Waterworks. QUT Extreme Science

Transcription

1 Waterworks QUT Extreme Science

2 Glossary QUT Extreme Science Contaminants Dependent variable Fair test Filtration Independent variable Microbes ph indicator Salinity Turbidity Something that contaminates or makes something impure (e.g. dirt) The part of your experiment that changes depending on the change in the independent variable A science experiment which confirms that what has been changed (independent variable) has affected what is measured (dependant variable) A method used to remove impurities using a filter (e.g. cloth, paper, charcoal, sand etc) The part of an experiment under the control of the researcher. Changing the independent variable means that the impact of changes to the variable in the experiment can be measured. Any organisms too small to be viewed by the unaided eye, e.g. bacteria A chemical that reveals by colour change if a solution is acidic or alkaline. Of or relating to salt Not clear or transparent because of stirred-up sediment or the like Glossary extracts from Objectives Learn to predict the result of an experiment based on prior knowledge Learn to carry out a fair test and what makes a test fair or not Learn how to test water for ph and turbidity Learn to identify organisms commonly found in pond water, using microscopes and distinguish between a living and a non-living thing, based on its characteristics Learn to explain why a result came about Learn to compare your results with your predictions Learn to describe and share observations in small groups and as a class Equipment list Activity 1: Pond water under the microscope 4 light transmitting microscopes Glass slides with a drop of pond water (prepared by instructor, not to be handled by students) Information sheets with pictures of commonly found pond organisms

3 Activity 2: Water filtration 4 lots of 3 filtration tubes in cups labelled A (DE powder), B (rocks) and C (sand) Dirty water for filtration 4 small beakers decanting the dirty water 4 measuring cylinders 4 stereo microscopes Activity 3: Water testing ph indicator (purple cabbage water) to be prepared by presenter for each workshop Water samples 1 and 2 Beakers Pipettes Testing trays Turbidity cylinders Salinity measurer Safety notes Electrical extension cords and powerboards are used in this workshop, and care should be taken to minimise trip hazards from cords Students should not touch the powerboards Pond water microscope slides should only be prepared by the presenter and not the students Only the student using the microscope should adjust any of the settings Students should be careful not to get the dirty water samples in their eyes and mouths Background One in 5 people in the world do not have access to clean drinking water. Water quality can depend on geographic region (lower water supply available in arid areas), but can be heavily impacted by salinity, turbidity and contaminants such as microorganisms (viruses and bacteria) and industrial pollution (pesticides, herbicides, radioactive materials and heavy metals). Lack of access to water filtration and purification technologies to remove such contaminants from the water is a major problem in poor and isolated communities around the world. Scientists such as chemists, environmental scientists and hydrogeologists work to ensure that water is safe for drinking. In this workshop, students explore water contaminants and conduct tests relating to salinity, ph (acidity and alkalinity), turbidity and the presence of microorganisms. Students also explore basic methods of water filtration.

4 Workshop activities In this workshop there are 3 main activities. The class is split into 3 groups and told which activity to start at. Each activity takes about 10 minutes. Activity 1: Pond water under the microscope Students examine pond water/hay water samples under the microscope and try to find any organisms. If they are able to see organisms, they should try to identify it from the common pond water organisms list provided. Activity 2: Water filtration Students measure out (with the measuring cylinder) 10mL of the dirty water from their small beakers and pour them into each column (A, B and C). Whilst the water is filtering (it takes 5 mins), they examine the filtering materials under the microscope and make a prediction as to which material will give the cleanest water. They then examine the water that has been filtered through the columns. Activity 3: Water testing Students perform 3 tests on each of the three water samples to learn about some of the properties of contaminated water samples. This includes: 1. ph testing add cabbage water to sample in the testing tray and note the colour change 2. turbidity testing pour each sample into tube and record the turbidity unit 3. salinity testing put a drop on the salinity meter and read the measurement Rundown of workshop Time Activities 0-15 Introduction and explanation of microscopes, get students into groups Activity round Activity round Activity round Discussion An example of a good setup for this workshop is illustrated below. The best setup will change depending on the location of the power points in the room, how many tables you re given, and how big they are. Make sure you leave space for the class to come in that is clear from power cords, and

