States of matter
The three states of matter described in P3, as shown in Table P3.01.
What are solid, liquid and gas?
Gas particles constantly collide with the walls of their container. This is what those collisions create on the container walls.
What is gas pressure?
The name given to the increase in volume of a material when its temperature rises, as defined in the P3 Key Words box.
What is thermal expansion?
A substance that conducts very little thermal energy, examples from the book's Figure P3.26 include glass wool, rubber, and wood.
What is a thermal insulator?
The type of electromagnetic radiation, part of the electromagnetic spectrum and invisible to the naked eye, that carries thermal energy from the Sun through the vacuum of space to Earth.
What is infrared radiation?
In this state of matter, particles are widely separated and move freely, bouncing off one another and off the walls of the container.
What is a gas?
When a sealed gas is heated at constant volume, the particles move faster and hit the walls more often and with more force. This is what happens to the pressure.
What is it pressure increases?
This device, made of two different metals bonded firmly together, bends when heated because one metal expands more than the other. It is used in fire alarms and thermostats.
What is a bimetallic strip?
The two states of matter in which convection occurs, because their particles are free to flow.
What are liquids and gases (fluids)?
According to the book, this type of surface is simultaneously the best absorber AND the best emitter of infrared radiation.
What is a matte black surface?
In 1827, Robert Brown observed tiny pollen and dust particles jiggling randomly. This is the name now given to that motion, caused by bombardment from invisible fast-moving particles.
What is Brownian motion?
A balloon inflated with air is placed in a freezer. The particles slow down, push on the walls with less force, and this happens to the balloon's volume.
What is it decreases (the balloon shrinks)?
Bridges are built in sections with these between them, visible in Figure P3.13 of the book, which allow the structure to expand on hot days without buckling or bending.
What are expansion joints?
These free, negatively charged particles in metals (not attached to any single atom) are the reason metals are much better thermal conductors than non-metals.
What are delocalised (mobile) electrons?
Radiation is the ONLY method of thermal energy transfer that can travel through a vacuum. This is why, while conduction and convection cannot.
What is that radiation travels as electromagnetic waves and does not require particles or any medium to travel through?
When ice is melting, energy is continuously supplied, yet the temperature stays at 0°C. This is what the energy is actually doing during that flat section of the graph.
What is overcoming the attractive forces (breaking bonds) between particles, rather than increasing their kinetic energy?
When a gas is compressed into a smaller space, the particles do not travel as far between collisions and hit the walls more often. This is the result for the pressure.
What is the pressure increases?
When a gas is heated, its volume increases but its mass stays constant. This is what happens to its density as a result, which also explains why hot air rises.
What is it decreases (density decreases)?
The reason convection cannot transfer thermal energy through a solid, unlike through a liquid or gas
What is that particles in a solid are in fixed positions and cannot flow or move from place to place?
Between a shiny silver teapot and a dark brown teapot both containing equally hot tea: this one stays hot longer, and this is why.
What is the shiny silver teapot? Shiny surfaces are poor emitters of infrared radiation, so it loses thermal energy more slowly.
Unlike boiling, this process occurs at ANY temperature, happens only at the SURFACE of a liquid, and cools the remaining liquid because the most energetic particles escape.
What is evaporation?
A sealed tin can of air is heated. Using the kinetic model, describe what happens to: (a) the speed of the molecules, (b) how often they hit the walls, and (c) the pressure on the walls.
What is: (a) speed increases, (b) they hit the walls more often AND with more force, (c) the pressure increases?
Using the kinetic particle model, give a full explanation of why solids expand when heated.
What is: particles gain kinetic energy, vibrate more vigorously, push each other further apart, so the overall volume of the solid increases?
The reason the freezing compartment of a refrigerator is placed at the top, as explained in Section P3.04 of the book.
What is that cold air from the freezer is denser and sinks, displacing warmer air upward to be cooled, setting up a convection current that cools all the food in the fridge?
Three beakers are in a room at 20°C: beaker A contains water at 0°C, beaker B at 20°C, beaker C at 100°C. Describe what happens to the temperature of each beaker over time and explain why, using ideas from Figure P3.42.
What is: beaker A (0°C) warms up (cooler than surroundings) absorbs more radiation than it emits; beaker B (20°C) stays constant (same temperature as surroundings) absorbs and emits equally; beaker C (100°C) cools down (hotter than surroundings) emits more radiation than it absorbs?