Science Resource Package: Grade 8

1 Fluids: Forces in Fluids

Fluids:

Forces in Fluids

New Brunswick Department of Education September 2009 Acknowledgements

The Department of Education of New Brunswick gratefully acknowledges the contributions of the following groups and individuals toward the development of the New Brunswick Science Resource Package for Grade 8 Fluids: Forces in Fluids:

 The Science Resource Package Development Team:

• Adam Bentley, School District 10 • Danny Marmen, School District 8

 Science East:

• Michael Edwards, Director of Programming • Karen Matheson, Director of Education

 Kathy Hildebrand, Learning Specialist, Science and Mathematics, NB Department of Education

 Science Learning Specialists and science teachers of New Brunswick who provided invaluable input and feedback throughout the development and implementation of this document.

Note that at the time of posting, all URLs in this document link to the desired science content. If you observe that changes have been made to site content, please contact Kathy Hildebrand [email protected], Science Learning Specialist, at the Department of Education.

2009 Department of Education Educational Programs and Services TABLE OF CONTENTS

RATIONALE...... 1 BACKGROUND INFORMATION...... 3

PRIOR KNOWLEDGE:...... 3 COMMON MISCONCEPTIONS:...... 3 DID YOU KNOW?...... 3 INSTRUCTIONAL PLAN...... 4

ACCESS PRIOR KNOWLEDGE...... 4 1ST CYCLE...... 5 Sinking and Floating Objects...... 5 Reflection: Class Discussion...... 6 Reflection: Journaling...... 6 2ND CYCLE...... 7 Make a Cartesian Diver Activity...... 7 Reflection: Discussion...... 8 3RD CYCLE...... 10 Quantify the Forces Activity...... 10 Reflection...... 11 Reflection: Journaling...... 12 SUPPORTING CLASS DISCUSSION...... 14 MATERIALS LIST...... 16 STUDENT VERSION OF OUTCOMES...... 17 SINKING AND FLOATING OBJECTS...... 18 CARTESIAN DIVER...... 19 QUANTIFY THE FORCES ACTIVITY...... 20 MAKE A DYNAMOMETER...... 22 OBSERVATION CHART SHEET...... 23 CHECKLIST SHEET...... 24 OBSERVATION CHECKLIST...... 25 STUDENT RECORD...... 26 ARCHIMEDES...... 27 1 Fluids: Forces in Fluids

Rationale This resource package models current research in effective science instruction and provides an instructional plan for one topic selected from the Grade 8 Atlantic Canada Science Curriculum. This curriculum includes STSE (Science, Technology, Society and Environment) outcomes, Skills outcomes, and Knowledge outcomes – all of which are important for building a deep understanding of science and its place in our world.

As has been true of our ancestors, we all develop “explanations” about what we observe which may or may not be valid. Once ideas are established, they are remarkably tenacious and an alternate explanation rarely causes a shift in thinking. To address these misconceptions or alternate conceptions, students must be challenged with carefully selected experiences and discussion.

A key part of this instructional plan is accessing prior knowledge. It is recorded in a way that it can and will be revisited throughout the topic. The intent is to revise, extend, and/or replace students’ initial ideas with evidence-based knowledge.

Science is not a static body of facts. The process of exploring, revising, extending, and sometimes replacing ideas is central to the nature of science. Think of science as an ongoing evidence-based discussion that began before our time and that will continue after it. Science is often collaborative, and discussion plays a key role. Students’ learning of science should reflect this as much as possible.

The intent of this instructional plan is to encourage a constructivist approach to learning. Students explore an activity, then share, discuss and reflect. The telling of content by the teacher tends to come after, as an extension of the investigation (or experience) explored by the students.

The learning is organized into cycles. The partial conceptions and misconceptions are revisited in each cycle so that students’ ideas will be revised. Each cycle will result in deeper and/or extended learning.

New Brunswick Science Resource Package: Grade 8 2 Fluids: Forces in Fluids Hands-on activities are part of the instructional plan. Inquiry activities tend to be most structured in the first cycle. The teacher provides the question to investigate and gives a procedure to follow. In subsequent cycles, less structure tends to be given. For example, students may be given a question and asked to develop an experimental plan which they then implement. The goal is to move towards open inquiry in which students generate a testable question, develop an experimental plan using available materials, implement the plan, record relevant observations, and make reasonable conclusions. The included activities are meant to start this journey.

