P2 (Thermal physics) Flashcards
Properties of a solid
-High density
-Fixed volume, cannot be compressed
-Fixed shape
-Cannot flow
Properties of liquids
-High density
-Can flow
-Fixed volume, cannot be compressed
-Takes the shape of the container
Properties of gases
high density
Flows very quickly
Can be compressed
Fills up the volume of the whole container
Molecular structure of solids
arrangement:
-regularly arranged
-closely packed together
-Held in place by strong attractive forces
movement:
-Vibrate in place
Molecular structure of liquids
arrangement:
-closely packed as in solids (thus not compressible)
- irregular, random pattern
movement:
slide past each other due to weaker imf than solid (thus liquids can flow and fill a container)
Molecular structure of gases
arrangement:
far apart- more kinetic energy
randomly arranged
movement
-flow quickly from place to place
-unlike liquids they fill the container
-move in straight line until collisions
Why are gases compressible
because they have plenty of space between them.
What happens to its particles as a gas cools?
slow down- eventually they will become closer and move slower so that forces can form between them
It becomes a liquid
What happens to its particles as a liquid cools?
slow down- the particles lose enough energy to form a fixed structure- its become a solid
What happens to its particles as a solid cools?
vibrations become smaller and smaller
What can heating solids cause
Changes in the vibrations of the particles or the bonds between them
e.g- moving more rapidly or slightly further
What will heating gases cause
The hotter the gas is, the higher the MEAN (as they don’t all move at the same speed) speed of the particles
What is the pressure of a gas caused by?
The huge number of tiny collisions happening between the gas particles and the walls of the container
Increasing the rate of _________ will increase the pressure
Collisions
What relationship does temperature and pressure have?
directly proportional
Temp ⬆️ pressure ⬆️
Temp ⬇️ pressure ⬇️
What relationship does volume and pressure have?
inversely proportional
Volume ⬆️ pressure ⬇️
Volume ⬇️ pressure ⬆️
What is brownian motion
The random, continuous movement of microscopic particles in a fluid (liquid or gas), caused by collisions with smaller, fast-moving molecules.
What can brownian motion be proved with?
tiny particles contained in pollen grains move around randomly when floating on water (where water molecules were moving the particles around)
What is the momentum of a small object moving quickly =
Large objects moving slowly
This is why a tiny air molecule can effect a smoke particle which is thousands of times larger.
What are the two methods for observing brownian motion?
-suspension in water
-smoke cell
explain the suspension in water method
equipment:
some microscope slides
very finely ground carbon powder
water
a dropper
an optical microscope.
Method:
Mix a small quantity of very fine carbon powder and water.
Prepare a microscope slide with a single drop of the suspension.
Observe the behaviour of the carbon particles in the water using a microscope.
Explain the smoke cell method of observing brownian motion
equipment:
a light source, such as a lamp or torch
a smoke cell or a clear container with a lid
a piece of card or paper straw
a match or lighter
an optical microscope.
method:
Use a flame to set alight a small piece of card or a paper straw.
Blow out the card/straw and direct some smoke into a smoke cell (Glass chamber with illuminated smoke particles) .
Observe the behaviour of the smoke inside the chamber using a microscope.
What are the results of the smoke cell and water suspension method
Carbon particles move around inside the liquid water in a random pattern due to impacts with water molecules which are moving rapidly.
Smoke particles show similar behaviour when they are suspended in the air due to fast air molecules colliding with them.
What results in the properties of each state of matter?
the arrangement and movement of the particles.
What states of matter can brownian motion be observed in
liquids and gases - as the particles are free to move and collide with smaller, visible particles
As the temperature of a gas increases, the particles move ________. there fore they collide with walls of the container with more __________ and more ________
faster
force
frequently
What does the increase in movement of particles cause
objects or materials to become slightly larger as they are warmed up
What is thermal expansion?
the increase in the size of a solid, liquid, or gas when its temperature rises due to particle movement increasing and spreading further apart.
