Day 30 What is dew point? the temperature at which the air is saturated and water will change from gas to liquid Humid air already has a lot of water vapor, so it doesn’t have to get much cooler before water vapor will change to liquid water. Dry air doesn’t hold much water vapor, so it has to get much cooler before water vapor change to liquid water. Is the dew point higher when the air is humid or when the air is dry? The dew point is higher when the air is humid. It doesn’t have to get much cooler to reach saturation. 1

Condensation & Dew Point, cont. Investigation 6, Part 3b Water in the Air

Wet-Bulb/Dry-Bulb One way to determine relative humidity is to compare the temperature of the air and the temperature of a wet cloth. These are called dry-bulb and wet-bulb readings. What happened when we wet the fabric on the thermometer and waved it in the air? The temperature dropped as the water evaporated. Daily Warm-Up Exercises 3

Demonstration Record the temperature of both thermometers. Dampen the fabric on the wet-bulb thermometer and wave both for five minutes. Record both the temperatures. We will use this data to calculate the relative humidity in our room. Daily Warm-Up Exercises 4

Demonstration Turn to the Humidity Calculator on page 79 in the Resources book. Subract the wet-bulb temperature from the dry-bulb temperature. Find this number in the row across the top of the chart. Find the dry-bulb temperature on the chart. Find the square where the two readings intersect. This is the relative humidity. Daily Warm-Up Exercises 5

Labels and Connection to text >>>next slide<<< Visualization Exercise 6.1

Resource P. 35 Exercise 6.1 Image comprehension focus: Labels and Connection to text Rationale: When reading text, students may often skip diagrams which can often be elaborated on by the text and vice versa. It is important that students learn to integrate these two components to gain a more comprehensive understanding of the concept being explained. Additionally, students may also tend to skip labels that can contain information crucial to understanding the diagram. Type of Activity: Teacher Comment Objective: To reinforce student understanding of the diagramming conventions labels and connection to text. Module Images: Resources, P. 35 Procedure: After students have read the text, show them the diagrams. Note: Because of the small size of the type, students may not be able to read the labels from a distance. Instruct students to open their books to page 35 and read the labels on the original image. The projected image will still be useful as a way of showing students what parts of the diagrams to pay attention to as you work through the exercise. Ask: “Under each picture, there is some writing. For example, under the first picture it says, ‘10% relative humidity at 35 degrees Celsius.’ What do we call this writing?” [Students may call it a caption – but a caption refers to an entire diagram. This is an example of an explanatory label. It is informative in the same way that a caption would be, but it only refers to a part of the diagram – in this case the left-hand picture only.] Explain: “In this set of pictures, water particles have been drawn as though they are visible. This image is similar to some of the other diagrams that we have seen with air particles, like the images of the syringes full of air. There is, however, one very important difference this time. In the earlier examples we talked about the fact that the blank area around the particles stood for empty space. In this case, if we were to draw the picture accurately, some of the blanks in the picture would be taken up air particles, which would be about the same size as the water particles. It is not that there are large differences in the number of particles from one picture to the next – instead, the pictures show us what percentage of the particles are water.” Ask: “What is the same in all three left-hand pictures?” [They all show 3.5 grams of water vapor, and they show the water vapor with the same density.] Ask: “What is different from one left-hand picture to the next?” [The percent relative humidity is getting higher as the temperature is getting lower.] Ask: “Put together the things that are the same, and the things that are different, and explain in your own words what it means? [Encourage students to contribute their own answers. If necessary, guide them to the idea that a small amount of water vapor is all that can be ‘held’ in cold air – while the same amount of water vapor represents only a fraction of what could be ‘held’ by warmer air.] Ask: “What is different from one right-hand picture to the next?” [The percentage of particles that are water particles gets smaller as the temperature gets lower] Ask: “What is the same in all three right-hand pictures?” [In all three cases, the image shows 100% relative humidity – or the maximum amount of water that can be ‘held’ by the air at a particular temperature.] Ask: “Put together the things that are the same, and the things that are different in the right-hand pictures, and explain in your own words what it means? [Again, encourage students to contribute their own answers. The essential point is the same as it was for the left-hand images. If necessary, guide them to the idea that a small amount of water vapor is all that can be ‘held’ in cold air – but if the air is warmer then it can contain more water.] >>>end of exercise<<<

Reading Turn to page 34 in the Resources book. Read Dragons Breath and answer the questions on page 36. Write a 20 word summary, no more, no less All should be on the same paper as your Humidity chart Daily Warm-Up Exercises 8