Discussion and written reflections are key parts of the lessons. Discussion (both oral and written) is a vehicle that moves science forward. For example, when scientists publish their evidence and conclusions, other scientists may try to replicate results or investigate the range of conditions for which the conclusion applies. If new evidence contradicts the previous conclusions, adjustments will be required. Similarly, in this instructional plan students first do, then talk, then write about the concept. A section on supporting discussion is included in this resource package.

Assessment tasks are also included in the instructional plan and assess three types of science curricular outcomes: STSE, Skills, and Knowledge. These tasks are meant to be used as tools for letting the teacher and the students know where they are in their learning and what the next steps might be. For example: Has the outcome been met or is more learning required? Should more practice be provided? Is a different activity needed?

When assessment indicates that outcomes have been met, it will provide evidence of achievement. This evidence may be sufficient and further formal testing (paper-pencil tests) may not be required to demonstrate that outcomes have been met.

New Brunswick Science Resource Package: Grade 8 3 Fluids: Forces in Fluids

Background Information

Prior Knowledge: In grade 6, students learn about Bernoulli’s principle as applied to air.

Students were exposed to the particle model of matter in grade 7 and have continued to expand on this in grade 8. Students should understand that all matter is made up of particles and that particles are continuously in motion.

Grade 8 students have learned about density of fluids in the current unit.

Common Misconceptions: FACT MISCONCEPTION “Gases are not fluids because they Gases are fluids. A fluid is any are not liquids” substance that is able to flow.

“Heavy things sink and light things Things that appear heavy may, in fact, float” have a low average density. (For example, a ship which contains a large volume of air.)

Did You Know? Density is the “crowdedness” of particles, or more properly, the amount of a substance that occupies a particular space.

Average density: the total mass of all substances in a given volume divided by the total volume. For example, when the weight of the ship and cargo is spread out over a large enough volume, the ship’s average density is less than the density of the water.

Archimedes’ principle: the buoyant force acting on an object equals the weight (force of gravity) of the fluid displaced by the object. The volume of an object is equal to the volume of fluid displaced by the object.

Buoyancy: the tendency of an object to rise or float in fluids, the ability of a fluid to support an object floating in or on the fluid. The particles in a fluid exert a force in a direction opposite to the force of gravity.

Floating: when an object does not fall in air or sink in water, but remains suspended in the fluid

 Instructional Plan

 Access Prior Knowledge  In small groups, have students brainstorm and record a list of things that float and another list of things that sink

 Have students discuss this in pairs or small groups before sharing ideas with the whole class.

 Then as a whole class, share one item from each group and record on the board or on chart paper. Continue until all ideas are shared.

 Accept all ideas and record them in a way so these ideas can be revisited in later lessons. If students disagree with each other, allow them to express their thinking and reasons to each other. See supporting discussion tips on pages 14-15.

 Ask students if the items can be clustered as to why they sink or float. Cluster items with a card indicating why they have been placed together.

You could have students print ideas on index cards or on pieces of paper with markers. These can be tacked to a bulletin board as they are shared and are easy to move around for the clustering part of the activity.

 Assessment: Note the concepts and misconceptions students are expressing. You will need to know these to plan effective questions for subsequent activities and discussions so that students will examine and adjust their alternate conceptions. Notice what sorts of examples students came up with. What reasons are being given for why specific items sink or float?

Post student versions of curricular outcomes on chart paper (see page 17). Inform students that these outcomes will be addressed over the next portion of the unit. Point out to students which outcomes are being addressed in each activity.

 1st Cycle

 Curriculum Outcomes 208-6 Design an experiment and identify major variables. 210-13 Test the design of a constructed device or system. 210-14 Identify and correct practical problems in the way a prototype or constructed device functions. 211-3 Work co-operatively with team members to develop and carry out a plan, and troubleshoot problems as they arise.

