Red Alert!

Grand Valley State University, Target Inquiry
Type Category
Instructional Materials
Student Guide , Lesson/Lesson Plan , Experiment/Lab Activity
This resource, vetted by NSTA curators, is provided to teachers along with suggested modifications to make it more in line with the vision of the NGSS. While not considered to be "fully aligned," the resources and expert recommendations provide teachers with concrete examples and expert guidance using the EQuIP rubric to adapted existing resources. Read more here.



This resource is a teacher guide to a lab where students investigate the effect of temperature and concentration on the rate of a reaction between red food dye and bleach. Using a spectrophotometer, students use absorbance to measure the rate of the reaction as the color of the reaction mixture changes from red to colorless. Student Guide available at the following URL:

Intended Audience

Educator and learner
Educational Level
  • High School
Access Restrictions

Free access with user action - The right to view and/or download material without financial barriers but users are required to register or experience some other low-barrier to use.

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.

Clarification Statement: Emphasis is on student reasoning that focuses on the number and energy of collisions between molecules.

Assessment Boundary: Assessment is limited to simple reactions in which there are only two reactants; evidence from temperature, concentration, and rate data; and qualitative relationships between rate and temperature.

This resource is explicitly designed to build towards this performance expectation.

Comments about Including the Performance Expectation
To address both variables in this PE, the teacher should organize lab groups to address at least 3 different temperatures and 3 different concentrations. This will generate enough data to establish a trend for temperature and concentration when analyzing the graphs as a class. The teacher should refer to the chemical equation (shown in student guide) for the hypochlorite ion reacting with the red ye to help explain why percent transmittance is a measure of this particular reaction. Students may need additional support in drawing a model of how their variable changes over time at the molecular level in the discussion questions. The discussion questions will help students use their evidence collected to develop their reasoning explanations.

Science and Engineering Practices

This resource is explicitly designed to build towards this science and engineering practice.

Comments about Including the Science and Engineering Practice
For students that have not yet worked with a spectrophotometer, the teacher should provide a demonstration about how to prepare the cuvettes and use the spectrophotometer properly. The lab may be more directed than inquiry, however, student discussion of constructing an explanation based on the data results and why each trend occurs at a molecular level can remain inquiry based as students support their explanation for the phenomena observed.

Disciplinary Core Ideas

This resource is explicitly designed to build towards this disciplinary core idea.

Comments about Including the Disciplinary Core Idea
Students may need support in making the connection that concentration changes the number of particles, and that temperature changes the kinetic energy of the molecules and therefore increases the number of collisions. The teacher will have to make it more explicit how changes in each variable are related to the collisions of molecules.

Crosscutting Concepts

This resource is explicitly designed to build towards this crosscutting concept.

Comments about Including the Crosscutting Concept
The desired effect of the activity is to increase the rate of the reaction between red food dye and bleach. The teacher should explicitly discuss the variables that are being investigated and how changes to these variables can be maximized to increase the reaction rate.

Resource Quality

  • Alignment to the Dimensions of the NGSS: This lab can be modified to be more scaffolded, but as written asks students to design a procedure (as a class) for investigating both the variables of temperature and concentration on reaction rates. There are notes to the teacher about common errors within the lab with tips to facilitate a discussion of how to limit them. This activity also connects to students’ lives through observing and manipulating variables of the specific reaction of bleaching.

  • Instructional Supports: The teacher guide provides tips and supports for facilitating the lab procedure, and examples of students responses. This lab assumes familiarity with spectrophotometers as well as understanding of absorbance and percent transmittance. Graphing is an additional skill being required by this lab, that some students may need additional support with.

  • Monitoring Student Progress: The teacher will need to guide both the pre-lab discussion and post-lab analysis. Further, the teacher should be actively circulating during the lab procedure, answering questions and supporting students in the technical steps and posing probing questions to evaluate what students are learning and what they are having difficulty with. This lab, or selected portions, could be used to formally or informally assess student understanding of the PE.

  • Quality of Technological Interactivity: If graphing software is used to make the graphs, students can add a “trendline” to fit their data and then further compare the slopes of their lines within their discussion. If this technology is used, it could be leveraged for a more thorough analysis of the data.