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How long can a bubble last?<br />You have recently been placed in a research team to help provide information for your company about their soap product.<br />A customer has complained – she says that the liquid produces bubbles that burst instantaneously.<br />
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Your task<br />Your team’s task is to carry out experimental procedures and discover the conditions needed to produce long lasting bubbles.<br />
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Safety<br />This is a fairly low risk lab<br />You will be using a glass dropper which will cut you if you break it<br />Don’t let the soap solution get into your mouth<br />Remember: Tell the teacher about any spills or breakage<br />
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Equipment checklist<br />Find the equipment checklist in your box<br />Make sure you have all of the equipment<br />You will have to check everything on the list back in at the end of class so make sure it’s not missing before you start<br />
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Set up your notebook<br />Write a title – center it, underline it, make it look like a title. <br />Call it “Investigating factors effecting bubble lifetime.”<br />
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Objectives<br />You will:<br />Investigate the effect of soap concentration on the lifetime of bubbles<br />Design an experiment to test the effect of bubble size on lifetime<br />Plot graphs of your data to help you interpret it<br />Report your findings to the company<br />
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Practice blowing bubbles<br />For these experiments, you will need to be able to blow bubbles that are consistent - the same every time. <br />Before starting, follow the following instructions and get some practice.<br />
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First make your “Blower”<br />Make sure your whiteboard is clean of dust. <br />Insert one end of the straw into glass dropper (that doesn’t have a rubber bulb on it)<br />Then tape around the join.<br />
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Set up the soap solution<br />Using the other dropper, put 1ml (20 drops) of soap solution in the center of the circle. <br />
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Blow the bubble<br />Insert the sharp end of your “Blower” into the pool of soap solution and blow gently until the bubble fills the circle. Then Stop. <br />If more than one bubble forms, wipe the whiteboard and start again<br />
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Take some data<br />Write a heading in your notebook and copy this table.<br />
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Taking data<br />Now blow a bubble<br />Stop as soon as they reach the size of the circle and start your stopwatch<br />Stop the watch when they pop<br />Write the time in table<br />Repeat four times<br />
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Analysis<br />Why do we need to do it more than once?<br />Write the answer in your notebook as a full sentence:<br />“We timed four bubbles because…”<br />
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Experiment One:The effect of concentration<br />A Concentrated soap solution has more soap in the same amount of water than a Dilute solution.<br />Concentrated<br />Dilute<br />
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Your task<br />You are going to investigate what happens to the lifetime of a bubble as the concentration of the soap solution increases and becomes more concentrated.<br />
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Hypothesis<br />Scientists start an investigation with a hypothesis – a prediction. The hypothesis does not have to be correct and often are found to be wrong. Not a problem – it all adds to scientific knowledge. <br />What do you expect to happen to the lifetime of the bubbles as concentration increases? Do you think they will last longer with a concentrated, strong soap solution or a weaker, dilute solution?<br />
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Write a hypothesis<br />Write a title “Hypothesis” in your lab book and write what you think – include enough words so that it’s clear to anyone who picks up your book.<br />Start it like this:<br /> “If the concentration of the soap solution increases, then bubble lifetime will ……”<br />
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Procedure<br />Your Sample will be 4 bubbles.<br />3 different concentrations of soap solution are provided:<br />4ml soap per 100ml<br />6ml soap per 100ml<br />10ml soap per 100ml<br />Which is most concentrated? Check your answer with a teacher.<br />For each concentration of soap solution, you will blow an 8cm bubble and measure its lifetime.<br />
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Collect data<br />Draw this table in your lab book and collect your data:<br />
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Analysis<br />What is your Independent Variable ? This will go on your X axis. (HINT: Which variable are YOU changing?)<br />What is your Dependent Variable? (HINT: Which are you measuring?)<br />Write a note in your notebook:<br /> Independent variable: _________________<br /> Dependent variable: ___________________<br />
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Graphing<br />You need to draw a graph of your data. What kind will you draw? <br />Remember that you use:<br />a bar chart you are measuring a series of unconnected data; <br />a line graph if you are analyzing data that changes continually; <br />or a pie chart if you are comparing fractions or percentages of a whole.<br />
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Graphing (cont.)<br />Draw your graph on graph paper and stick it into your notebook .<br />Remember to label the graph and label each axis.<br />
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Analysis (cont.)<br />What happened to the lifetime of the bubble as you increased the concentration?<br />Was your prediction correct?<br />Whether you predicted the correct result or not does not matter – now you know the answer.<br />Write your answers in your notebook<br />
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Experiment 2: The effect of Size<br />Will larger bubbles last longer than small ones? You must find out. Investigate the lifetimes of bubbles with diameters between 3 and 8cm. <br />Diameter<br />
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Hypothesis<br />What do you think will happen to the lifetime of bubbles as you increase the diameter?<br />Add a new heading to your notebook for this experiment and write a hypothesis.<br />HINT: look at your last hypothesis for ideas…<br />
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Variables<br />What will your Independent Variable be?<br />What will your Dependent Variable be?<br />What will you keep constant?<br />Write a list in your notebook:<br />Independent variable = ___________________<br />Dependent variable = ____________________<br />Constants = _____________________________<br />
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Procedure<br />Now you know:<br />What you are changing<br />What you are measuring<br />What stays the same<br />Write a Procedureto check your hypothesis<br />Use numbered steps so that anyone would understand it and know what to do<br />
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Data<br />Before you start, draw a data table in your notebooks.<br />Ask a teacher to check it and your procedure before you go any further.<br />
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Analysis<br />Plot your data on a graph – use graph paper.<br />Remember:<br />The independent variable goes on the x axis <br />The dependent variable goes on the y axis<br />What kind of graph are you going to use?<br />According to your graph, what happens to bubble lifetime as bubbles get bigger? Was your prediction correct?<br />
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Report<br />Now write a short Memo to your boss explaining what you have discovered.<br />Do the bubbles burst instantaneously like the customer complained?<br />What should your boss tell the customer to do if they want their bubbles to last longer?<br />Write the report in the style of a “Memo”. That is how people write to eachother inside a company. The next slide shows you how to format the memo.<br />
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Memo<br />From: Your name<br />To: Your boss’s name<br />Date: Today’s date<br />Blah, blah, blah…<br />
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Cleanup<br />Congratulations – you have finished the assignment<br />Now wipe off your whiteboard<br />Throw away the straw that you used in your “Blower”<br />Put everything back into your lab box and check the equipment list as you do so.<br />Call a teacher to check that everything is in the box before you put it away.<br />
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