 Sinking and Floating Objects

Materials: Tin foil Modelling clay Wax paper Water Container to test shapes – one large container to share or smaller containers for each group Paper towels

Provide students with a variety of substances (tin foil, modelling clay, wax paper) and ask them to create shapes from each and explore if the shapes will sink or float. They can draw pictures that show the shapes they made and whether the shape sank or floated. A possible recording sheet is given on page 20.

 Assessment: During student activity, make notes on outcomes (or parts of outcomes) you observe being addressed. Process skill outcomes are part of the curriculum and should be assessed. Using the observation chart or the checklist (on pages 23-25) on a clipboard may be helpful to you. Develop your own code for quick notes.

A suggested code: √ observed and appropriate, WD with difficulty, RTT refused to try, A absent.

This chart may be used on multiple days, using a different coloured pen or pencil each day and putting the date in the corner. You may not have a symbol or note for every child every day. Some teachers like to focus on a group or two each time. However you choose to make note of your observations, you will always have a sense of who you need to take more notice of and who might need extra support. The information will also help you when it is reporting time.

 Reflection: Class Discussion

 First ask students to discuss and record in their small groups: What characteristics are necessary to have a sinking object? What characteristics are necessary to have a floating object?

 Have groups share these ideas with the whole class to come up with an overall list of requirements for each. Record student ideas on chart paper.

The Explore Learning site has simulations called Gizmos. The simulations may be useful to test student generalizations arising during the discussion. The link below is to a “Gizmo” on Archimedes Principle. The Gizmo allows the width, height and length of a “boat” to be adjusted, weights to be added and the density of the fluid to be changed. http://www.explorelearning.com/index.cfm?method=cResource.dspView&ResourceID=603 This is an excellent resource for showing students how these factors affect whether something floats or sinks. This also provides a visual way to explain “average density”. The “Gizmo” site allows unregistered users to run each Gizmo for 5 minutes a day. It is also possible to sign up for a free trial. Membership is not free.

 Revisit the sinking and floating ideas created in the Accessing Prior Knowledge activity (page 4). Ask: Are there any items that should be added to or revised. Is there other information we could add? Remind your class about respectful discussion. The discussion tips on pages 14-15 may be helpful.

 Reflection: Journaling

Have students explain floating and sinking with these sentence starters.

Objects will float when . . .

Objects will sink when . . .

 Assessment: Journal entries should not receive a score or mark. A positive comment followed by a question to refocus attention or suggest the next step in learning is very effective. When reading the journal entries, note which students are using appropriate characteristics to explain sinking and floating.

 2nd Cycle

 Curriculum Outcomes 210-13 Test the design of a constructed device or system. 211-3 Work co-operatively with team members to develop and carry out a plan, and troubleshoot problems as they arise. 309-2 Describe the movement of objects in terms of balanced and unbalanced. forces.

 Make a Cartesian Diver Activity Although this activity can be found on page 149 of the SCIENCEPOWER 8 resource, an alternate method is detailed below.

Materials: 2 litre pop bottle Plastic pipette or ballpoint pen cover Metal nuts or modelling clay

Method: Using a pipette:  Cut off the stem of the pipette, about 2 cm under the bulb.  Slip at least one nut onto the end of the pipette – depending on the size of the nuts, it might be necessary to use a glue gun to keep the nut in place.  Place the pipette into a glass of water, and squeeze some of the air out so that it just barely floats. Ideally, this should happen when the water level inside the bulb is approximately ¼ to ½ of the bulb – the diver is now ready to be used. If it takes too much water to make it sink, or it will not sink at all, add an additional nut to the end of the pipette. Alternative to pipette:  Place some modeling clay on the ballpoint pen cover (see photo). The cover must not have holes in it. Then:  Completely fill the pop bottle with water, and then add the diver to the bottle.  Screw on the lid of the bottle, and squeeze the sides of the bottle.  Record observations  Assessment: On observation chart (or other record), note how students are performing on the skill outcomes.

