Chapter 3, Section 1 - Matter and Energy
The Kinetic Theory of Matter
- Matter is made of atoms and molecules.
- Atoms and molecules act like tiny particles that are always in motion.
- The higher the temperature, the faster the particles move.
- The more massive the particle is, the slower it will tend to move.
States of Matter
- Definite shape.
- Definite volume.
- Molecules are packed tightly, so they vibrate in place.
- Shape changes.
- Definite volume.
- Molecules can slide past each other.
- Shape changes.
- Volume changes.
- Molecules move around a lot, occasionally bumping into each other.
- Shape changes.
- Volume changes.
- Made of ions and electrons - otherwise similar to gases.
- Found in the Sun, lightning, fire, fluorescent lights.
- Can conduct electricity (unlike gases).
Energy - The ability to do work (to change/move matter).
Kinetic Energy - Energy of motion.
- Since all atoms/molecules are constantly in motion, all particles of matter have kinetic energy.
- Temperature is a measure of the average kinetic energy of the particles in an object. (How hot/cold something is.)
- The more energy an object's particles have, the higher its temperature.
- Thermal Energy is the total kinetic energy of the particles in an object.
- Thermal energy depends on the particle speed and the number of particles.
- (Temperature only depends on particle speed!)
Chapter 3, Section 2 - Changes of State
When a substance changes state...
- its energy changes,
- its identity does not change.
Some changes of state require energy.
- Melting - Changing from solid to liquid.
- Melting Point - The temperature at which a solid melts.
- Evaporation - Changing from liquid to gas.
- Boiling - Evaporation throughout the liquid at a certain temperature and pressure.
- Boiling Point - The temperature at which a liquid boils.
- Sublimation - Changing from solid to gas.
Some changes of energy release energy.
- Condensation - Changing from gas to liquid.
- Condensation Point - The temperature at which a gas becomes liquid.
- Freezing - Changing from liquid to solid.
- Freezing Point - The temperature at which a liquid becomes solid.
- Freezing and melting happen at the same temperature, so freezing point = melting point.
Temperature does not change during a change in state.
- If you add heat to water, it will get hotter and hotter until it boils at 100oC. It will remain at 100oC - even if you keep adding heat - until all of the water has turned into steam. The steam can then get hotter, as more heat is added.
- The temperature doesn't change during the change in state.
Conservation of Matter and Energy
- Mass cannot be created or destroyed. (Law of Conservation of Mass)
- There is always the same amount of mass before and after a physical or chemical change.
- Energy cannot be created or destroyed. (Law of Conservation of Energy)
- The total energy present before and after a change is the same.
- Energy that is added to a substance during the change must come from someplace.
- Energy that is released during a change must go someplace.
Chapter 3, Section 3 - Fluids
Pressure - The amount of force exerted on a given area of surface.
- Fluids exert pressure evenly in all directions.
- Pascal (Pa) - The SI (metric) unit of pressure.
- 1 pascal = 1 newton of force over an area of 1 square meter
- 1Pa = 1N/m2
- 1000 Pa = 1 kPa (kilopascal)
- Newton (N) - The SI (metric) unit of force.
- 1 newton = the force needed to move 100g of mass.
Buoyant Force - The upward force that causes an object to float in a fluid.
- All fluids exert an upward buoyant force on matter.
- Pressure increases with depth.
- The forces pushing up on an object in a fluid are greater than the forces pushing down - this creates a net upward force (buoyant force).
- Archimedes' Principle
- The buoyant force on an object in a fluid is equal to the weight of the fluid displaced by the object.
- So, if the weight of the water displaced is equal to the total weight of the object, then the object will float.
- Density determines whether an object will float or sink.
- Density of water = 1g/m3
- Density of steel = about 8g/m3
- Result = Steel will sink!
- However, steel ships float because they have a hollow shape. The density of the boat is less than the density of water!
Pascal's Principle - A change in pressure at any point in an enclosed fluid will be transmitted equally to all parts of the fluid.
- P1 = P2
- Since P = F/A, we could also write it as F1/A1 = F2/A2.
- We see this principle when you squeeze a tube of toothpaste from one end and the paste comes out the other end. (The pressure at one end is transmitted throughout.)
- This is also the principle behind hydraulic lifts.
Fluids in Motion
- Fluids move faster through smaller areas than through larger areas - IF the overall flow rate remains the same.
- When you put your thumb over the end of a hose, the water speeds up to squeeze through the opening.
- Different fluids vary in the rate at which they flow.
- Viscosity - A liquid's resistance to flow.
- Example - Honey is more viscous (has a higher viscosity) than lemonade.
- Bernoulli's Principle
- As the speed of a moving fluid increases, the pressure of the fluid decreases.
Read pg. 89-95. Do #4-9 on pg. 94.
Chapter 3, Section 4 - Behavior of Gases
Properties of Gases
- Gases expand to fill the container they are in.
- Gases spread out and mix with each other easily.
- Gases have low density.
- Gases are compressible (you can change the volume of a gas by compressing it).
- Gases are mostly empty space.
- Gases exert pressure on their containers.
- The gas particles move around and bump against the sides of their container. This creates pressure.
- Laws that state the mathematical relationships between the volume, temperature, pressure and quantity of a gas.
- Boyle's Law
- For a certain amount of gas (at constant temperature),...
- the volume of the gas increases as the gas' pressure decreases.
- the volume of the gas decreases as the gas' pressure increases.
- Since pressure and volume are inversely proportional, pressure times volume is constant.
- Gay-Lussac's Law
- For a certain amount of gas (in a constant volume),...
- the pressure of the gas increases as the temperature increases.
- the pressure of the gas decreases as the temperature decreases.
- This is because higher temperatures mean that the gas molecules have more kinetic energy, so they move faster and collide harder and more often with each other and with their container. This means greater pressure.
- Charles' Law
- For a certain amount of gas (under constant pressure),...
- the volume of the gas increases as the temperature increases.
- the volume of the gas decreases as the temperature decreases.
- This is because higher temperatures mean that the gas molecules have more kinetic energy, so they move faster and collide harder and more often with each other. This causes them to spread out more.
Read pg. 96-101. Do #1-2, 4-5, 7-10 on pg. 101.