P3 Flashcards
What is matter?
anything that occupies space and has mass
What are the properties of solids?
Rigid
Fixed shape
Fixed volume
Cannot be compressed
Strong bonds
No flow
What are the properties of a liquid?
Not rigid
No fixed shape
Cannot be compressed
Weak bonds
Flow
What are the properties of gases?
Not rigid
No fixed shape
No fixed volume
Can be compressed
No bonds
Flow
What do forces between particles affect?
Magnitude of forces -> affect relative distance and motion of particles
Affects ability of substance to:
Change shape, volume, flow
How do intermolecular forces and the motion of particles affect the state of matter?
Solids:
Molecules -> held in place via strong intermolecular force
Only vibrate in position
Distance between -> fixed -> rigid shape and fixed volume
Liquids:
Molecules -> enough energy to overcome forces, still held close together
Volume is rigid but molecules can slide past each other -> change shape and flow
Gases:
Molecules -> overcome intermolecular forces -> more energy and move randomly at high speeds
Large space between molecules -> easily compressed and expanded + easily flow
Describe the molecular structure of a solid, liquid and gas (including energy levels)
Solid:
Molecules are close (high density)
Arranged in a regular pattern
Molecules vibrate in a fixed position
Low energy
Liquid:
Molecules are relatively still close together (medium density)
No regular pattern
Molecules able to slide past each other
Medium energy
Gas:
Molecules are very separated
No regular pattern
Molecules move at random and high speeds
High energy
How does the temperature of a gas relate to the amount of pressure it exerts?
Gas particles gain kinetic energy as their temp increases -> molecules are more likely to hit the sides of the container
Higher temp, higher pressure
What is absolute zero?
The temperature at which gas exerts no pressure (no longer moves) -273°C or 0K (k because Lord Kelvin discovered it)
How does the temperature of a solid liquid or gas relate to the motion of the particles? How can this explain a change in state as a result of changing temp?
Heat of substance increase -> kinetic energy increase -> rise in temp
As particles move faster -> vibrations take up more space -> expansion in distance -> change in states
Describe pressure caused by gas in term of the motion of molecules
Gas molecules are constantly and randomly moving -> collide with things like: walls of contain and other molecules
Pressure is caused by collisions with the walls of the container
Collisions produce force at right angle to the walls -> gas at high pressure exert greater force
Higher pressure -> higher force exerted/unit area
What is Brownian motion? How was it discovered and what did it show?
Brownian motion-> the random movement of particles in a liquid/gas produced by large numbers of collisions with smaller particles (too small to see)
Scottish scientist Robert Brown first described the random motion of pollen grains in water, which he saw under a microscope
Later found to show substance are made of particles that are constantly moving
What are three types of thermometers?
Hot wire
Mercury
Color change
How are celcius scale thermometers calibrated?
By putting in freezing (0°C) then boiling water (100°C), marking changes in temp
How do thermometers work?
Most liquids expand when heated -> used in thermometers filled with alcohol and mercury
How are thermometers engineered to measure temperature?
Sensitivity:
Narrower tube -> more liquid moves -> more sensitive to change in temp
Alcohol expands more than mercury -> mercury tube thinner
Range:
Mercury -> -39°C - 356°C (bigger range)
Alcohol -> -115°C - 78°C
Responsiveness:
Thermometers with thick glass or large bulb -> responds less quickly
What changes when matter changes state?
The amount of energy it has
Define melting
Melting happens when a solid turns into a liquid
Define freezing
Occurs when a liquid turns into a solid
Define boiling
Occurs when a liquid turns into a gas
Also called evaporating
Define condensing
Occurs when a gas becomes a liquid
Why does the substance not change temp when changing state?
