PALS - Administration Procedures

Temperature and Enzymes

Administration Procedures

Grades 5-8 Performance Task
Contributed by: Council of Chief State School Officers (CCSSO/SCASS)

Description:

Students compare the times it takes the milk in each of two cups to curdle. Students are told that an enzyme that is added to the milk, rennin, is involved in the natural curdling process of milk. They are asked to consider what relationship, if any, exists between the temperature of the milk and the time it takes to curdle.

This exercise presents a scientific test of a simple multivariate problem examining the effects of the enzyme rennin and temperature on the milk curdling process. Students are asked to explain the use of multiple controls in the experiment.

This task is designed to take students approximately 40-50 minutes to complete.

Overall Task Content Area:

: Physical Science

Specific Knowledge Areas:

: Properties and changes of properties in matter

Performance Expectations:

conducting investigations
using equipment
gathering, organizing, and representing data
formulating conclusions from investigational data
applying scientific principles to develop explanations and solve new problems

National Science Education Standards:

8 B PS 3: Transfer of energy: Grades 5-8
3.5 In most chemical and nuclear reactions, energy is transferred into or out of a system. Heat, light, mechanical motion, or electricity might all be involved in such transfers.

12 B PS 3: Chemical reactions: Grades 9-12
3.5 Catalysts, such as metal surfaces, accelerate chemical reactions. Chemical reactions in living systems are catalyzed by protein molecules called enzymes.

8 A SI 1: The ability necessary to do scientific inquiry: Grades 5-8
1.4 Develop descriptions, explanations, predictions, and models using evidence. Students should base their explanation on what they observed, and as they develop cognitive skills, they should be able to differentiate explanation from description — providing causes for effects and establishing relationships based on evidence and logical argument. This standards requires a subject knowledge base so the students can effectively conduct investigations, because developing explanations establishes connections between the content of science and the contexts within which students develop new knowledge.

(Use the "hot" link on the PALS home page to check the full text of related National Science Education Standards, if desired.)

National Council of Teachers of Mathematics:

AL1: Understand patterns, relations and functions:
Grades 6-8 f. represent, analyze, and generalize a variety of patterns with tables, graphs, words, and, when possible, symbolic rules

AL2: Represent and analyze mathematical situations and structures using algebraic symbols :
Grades 6-8 f. develop an initial conceptual understanding of different uses of variables

DAP3: Develop and evaluate inferences and predictions that are based on data:
Grades 6-8 e. use conjectures to formulate new questions and plan new studies to answer them

PS2: Solve problems that arise in mathematics and in other contexts:
Grades 6-8

General Instructions to the Teacher:

This task is designed to take students approximately 40-50 minutes to complete.

Students will be working in groups of 4-6 for the experiment/activity part of this exercise. Each student must record the information in his or her own booklet (test papers). Allow from 20 to 25 minutes to complete the group work, and a similar time period for students to do their individual answers to the test questions.

Students should be ready to work as soon as the period begins. Group assignments should be made in advance. The materials should be set out at each lab station, if possible. A central supply area, if needed, should be accessible. All supplies should be clearly labeled.

Materials for "Temperature & Enzymes":

These materials are required for each student station:

1 Celsius thermometer
1 plastic pipette
1 25 ml graduated cylinder
1 plastic bottle with cap, 5-10 ml capacity
6 90 ml disposable plastic cups
6 disposable coffee stirrers
2 Styrofoam cups
1 rennin tablets
container of crushed ice
10 ml 2% milk at room temperature (22-24^oC)/group
paper towels
digital watch or timer with second hand
10 ml 2% milk at 35^oC/group
10 ml 2% milk at 15^oC
1 permanent laboratory marker
1 pen or pencil per student

Advance Preparation:

Make the rennin solution before the class begins. Take the rennin tablets and plastic bottles with caps and measure out the needed quantity of distilled water. Add one rennin tablet per each 5 ml of distilled water. The tablets soften and dissolve with stirring. You can make a single batch of rennin solution for the entire class. For example, if 4 groups of students will be performing this lab exercise, add 4 rennin tablets, 1 or 2 at a time, to 20 ml of distilled water and mix well. Dispense in 5 ml portions into the bottles and label them "Rennin."

Enzymes vary in stability. It is suggested that the rennin solution be made up just prior to use. The rennin will be used at room temperature (about 22^o-23^oC).

Immediately before class, heat to 35^oC a quantity of milk sufficient to supply each group with 10 ml. Chill a similar quantity of milk to 15^oC. A third 10 ml. portion of milk will remain at room temperature.

Safety:

Be careful.
Teachers and students should always exercise appropriate safety precautions and utilize appropriate laboratory safety procedures and equipment when working on science performance tasks.