Kinetic theory Flashcards

Question

absolute zero temperature

Answer 1

-273 degrees celsius

Answer 2

joules (J)

Answer 3

heat is a type of energy. temperature is a measure of how intense the heat is, measured in degrees celsius (°C) or kelvin (K)

Answer 4

-an object with more mass has more internal energy at the same temperature as it has more particles -an object with a higher SHC may have more internal energy at the same temperature

Answer 5

when the temperature of a gas increases, the particles gain more kinetic energy. as a result, the particles move faster and collide with the walls of the container more frequently and with greater force. these increased collisions cause an increase in the pressure exerted by the gas on the container's walls.

Answer 6

as the temperature decreases, the kinetic energy of the gas particles decreases, causing them to move slower. this results in fewer collisions between the particles and the walls of the balloon. because the particles move more slowly, the gas occupies less space, therefore the volume of the balloon decreases.

Answer 7

a) as the temp of the gas increases, the kinetic energy of the gas particles also increases. therefore the particles move faster and collide with the walls of the container more frequently and with greater force b) this increase in the speed and frequency of collisions causes the pressure inside the container to increase. since the volume of the container is constant, the pressure rises as a result of the more energetic particle collisions.

Answer 8

boiling occurs when a liquid is heated to its boiling point, then turns into a gas. it occurs throughout the entire liquid. evaporation can occur at any temperature, and only occurs at the surface of the liquid.

Answer 9

conduction is the transfer of heat/electricity through a material without the material itself moving.

Answer 10

when the particles nearest to the heat source gain kinetic energy, they vibrate more vigorously. they will then collide into their neighbours, causing them to vibrate, and the process repeats until all the particles are vibrating more vigorously, and the object achieves thermal equilibrium with the heat source.

Answer 11

conduction primarily occurs in solids. there is a very small possibility of particles in liquids and gases colliding (since they're much further apart), therefore conduction is unlikely.

Answer 12

a good conductor has a lot of free electrons, which can move easily throughout the material, allowing energy (heat/electricity) to be transferred quickly. a good conductor also has particles which are closely packed, because it increases the change of collisions between the particles, so this would spread the energy throughout the object quickly and efficiently.

Answer 13

convection is the heat-transfer method in liquids and gases (not solids), as the particles can move and flow past each other.

Answer 14

a convection current occurs when a fluid is heated, causing the particles to gain kinetic energy, making the fluid less dense (see flashcard 39), and therefore rise. as the warm fluid rises, it cools down, becomes denser, and then sinks. this movement creates a continuous cycle, transferring heat throughout the fluid.

Answer 15

more kinetic energy causes the particles to spread out, making the fluid less dense.

Answer 16

good language (convection currents) -heated particles rise -particles vibrate more vigorously -fluid expands -fluid gets less dense

Answer 17

heating the liquid causes the particles to vibrate more vigorously so they have more kinetic energy. as the particles move faster, some gain enough kinetic energy to overcome the intermolecular forces completely, so they escape as gases. the particles that leave the liquid take their kinetic energy with them. since they had the most kinetic energy, the average kinetic energy of the liquid decreases. when the liquid's average kinetic energy decreases, so does its temperature.

Answer 18

the particles with higher kinetic energy which contribute to more internal energy leave the liquids

Answer 19

Infrared radiation is a type of electromagnetic wave emitted by all objects – the hotter the object, the more infrared radiation it emits, as hotter objects radiate more energy.

Answer 20

a perfect black body absorbs all radiation without reflecting or transmitting any and is the most efficient emitter of radiation.

Answer 21

not a good reflector, good absorber and emitter

Answer 22

good reflector, bad absorber and emitter.

Answer 23

Infrared radiation is the only thermal energy transfer process that can take place in a vacuum, since no particles are required. This is how the Sun is able to heat the Earth.

Answer 24

If infrared radiation is emitted from a planet at a greater rate than it is absorbed, the temperature of the planet will decrease (global cooling).

Answer 25

However, if radiation is absorbed at a greater rate than it is emitted, the temperature will increase (global warming).

Answer 26

we need to ensure that our home is sealed closed, so air isn't able to pass out. if air was able to pass out, we'd lose heat energy by convection. this is why we have foam seals around our doors and windows + why we draw our curtains at night

Answer 27

conduction= heat loss through a solid (walls, windows) houses tend to have thick walls made from materials with low thermal conductivity. houses also tend to have cavity walls, which is where there are 2 layers of bricks with a small gap (cavity) between them. this air gap reduces conduction, as air is a poor conductor. however, the air does allow convection, so to fix this we fill the gap with insulating foam, fibre glass, newspaper, etc. also, windows tend to have double/triple glazing (2/3 layers of glass) to prevent heat loss. there's also a tiny air gap/vacuum gap between them which reduces conduction. these can also soundproof and provide stronger windows.