 Reflection: Discussion  Have students discuss first in small groups. Why did the diver float at the beginning? What changed? (The pressure was increased by pressing on the bottle forcing more water into the diver. The diver becomes heavier, and overcoming the buoyant forces, sinks. When the pressure is released, the extra water in the diver comes out, the diver is lighter, and it rises).  Have students draw a diagram showing the forces acting on the diver (gravity - down, buoyancy- up)  Share diagrams and discuss as a class.

Students should be getting the idea that when something sinks, the force of gravity is greater than the buoyancy force. When something floats, the buoyancy force is greater than the force of gravity. When something neither sinks nor floats, the forces are balanced.

 Revisit the sinking and floating ideas created in the Accessing Prior Knowledge activity (page 4). Ask: Are there any items that should be added to or revised. Is there other information we could add? Remind your class about respectful discussion. The discussion tips on pages 14-15 may be helpful.

 Assessment: Students can draw diagrams of real situations that use arrows to show the magnitude and direction of forces when: a) an object sinks b) an object floats c) an object is suspended in a liquid

(See diagrams on page 151 of SCIENCEPOWER 8 resource) Note if students have the idea of two forces in opposition (gravity and buoyancy) and their relationship to floating and sinking.

New Brunswick Science Resource Package: Grade 8 9 Fluids: Forces in Fluids  The story of Archimedes

Use the story of Archimedes (beginning at page 27) to introduce Archimedes’ principle and give some perspective on the history of the development of scientific thought. The following site has simulations. The link is to a “Gizmo” on Determining Density via Water Displacement. Use this simulation to measure volume in much the same way as Archimedes. http://www.explorelearning.com/index.cfm? method=cResource.dspView&ResourceID=400 The “Gizmo” site allows unregistered users to run each Gizmo for 5 minutes a day. It is also possible to sign up for a free trial. Membership is not free.

 Video

The Bill Nye video “Buoyancy” is a good summary video at this point. It can be found at http://learning.aliant.net/school/index.asp Type buoyancy into the search box. When you click on the picture, the video will start with a table of contents to the right of it. Note that you can click on any part of the contents list to go to that portion. There is no need to view the entire video. (You need to register to use the videos on the Aliant site. Registration is free. If you try to watch the video without logging in, you are prompted to do so.)

Extension idea:

Make your Cartesian diver pick up sunken treasure. This slight variation provides students with the challenge of picking up a sunken diver.

 Students will need to add a short piece of wire to their Divers. The wire should be twisted around the stem of the pipette while the rest of the wire is bent into a hook. This may require some Crazy Glue.  The Treasure is similar to the diver, where a pipette is cut about 1cm above the bulb and a nut Diver is added. Using a longer piece of wire than that used for the diver, twist it around the stem, make a loop over the top of the bulb, and then twist the other end of the wire around the stem. It can be Treasure glued in place.  Place the treasure on the bottom of the pop bottle. The diver still barely floats. Can you make your diver descend and pick up the treasure?

 3rd Cycle

 Curriculum Outcomes 209-3 Use instruments effectively and accurately for collecting data. 211-3 Work co-operatively with team members to develop and carry out a plan, and troubleshoot problems as they arise. 307-10 Describe situations in daily life where the density of substances naturally changes or is intentionally altered. 309-2 Describe the movement of objects in terms of balanced and unbalanced forces.

 Quantify the Forces Activity Students will explore the forces acting on a weight and other objects in a variety of liquids.

This activity can be set up in stations to limit the amount of materials required and can be done in 2 parts or as one activity. Each station can have a different type of liquid to test. Students can move from station to station floating/sinking objects and measuring the buoyant force with the spring scales.

Materials: 4 or 5 different fluids of varying densities - rubbing alcohol, pop, molasses (or corn syrup), water, salt water Plastic cups or other containers for liquids Spring balances Objects to test – corks, sections of candles, large metal nuts or washers Weights (the kind used with pan balances)

Method: Part 1 – to determine the change in force on a weight in different liquids  Have students predict and record the liquids from most dense to least dense.  Have students put a weight/mass on a spring balance, suspend it in air and record the force.  Have students submerge the weight into each test liquid (e.g. salt water) and make a note of the reading on the spring balance. (a possible recording sheet is given on page 20.

