Thermodynamics and States of Matter
There are three states (also called phases) ) of matter. The picture to the side represents the same chemical substance, just in different states.
There are three states (also called phases) ) of matter. Solid: : Matter that has both a definite shape and definite volume. Molecules or atoms are very close together and can only vibrate a little. They do not move past each other.
There are three states (also called phases) ) of matter. Liquid: : Matter that has a distinct volume but no specific shape. Molecules or atoms are close together but have the ability to slide across one another very easily.
There are three states (also called phases) ) of matter. Gas: : matter that has no fixed volume or shape. It conforms to the volume and shape of its container. Its molecules or atoms are very far apart from each other and move very fast.
Density Comparison If you consider the solid, liquid, and gas state of one particular substance, this rule holds true in most cases: Solid is more dense than liquid Liquid is more dense than gas
Water is Weird A notable exception is water! The solid state of H2O, ice, is less dense than liquid water. This is why ice floats. This is true because of the way hydrogen bonds form when liquid water freezes. The hexagonal pattern results in empty space between the molecules.
Liquids Fluidity liquids (and gases) have the ability to flow.
Liquids Viscosity the measure of the resistance of a liquid to flow. Cold pancake syrup is very resistant to flow it is viscous. Water flows easily it is less viscous.
Viscosity Viscosity decreases with temperature. Ex: heating up the syrup in the microwave makes it pour easier.
Phase change The temperature of a substance is the measure of the average kinetic energy of the particles in the substance. Gas > Liquid > Solid Matter can change from one phase to another by adding or removing energy. There are six phase changes.
Phase Change terms Solid Liquid Melting Liquid Solid Freezing Liquid Gas Boiling / Vaporization Gas Liquid Condensation Solid Gas Sublimation Gas Solid Deposition
Phase Change Diagram
Phase Change Atmospheric pressure plays a role in phase change as well. At higher elevations (lower atmospheric pressure) the boiling point of a liquid is much lower. (ex. Water boils below 100 C) It is possible to boil water at room temperature. How?
Phase Diagram A phase diagram shows what phase a substance will be in at a certain temperature and pressure. Pressure is measured in atmospheres (atm( atm).
Phase Diagram Triple Point is the point on a phase diagram that shows the temperature and pressure combination at which three phases of a substance can coexist.
Heat Heat is a form of energy. What unit is energy measured in? (think back to kinetic and potential energy) Joules (J)
3 Ways to transfer heat: Conduction transfer of heat by contact. Ex) frying pan heating up a piece of meat Convection transfer of heat through fluids (liquid or gas). Ex) convection oven heating up a piece of meat Radiation transfer of heat by electromagnetic radiation. Ex) microwave or light bulb heating up a piece of meat
Specific Heat It takes time for water in a swimming pool to warm up during the early part of the year. Once it is warmed, it cools down slowly when the outside temperature drops. It takes time to heat up a pot of water to boiling, then after turning off the heat takes time to cool. This property of water that you have probably observed is called specific heat.
Specific Heat Specific heat - Measure of the heat energy required to raise the temperature of one gram of a substance by 1 C. 1 Ex) Water has a specific heat of 4.18 J/g C. This means it takes 4.18 Joules of heat to raise 1 g of water by 1 C. 1 On the other hand, you must remove 4.18 Joules of heat to lower a 1 g sample of water by 1 C.
Specific Heats of Various Substances Which substance has the lowest heat capacity? Which has the highest heat capacity? What does that tell you about how the temperatures of these substances will fluctuate? How might your body being mostly water help you to survive?
Specific Heat The equation relating heat energy to specific heat capacity is: Q = m c Tc where Q is the heat energy put into or taken out of the substance, m is the mass of the substance, c is the specific heat capacity, and T is the change in temperature.