How big is the force produced by a solid material?
very large
Whats an example of thermal expansion in solids in real life
The forces produced by a solid material when it expands are very large. A long piece of metal, such as a railway line, can bend because of the large forces produced when it heats up on a sunny day.
To avoid damage, small air gaps can be left between each length of track to allow for expansion.
What are some methods of investigating thermal expansion?
Bimetallic strip
Flask of liquid
Explain the flask of liquid method to investigate thermal expansion
equipment:
a round-bottomed or conical flask
a holder for the flask so it can sit upright
food colouring
a stopper for the flask that has a capillary tube inserted through it
a marker pen.
- Fill the flask to the brim with water.
- Add some food colouring to the water.
- Insert the stopper into the flask so that some of the water rises up the capillary tube.
- Rest the flask on its holder and use the marker pen to record the height of the fluid in the capillary tube when the liquid is cool.
- Hold the flask in your hands for 2 minutes, warming the water.
Observe any changes in the height of the water in the capillary tube.
Explain the Bimetallic strip method to investigate thermal expansion
equipment:
bimetallic strip containing a layer of brass and a layer of steel
Bunsen burner
heatproof glove or tongs
suitable heatproof mat to lay the strip down.
Method:
- Heat the bimetallic strip strongly in a Bunsen burner flame with the brass layer downwards towards the flame.
- Observe any changes in the shape of the strip.
- Allow the strip to cool and observe how it changes shape.
- Once the strip is straight again, repeat the experiment but place the steel layer downwards towards the flame
What results should you expect in the bimetallic strip experiment
When the brass layer is heated (brass downwards in the flame), the strip bends away from the flame because brass expands more than steel when heated.
When the experiment is repeated with the steel layer towards the flame, the strip bends towards the flame because steel expands less than brass.
what is a real life application of the liquid in flask method?
Thermometers: rely on the expansion of liquids to measure temperature
It consists of a thin glass capillary tube containing a liquids that expands with temperature
Whats a real life application of the bimetallic strip method?
Temperature activated switches- consists of two metals that expand at different rates and bends by a predictable amount at a given temp.
Whats a real life example of thermal expansion in gases?
hot air balloon:
When the air inside the balloon is heated, the gas particles move faster and spread out, causing the air to expand.
This makes the air less dense than the cooler air outside, causing the balloon to rise.
What happens when water boils?
The liquid starts to change into a gas throughout, which results in bubbles of gas forming inside the liquid.
When boiling, the liquid does not get any hotter. Water stays at 100 °C until it has all boiled away.
What is another way of a liquid turning into a gas (not by boiling)
evaporation- This process only happens at the surface of the liquid and occurs at any temperature.
What increases when a material heated?
its internal energy - we normally see a temp rise or a change of state
What is the melting point, freezing point and boiling point of water?
0,0, 100 C
What state is a substance if the temp is below its melting point, above its boiling point, or in between melting and boiling?
Below the melting point: The substance is in a solid state.
Above the boiling point: The substance is in a gas state.
Between melting and boiling points: The substance is in a liquid state.
What does a material lose as temperature decreases?
internal energy
What happens as a gas cools and reaches boiling point?
temp decrease stops. The arrangement of molecules changes and condensation occurs
What is condensation?
When the molecules in a gas form stronger forces between themselves and end up much closer together,forming a liquid
What happens as liquid cools to its melting point
the forces between the molecules become much stronger and they can no longer move about.
Instead, they end up in fixed positions. Freezing happens
What is evaporation?
the process by which a liquid turns into a gas at the surface, below its boiling point, due to the absorption of heat.
What happens when liquid evaporates?
aster-moving particles near the liquid’s surface escape into the air, reducing the liquid’s volume over time. Slower particles remain, as only the fastest can escape.
What happens to the mean speed of the remaining particles in a liquid after evaporation?
decreases- the fastest particles escape first. This means that the speed thus temp temperature of the remaining liquid decreases – the average energy of the particles is less.
What factors affect the rate of evaporation?
Temperature : Increases kinetic energy, speeding up evaporation or reactions.
Surface Area: Larger surface area exposes more particles, increasing the rate of evaporation or reaction.