Although energy is transferred away from thermal energy store, heat is used to break intramolecular forces instead of rising temps
What is internal energy?
total energy stored inside a system by the particles that make up the system due to their motion and position
Kinetic energy + potential energy = internal energy
Explain boiling+condensation in terms of energy transfer
Liquid water heated by adding thermal energy -> temp rising until boiling point, doesn’t get hotter (internal energy doesn’t change) -> added thermal energy used to overcome intermolecular forces -> forces overcome, water becomes vapor (evaporation)
Repeated backwards for condensation (cooling)
Explain melting and freezing in terms of energy transfer
Solid heated (adding thermal energy) -> melting point (internal energy is not changed) -> added thermal energy overcomes intermolecular forces -> forces overcome -> solid becomes liquid
Process goes backwards for freezing
Define melting point
Melting point -> temp at which its solid and liquid phases are balanced
Define boiling point
The temp at which a substance changes state from liquid to gas
What is the difference between evaporation and boiling?
Evaporation -> on the surface of the liquid
Any temp
Boiling -> within the liquid (change of state all throughout the liquid (bubbles))
Only happens at boiling point
Describe condensation in terms of energy transfer
Gas loses heat energy -> lose kinetic energy and move more slowly -> don’t have enough energy to overcome intermolecular forces -> particles get closer together -> only have enough energy to slide -> liquid
REMEMBER -> doesn’t change TEMPPPP
Describe solidification in terms of energy transfer
Liquid lost heat energy -> lose kinetic energy -> move slower, no enough energy to overcome forces -> particles get closer -> only enough energy to vibrate -> solid
Explain evaporation in terms of more energetic molecules escaping
Molecules in liquid -> range of energies (average energy is temp)
Evaporation -> more energetic molecules moving near surface have enough energy to escape
Average (heat) energy reduced -> Liquid cooled by evaporation
How do temp, surface area and draught influence evaporation?
Increased temp -> increased evaporation:
More energy -> more likely to overcome forces
Increased surface area -> increased evaporation:
Only escape at surface -> more surface, more evaporation
Increased air movement/draught -> increased evaporation:
Air movement carries away water vapor -> new air, more evaporation
How does a change of temp at a constant volume effect the pressure of a gas?
Average speed of molecules increases as temp increase
Increased temp -> increased kinetic energy in same amount of space -> collide with walls more often -> increase pressure
Increased temp -> increased pressure
How does a change of volume at a constant temp effect the pressure of a gas?
Compressed -> decreased volume, increased pressure
Expanded -> increased volume, decreased pressure
How does a change in pressure cause a change in volume? (Balloon but say like DA MOOOOON)
Vacuum pump used to remove air
Gas compressed (deflated) -> molecules hit walls of container more -> higher pressure
Absence of gas -> less pressure -> volume of ex. Balloon increases
What happens to materials when heated? Why?
They expand
Molecules move/vibrate faster -> knock into each other and push apart -> space taken up increases
What state of matter tends to expand the most when heated? Why?
Gas-> expand most
High energy molecules have enough energy to completely overcome forces
Liquid-> expand moderately
Molecules have enough energy to overcome forces
Solid-> expand least
Low energy molecules cannot overcome forces
What is an everyday use of thermal expansion?
Thermometers rely on expansion of liquids
Temp activated switched work with a bimetallic strip
How does a temp activated switch work?
bimetallic strip -> 2 metals that expand at different rates, bending at predicable amounts at a given temp
Low expansion metal + high expansion metal -> as it is heated the high expansion metal expands more and bends
What are some bad consequences of thermal expansion?
Metal railway tracks, road surfaces and bridges -> Buckling, space of expansion in cracks or spaces
What physical properties can change with temp?
The volume/density
The electrical resistance
What is important to understand linearity?
Most often, there is an assumption the properties change linearly/ at a steady rate
Can be useful for data and relationships -> but important to know that it can be nonlinear
Describe the structure of a thermocouple
2 different types of wire attached to each other
Joint of wires heated -> voltage is created between the wires
Increased temp -> increased voltage
Why is a thermocouple more preferable for measuring high temps and those that change rapidly?
Not as sensitive and liquid in glass thermometer -> but metals have higher melting point -> can be used to measure higher temps
Also responsive the rapidly changing temps
What is a fixed point?
A temp where an easily identifiable change occurs (ex: melting or boiling points)
Why is it important to identify fixed points when building a thermometer?