Answer 28

the resistance that an object encounters when moving over a solid/through a fluid. friction reduces the efficiency of energy transfer and can cause objects to heat up.

Answer 29

The payback time of an insulation method is the length of time to recover the cost of the insulation based on the annual savings on the energy bill. payback time = initial cost/annual savings

Answer 30

You can also determine how much profit you would make over a given period of time. This is useful for determining which method would be the best long-term investment. profit = (annual savings x time) - initial cost

Answer 31

A significant amount of heat loss happens through the roof. Fibreglass loft insulation is made of many fibres, trapping air and preventing heat loss by conduction and convection at the top of the house.

Answer 32

placing reflective foil behind radiators reduces heat loss through the walls (conduction). the foil reflects infrared radiation emitted by the radiator back into the room, instead of allowing it to be absorbed by the wall.

Answer 33

the insulated jacket around a hot water tank traps air between the tank and the jacket. air is a poor conductor of heat, so it prevents heat from escaping the tank by conduction. the insulation also reduces heat loss through convection, as it stops warm air from moving away from the tank, blocking the convection currents that would otherwise make the tank lose heat.

Answer 34

A ‘U-value’ is a method of determining how effective an insulator a material is, measured in W/m2/°C.

Answer 35

The specific heat capacity of a substance is the amount of energy needed to raise the temperature of 1kg of that substance by 1°C, measured in J/kg/°C It also states how much energy would be released from 1kg of a substance as it cools down by 1°C. Each substance has its own SHC value – generally, good thermal conductors have lower SHC values, as they can transfer heat quickly. ENERGY = MASS x SHC x TEMPERATURE CHANGE E = m x c x ∆θ

Answer 36

If the temperature of the system increases, the increase in temperature depends on the mass of the substance heated, the type of material and the energy input to the system.

Answer 37

1) place an insulating mat under a metal block. insert a heater and a thermometer into the block. 2) measure the block's mass 3) connect the heater to a power supply with an ammeter and voltmeter 4) record the initial temperature, then turn on the power supply and start a stopwatch 5) measure the temperature at regular intervals and record the voltage, current, and time 6) calculate the energy supplied using E = IVT, and use the shc equation to find the SHC. Conclusion- the specific heat capacity of the material can be calculated by determining the energy supplied to the block and dividing it by the product of its mass and temperatue change Evaluation- Sources of error- heat loss to the surroundings reduces accuracy Improvements- insulate the block to minimise heat loss and ensure the thermometer makes good thermal contact Accuracy- repeating the experiment and averaging the results improves reliability.

Answer 38

The specific latent heat of a substance is the amount of energy needed to change the state of 1kg of the substance with no change in temperature. Each substance will have two different SLH values: one for melting/freezing; one for boiling/condensing.

Answer 39

When energy is supplied to a substance and the temperature is not changing, the energy is being used to break the bonds that hold the substance together, therefore resulting in a change of state.

Answer 40

The specific latent heat of fusion of a solid is the amount of energy needed to melt 1kg of the substance from a solid to a liquid with no change in temperature. It also states how much energy would be released from 1kg of a liquid as it freezes.

Answer 41

The specific latent heat of vaporisation of a liquid is the amount of energy needed to boil 1kg of the substance from a liquid to a gas without a change in temperature. It also states how much energy would be released from 1kg of a gas as it condenses.

Answer 42

ENERGY = MASS x SPECIFIC LATENT HEAT E = mL This equation can be used to calculate: the energy required to melt/boil a substance; the energy released during freezing/condensing; the SLH of a substance (fusion or vaporisation).

Answer 43

1kJ = 1,000J

Answer 44

1MJ = 1,000,000J

Answer 45

1MJ = 1,000 kJ

Answer 46

kg/m cubed (m^3)

