and Quantity. Algebraic thinking is used to examine scientific data and predict the effect of a change in one variable on another (e.g., linear growth vs. exponential growth). Stability and Change. Change and rates of change can be quantified and modeled over very short or very long periods of time. Some system changes are irreversible.

Materials

Materials per group of 2–4 students:

• Flashlight
• 200 mL beaker
• Water (ice water, room temperature water and hot tap water)
• 3 mL graduated pipette
• 500 mL measuring cylinder
• 50 mL beaker (alternatively use a disposable 2 oz mini cup)
• Smartphone or tablet with Google's Science Journal app, available for free on Google Play for Android devices (version 4.4 or newer) or from the App Store for iOS devices (iOS 9.3 or newer).
  Note: This project was tested with the Android version of Science Journal in which light intensity is measured using the ambient light sensor and given in lux. The iOS version uses the phone's camera to measure brightness resulting in data expressed in EV (Exposure Value). Lux values and Exposure Values are not the same. Whereas Exposure Value is a base-2 logarithmic scale, the lux scale is linear. This might affect your data and result in different values and graphs when you are using an iOS version of the app—both versions will work for this project though. The graph examples given in the procedure show light intensity in lux.
• Object to lean the phone against, such as a textbook

Materials that can be shared in the classroom:

• Food coloring (McCormick, Yellow #5) (1 vial, 0.3 oz, for approximately 4 groups)
• Bleach (8.25% hypochlorite)
• Thermometer for liquids

Materials for teacher only:

• Mini cups (2 oz) or 50 mL beakers (3) for teacher demonstration