The cycle continues as the puddle slowly disappears. Boiling is a faster process because the surroundings the hot plate heat the liquid to a higher temperature where more molecules have high energy, so vaporization is faster. The hot plate is hotter than the liquid, so thermal energy transfer is fast enough to keep the liquid temperature constant at the boiling temperature.
Evaporation can take place at any temperature because some of the molecules in a liquid—the ones at the higher end of the distribution—will always have enough energy to enter the gas phase.
To sum up, temperature represents the average kinetic energy of the particles of substance. If you do not respond, everything you entered on this page will be lost and you will have to login again.
Skip Navigation. Vimeo ID: Video Transcript. Chris Ah, the humble thermometer. Chris When we think about a phase change from liquid to gas, we often think about adding thermal energy to a liquid by heating it up. But how can a puddle of water evaporate at room temperature? How is energy related to the phases of matter? How many different phases of matter are there? What are the phases of matter? Question ea. Question How does matter change from a solid to a liquid to a gas?
Question 56a0f. What state of matter describes fluids? The total amount of energy at the beginning of a chemical reaction must be the same as the total amount of energy at the end of the chemical reaction first law. But the second law says that the available, useable energy must be less and the entropy must be higher. Different covalent bonds hold different amounts of energy; some higher amounts some lower amounts. If, during a chemical reaction, two 'high energy' covalent bonds are broken, the new ones that form must be at a lower level of energy.
For example when molecular hydrogen and molecular oxygen react together to form water, the energy stored in the covalent bonds of the hydrogen and oxygen molecules is higher than that found in the hydrogen-oxygen bonds of water. Some of the 'extra' energy that is lost as this happens becomes kinetic energy and the water molecules move faster and further.
We say that the liquid becomes 'hot'. During chemical reactions of this type, therefore, potential chemical energy in the bonds holding the reacting molecules together, become lower energy covalent bonds in the product molecules the amount of available energy is decreased , and at the same time the product molecules have more kinetic energy and move faster.
This can be expressed with the following equation where k represents the Boltzmann constant. The bar above certain terms indicates they are average values. Since average kinetic energy is related both to the absolute temperature and the molecular speed, we can combine the equation above with the previous one to determine the rms speed. This demonstrates that the rms speed is related to the temperature.
This form of the equation demonstrates that the rms speed of gas molecules is also related to the molar mass of the substance. Comparing two gases of different molar mass at the same temperature, we see that despite having the same average kinetic energy, the gas with the smaller molar mass will have a higher rms speed. Knowing that , we can convert to metres per second:.
The kinetic molecular theory can be used to explain or predict the experimental trends that were used to generate the gas laws. Volume is located in the denominator of the equation, and it is being decreased. This means the rest of the equation is being divided by a smaller number, so that should make the pressure larger. The kinetic molecular theory can be used. Since the temperature is remaining constant, the average kinetic energy and the rms speed remain the same as well. The volume of the container has decreased, which means that the gas molecules have to move a shorter distance to have a collision.
There will therefore be more collisions per second, causing an increase in pressure. What will happen to the pressure of a system where the temperature is increased and the volume remains constant? Again, this type of problem can be approached in two ways:.
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