Fixed points allow you to know temp without measuring
2 fixed points used:
Lower -> melting point (high on a resistance:temp graph)
Upper -> boiling temp (lower on a resistance:temp graph)
Once a property has been measured at 2 fixed points -> figure out at other temps
How does the structure of liquid in glass thermometers relate to sensitivity, range and linearity?
Sensitivity:
Liquid expands more
Thin glass capillary tube -> heat transfers better
Larger glass build -> more liquid -> larger change
Narrow tube -> small change in volume results in liquid moving a larger distance
Linearity:
Liquid chosen expands linearly
Range:
Low freezing and high boiling point
Describe the structure of a thermometer
Thin glass capillary tube
Contains liquid -> expands with temp
Glass bulb -> contain liquid which when heated goes up the tube
Scale on the side -> allows temp to be measured
What is conduction?
Particles that are close transfer heat energy as they vibrate
What are some good thermal conductors?
Metal pan or ceramic tea cup
What are some bad heat conductors (and what is their alternative name)?
Insulators
Woollen blanket or layers of cardboard
Why are metals such good conductors?
Metals have free electrons which can move with heat very easily
When a metal is heated the electrons gain kinetic energy and move quickly
Explain (procedure and explaination) an experiment:
Comparing conduction in tiles and textiles
In the same room (must have tiled floor) but a textile (must be thick)
But stay are a few hours to ensure thermal equilibrium
Stand with bare feet, one foot one each
Observe apparent temp of 2 materials through feet
Feel like tiles are cold while rug is warm -> but they are the same temp
Explanation:
Tiles are good conductors
Foot touches tiles -> heat transfer away -> feels cold
Textiles are good insulators
Foot touches textile -> heat not transfer -> feels warm (in comparison)
Explain (procedure and explanation) an experiment:
Comparing conduction in wood and metal
Cylindrical rod of half wood half metal wrapped in paper
Gentle flame with rod above the tip of the flame
heat paper at the join of the 2 materials (turn rod)
Stop when paper is clearly discolored
Observe burn pattern on paper
-> paper touched metal -> un damaged
-> paper touch wood -> charred
Explanation:
Metal -> good conductor
Paper touched metal -> heat transferred to metal -> paper prevented from getting hot
Wood -> good insulator
Paper touched wood -> heat not transferred -> paper burned
Explain (procedure and explanation) an experiment:
Demonstrating different rates of thermal conduction in metals
Stand holding a conduction ring
‘Cross’ of four metals stuck to ring -> meeting point is at the center of the circle
Ball bearing at the ends+underside of each metal using wax
Bunsen burner under the center
Center heated with a candle/bunsen burner
Metals heated -> wax melt -> ball bearing dropped
Amount of time shows their relative thermal conductivity
Explain conduction in terms of energy transfers and vibrations
Conduction -> main form of thermal energy transfer in solids
Conduction occurs when 2 solids of different temps come into contact -> Thermal energy transferred
When substance heated -> atoms/ions vibrate more -> atoms of hotter material bumps into atoms of cooler material -> energy transferred -> internal energy transferred until equilibrium is reached
What does convection rely on? Why does this affect what state of matter it occurs most in?
Convection uses density of the substance
Main way heat travels through liquids and gases -> atoms can flow (cannot happen in solids)
What is/how does a convection current work?
Liquid heated -> molecules pushed apart -> expansion -> less dense -> hot substance rises because it is les dense -> eventually it cools -> contracts -> sinks back down
Remember: convections currents can be cause by heating or cooling
Describe an experiment designed to show convection in liquids/gases
Beaker of water with few crystals of potassium permanganate
When water is heated on bottom -> potassium permanganate dissolves in heated water
Rises with the heated water, showing convection current
What are properties of (thermal) radiation?
Doesn’t require a medium to travel thought
Part of em Spectrum -> infrared
Only way heat travels through a vacuum -> like space
Color of object will affect how good it is at emitting+absorbing radiation
How does color and texture affect the emission/absorption/reflection of radiation?
