Question

Tanks of compressed gas must be kept away from heat sources. If a compressed-gas tank is heated too much, it may explode and cause a great deal of damage. Which of the following best explains why a compressed-gas tank can explode if it is heated?

Answer 1

1. For this question, consider your choices. We know that when molecules are heated, they RECEIVE energy and move FASTER.
Choice b is wrong because heat doesn't always result in chemical reaction. Remember that if there are molecules being broken apart then it MUST be a CHEMICAL reactions.
Choice c is wrong. It doesn't make sense since molecules are supposed to receive energy.
Choice d is kinda nonsense since if molecules receive energy, they are supposed to move faster.
So my choice would be a.

2. Kinetic energy is the energy associated with speed and mass of a particular thing that you're dealing with.
Kinetic energy = (mass*velocity^2)/2
So imagine that we take one molecule out of each sample, which one will have the greatest kinetic energy? Of course they have the same mass since they're all water molecules. Then velocity will be the factor that determine kinetic energy. Remember what we did for problem 1? We know that when molecules are heated, they receive energy and move faster.
Water vapor has the greatest velocity, so its molecule will have more kinetic energy.
Choice b is correct.

3. Solids have a fixed shape, they DO NOT expand to fill the container (put a rock into a cup to see if it expands). However, liquid and gas DO expand (for example, water and air). But compressibility, the ability to be compressed is a typical property of gases.
So choice c, neon gas is the right answer.

4. The basic idea is that when a liquid is cooled to its freezing point, the molecules are closely held together. Say, you have some liquid at 80F dropping its temperature until all the water is frozen. The liquid needs to RELEASES ENERGY into its environment to lose energy and become cooler and cooler. So, as stated in question 1 above, the liquid molecules gradually lose energy and move slower. As a result, when the energy released is sufficient, the molecules' movement and energy will be very limited, which turns them into their solid state.

I hope it helps a little bit.

Answer 2

Kinetic energy of gas molecule increase and it excert force on walls of container.. likely on inc. in heat can bring out higher K.E.. result in inc. in motion..