Moooooooving Science Fun with Butter!

Transcription

1 Moooooooving Science Fun with Butter! Elementary-Middle-High School (5-9) Materials Activity 1 8oz Ball plastic freezer container with lid (10) 1.5 quart heavy cream room temperature Cold water for rinsing Tasting spoons (30) Crackers and Salt (to taste) Small collection cups (20) Timer (10) Paper towels Activity 3 Plastic Culture Tubes (90) Test Tube Rack (10) Biuret Solution Pasteur Pipettes (70) 70% Ethanol Distilled Water ½ pint Heavy Cream Butter (from Part 1) Buttermilk (from Part 1) Stir rods Gloves, Goggles and Lab Coats Paper Towels Baking Soda (1 box) Activity 2 Test Tube Rack (10) Plastic Culture Tubes (20) Saline Solution ½ pint Heavy cream Vegetable Oil Dishwashing soap Stir rods (20) Droppers (20) Paper towels Dropper bottles of food coloring (10) Water Small laser pointer (10) Safety: These activities require the use of dairy products. Be sure to survey students for dairy allergies. Due to the use of crackers in Activity 1, survey students regarding any gluten allergies. Biuret s reagent (Activity 3) is an acid and requires use of laboratory gloves, lab apron and goggles. Ethanol is flammable and should not be ingested Objectives The students will: Determine and test the physical properties of solutions and colloids Understand how force provides energy that can enable molecules to separate when in an emulsion and how this relates to the physical nature of emulsions Analyze differences in the organic molecules that comprise dairy products Illinois Math and Science Academy 1

2 Standards NGSS: PS1.A: Structures and Matters of Property (MS-PS1-2, MS-PS1-3, MS-PS1-4) HS-PS1: Matter and its Interactions (HS-PS1-5, HS-PS1-3) CCSS: CCSS.ELA-Literacy.RST CCSS.ELA-Literacy.RST References to Common Core are adapted from NGA Center/CCSSO Copyright National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved. References to Next Generation Science Standards are adapted from NGSS. NGSS is a registered trademark of Achieve. Neither Achieve nor the lead states and partners that developed the Next Generation Science Standards was involved in the production of, and does not endorse, this product. Introduction Milk served as an important source of nutrients for people in ancient and medieval times. Unfortunately, because there was no refrigeration, milk was not easily stored for later use. Butter, however, could be heavily salted and stored in earthenware pots for future use. Beginning with agitating cream in an animal skin bag to the use of mechanical churns, through history one can chart how people adapted technology to better separate butter from cream derived from raw milk. Raw milk is complex in structure. Proteins and minerals are suspended in water, amongst emulsified fat. The milk fat forms solid fat globules when at room temperature; yet is liquid (oil) at 37 o C, which is at body temperature ( As fats or lipids- tend to be uncharged molecules, and water is a polar molecule, suspensions of oil/fat and water are naturally unstable and move toward separation. Proteins, however, often have charged and uncharged areas within the molecules, allowing for an interaction with both lipids and water. Various proteins within milk allow for the emulsification of the fats into the watery solution. As temperature rises, protein structure changes and the fat globules in milk become more unstable in the water and begin to separate. This separation can be quickened through agitation of the mixture Illinois Math and Science Academy 2