Color:
Black -> good absorber, good emitter
Darker colors -> reasonable absorber, reasonable emitter
White -> poor absorber, poor emitter
Texture:
Shiny -> very poor absorber (reflects), very poor emitter
Emits little so it takes longer to cool
Describe an experiment that can investigate the properties of good/bad emitters/absorbers (including variables, equipment, experiment, analysis, results)
Variables:
Independent -> color
Dependent-> temp
Control -> flask, amount of water, starting temp of water, time
Equipment:
kettle (boil water)
4 thermometer (measure temp)
Flask (one gray, black, white silver)
Heatproof mat (protect surface and prevent heat loss)
Stopwatch (record time)
Experiment: set up 4 flask (identical), all painted different colors
Fill flask with hot water (same amount and temp)
Cover top and add thermometer
Note starting temp, measure temp at regular intervals for 10min (in a table)
Analysis:
Intensity of radiation depends on temp, surface area, color
Most heat lost via conduction and convection -> but doesn’t matter because the amount will be the same for all flask
To compare heat loss-> graph (temp against time) with curve of best fit
Results:
Black -> fastest -> good at both
Dull gray -> 2nd fastest -> reasonable at both
White -> 2nd slowest - >poor at both
Silver -> slowest -> very poor at both
Pt.2 Describe an experiment that can investigate the properties of good/bad emitters/absorbers (possible errors, safety considerations)
Systemic errors:
Hard to ensure that water in each flask is the same temp -> cools quickly
Digital thermometer can be used for most accurate reading
Random errors:
Hole for thermometer isn’t too big
Repeated readings
Read thermometer at eye level -> no parallax error
Safety:
Keep away from electrical equipment
Don’t touch hot water
Do not overfill kettle
Avoid knocking over equipment
Carry out while standing -> faster reaction
Explain and give an example of an everyday application of (+consequences):
Conduction
Conduction: main form of thermal energy transfer in solids
Heated -> atoms vibrate -> collide -> transfer energy
Mention metal -> usually conduction
Metal good conductor
Non metal bad conductor
Hot coffee transfers heat to cool mug -> heat up mug -> mug become hot -> heat transferred to cold hand -> warm hands
Explain and give an example of an everyday application of (+consequences):
Convection
Convection: main means of thermal energy transfer in liquids and gases
Heated -> expand -> less dense -> rise -> cools -> falls
If heat source at bottom/cooling at top -> usually convection
Steam rises away from coffee
Explain and give an example of an everyday application of (+consequences):
Of all three types of thermal energy transfer at same time
In irl situations -> usually more that one form at once
Conduction: heat lost from cup via contact
Convection: steam rises away from tea (air above tea)
Radiation: emitted from surface of any hot object, ex: cup of tea
Heat loss until thermal equilibrium
How is a rise in temp related to the internal energy?
Internal energy is all energy stored in the system (kinetic and potential)
Heat -> increased kinetic energy -> increase internal energy
What factors determine how much the temp of a system will increase?
Mass of substance
Type of material
Amount of thermal energy transferred
What is specific heat capacity?
The amount of energy required to raise the temp of 1kg of a substance by 1°C
Also called c
What does low and high c mean?
Low:
Heats up and cools down quick (takes less energy to change temp)
Ex: copper
High:
Heats and cools slowly (takes more energy to change temp)
Ex: water
How can specific heat capacity be calculated?
ΔE=mcΔθ
ΔE = change in thermal energy, in joules (J)
m = mass, in kilograms (kg)
c = specific heat capacity, in joules per kilogram per degree Celsius (J/kg °C)
Δθ = change in temperature, in degrees Celsius (°C)
What is thermal equilibrium?
Object absorbs thermal radiation -> hotter -> emit more radiation
Temp of body increase when body absorbs more than it emits
Temp of body decreases when body absorbs less than it emits
Eventually -> reach a point of constant temp where absorbing and emitting rates are the same
What is boyles law?
Pressure is inversely proportional to volume of a(n ideal) gas
What is the equation for the relationship between pressure and volume for gas at a constant temp?
P1V1=P2V2
X1 -> initial
X2-> final
Note: orignal units can be used, but must remain the same
