Simulation: Heating Curve of Water FOR THE TEACHER Summary In this simulation, students will investigate qualitatively and quantitatively what happens as water changes states. This lesson accompanies the simulation from the May 2015 issue of Chemistry Solutions. Grade Level High or middle school Objectives By the end of this lesson, students should be able to • Understand the difference between the states of matter. • Realize that when a state change occurs, a temperature change does not take place. • Quantify how much energy it takes to heat water from one temperature to another. Chemistry Topics This lesson supports students’ understanding of • Heating curve • State change • Specific heat • Intermolecular forces • Molecular motion Time Teacher Preparation: 10 minutes Lesson: one class period Materials • Computer with internet access • teachchemistry.org/heating-curve Safety No specific safety considerations are needed for this investigation. Teacher Notes • Students can only click left to right (for example, if they choose 120 oC as T1, T2 has to be higher than 120 oC). • For younger students, they can skip the “calculate” step. • The values used to calculate the energy required in this simulation are as follows: o Specific heat of ice(cice): 2.09 J/goC o Heat of fusion (∆Hf): 6.01 kJ/mol o Specific heat of water (cwater): 4.184 J/goC o Heat of vaporization (∆Hv): 40.7 kJ/mol o Specific heat of steam (csteam): 1.84 J/goC o MWwater: 18.01 g/mol
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There are 10 possible diagrams students will see in the T1 and T2 boxes (see diagrams below). These diagrams are meant to be relative to one another. Water molecules are represented as one complete sphere.
FOR THE STUDENT Student Activity Sheet: Heating Curve of Water Lesson Background The three states of matter are solid, liquid, and gas. To change from one state to another, energy is either added to or removed from the system. In this investigation, you will look at heating up water. Does that involve adding or removing energy? Explain. In the squares below, draw how you think particles are arranged in the three states. Use spheres to represent the particles and label each box with the state it represents.
When changing from one state to another, what happens to particles in terms of energy?
Procedure 1. Visit teachchemistry.org/heating-curve. You should see this on your screen.
2. On the heating curve above, label the states of matter. Include the state changes. 3. Choose an initial point on the graph. This is your starting temperature/state. Choose a second point that is the same state. Draw the two particle diagrams in the squares. Explain why the diagrams look the way they do.
4. Calculate the energy required to heat up 65.0 mL of the sample. Show your work. Verify your answer by clicking “Calculate.” 5. Choose an initial point on the graph. This is your starting temperature/state. Choose a second point that is a different state. Draw the two particle diagrams in the squares. Explain why the diagrams look the way they do.
6. Calculate the energy required for 30.0 mL of water to undergo this state change. Verify your answer by clicking “Calculate.”
7. Pick a point on the ice part of the heating curve. Click on a point about 75 oC warmer. What state is this?_________ Record the T1 and T2 T1=_____ values. How much energy is required to heat 15.0 g ice to T2? T2=_____ Show your work. Verify your answer by clicking “Calculate.” 8. Pick a point on the liquid part of the heating curve. Click on a point about 75 o C warmer. What state is this? _________ Record the T1 and T1=_____ T2 values. How much energy is required to heat 15.0 mL of T2=_____ water to T2? Show your work. 9. Why are your answers to questions 7 and 8 not the same? Explain.