Part 2 – to test the floating and sinking of different items in those fluids (differences in density) New Brunswick Science Resource Package: Grade 8 11 Fluids: Forces in Fluids  Based on the results in part 1, have students predict whether different items such as a cork, a piece of candle and a metal nut or washer will sink or float in each liquid.  Have students test their prediction and record their observations (suggested recording sheet on page 21).

 Assessment: On observation chart (or other record), note how students are performing on the skill outcomes.

 Reflection Alternate between small group and whole class discussions as these items are discussed:  Have students share diagrams of the forces acting on the mass in each liquid. Ask: How do we know the forces are different in different liquids? What are these forces acting on – the spring balance or the objects?

 Have students rank the liquids from the liquid with the most buoyant force to the least buoyant force. Can they justify the rankings?

 Have students rank the liquids from the liquid that is most dense to the liquid that is least dense. Can they justify these rankings?

 What do they notice about the two lists (buoyant rankings and density rankings)? Ask: What is the relationship between density and buoyancy?

 Have students rank the items tested for sinking and floating from most dense to least dense.

 Have students write one sentence that explains how to predict if something will sink or float based on density of the object and density of the fluid.

There are several simulations at http://www.explorelearning.com/index.cfm? method=cResource.dspResourcesForCourse&CourseID=308 which will allow students to explore ranking objects by density by testing whether they sink or float in various liquids. Try “Density via Comparison”, “Density”, and “Density Laboratory”.

New Brunswick Science Resource Package: Grade 8 12 Fluids: Forces in Fluids The “Gizmo” site allows unregistered users to run each Gizmo for 5 minutes a day. It is also possible to sign up for a free trial. Membership is not free.

 Revisit the sinking and floating ideas created in the Accessing Prior Knowledge activity (page 4). Ask: Are there any items that should be added to or revised. Is there other information we could add? Remind your class about respectful discussion.

 Reflection: Journaling

Thinking about the cork, metal washer and piece of candle - why did some objects always float, some objects always sink and some do both depending on the liquid they were added to?

How would the results of the above experiment change if the same mass used to measure buoyancy was in the shape of a small 1cm cube square?

 Assessment: Journal entries should not receive a score or mark. A positive comment followed by a question to refocus attention or suggest the next step in learning is very effective. When reading the journal entries, note which students are discussing densities or forces to explain floating and sinking. Students should come away with: if an object is less dense than the fluid in which it is immersed, it will float; if an object is more dense than the fluid in which it is immersed, it will sink.

Where in real life are there situations where density of an object is naturally or intentionally changed?

 Research activity:

Explain _____ using the ideas of density and buoyancy.

Suggestions include: scuba divers, submarines, submersibles, floating docks, hot air balloons

New Brunswick Science Resource Package: Grade 8 13 Fluids: Forces in Fluids Extension:

Students can make their own dynamometer (similar to the spring scale) to test. (see page 22)

This can be done by using a ruler, a rubber band or spring and a weight (for example, a small bag of nuts, wet sand or anything else heavy).

Attach the rubber band or spring to the top of the ruler either by making a hole in the ruler or by taping it in place. The elastic or spring should stretch at least ¾ down the ruler. A paperclip or paper arrow pointer can be used to mark the changes in the force in different liquids.

New Brunswick Science Resource Package: Grade 8 14 Fluids: Forces in Fluids Supporting Class Discussion No one person is as smart as all of us together.

Page Keeley, in the book “Science Formative Assessment” (2008), uses the analogy of ping-pong and volleyball to describe discussion interaction. Ping-pong represents the back and forth question-answer pattern: the teacher asks a question, a student answers, the teacher asks another question, a student answers, and so on. Volleyball represents a different discussion pattern: the teacher asks a question, a student answers, and other students respond in succession; each building upon the previous student’s response. Discussion continues until the teacher “serves” another question.

A “volleyball” discussion encourages deeper student engagement with scientific ideas. Students state and give reasons for their ideas. Through the interaction, ideas may be challenged and clarified. Extensions and applications of ideas may arise as well. Discussions should avoid the personal and always revolve around ideas, explanations and reasons. The goal is for students to achieve better understanding.