5 also that you leave a space for the class to sit. Do your best to keep all power cords and power boards out of the way of the students. Some further examples of set up are on the following page. Water filtration 4 sets 4 stereo microscopes with filtration materials Water testing ph, turbidity and salinity Students are seated in this area for introductory talk, activity instructions and wrap-up discussion 4 transmission microscopes with slides and pond water Script Introduction takes around 10 minutes. Dialogue is in italics. Lots of scientists work with water. They might be environmental scientists, chemists or hydrogeologists. Today we are going to be investigating water. First of all though I m going to share with you some interesting facts about water. Do you know that 1 in 5 people (or just over 1 billion of the worlds 6 billion population) do not have access to clean drinking water. Do you know that out of all the water in the world 97.5% is salt water. Of the remaining 2.5% of fresh water is in glaciers and is inaccessible for human use. Of all the water on the surface of the earth only 0.007% is available for human consumption. o Do a demonstration of this: fill a beaker with 1 litre of water. Ask a student to withdraw some water using plastic disposable pipette - the 1 litre represents all of the water on earth and the amount in the pipette represents what is available for humans to drink. Do you have any idea how much water your family uses in a year? Ask a random student how many people are in their family and then tell them that the number of people equals the amount of Olympic swimming pools their family would use per year. This means that water is a very precious resource that needs to be conserved and not wasted. The job of monitoring our fresh water supplies is in the hands of environmental scientists. Today we will perform some of the tests that environmental scientists do.

6 Hand out sheets and advise students to put their name on their sheets and to KEEP SHEETS AWAY FROM THE EXPERIMENT TABLES or they will get wet! The first activity involves looking at the micro-organisms that live in pond water. Environmental scientists can often determine how healthy the water is by looking at the microbes that live in the water. You need to look down the microscope and draw the microbes you see. You can then use these pictures to see if you can name or identify any of your microbes. You will not be preparing the slides - the microscopes are already set up with slides for you to view. You look down the eyepieces. The controls that you can use are marked with a sticky dot. This one is the fine focus. It allows you to make little adjustments to the focus as everyone s eyes are slightly different. This next control allows you to chase the microbes around by moving the glass slide back and forth. Please do not use any of the other adjustments as the slide is easily broken!!!!!! The second activity we will be doing some water filtration. Who knows what this is done for? The water is filtered to get out the suspended particles, and chemicals are added to kill bacteria and other micro-organisms. In this next activity you will investigate which materials filter best. There are 3 different syringes labelled A, B and C. Each one has a different material in them. A is a fine white powder called diatomaceous earth, or DE powder. B is small rocks and C is fine sand. Take your muddy water sample and give it a stir. Then pour 10mls of water into the measuring cylinder like this. Next pour this water from the cylinder into the syringe labelled A. Repeat this for syringes B and C. Then examine the water that comes out the bottom and see which one gives the cleanest water. DO NOT STIR OR MIX THE MATERIAL IN THE SYRINGES TO MAKE IT GO FASTER AS THIS WILL RUIN THE FILTERING MATERIALS!!!!!!! While you wait for the water to come through the filtering materials you need to make a prediction about which material you think will give you the cleanest water. Who knows what a prediction is? A prediction is sort of like a guess, but it is important to have a reason to support your guess. To help you make your prediction you can examine the filtering materials in these small containers using the microscope. By the time you have looked at the materials under the microscope and made your prediction the water should have come through the filtering materials and you can fill out the remaining questions on your sheet. The last activity is looking at different properties of water. We will measure 3 things: firstly the turbidity of the water sample. Turbidity is a measure of how murky or cloudy the water is. The environmental scientist can t just write on their report that the water was brown. They need to measure how brown or cloudy it is. To do this you stir your sample and pour it slowly into this long tube. On the base of the tube are 3 squiggly lines. You keep slowly pouring water until the squiggly lines are no longer visible when you look through the tube from the top. Then you read the number closest to the water level and record this on your sheet. You need to be very careful when you pour the water out of the tube as it rushes out very fast, so go SLOW! Secondly, you will measure the ph of the water. The ph is a measure of how much acid is in the water. You may have heard of acid or ph associated with your swimming pool. If there is too much acid then this is bad but if there is not enough acid this is also bad. To measure the ph, use this plastic dropper to suck up some of your water sample and stick it into one of these holes in the plastic dish. Then add 3 drops of this smelly purple solution. This is actually red cabbage water and it changes colours in liquids with different amounts of acid. Record your result on your sheet.

7 There are 3 work stations with 4 sets of equipment at each so everyone needs to be in groups of 2 or 3. Ask the teacher to organise groups. Allow about 30 minutes to do the activities. They should spend about 10 minutes at each activity. The water filtration generally takes the longest, so try and get them to pour their water quickly. Allow 10 minutes to wrap up. Go through the results for ph and turbidity. Discuss possible reasons for wide variation in results. Generally due to mixing up the 2 samples or not mixing sample first. Ask the students which filtering material gave them the cleanest water. It will generally be A but may be C. In theory A has the smallest particle size so should give the cleanest water but as the particles are so fine they often leach into the water making the water appear cloudy. Try to get across the relationship between particle size, flow rate and cleanness of water. For the pond microbe activity ask students what creatures they saw. You need to emphasise that this is pond water and NOT tap water. Advise teachers that students need to wash their hands on the way back to class. Worksheet On the following page is the worksheet which is used for this workshop. Acknowledgements This document was compiled by Phillipa Perrott and Maria Barrett.