Storm Chasers – how heat and convection help to form storm clouds Author: David Dieckfoss This resource was developed as a result of participation in CSIRO’s teacher professional learning program, Educator on Board. © Storm Clouds – how heat and convection help to form storm clouds (created by David Dieckfoss) (2020). Copyright owned by Department for Education, Tasmania. Except as otherwise noted, this work is licenced under the Creative Commons Attribution 4.0 International Licence. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/ cid:image005.png@01D4620F.F55F9320 Storm Chasers – How Heat and Convection Help to Form Storm Clouds Activity 1 - Student Activity “What is temperature?” Suggested activity duration 10 minutes Step 1. Watch the video: “Curiosity starter – What is temperature”. ( 1 min) https://www.youtube.com/watch?v=_4BX_W8h7fs Step 2. Ask the students to estimate the temperature of various objects in the classroom. Eg the air, desk top, metal legs on the desk, metal in the sink, carpet, walls and write their estimate down in their books. Step 3. The teacher or selected students can measure the actual temperature using a digital probe thermometer or a digital infrared thermometer. Step 4. As a class (or in small groups) – discuss reasons for why the temperature of some objects “feel” different to others. Step 5. Students to write a definition of “Temperature” and why some objects may feel colder than other objects. For the teacher • Objects in the room will all be approximately the same temperature, but they will “feel” different. Metal objects will “feel” colder than most non metal objects even though they are the same temperature. • Temperature is a physical property related to the average kinetic energy of the atoms or molecules of a substance. • Metal is a better conductor of heat than other materials. The metal will “feel” colder than the ambient room temperature because it conducts heat away from your hand which is at 37 degrees Celsius. Reference for activity 1: Science as a Human Endeavour. (2020, Jun 2). What is Temperature? [Video]. https://www.youtube.com/watch?v=_4BX_W8h7fs Activity 2 - Teacher Demonstration “Boiling water without adding extra heat” This demonstration “boils” water at lower temperature by lowering the air pressure. This is a good “wow” demonstration. Step 1. Watch the video: “Curiosity starter – Can you boil water without heating it”. ( 1 min) https://www.youtube.com/watch?v=fP812b17gBc A picture containing man, indoor, person, table Description automatically generated Step 2. Ask the students if they know the temperature at which water boils. Most will say 100 degrees. Step 3. Draw up some warm water (40 degrees Celsius) into a 50ml or 100ml needleless syringe. Image credit: D Dieckfoss 2020 Step 4. Place your finger over the inlet and draw the plunger out to reduce the air pressure. The water will form bubbles and start to boil. Water boils at lower temperatures with lower pressure. Step 5. Further discussion. When water boils it changes state from liquid to a vapour. Why does water evaporate from puddles, off the road or path when it doesn’t reach 100 degrees? For the Teacher • Temperature is a physical property related to the average kinetic energy of the atoms or molecules of a substance. The average temperature of a puddle of water may be only 10 or 15 degrees but molecules at the surface will have a far greater kinetic energy due to absorbing more of the Sun’s energy. These molecules become vapour and “evaporate”. • At standard atmospheric pressure (1 atmosphere = 0.101325 MPa), water boils at approximately 100 degrees. Air pressure varies constantly and on top of mountains it is considerably less than at sea level. On top of Mt Everest water boils at approximately 70 degrees Celsius. • Heat causes some of the liquid water – from places like oceans, rivers and swimming pools – to change into an invisible gas called water vapor. This process is called evaporation and it's the start of how clouds are formed. • Clouds are created when water vapor, an invisible gas, turns into liquid water droplets. These water droplets form on tiny particles, like dust, that are floating in the air. Reference for Activity 2: Science as a Human Endeavour. (2020, Jun 2). Can you boil water without heating it”. ( 1 min) https://www.youtube.com/watch?v=fP812b17gBc Activity 3 – Student Activity “Swirly colours by convection”. Heat transfer by convection. *Suggested activity duration: 10 to 15 minutes. * Teacher supervision is required. Please ensure that you have assessed this activity for risk and that any potential risks are mitigated with appropriate strategies outlined in