Notes

3. Describe what happens to form a foggy mirror or what happens when exhaling on a cold mirror.
When exhaling on a cool mirror, water particles from your breath start to condense and make the mirror foggy. This is because your body temperature is higher than the temperature of the room and mirror. Water particles from your breath condense when they touch the mirror because the mirror has a lower temperature than your breath. For example, your body temperature is 37°C, and the mirror temperature is 22°C. When you exhale, the water particles touches the mirror and condenses. We know that energy moves from areas of high energy to areas of low energy. We also know that energy being transferred is called heat energy. So, energy moves from water particles to the mirror. Since energy is released from water vapor, the water particles move slower. They don’t move as far away from each other. They have stronger attractions between them and that makes them go into the liquid state.

12. Describe how energy is emitted by electrons in an atom.
Electrons absorb quanta of energy that matches the frequency of the movement of the electron. The electron is now in an excited state and it moves to a higher energy level. Electrons in excited states don’t remain there for long. They emit energy in the form of electromagnetic energy as they move to lower energy levels. If the electromagnetic energy is within the visible spectrum, we can see the color related with the energy in the emission spectrum of the element. For example, when electrons in hydrogen atoms move from n=3 to n=2, we can see a bright yellow line in the emission spectrum.

13. Describe the equipment needed to explore emission spectra of elements.
When white light is passed through a gas and separated by a prism, some wavelengths of light are absent because they were absorbed by the atoms in the gas. This causes black bars to appear in the absorption spectrum. An emission spectrum is created when gas emits light. For example, imagine a laser is pointed at a container of hydrogen gas. The electrons in the gas move from excited states to ground states. As they do so, they emit energy. This energy is often within the visible spectra. A prism is detected on the screen. The black bar represents the absorbed energies or photons.

14. Describe what happens to an electron when it absorbs a tiny packet of light called photon.
When an electron is hit by a photon of light whose wavelength matches the wavelength of the moving electron, it absorbs the quanta of energy the photon is carrying and moves to a higher energy state. The electron is now said to be in an excited state. Electrons move from energy level to energy level within an atom as they gain or lose energy. For example, when a photon with an energy value of 10.2eV enters a hydrogen atom, it gets absorbed by the electron. The effect of the electron is that the electron moves to a higher energy level. The electron is in the excited state. In this case, the electron in its ground or lowest energy position was moving in energy level one. When it absorbs 10.2eV, it moves to energy level 2.

15. Describe what happens to an electron when it emits a photon.
When an electron absorbs energy, it moves to a higher energy level. It is now in an excited and unstable state. An electron in an excited state releases energy and moves to a lower energy level as it does so. When this happens, energy is released, it is called electromagnetic energy. Units of electromagnetic energy are called photons. Humans can see a small number of these photons of electromagnetic energy. The set of photons we can see are called the visible spectrum. Sometimes, the energy released by the movement of electrons from an excited to a lower energy state is within the visible spectrum and so we can see it. For example, when an electron in a hydrogen atom gains 1.9eV, the electron moves from n=2 to n=3. The electron is in a excited state at the higher energy level. It is unstable and so it moves back to n=2, emitting energy as it does so. The electromagnetic energy released has an energy of 1.9eV and is within the visible spectrum. We see this light as yellow light in the emission spectrum for hydrogen.

7. Use data to describe variation in pressure and volume of a sample of gas with a constant number of particles and constant temperature.
A decrease in volume results in an increase in pressure for a sample of gas at constant temperature. This is true if the number of gas particles and the lowest pressure because it has the largest end of the piston. Looking at the formula p=f/a in this case, A is larger and F stays the same. So, the value of P increases. For example, if you say the are of the end of the piston has a value of 1 and the force has a value of 2, pressure for system would be p=2/1, which is equal to 2.5. If you say the area of the end of the piston has a value of 2 and the force remains at 2, then the pressure for this system temperature stays constant. If we were to graph volume vs pressure for a sample of gas at constant temperature, it would look like the graph below.

31-32. Compare the sizes, charges, and relative positions of the subatomic particles: protons, neutrons, and electrons. Relate an atom’s number of protons to its charge, name, and atomic number.
Atoms consist of protons, neutrons, and electrons. Protons are positively charged and located in the nucleus of the atom. Neutrons have no net charge and are located in the nucleus of the atom. Both protons and neutrons are made up of smaller particles called ups and downs. Each has three of these particles. The net charge and mass of the proton and neutron come from three smaller particles present. The sum of the charges of the smaller particles in a proton is +1. The sum of the charges of the smaller particles in a neutron is 0. The mass of proton and neutron are the same. Electrons are negatively charged. They are located around the nucleus in regions called energy levels. The mass of electrons is so small that it is considered unimportant. Atomic number of an atom (z) is equal to the number of protons in the atom. Atomic number (z) determines which element an atom belongs to. For example, all atoms with 8 protons in their nuclei are atoms of oxygen (atomic number 8). All gold atoms with 79 protons are atoms of gold (atomic number 79).

64. Use lab data from a heat of fusion of ice investigation to determine % error.
To determine the percent error we will need to know the heat needed to melt 1g of ice (J/g) and the accepted value for the heat of fusion of the ice. The heat of fusion of the ice is already given, it is 334 J/g. In lab, the heat needed to melt 1g of ice was 28.1 J/g. To calculate the percent error, we need to subtract the accepted value from the calculated value. Then, divide the difference by the accepted value. Finally, multiply the quotient number you are left with by 100. Everything is shown below:
% error= calculated value-accepted value / accepted value x 100

% error= 28.1J/g-334J/g / 334J/g x 100

% error= 305.9 / 334 x 100

% error= 0.9 x 100

% error= 90