Question

13 during a phase change, what happens to the temperature? 14 if water is at 55°c what is the state of matter? 15 if water is at -10°c, what is the state of matter? 16 if water is at 115°c, what is the state of matter? 17 what temperature does water freeze (in kelvin)? 18 what temperature does water boil (in kelvin)? 19 true or false: you are boiling water on the stove top and over time the volume of water decreases. the water is disappearing and no longer exists because the water molecules are destroyed. if false, explain why. 20 “is the glass half empty or half full?” is a proverbial phrase, used to indicate that a particular situation could be a cause for pessimism (half empty) or optimism (half full). however, in chemistry class we know that the glass is always 100% full. explain why?

Explanation:

Step1: Recall phase - change concept

During a phase change, energy is used to break or form intermolecular forces rather than increasing the kinetic energy of the molecules. So, the temperature remains constant.

Step2: Identify water's state at 55°C

The melting point of water is 0°C and the boiling point is 100°C at standard atmospheric pressure. At 55°C, water is in the liquid state.

Step3: Identify water's state at - 10°C

Since - 10°C is below the melting - point (0°C) of water, water is in the solid state (ice).

Step4: Identify water's state at 115°C

As 115°C is above the boiling - point (100°C) of water at standard atmospheric pressure, water is in the gaseous state (steam).

Step5: Convert freezing point to Kelvin

The freezing point of water in Celsius is 0°C. To convert to Kelvin, use the formula $K = °C+273.15$. So, $K=0 + 273.15=273.15$ K.

Step6: Convert boiling point to Kelvin

The boiling point of water in Celsius is 100°C. Using the conversion formula $K = °C + 273.15$, we get $K=100+273.15 = 373.15$ K.

Step7: Analyze boiling water statement

False. When boiling water, the water molecules are not destroyed. They gain enough energy to change from the liquid state to the gaseous state (evaporation). The water is changing phase, not ceasing to exist.

Step8: Explain the glass statement in chemistry

In chemistry, a glass that appears half - empty is still full. The "empty" part is filled with air, which is a mixture of gases. So, the glass is always 100% full of either liquid (water) or gas (air).

Answer:

1. The temperature remains constant.
2. Liquid.
3. Solid.
4. Gas.
5. 273.15 K.
6. 373.15 K.
7. False. Water molecules are changing phase from liquid to gas, not being destroyed.
8. The "empty" part of the glass is filled with air, so the glass is always 100% full of either liquid or gas.