a plan. All students should have prior experience with the safe practice of lighting a Bunsen burner. Aim – To investigate heat transfer by convection. Method – Step 1. Pour 200ml of water into a 250ml beaker. Step 2. Place the beaker on a tripod with a gauze mat over a Bunsen burner or on a hot plate. Step 3. Carefully place a drop of food colouring into the beaker via a straw or dropping pipette so that the food colouring touches the bottom of the beaker. Be careful not to stir the water. Step 4. Light the Bunsen burner and position it underneath the beaker. As the water is heated, the process of convection can be observed. • Note The water will only need to be heated for a short period of time and should not be heated to boiling point. Image credit: D Dieckfoss 2020 Image credit: D Dieckfoss 2020 For the Teacher • Convection transfers heat from one place to another by the motion of a fluids or gases. Convection is different from conduction, which is a transfer of heat between substances in direct contact with each other. • Convection currents form because a heated fluid or gas expands, becoming less dense causing it to rise away from the heat source. As it rises, it pulls cooler fluid down to replace it. This fluid in turn is heated, rises and pulls down more cool fluid. This cycle establishes a circular current that stops only when heat is evenly distributed throughout the fluid. Activity 4 – Teacher Demonstration “Cloud in a jar”. Step 1. Obtain a large jar or measuring cylinder Step 2. Boil some water in a jug. Step 3. Pour a small amount of the boiling water into the measuring cylinder and cover top with a watch glass with ice. Step 4. A match can be lit, blown out and dropped in the beaker to provide a little smoke aiding the formation of the cloud. Image credit: D Dieckfoss 2020 For the Teacher • Some of the hot water changes into invisible water vapor. This layer is just above the water and looks clear. • Clouds are created when water vapor cools and turns into tiny liquid water droplets near the top of the measuring cylinder. These water droplets form on tiny particles, like dust, that are floating in the air. Activity 5 – Student Activity “Storm Chasing Science” Science as a human Endeavour Step1. Download and view the “Stormchaser” profiles document. https://drive.google.com/drive/folders/18e0equLMa7XVDWX8rVHWvUBacLRFOlEa? usp=sharing Step 2. Watch the Stormchaser video. (2 min) https://www.youtube.com/watch?v=dOI1Mah9YrE&list=PLaqmyvBWI1xfFRAD- 93JNnLBj8am3kGGh&index=3 A screenshot of a social media post Description automatically generated Step 3. Discussion or assignment questions. 1. What do you think it would be like to be a “Storm Chaser”? 2. What sort of “technological advances are on the Investigator that make it a valuable tool in weather forecasting? 3. Why do you think some storms are more violent than others? 4. Write your own “Storm Chaser” profile. References for Activity 5: Science as a Human Endeavour : Channel https://www.youtube.com/channel/UCa7l9VWsg7jP25saQLnP14g/ Science as a Human Endeavour. (2020, Apr 15). Storm chasing on the RV Investigator – 25th December 2019. [Video]. https://www.youtube.com/watch?v=dOI1Mah9YrE CSIRO. RV Investigator. Available at: https://mnf.csiro.au/en/RV-Investigator Activity 6 – Student Activity “Putting it all together” Ask students to write the steps involved in the formation of storm clouds. For the teacher. 1) Temperature is a physical property related to the average kinetic energy of the atoms or molecules of a substance. 2) Heat can be transferred by conduction (Activity 1) or by convection (Activity 3) 3) Water molecules can absorb heat and change state from liquid to vapour 4) Lowering the air pressure changes the boiling point (and freezing point) of water (Activity 2) 5) Hot water and hot air rise and help the atmosphere to circulate – convection (Activity 3) 6) As moist air rises due to convection it moves up to where temperatures and pressures are lower. The moist air condenses into clouds (Activity 4) 7) Storm clouds develop where the convective process is strongest. Hot moist air moving rapidly up in top colder low pressure regions higher in the atmosphere. (Activity 5) 8) There is still much we don’t know about how storms develop, and researchers continue to be curious and use ships like the RV Investigator to increase our understanding of weather patterns and storm development. (Activity 5) Reference for Activity 6: Bureau of Meteorology – What’s that cloud (15 Feb 2016) http://media.bom.gov.au/social/blog/895/whats-that- cloud/#:~:text=Cloud%20formation&text=As%20this%20moist%20air%20rises,than%20raindrops)%2C%20forming%20clouds.