3 ( The activities in this handout explore various aspects of the physical nature of cream and butter. Activity 1 involves the use of force to provide energy that enables the separation of fat from a colloid (cream). Activity 2 further explores the physical nature of cream, specifically investigating how molecules are dispersed in a colloid when compared to a solution and examining how emulsions may be formed. Through an analysis of proteins and lipids, Activity 3 investigates the molecular make-up of cream, and two substances derived from it: butter and buttermilk. Inquiry Overview: Not all scientific data is quantitative. Science often begins with an observation and a question. The activities in this lesson focus on the power of observation and the importance of asking and ultimately attempting to answer questions derived from what is perceived. The focus of these activities is on the physical nature of a common substance, cream. Through observations and questioning, students will explore the following concepts: Force and Energy, Properties of Matter and Molecular Biology. The strategies used to formulate ideas and understand these concepts through observation are integral to science and can be utilized across the curriculum and through many grade levels. Activity 1: Advanced Preparation: Heavy cream should be left at room temperature for approximately 4 hours. Prepare the freezer cups with 4 oz. of cream prior to start of the activity. Make sure all other materials (collection cups, tasting spoons, crackers and salt and student pages) are also prepared prior start of this activity Begin this activity with your students by first placing them in groups of 3 to 4 students. Hand out the Tasty Butter Survey to each of the groups and allow 5-10 minutes for the groups to read and discuss the questions. In a large group setting, allow the groups to report their answers and discuss any similarities or differences. At this point, do not focus on whether the answers are correct. Record the similarity and differences in the answers. Next, hand out the Making Butter student procedures and the Making Butter Data Sheet to each of the groups. Inform the students that they will be making butter using one of the oldest known techniques Illinois Math and Science Academy 3

4 Allow the students a few minutes to read the procedure and collect the prepared materials, and then verbally read through the procedures with the students once before they conduct the activity. As the students conduct the activity, be sure that one student is timing each turn (1 minute per turn). Make sure the students collect observations throughout the activity and remember to collect (and label) a portion of the butter, and all of the buttermilk. As the above activity ends, ask your students to compare their results with any cream left standing unused in the experiment. Debrief: In a large group setting, ask your students to report their observations during the Making Butter part of the activity. Be sure to ask: Did standing, un-agitated cream show any physical changes compared to that which was shaken during the activity? What were the main physical changes observed during the process? Why do you think these changes occurred with agitation what was the purpose of agitating the cream? How long did it take (in minutes or in turns) to turn cream into butter? Why did we use room temperature cream? Do you think temperature may make a difference in the procedure? The desired outcome of the debrief questioning is that the students note a distinct physical change from the liquid cream to a solid butter (and a liquid buttermilk). The next activity further explores the composition of cream. Your students may be familiar with solutions and mixtures. Students will compare physical characteristics of cream, salt-water (saline solution) and oil and water to note the differences between solutions, suspensions, colloids (and colloid emulsions). One goal is for the students to reach the understanding that cream is an incredibly complex substance containing a multitude of different substances that can be analyzed. Activity 2: Advanced Preparation: Prior to the start of the activity, prepare the lab stations and materials for each student group: 1 test tube rack, 2 culture tubes (1 tube prefilled 2/3 way with Saline solution, 1 tube left empty), 2 wooden stir rods, 1 small paper cup of vegetable oil, 1 small paper cup of heavy cream, 1 small cup of water, 2 droppers, 1 dropper bottle of food coloring, 1 small cup of dishwashing soap, 1 small laser pointer, and paper towel. Illinois Math and Science Academy 4

5 Ask the students what they recall about solutions and mixtures. Inform them that the cream used in Activity 1 was store-bought, and therefore, processed from raw milk. When raw milk is left to sit at room temperature, the cream will rise to the top, separating from the rest of the milk. Ask the students why cream would rise to the top and not sink to the bottom of the milk. After discussion of answers to the above question, inform the students that they will be exploring this question further by observing some of the physical characteristics of materials used in butter-making. Pass out the Murky Directions sheet as well as the Murky Data Sheet to each group of students. Review the directions with the students and then allow minutes for the students to explore this activity and answer the questions on the data sheet. After students have been given time to conduct the activity and discuss questions in their groups, reconvene as a large group to debrief. Debrief: In a large group, discuss what was observed. The students should have seen that the light beam seemed to disappear in the saline, but was dispersed through the diluted cream. Students also should have seen that the oil and water do not mix unless something else (the soap) was added. Ask the students if the cream, the saline and the oil and water look like they are one singular substance, or as if they contain multiple parts? Ask if the students feel as if the appearance of cream and saline is deceiving (ex: if they feel cream looks singular but is not) ask the students to explain their answers Ask if the students why they believe the light was visible in the cream but not in the saline? You may choose to inform the students that the test used in this activity involves the Tyndall Effect (or Tyndall Scattering). In the cream, light scatters amongst large particles dispersed in water. These particles are dispersed well, but do not create a uniform mixture. In the saline solution, the salt (NaCl) breaks into their parts. These ions, Na + and Cl -, evenly mix with the water, creating a uniform, or homogenous, substance. These particles are too small to scatter the light and therefore, the beam is not visible (light is not scattered) through the saline. This test can be used to determine a solution (a solute is homogenously dissolved in a solvent) from a colloid (large particle solutes are not homogenously dissolved, but remain distributed amongst a solvent without Illinois Math and Science Academy 5

