KUD: Unit 3 – Energy and States of Matter KEYKnow:

● Density: how compact matter is

● Definite shape: it’s own shape

● Indefinite shape: takes the shape of the container

● Solid

● Liquid

● Gas

● Pressure: force per unit area

● Kinetic energy: energy of motion

● Average kinetic energy: median of energy of all particles

● Potential energy: energy stored

● Temperature: average kinetic energy

● Mole: conventional unit measurement

● Absolute Zero: temperature at which all particle motion stops

● Kelvin: absolute temperature

● Kinetic Molecular Theory

● Volume

● STP: standard temperature and pressure

● Compressibility: distance between particles can be reduced

Understand:

● Explain why gases are more compressible than solids and liquids using a particle diagram: Gases have more distance between particles than liquids and solids

● Explain pressure of a gas in terms of force: the impact of the force with which particles collide with the walls of the container

● Use a particle diagram to represent temperature (average kinetic energy); draw one diagram with a low temperature and draw a second diagram with a high temperature.

● Describe the postulates of the Kinetic Molecular Theory: KMT describes the motion of gas particles

● What are the four variables scientists use to study gases? Pressure, temperature, volume, number of moles

● Why do they have to pressurize the cabin on airplanes? To compensate for the lower atmospheric pressure at high altitudes

● A bubble forms at the bottom of a lake. As it rises to the surface (but before it gets there), will it grow, shrink, or pop? Explain your answer. The air bubble will grow, because the pressure surrounding it get lower and lower as it moves towards the surface.

● You received balloons for your birthday and you don’t want them to lose helium so you put them in the freezer for safe keeping. What will they look like the next morning? Explain why this happens? The balloons will shrink in the freezer. Lower temperature causes the particles to move slower, decreasing the pressure inside the balloon. The volume of the balloon will decrease until pressure is equilibrated.

● Gas particles are trapped inside an aerosol can. Use a particle diagram to show what happens to the pressure inside the can before heating and after heating.

● Why does a flat tire take up less space than an inflated tire? Volume is lower, due to decrease in number of particles inside

● What will happen to the volume of the container as it is heated (pressure constant)? Draw a particle diagram of what it would look like after raising the

temperature:

● What will happen to the volume of the containeris the pressure on the piston is increased(temperature constant)? Draw a particle diagram of what it would look like after the pressure is increased:

● What will happen to the pressure in the container if the temperature is

increased (volume constant)? Draw a particle diagram of what it would look like after the temperature is increased (use vector arrows). The pressureincreases because particles move faster, colliding more often with the walls.

Do (I can):

● A constant volume of oxygen is heated from 100°C to 185°C. The initial pressure is 4.1 atm. What is the final pressure?

● A sample of 25L of NH3 gas at 10°C is heated at constant pressure until it fills a volume of 50L. What is the new temperature in °C?

Volume increases

pressure increases

● An unknown gas has a mass 34g and occupies 6.7L at 2 atm and 245K. What is its molecular weight?Skip, K only

● An ideal gas occupies 400ml at 270 mm Hg and 65°C. If the pressure is changed to 1.4 atm and the temperature is increased to 100°C, what is the new volume?

● What is the volume of 23g of neon gas at 1°C and a pressure of 2 atm?

● Explain what each of the following changes would do to the pressure in a closed container (increase or decrease pressure):

o Part of the gas is removed: pressure will decrease due to less collisionso The container size (volume) is decreased: pressure will decrease due to less collisions, more space to move intoo Temperature is increased: pressure will increase due to more collisions, particles are moving faster.