Answer 47

the different states of matter and the differences in density

Answer 48

in its particles

Answer 49

aim- to investigate how different types of surfaces have different tendencies to absorb, emit and reflect infrared radiation emitters method: 1) arrange 3 boiling tubes in a rack with equal amounts of boiling water in each- eg 20cm^3. Ensure one is plain, one is coated in matt black paint, one is coated in shiny silver paint. 2) Insert a thermometer into each tube and record the initial temperature of the water in each tube 3) Start a stopwatch and record the temp in each tube at regular intervals (eg every 1 min for a total of 15 mins) 4) Compare how quickly the water cools in each tube; this will show which surface is the best emitter of infrared radiation. absorbers method: 1) arrange the same 3 boiling tubes in a rack. replace the water with the same volume of water. 2) record the initial temp of the water in each tube using a thermometer 3) place the boiling tubes in front of an infrared heater. switch on the infrared heater, and start a stopwatch. record the temp of the water in each tube at regular intervals (eg every 1 minute for a total of 15 mins) Results: -For the emitters method, matt black surface would lose heat the fastest as it emits infrared radiation most effectively. Shiny silver surface would retain the heat the longest as it's the poorest emitter. -For the absorbers method, the matt black surface should heat up the most, as it absorbs the most infrared radiation. the shiny silver surface would heat up the least as it reflects most of the radiation it absorbs. Improvements to the experiment: -Conduct the experiment in a room with minimal airflow/ draughts to prevent heat loss by convection -Ensure the room temp is constant so it doesn't affect heat transfer -repeat the experiment multiple times and take an average of the results why do u use cold water and hot for diff methods -for the emitter experiment, boiling water is used as the purpose is to observe how well different surfaces emit infrared radiation -for the absiorber experiment, cold water is used as the aim is to see how much infrared radiation is absorbed by different surfaces. you measure the temp increase of the water ti see how effectively the surfaces absorb radiation.

Answer 50

Changing the temperature of a gas, held at constant volume, changes the pressure exerted by the gas.

Answer 51

faster molecules motion = higher temperature and higher pressure opposite for slower molecular motion

Answer 52

A gas can be compressed or expanded by pressure changes. The pressure produces a net force at right angles to the wall of the gas container (or any surface). *pressure increases as temperature increases, as the gas particles have more kinetic energy therefore vibrate faster therefore collide with the contiainer walls more frequently and with greater force, leading to higher pressure*

Answer 53

when the volume of a gas increases at constant temperature, the gas molecules have more space to move. this leads to fewer collisions between the molecules and container walls, which decreases the pressure.

Answer 54

pressure = force/area

Answer 55

Work is the transfer of energy by a force.

Answer 56

Doing work on a gas compresses its molecules which increases their kinetic energy, as the molecules are forced into a smaller space, which results in the molecules colliding more frequently + with greater force (they have more kinetic enegy = higher temperature) More kinetic energy=more internal energy, So in short doing work on a gas increases the internal energy of the gas and the temperature of the gas.

Answer 57

aim- to investigate the effectiveness of different materials as thermal insulators. method 1) take 3 beakers, wrap one in 1 layer of insulation, the second in 2 layers of insulation, and leave the third beaker uncovered (as a control to see how well the insulating materials work in comparison to no insulation). 2) pour equal amounts of boiling water into each beaker, then cover each beaker with a lid. record the initial temp of the water in each beaker using a thermometer which goes in a small hole in the lid. 3) start a timer. record the temp of the water in each beaker at regular interbals (eg 1 every 1 min for a total of 15 mins) 4) calculate the temp change by subtracting the final temp from the initial temp. repeat the experiment for other materials if time allows, to compare which one keeps the water the warmest. Improvements -the lid may not fully cover the beaker- heat could escape, therefore use a lid which fully covers the beaker -insulate the beaker lid to prevent heat loss. when hot water is exposed to the air, heat can be lost from the top of the beaker through convection. -ensure your readings are correct (thermometer at eye level, etc) -insulate the bottom of the beaker to prevent heat loss through the base. heat loss through the base occurs through conduction. example of a random error- conclusion materials that prevent the temp from dropping the most = best insulators. -materials like wool, foam, bubble wrap trap air within them. air is a poor conductor so these materials reduce heat loss through conduction and convection -thicker insulating materials provide good insulation as it provides more resistance to heat transfer -materials with a shiny/reflective surface like aluminium foil can reflect infrared radiation, preventing heat loss by radiation. -materials with a lower density like foam tend to trap more air and have lower thermal conductivity, making them better insulators you use the lid: -if the beaker isn't covered water can evaporate from the surface, taking heat energy away with it. insulating/covering the lid can prevent this. -insulating/covering the lid stops warm air from escaping and the cooler air from entering (through convection), helping to keep more heat in the beaker. bubble wrap + foam + wool = best insulators in the experiment fabric, aluminium and cling film = worst insulators in the experiment advantages of using data-logging apparatus: -high accuracy -time efficiency disadvantages: -technical issues -power failure could cause the experiment to be disrupted, the data could be lost due to this.