6 separation). Ask the students if they believe the saline and the cream are solutions or colloids? Ask the students about the water and oil do they believe it would fit as a solution or as a colloid? Discuss what occurred when the students added the dishwashing soap to the oil and the water and ask to try and explain the results. The students should note that without the addition of the soap, the oil and water quickly separate (this indicates that it s a suspension). A healthy discussion about why adding the soap helps the oil and water mix should ensue. Ask the students to describe oil and describe water (ex: oil is fatty ) If terms like fatty are used, ask the students if they know what fat is or if they know of other molecules often mentioned with regards to food (ex: proteins, carbohydrates). This may lead into a discussion of how water is a partially charged molecule and is attracted to other substances with a charge. Oil, or fat, is not charged and therefore is repelled by water. Soaps have parts that are both charged and noncharged and can interact with both water and fat. A good online resource for reviewing general properties of water can be found at the following website: water.html. Understanding that water is somewhat charged and is attracted to other charged molecules will help students to understand why water does not mix well with the non-charged fats (oil). The soap, having both charged and uncharged parts to it, helps surround the fat, thereby helping it mix with the water. In the next activity students explore some of the molecules that make up the cream used for butter making. Specifically, students will compare the amounts of lipid (fat) and protein in cream, butter and buttermilk. Activity 3: Advanced Preparation: Prior to the start of the activity, set up the lab materials per student group: 1 test tube holder and a set of 9 test tubes, a small bottle of Biuret s reagent, a small bottle of cold ethanol, a long piece of brown paper towel, 9 disposable stir rods, small paper cups containing cream, the butter and the buttermilk they produced, distilled water and three droppers. SAFETY: For these procedures, students should wear lab aprons, goggles and laboratory gloves. Dispose of the Biuret s Reagent by slowly adding baking soda to all tubes containing Biuret s until the bubbling stops at which point the solution may be washed down the sink. Illinois Math and Science Academy 6

7 To begin this part follow up on the concepts discussed during the debriefing for the prior two activities. Inform the students that they will now be exploring some of the components of the cream they used to make butter; and the butter and buttermilk they produced; specifically proteins and lipids which may or may not be a part of these substances. Hand out the Organic Tests Protocols, Organic Test Observations & Questions student sheets, and the Grease Spot Test Reading for Transparency Page prior to the lab activity. Read through the protocols with the students and allow the students to experiment and discuss/answer questions as a group. Debrief: After the students have completed their activities, compare the results of each group. The results should show the lipid content as follows butter > cream > buttermilk. The buttermilk should have the least lipid content as most of the fat (butter) has been separated from the watery/protein colloid (buttermilk). Ask the students to explain their results for the lipid tests. If the students fail to bring up the idea of concentration (butter has more of a concentration of lipids than cream and buttermilk): Ask the students if the constituents of butter are in the cream, why would the lipid content of cream be less than that of butter? Ask the students to share their results for the protein test. Ask them to explain why they feel these results occurred. Conclusion Taken together, these three activities are designed to develop the understanding of how butter is separated from the cream from which it originated. Students should enhance their knowledge regarding mixtures, solutions and colloids, as well as the molecular structures and interactions that make up the food we eat. In ancient and medieval times, people would not have had the technology necessary to understand food structure on a molecular level. What they did have, and develop, was a keen sense of observation and an understanding of action and consequence. Through observing how foods behave in different environments, people could develop new foods and technologies to enhance their situation. Illinois Math and Science Academy 7