Share the ping-pong and volleyball analogies with your students. Good discussion takes practice. You and your students will improve. Many teachers find discussion works best if all students can see each other, such as in a circle, at least until they become accustomed to listening and responding to each other.

As the teacher, you will need to: o establish and maintain a respectful and supportive environment; o provide clear expectations; o keep the talk focused on the science; o carefully orchestrate talk to provide for equitable participation.

It is important to establish discussion At first, discussions are apt to seem somewhat norms with your class. Your expectations artificial. Initially, a bulletin board featuring may include: carton talk bubbles with suggested sentence o Everyone has a right to participate and starters may be helpful. be heard. I respectfully disagree . . . o Everyone has an obligation to listen I had a different result . . . and try to understand. Could you show how you got that o Everyone is obliged to ask questions information? when they do not understand. When I was doing ___, I found that . . . Even though you said ___, I think . . . o The speaker has an obligation to The data I have recorded in my attempt to be clear. notebook is different from what you shared. I found . . .

New Brunswick Science Resource Package: Grade 8 15 Fluids: Forces in Fluids It is helpful if teacher questions refer to a big idea rather than specifics. (Could humans and chickens move their bones without muscles?) Questions should be phrased so that anyone can enter into the conversation. Opinion questions are especially good for this (What do you think . . . ? How do you think . . . ? What if . . . ? Why . . . ?).

Provide plenty of wait time for students. Students give more detailed and complex answers when given sufficient wait time. Allow wait time after student responses. When students are engaged and thinking, they need time to process other responses before contributing. If the discussion is not progressing, have students engage in partner talk. Partner talk enables the teacher the opportunity to insert “overheard” ideas.

Helpful teacher prompts: 1. What outcome do you predict? 2. Say more about that. 3. What do you mean by . . . ? 4. How do you know? 5. Can you repeat what ____ said in another way? 6. Does anyone agree or disagree with . . . ? 7. Does anyone want to add to or build on to . . . ? 8. Who understands ___’s idea and can explain it in their own words? 9. Let me see if I have got your idea right. Are you saying . . . ? 10. So you are saying that . . . 11. What evidence helped you to think that? 12. Okay, we do not agree. How does each position fit the evidence? What else could we find out? References:

Keeley, Page (2008). Science Formative Assessment. Thousand Oaks, CA: Corwin Press and Arlington, VA: NSTA Press

Michaels, Sarah, Shouse,Andrew W., and Schweingruber, Heidi A. (2008). Ready, Set, SCIENCE! Washington, DC: The National Academies Press

New Brunswick Science Resource Package: Grade 8 16 Fluids: Forces in Fluids Materials List materials amounts Tin foil 1 small square/group Modelling clay 1 small ball/group Wax paper 1 small square/group Water Container to test shapes 1 large to share or smaller containers for each group 2 litre pop bottle 1/group Plastic pipette or ballpoint pen cover 1/group Metal nuts or modelling clay 1/group 4 or 5 different fluids of varying densities: rubbing alcohol, pop, molasses (or corn syrup), water, salt water Plastic cups 1 per liquid for each station Spring balances 1/group Different objects to test: corks, sections of 1 of each per station candles, large metal nuts or washers Weights (the kind used with pan balances) 1/group

New Brunswick Science Resource Package: Grade 8 17 Fluids: Forces in Fluids Student Version of Outcomes

208-6 Plan an experiment and identify major variables.

209-3 Use instruments accurately for collecting data.

210-13 Test the design of a constructed device.

210-14 Identify and correct problems in the way a constructed device works.

211-3 Work co-operatively with team members to develop and carry out a plan, solving problems as they arise.

307-10 Describe real situations where the density of substances or objects changes.

309-2 Explain the movement of objects in terms of balanced and unbalanced forces.

Sinking and Floating Objects

Material Draw shape Sink or Float?

New Brunswick Science Resource Package: Grade 8 19 Fluids: Forces in Fluids Cartesian Diver Materials:

2 litre pop bottle Plastic pipette or ballpoint pen cover (without holes) Metal nuts or modeling clay

Method:

 Cut off the stem of the pipette, about 2 cm under the bulb. Slip at least one nut onto the end of the pipette – depending on the size of the nuts, it might be necessary to use a glue gun to keep the nut in place.