Air Movement/Wind: Removes particles from the surface, speeding up evaporation by maintaining a concentration gradient
when a material is heated, it will expand as particles move further apart, when it it is cooled it will ______
contract
solids typically expand ______ than liquids because their particles are held in fixed positions
less
What condition should be fixed for a change of state to happen
fixed temperature
What happens at points of change in state? (like melting points and boiling point)
temperature doesn’t increase- het energy being provided doesn’t increase the internal energy
instead it is used to overcome the intermolecular forces between molecules
What are good thermal conductors?
materials that allow heat to pass through them easily. These include metals such as:
Copper
Aluminum
Silver
Iron
What are bad thermal conductors?
insulator- materials which do not transfer heat well
good insulators:
non metals or organic materials- plastic, wood, rubber and polystyrene
How does thermal conduction in solids work?
Molecules vibrate more when they have more energy
The vibrations get passed from molecule to molecule
In a metal, the free electrons also gain more kinetic energy and they move throughout the metal, colliding with other molecules.
Why are metals the best thermal conductors?
Free electrons
What two mechanisms can conduction occur through?
Atomic vibration
Free electron collisons
Conduction only happens in _______ because __________
solids
particles are closely packed and can transfer heat energy through collisions.
what is convection?
Convection is the process of heat transfer in fluids (liquids and gases) where warmer, less dense regions of the fluid rise, and cooler, denser regions sink. This creates a convection current.
What are convection currents?
are circular movements in a fluid caused by temperature and density differences. Heated fluid rises as it becomes less dense, then cools, sinks, and repeats, transferring heat.
explain convection on a molecular level.
When a liquid or gas is heated (e.g., by a radiator), its particles gain energy, move faster, and spread apart, causing expansion.
This makes the fluid less dense than its surroundings, so it rises.
Cooler, denser fluid moves in to replace it.
As the rising fluid cools, it contracts, becomes denser, and sinks.
This continuous cycle creates a convection current.
What is thermal radiation?
The only way in which heat can travel through a vacuum.
Heat energy transferred by electromagnetic waves- mainly infrared and visible light
Thermal radiations does not need a ________ unlike _______ and ________
medium
conduction
convection
What do all objects give off
thermal radiation
The __________ an object is the more ___________ it emits
hotter
thermal radiation
How does heat from the sun reach us?
Thermal radiation- the only way in which heat can travel through a vacuum.
Design an experiment investigating the relationship between colour and radiation.
equipment:
1 white can
1 black can
2 thermometers
styrofoam lids
method:
Pour hot water into each can
Measure the temperature of each can every 10 seconds
possible sources of error: heat lost through conduction/convection which the lid will prevent
(you may choose to add shiny and matte can to test it on texture)
what should results show for investigating the relationship between colour and radiation?
black can heats up faster than the silver can. This is because the black surface absorbs heat more effectively (due to its higher absorption of radiation) while the silver surface reflects more heat
black dull surfaces __________ and ___________ more thermal radiation than _______, ________ surfaces
absorb
emit
white
shiny
Black objects are __________ absorbers and good _________
good
emitters
Dull/dark objects are ___________ absorbers and reasonable _________
reasonable
emitters
white objects are ___________ absorbers and ________ _________
poor
poor emitters
shiny objects are _______ _____ absorbers as it reflects and very ________ emitters
very poor
poor
does heat rise?
Heat does not rise - it is the hot gases or liquids which rise due to the change in density when they were heated.
what are some examples of thermal radiation?
A black car becoming hot to the touch on a sunny day
explain the greenhouse effect
Greenhouse gases (e.g., CO₂ and water vapor) absorb and re-emit heat radiation from Earth’s surface, trapping heat in the atmosphere and increasing global temperatures.
What does the temperature of earth depend on
Energy received from the Sun (mainly as shortwave radiation).
Energy radiated back into space (mainly as infrared radiation).
The greenhouse effect, which traps heat in the atmosphere
When you draw a thermometer in a test, what do you need to remember
draw the thermometer in the water
