Concept: After students have examined Water Cycles in their unitt on Weather Dynamics introduce this discrepant event in order to expand on prior knowledge and advance students exploration with regards to energy exchanges within the hydrospheree and atmosphere. This activity will help further investigate heat flow in gases and liquids ass well as the subsequent effect of heat on matter. New Brunswick Board of Education Curriculum Grade 10 Earth and Space Science: Weather Dynamics- Heat energy, its transfer, and Weather Dynamics. Outcomes: Students will be expected to use weather data to describee and explain heat transfers in the hydrosphere and atmosphere, showing how these affect air and water currents (214-3, 331-2). Materials: 1. An Erlenmeyer flask (5000 ml). 2. A round, helium quality, balloon. 3. A hot plate. 4. Tap water (100 ml). 5. Protective gloves for dealing with boiling hot water. Procedure: 1. Put a small quantity of water in the flask (less than 100 ml) and place on hot plate, and heat it to a boil. 2. Allow the water to boil rapidly for one full minute. 3. Remove flask from hot plate onto a flat surface (counter-top or table) and place the balloon over the mouth of the flask. 4. Ensure the balloon is securely in place and let stand. 5. Watch balloon be sucked inside out into the flaskk and blow up. Misconception: Most students will think the balloon will inflate since the flask was heated to boil and because the hot air molecules are escaping from the flask.
Experimental Setup: ONE: : Put 100 ml of tap water into flask. + TWO = O: Put flask on hot plate. + THRE EE:Bringg water to a rapid boil for 1 full minute. FOUR R: Remove flask from hot plate and place balloon over the mouth. FIVE E: Watch balloon get sucked inside out into the flask and blow up.
Leading Questions: Here are some basic questions that you can use as prompts while showing students this discrepant event. I have listed the questions in order based on the events that will happen during the presentation. I have also included possible answers (a.) the students will provide, and supplied extension questions for deeper exploration of what is really happening (i. & ii.). 1. What is inside the flask? a. Water, air, students might guess something else that they think you re using to trick them. i. Some might go deeper and say: Oxygen and Carbon Dioxide molecules. ii. Note: The composition of air (% by volume) is 78.09% Nitrogen, 20.95% Oxygen, 0.98% Argon, 0.03% Carbon Dioxide. 2. What happened when the water was heated? a. The water boiled. Evaporation occurred. Air molecules were forced up and out. 3. What happened when I placed the balloon over the flask? a. The air became trapped inside the flask. b. What happened when the flask was removed from the heat source? i. The temperature inside began to cool or try to return to room temperature. 4. Why is the balloon being sucked into the flask? a. Because it is acting like a vacuum. i. Note: This is not an accurate answer and should be identified by the teacher. In order to have a perfect vacuum, in essence there would be no particles present. This is certainly not the case in this discrepant event. b. What is happening here? i. What is happening to the water vapour as it cools? ii. If the air inside the flask is condensing then why is the balloon blowing up? 5. Why is the balloon expanding inside the flask? a. Because of the air outside. i. Because the air outside is greater than inside. (more pressure) ii. Because the atmospheric pressure outside is greater than inside Solution: When the water is brought to a rapid boil the temperature of the gas inside the flask increases, which causes the volume of the gas to expand and push its way out of the flask. Once the gas inside was forced out there was less gas molecules than were initially present, before the heating of the water. As heat energy is removed, the kinetic energy of the gas particles decreases which is seen in the temperature drop. A drop in temperature results in a decrease in the volume of the confined gas. As confined gas contracts, due to the energy of the particles decreasing, the volume of the gas also decreases. This reduction of pressure is why the balloon is sucked into the flask. The atmospheric pressure external to the flask remains constant, therefore forcing the balloon inside the flask, because it is greater than the pressure within the flask. The balloon blows up once inside the flask as a result of the greater external atmospheric gas.
Real Life Examples: Atmospheric pressure as displayed in this experiment affects our lives daily, but often goes unrecognized. Ask your students if they have ever left a soccer-ball, basketball or football outside on a cold day and returned to find it slightly deflated. The reason for this occurrence is due to the temperature outside changing the air pressure inside the ball, giving an under inflated effect if it is cold or an over inflated effect if it is warm. Also in this experiment students witnessed that when air expands it rises, demonstrated in the boiling water forcing all the gas outside of the flask. When warm air rises it cools, cold air holds less moisture than warm air which causes water vapour to condense and form clouds. References: 1. Invitations To Science Inquiry 2 nd Edition by Tik L. Liem 2. Brain Powered Science; Teaching and Learning with Discrepant Events by Thomas O Brien, 2010. 3. New Brunswick Department of Education: Science Curriculum Documents Watch a video of this experiment online: http://www.youtube.com/watch?v=r9sq4uiyw1s
Predictions: Draw what you think will happen in the box provided below: Why do you think this will happen? What are your reasons? Comment: Observations: What is happening during the experiment? Make notes in the box below: Notes: Explanatio on: What happened?