 Place the pipette into a glass of water, and squeeze some of the air out so that it just barely floats. Ideally, this should happen when the water level inside the bulb is approximately ¼ to ½ of the bulb – the diver is now ready to be used. If it takes too much water to make it sink, or it will not sink at all, add an additional nut to the end of the pipette.

 Alternative to pipette: place some modeling clay on the stem of the ballpoint pen cover. The cover must not have holes in it.

 Completely fill the pop bottle with water, and then add the diver to the bottle. Screw on the lid of the bottle, and squeeze the sides of the bottle.

Record observations:

Why did the diver float at the beginning?

What changed?

Quantify the Forces Activity Part 1

1) Rank the liquids from what you predict to be the most dense to the least dense before starting the experiments.

2) Put a weight/mass on a spring balance, suspend it in air and record the force.

3) Submerge the weight into each test liquid ensuring the weight does not touch the bottom of the container.

4) Record the reading on the spring balance.

Reading on Spring Scale in Liquid Reading on Spring Scale in Air Liquid Water

Molasses

Corn Syrup

Salt Water

Draw a diagram of the forces acting on the mass in each liquid. Why are the forces different in the different liquids?

New Brunswick Science Resource Package: Grade 8 21 Fluids: Forces in Fluids Quantify the Forces Activity

Part 2

1) Based on the reading, predict whether different items such as a cork, a piece of candle and a metal nut or washer will sink or float

2) Test your prediction and record your observations.

Liquid Sink or Sink or Sink or Sink or Sink or Sink or Float? float? Float float? Float float? Prediction Actual Prediction Actual Prediction Actual Candle Candle Cork Cork Metal Nut Metal Nut

Molasses

Corn syrup

Salt water

Make a Dynamometer Materials:

Ruler Rubber band or spring Weight (for example, a small bag of nuts, wet sand or anything else heavy).

Method:

 Attach the rubber band or spring to the top of the ruler either by making a hole in the ruler or by taping it in place. The elastic or spring should stretch at least ¾ down the ruler.

 Attach a paperclip or paper arrow pointer midway down the elastic or spring. This pointer will be used to mark the changes in length of the elastic/spring in different liquids.

 Try it out and make adjustments if necessary.

Observation Chart Sheet Outcomes:

name name name name name

New Brunswick Science Resource Package: Grade 8 24 Fluids: Forces in Fluids Checklist Sheet

Outcomes Correlations with Cycles Yes No SKILLS

208-6 Design an experiment and 1st cycle: Mark/record observations identify major variables during sinking/floating activity

209-3 Use instruments 3rd cycle: Mark/record observations effectively and accurately for during buoyancy activity collecting data

1st cycle: Mark/record observations 210-13 Test the design of a during sinking/floating activity constructed device or system 2nd cycle: Mark/record observations during Cartesian diver activity

210-14 Identify and correct practical problems in the way a 1st cycle: Mark/record observations prototype or constructed device during sinking/floating activity; journal functions

st 211-3 work cooperatively with 1 cycle: Mark/record observations team members to develop and during sinking/floating activity 2nd cycle: Mark/record observations carry out a plan, and during Cartesian diver activity troubleshoot problems as they 3rd cycle: Mark/record observations arise during buoyancy activity KNOWLEDGE 307-10 Describe situations in daily life where the density of 3rd cycle: Journal substances naturally changes or is intentionally altered

2nd cycle: Mark/record observations 309-2 Describe the movement of during Cartesian diver discussion; objects in terms of balanced and assessment question unbalanced forces 3rd cycle: Mark/record observations during buoyancy activity and discussion

New Brunswick Science Resource Package: Grade 8 25 Fluids: Forces in Fluids Observation Checklist

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Student Record Outcome goal Evidence New Brunswick Science Resource Package: Grade 8 26 Fluids: Forces in Fluids

I can plan an experiment and identify the major variables. (208-6)

I can use instruments accurately for collecting data (209-3)

I can test the design of a device I have constructed. (210-13)

I can identify and correct problems in the way a constructed device works (210-14)

I can work cooperatively with team members to develop and carry out a plan, solving problems as they arise. (211-3)

I can describe real situations where the density of substances or objects changes. (307-10)

I can explain the movement of objects in terms of balanced and unbalanced forces. (309-2)

Archimedes

Archimedes was born in Syracuse, Greece in 287 BC and died in 212 BC.

