A Chilling Investigation
Students will observe the difference in bacterial count between a hamburger that’s left out at room temperature and a hamburger that’s kept refrigerated. The lab reinforces the concept that food must be properly chilled in order for it to remain safe to eat. This lab will be conducted as a teacher demonstration.

Background
Lesson Activities
Recommended Companion Resources
Credits
Author
Food and Drug Association (FDA) and National Science Teaching Association (NSTA)
Acknowledgements
The Science and Our Food Supply Curriculum was brought to you by the Food and Drug Administration Center for Food Safety and Applied Nutrition and the National Science Teaching Association.
- FDA Education Team Leader Food Safety Initiative: Marjorie L. Davidson
- FDA Science and Our Food Supply Project Director: Louise H. Dickerson
- FDA/NSTA Associate Executive Director and Science and Our Food Supply Program Director: Christina Gorski
- FDA/NSTA Science and Our Food Supply Program Assistant: Jill Heywood
Standards
Texas Content Area Standards
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Principles of Agriculture, Food, and Natural Resources: 130.2.c.1
The student demonstrates professional standards/employability skills as required by business and industry. The student is expected to:
- Principles of Agriculture, Food, and Natural Resources: 130.2.c.1.C: demonstrate knowledge of personal and occupational safety, environmental regulations, and first-aid policy in the workplace.
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Principles of Agriculture, Food, and Natural Resources: 130.2.c.6
The student demonstrates appropriate personal and communication skills. The student is expected to:
- Principles of Agriculture, Food, and Natural Resources: 130.2.c.6.A: demonstrate written and oral communication skills appropriate for formal and informal situations such as prepared and extemporaneous presentations.
- Principles of Agriculture, Food, and Natural Resources: 130.2.c.6.B: demonstrate effective listening skills appropriate for formal and informal situations.
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Principles of Agriculture, Food, and Natural Resources: 130.2.c.7
The student applies appropriate research methods to agriculture, food, and natural resources topics. The student is expected to:
- Principles of Agriculture, Food, and Natural Resources: 130.2.c.7.C: describe scientific methods of research.
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Principles of Agriculture, Food, and Natural Resources: 130.2.c.13
The student describes the principles of food products and processing systems. The student is expected to:
- Principles of Agriculture, Food, and Natural Resources: 130.2.c.13.A: evaluate food products and processing systems.
- Principles of Agriculture, Food, and Natural Resources: 130.2.c.13.C: discuss current issues in food production.
- Principles of Agriculture, Food, and Natural Resources: 130.2.c.13.D: use tools, equipment, and personal protective equipment common to food products and processing systems.
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ELA: 6.110.22.b.1
Developing and sustaining foundational language skills: listening, speaking, discussion, and thinking- oral language. The student develops oral language through listening, speaking, and discussion.
- ELA: 6.1.D: The student is expected to participate in student-led discussions by eliciting and considering suggestions from other group members, taking notes, and identifying points of agreement and disagreement.
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ELA: 7.110.23.b.1
Developing and sustaining foundational language skills: listening, speaking, discussion, and thinking- oral language. The student develops oral language through listening, speaking, and discussion.
- ELA: 7.1.D: The student is expected to engage in meaningful discourse and provide and accept constructive feedback from others.
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ELA: 8.110.24.b.1
Developing and sustaining foundational language skills: listening, speaking, discussion, and thinking- oral language. The student develops oral language through listening, speaking, and discussion.
- ELA: 8.1.D: The student is expected to participate collaboratively in discussions, plant agendas with clear goals and deadlines, set time limits for speakers, take notes, and vote on key issues.
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Social Studies: 6.113.18.c.21
Social studies skills. The student communicates in written, oral, and visual forms. The student is expected to:
- Social Studies: 6.113.18.c.21.C: express ideas orally based on research and experiences
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Science: 6.112.26.b.1
Scientific and engineering practices. The student, for at least 40% of instructional time, asks questions, identifies problems, and plans and safely conducts classroom, laboratory, and field investigations to answer questions, explain phenomena, or design solutions using appropriate tools and models. The student is expected to:
- Science: 6.112.26.b.1.B: use scientific practices to plan and conduct descriptive, comparative, and experimental investigations and use engineering practices to design solutions to problems
- Science: 6.112.26.b.1.C: use appropriate safety equipment and practices during laboratory, classroom, and field investigations as outlined in Texas Education Agency-approved safety standards;
- Science: 6.112.26.b.1.D: use appropriate tools such as graduated cylinders, metric rulers, periodic tables, balances, scales, thermometers, temperature probes, laboratory ware, timing devices, pH indicators, hot plates, models, microscopes, slides, life science models, petri dishes, dissecting kits, magnets, spring scales or force sensors, tools that model wave behavior, satellite images, hand lenses, and lab notebooks or journals;
- Science: 6.112.26.b.1.E: collect quantitative data using the International System of Units (SI) and qualitative data as evidence;
- Science: 6.112.26.b.1.H: distinguish between scientific hypotheses, theories, and laws.
