Many science classes use "cook book" labs that provide step-by-step procedures for students to follow. Students can usually follow these directions without ANY understanding of why they are done. While following directions is a useful skill, it is NOT science. Providing step-by-step procedures IS important in the lower grades. Cook book labs allow younger students to learn about basic lab equipment and techniques. Following directions is also important when learning about lab safety. Specific directions may be required in high school for a guided discovery experience. However, this type of lab should be held to a minimum. It is better for students to do simple Hypothesis-Based Labs to gain experience applying the scientific method than to do complex cook book labs just to gain experience with advanced lab techniques. The common chemicals and simple equipment used for most Hypothesis-Based Labs also help with budget and liability issues in schools.

What is a Hypothesis-Based Lab? Simply put, it is a lab experience in which students use the Scientific Method instead of just blindly follow directions. The first person I heard use the term was Dr. Mark Rockley, at OSU. At the time, he was giving students a hypothesis to test. Sometimes his hypothesis was correct, sometimes it was not. What his students did at the end of the experiment depended on whether they accepted or rejected the hypothesis. Most of my Hypothesis-Based Labs are presented as a question. Students are expected to form and test their own hypothesis. The Bubble Gum Lab was one of my first Hypothesis-Based Labs. I gave it to students after covering percentage composition in class. It is important to begin the year with very simple labs. Students build confidence as they find they can use the Scientific Method to discover answers for themselves.

 

Science is a process that can be used to solve any problem. Science students must be given the opportunity to USE the Scientific Method. Students can only understand how science works if they experience the whole process − from beginning to end. State the problem Research the problem Form a hypothesis Test the hypothesis Draw conclusions The purpose of an experiment is to test a hypothesis. There are only two possibilities − the hypothesis is either right or it is wrong. Here are three graphical representations.

 

Thinking begins with a question, not an answer. ANY definitive statement is an answer to a question. Students must know things in order to solve problems. The "research" step in the Scientific Method is often thought of as the place where things are learned. While this is true, it is not the whole story. Some "background" is needed before students can even begin to understand the question. In high school, this background comes from class concept material. A Hypothesis-Based Lab should require students to apply information that is currently being covered (or has recently been covered) in class.

 

	Hypothesis-Based Labs require information in addition to class concept material. Providing one place for students to find this "research" information will decrease the class time required. A Lab Key provides specific information needed for each lab. Some Lab Keys provide additional background. Some provide specific lab techniques. But none provide step-by-step lab procedures.

 

Time is always an issue with high school science labs. Hypothesis-Based Labs, done correctly, take more class time than cook book labs. For cook book labs, students walk into class and follow the printed directions. Most of their lab report is limited to filling in some blanks and answering a few questions. Students know the teacher will look for "right" answers when the lab report is graded. Hypothesis-Based Labs require students to spend time thinking about what they know and how that knowledge relates to the lab problem. They will probably need to do additional "research" related to the specific lab problem in order to form a hypothesis. Students then design an experiment to test their hypothesis. After the experiment, their observations are used to write a conclusion for the lab. To determine if they are "right or wrong", students must: Critically examine what they did during the experiment in order to find places where mistakes might have been made. Identifying the most likely source of measurable experimental error is part of the lab conclusion. Compare their procedures and results with other lab groups (peer review). Reach a class consensus. As many as three class days may be needed to complete the process: I usually introduce the lab at the end of a class period. Students use the next day to form a hypothesis and design the experiment. Students are encouraged to visualize themselves doing the experiment at their lab station. This helps them find potential problems with their experiment and determine what equipment will be needed. While an equipment list is not part of the lab report, students know to tell me if their experiment requires something that is not normally found at their lab station. The next day is Lab Day. For most labs, students are expected to complete all procedures, clean up the lab station, and begin their Formal Lab Report. The completed Lab Report is due by the beginning of class the following day. Peer review and reaching a class consensus is done during this class.

 

Do everything possible to avoid answering the "Is This Right?" question! It represents a lack of understanding of the process of science! It also allows students to deflect their responsibility for making decisions onto the teacher. When asked this type of question, teachers are presented with an opportunity to guide student thinking with Socratic questioning. In the real world, science is the process used to discover answers that are not already known. Schools traditionally give students the impression that the purpose of a teacher is to answer questions. This is the opposite of how school should actually work − especially in science class! When using Hypothesis-Based Labs, science teachers must be comfortable asking questions for which they have no exact "right" answer. After covering population sampling in Botany class, I have asked this question; "How many leaves are on the tree in front of the school?" Students usually think I have somehow counted the leaves. They can't imagine how I could expect them to answer a question for which I have no answer! All too often I hear, "how will we know if we get the right answer?" I have even heard the dreaded, "that's not fair!" This student attitude emphasizes the need for Hypothesis-Based Labs! Science students must understand the concept of "justifying" their answer, based on the quality of their procedures and whether their conclusion is supported by their data. They must also understand how performing an experiment multiple times and peer review of procedures and results are used in the real world to determine if an answer obtained through experiment is correct. On Lab Day, give students every opportunity to ask questions before the lab begins. Answer those questions, as long as they are not like the "Is This Right?" question. However, once the lab begins, students should work together in their group to reach a consensus if they have a question. The teacher should only get involved with students' performance on Lab Day for safety reasons. My evaluation rubric warns students that if I have to get involved it will cost the whole group points!

 

Teacher expectations guide the student experience during Hypothesis-Based Labs. These expectations are best communicated to students with a scoring rubric. Students not only know what the teacher thinks is important, they also gain experience with critical self-evaluation. Different teachers expect different things from student lab reports. My Lab Report Guide expects neat, concise communication of the lab experience. All my students have Web access to the lab material at any time. When I introduce a lab, I give each group one printed copy of these two pages stapled together - with the rubric on top. This constitutes the group's Formal Lab Report and is the only copy they get. The group is required to complete the "student evaluation" portion of the rubric before turning in the lab report.