You had a closed tank of air at a pressure of 4 atm and temperature of 20 degrees Celsius. When the tank and the air are heated to 40 degrees Celsius, what is the pressure if the volume remains constant?​

The pressure will be 4.27 atm.

Explanation:

Gay-Lussac's law can be expressed mathematically as follows:

Where P = pressure, T = temperature, K = Constant

This law indicates that the quotient between pressure and temperature is constant.

This law indicates that, as long as the volume of the container containing the gas is constant, as the temperature increases, the gas molecules move faster. Then the number of collisions with the walls increases, that is, the pressure increases. That is, the pressure of the gas is directly proportional to its temperature.

In short, when there is a constant volume, as the temperature increases, the pressure of the gas increases. And when the temperature is decreased, the pressure of the gas decreases.

You want to study two different states, an initial state and a final state. You have a gas that is at a pressure P1 and a temperature T1 at the beginning of the experiment. By varying the temperature to a new value T2, then the pressure will change to P2, and the following will be fulfilled:

In this case:

P1= 4 atmT1= 20 C= 293 K (being 0 C= 273 K)P2= ?T2= 40 C= 313 K

Replacing:

Solving:

P2= 4.27 atm

The pressure will be 4.27 atm.

The answer to your question really depends on three things: how much water you have, how cold it is to start out, and how cold the things around it are. water actually freezes when it gets to 32 degrees fahrenheit (0 degrees celsius), but the time it takes to get there may be different.  let's start with the first. if you take two glasses, and fill one with a tiny bit of water, and the other about halfway, then put them both in the freezer, the one with less water will freeze first (you can try this at home, but i recommend using plastic cups and not glass ones).  now let's move on to the second part. let's say you have two glasses, and you fill one with really cold water that has been in the refrigerator, and the other with really hot water from the sink. if you put both of them in the freezer, the one that started out colder will freeze first.  for the third part, let's imagine that you have two glasses with the same amount of water in them, and the water is at the same temperature. imagine putting one outside on a really really cold day in georgia, and having a friend in alaska put one outside on the same day. since it would be so much colder in alaska, the glass of water there would freeze before yours.  so, if you took a tiny bit of really cold water in a glass, and put it outside on a cold day in alaska, it would freeze a lot faster than a big glass of hot water outside on a cold day in georgia. 

They make up examples of physical properties