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Science: 6.112.26.b.2
Scientific and engineering practices. The student analyzes and interprets data to derive meaning, identify features and patterns, and discover relationships or correlations to develop evidence-based arguments or evaluate designs. The student is expected to:
- Science: 6.112.26.b.2.B: analyze data by identifying any significant descriptive statistical features, patterns, sources of error, or limitations;
- Science: 6.112.26.b.2.C: use mathematical calculations to assess quantitative relationships in data; and
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Science: 7.112.27.b.1
Scientific and engineering practices. The student, for at least 40% of instructional time, asks questions, identifies problems, and plans and safely conducts classroom, laboratory, and field investigations to answer questions, explain phenomena, or design solutions using appropriate tools and models. The student is expected to:
- Science: 7.112.27.b.1.B: use scientific practices to plan and conduct descriptive, comparative, and experimental investigations and use engineering practices to design solutions to problems;
- Science: 7.112.27.b.1.C: use appropriate safety equipment and practices during laboratory, classroom, and field investigations as outlined in Texas Education Agency-approved safety standards;
- Science: 7.112.27.b.1.D: use appropriate tools such as graduated cylinders, metric rulers, periodic tables, balances, scales, thermometers, temperature probes, laboratory ware, timing devices, pH indicators, hot plates, models, microscopes, slides, life science models, petri dishes, dissecting kits, magnets, spring scales or force sensors, tools that model wave behavior, satellite images, hand lenses, and lab notebooks or journals;
- Science: 7.112.27.b.1.E: collect quantitative data using the International System of Units (SI) and qualitative data as evidence;
- Science: 7.112.27.b.1.H: distinguish between scientific hypotheses, theories, and laws.
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Science: 7.112.27.b.2
Scientific and engineering practices. The student analyzes and interprets data to derive meaning, identify features and patterns, and discover relationships or correlations to develop evidence-based arguments or evaluate designs. The student is expected to:
- Science: 7.112.27.b.2.B: analyze data by identifying any significant descriptive statistical features, patterns, sources of error, or limitations;
- Science: 7.112.27.b.2.C: use mathematical calculations to assess quantitative relationships in data; and
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Science: 8.112.28.b.1
Scientific and engineering practices. The student, for at least 40% of instructional time, asks questions, identifies problems, and plans and safely conducts classroom, laboratory, and field investigations to answer questions, explain phenomena, or design solutions using appropriate tools and models. The student is expected to:
- Science: 8.112.28.b.1.B: use scientific practices to plan and conduct descriptive, comparative, and experimental investigations and use engineering practices to design solutions to problems;
- Science: 8.112.28.b.1.C: use appropriate safety equipment and practices during laboratory, classroom, and field investigations as outlined in Texas Education Agency-approved safety standards;
- Science: 8.112.28.b.1.D: use appropriate tools such as graduated cylinders, metric rulers, periodic tables, balances, scales, thermometers, temperature probes, laboratory ware, timing devices, pH indicators, hot plates, models, microscopes, slides, life science models, petri dishes, dissecting kits, magnets, spring scales or force sensors, tools that model wave behavior, satellite images, weather maps, hand lenses, and lab notebooks or journals;
- Science: 8.112.28.b.1.E: collect quantitative data using the International System of Units (SI) and qualitative data as evidence;
- Science: 8.112.28.b.1.H: distinguish between scientific hypotheses, theories, and laws.
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Science: 8.112.28.b.2
Scientific and engineering practices. The student analyzes and interprets data to derive meaning, identify features and patterns, and discover relationships or correlations to develop evidence-based arguments or evaluate designs. The student is expected to:
- Science: 8.112.28.b.2.B: analyze data by identifying any significant descriptive statistical features, patterns, sources of error, or limitations;
- Science: 8.112.28.b.2.C: use mathematical calculations to assess quantitative relationships in data; and