Archimedes loved geometry. He explored all kinds of shapes, trying to measure their areas and volumes.

Archimedes tried to work with very large numbers. The Greeks did not have digit symbols like we do and they had no zero. Numbers were represented with letters. It was difficult to do the math that you do easily.

Archimedes invented many items useful to his time. He invented several war machines, and then oversaw and helped with their construction. One of these can be seen to the right. It was known as Archimedes claw. The long ropes would have a claw like attachment on their ends. The operators (it took nearly the entire population of Syracuse to operate the claw) would ‘hook’ onto an incoming ship and then tip it over, wrecking the ship. When the ships were far from shore, Archimedes would use one of his many types of catapults, to hurl rocks, wood, or other objects at ships.

He also invented a machine, sometimes known as ‘the death ray’ which harnessed solar power, and could even set ships ablaze. Archimedes created many machines that were well ahead of his time.

When Archimedes was only 22 years old, his cousin Hiero, came to him for help.

New Brunswick Science Resource Package: Grade 8 28 Fluids: Forces in Fluids Heiro had been elected king of Syracuse after a great battle in which he had led the Syracusans to victory. Heiro felt he should have a golden crown made to show his gratitude to the gods for their assistance with the battle.

Heiro had weighed out a specific amount of gold and gave it to a goldsmith to make the crown. There were rumors that the goldsmith kept some of the gold. It was said the crown he had made for Heiro was actually made of both gold and silver mixed together. Heiro was very upset by the thought of being cheated.

Archimedes was unsure how to help his cousin at first. He watched the water spill over the sides of the tub when he stepped into the bath and he had an idea! Archimedes noticed that the further his body was in water, the more water poured over the sides of the tub. He knew how to solve Hiero's problem.

It is said, Archimedes was so excited by his discovery that he jumped right out of the bath, and ran home without even dressing. He shouted, 'Eureka, Eureka!' which is Greek for, 'I have found it! I have found it!'

He had discovered a way to measure the volume of an irregularly-shaped object. He found that an object, when submerged in water, displaced a volume of water equal to its own volume. By measuring the volume of the displaced water, the volume of the object could be determined, regardless of the its shape. We now know this discovery, relating to water displacement and buoyancy, as Archimedes principle.

Archimedes could measure the volume of the crown by measuring the volume of the water spilled when the crown was submerged in water. He compared this to the amount spilled with the same weight of pure gold.

New Brunswick Science Resource Package: Grade 8 29 Fluids: Forces in Fluids He proved the rumors to be correct – Hiero had been cheated by the goldsmith.

When Archimedes was 75, Syracuse was captured by the Romans. It is said Archimedes was so deep in thought when approached by a Roman soldier, he was killed by the soldier for ignoring him.

Without Archimedes our world might possibly be a very different. He was once quoted as saying “Give me a lever long enough and a fulcrum on which to place it, and I shall move the world.” Archimedes has inspired many people and many technologies.

Picture sources:

New Brunswick Science Resource Package: Grade 8 30 Fluids: Forces in Fluids 1. Archimedes www.scientific-web.com/.../images/Archimedes.jpg

2. The death of Archimedes www.gap-system.org/.../Archimedes_9.jpeg

3. Archimedes www.nndb.com/.../archimedes-1-sized.jpg

4. The golden Crown http://www.longlongtimeago.com/llta_greatdiscoveries_archimedes_ eureka.html

5. Archimedes claw http://images.google.ca/imgres? imgurl=http://www.math.nyu.edu/~crorres/Archimedes/Claw/claw_lazos.jpg&imgrefurl=h ttp://www.math.nyu.edu/~crorres/Archimedes/Claw/illustrations.html

New Brunswick Science Resource Package: Grade 8