Mao Doan

1. Vocabulary Review

2. Reading Comprehension

Read the text on page 102-103 and answer the questions. 

True or False?

1. Some species of fish do not need oxygen to survive.

2. Humans can have difficulty when oxygen levels in the air are high, similar to how fish are affected in water.

3. Water temperature is a significant factor in changing oxygen concentrations.

4. Water can hold more gases at higher temperatures.

5. In a can of soda, CO₂ is present in the form of dissolved gas.

6. When you shake a can of soda and then open it, the CO₂ stays dissolved because of the cold temperature.

7. Aquatic plants produce oxygen during photosynthesis, contributing to the oxygen levels in a lake.

8. Global warming may lead to an increase in the amount of dissolved oxygen and CO₂ in water, posing no threat to fish.

3. Listening

Audio: https://drive.google.com/file/d/1oQPq5Rj4_5i5WWkZFnULVMD8tRdpBT7Z/view?usp=sharing

Listening 1: True or False?

1. The term "soluble" means that a substance can dissolve into another substance.

2. In the context of solubility, oxygen is referred to as the solvent.

3. The solubility of gases in water remains constant regardless of temperature changes.

4. Warmer water can hold less dissolved gas compared to cooler water.

5. Shaking a can of soda before opening it can cause the soda to explode due to the release of dissolved carbon dioxide.

6. Fish require dissolved carbon dioxide to survive, while plants need dissolved oxygen.

Listening 2: Fill in the blanks.

Next I’d like to talk about the (1) … of gases in water. When we say that something is “(2) …,” we mean it can go into something. It can “(3) …” into water. The gas oxygen is soluble in something. In other words, oxygen can go into it. Can dissolve into it. We call the oxygen, in this case, the “(4) …”—the thing that’s dissolved. And the water, in this case, is called the “(5)…”—the liquid that holds the solute. 

Now, the solubility of gases doesn’t always stay the same. If (6) … change, so does solubility. When water is warmer, it is less soluble for gases. When water is cooler, it’s more (7) … for gases. I would like to demonstrate how this works by looking at something in your everyday life. People make cans of soda by dissolving the gas carbon dioxide under (8) … into water, inside a can. But if you shake the unopened can, you add heat to it. And as I said, heat makes the water less soluble. So the carbon dioxide leaves the water. When we open the can, the soda (9) …. I think everyone here has seen that!

So that brings me to why the solubility of gases is so important. For healthy lakes, there needs to be both oxygen and (10) … … in the water. Fish need (11) … oxygen for life. And plants need dissolved carbon dioxide. Both fish and plants are very important because each makes the gas that the other uses. To “breathe,” fish take in water through their mouths. As that water passes over their (12) …, the dissolved oxygen goes from the water into their bodies.