1) All elements found in the last column of the periodic table are known as the 'Noble Gases" Why are they called this? 2) Elements in the first column of the periodic table are know to bond easily. Why are the larger heavier elements in this column MORE available to bond than the lighter ones with fewer electrons if they all have only one valence electron.
1) Elements in the last column are know as Noble Gases as they do not bond with other elements readily. This is because their last shell of electrons (the valence electrons) is full. Therefor it is a stable element and does not readily bond with other elements. 2)The larger elements have more orbital shells. Thus the single electron that is attempting to get away is less restricted as the positively charged nucleus has less control over it as it would for a smaller element with fewer electrons.
An unknown material is tested for its physical properties. It is tested by placing it in a device that will strain the material with larger and larger amounts of strain. As the material is strained, it at a point begins to yield, or bend. As the strain increases the material begins to flow as a liquid. As more strain is added the amount of force needed to continue to strain the material begins to drop off. Once the strain is stopped and the material is removed it is compared to another sample of the same type. They no longer appear to have the same physical properties. What did we learn about this material from this one test?
1) This material is non-Newtonian meaning it is shear dependent. This material will not have the same viscosity as it flows at different rates. It is a structured material unlike simple liquids. 2) This material is a pseudo-plastic or shear-thinning material. Like most structured materials as they are placed under strain or shear they will have their viscosity drop and they will appear thinner. We know this from the drop off in force needed to move the material. 3) This material has a yield stress meaning it must be a visco-elastic solid. That is more solid like than liquid and will hold its shape indefinitely if it is not disturbed. 4) This material is not highly thixotropic, meaning this material did not recover to its original state. This is why it was compared to another sample that was not strained.
A 2 Kilogram ball is moving without friction at 5 meters per second. The ball is on top of a hill, moving toward a valley when it begins to roll down the hill. The hill is 10 meter tall. After the ball reaches the bottom of the hill it immediately begins to roll up another hill where it perfectly comes to rest. a) How fast is the ball moving once it reaches the bottom of the hill? b) How tall is the second hill?
a) The first portion to this question is a classic conservation of energy problem Initially the ball has both kinetic and and potential energy. Kinetic energy is determined as Ke=1/2mv^2 Potential energy is determined to be U=mgh So the initial kinetic energy is Ke=1/2( 2kg) ( 5m/s)^2 = 25J And the initial potential energy is U=(2kg)(10m/s^2)(10m)=200J (assuming gravity to be 10m/s^2) As total energy is potential energy plus kinetic energy Te=200J+25J=225J As we know energy is conserved, so the total energy at the top of the hill must also be the total energy at the bottom. We also know the ball is at its lowest at the bottom of the hill, so its potential energy will be 0. This means all of the 225J of energy will be kinetic. This means Te=Ke=1/2mv^2 225J=1/2(2kg)(v)^2 225J^(1/2)=1kg(v) v=15m/s b) The second part to this question is having all of the kinetic energy become potential energy. We already know the total energy is 225J and we also know all energy will become potential energy. so Te=U=mgh=(2kg)(10m/s^2)h 225J=20kg*m/(s^2)(h) h=11.25m