Heat

Question 1

explain why pressure decreases when volume increases by kinetic theory

Answer 1

1. speed/KE unchanged
2. frequency of collision on inner surface decreases
3. pressure decreases

Question 2

how to ensure sth has the same temperature as water when boiling

Answer 2

1. stop heating

2. mix well with a stirrer

Question 3

what is the advantage of big bulb in thermometer

Answer 3

improve sensitivity

Question 4

define specific latent heat of vaporization of a liquid

Answer 4

It refers to the energy required to change the liquid of unit mass to its gaseous state without changes in temperature

Question 5

what is thermal equilibrium

Answer 5

same temperature (even though different state)

Question 6

why the wet hand is stick to the metal handle on an extremely cold day

Answer 6

1. metal is a good conductor of heat
2. the rate of transfer of heat from the water on the hand to the metal handle is faster than the rate of transfer of heat from the hand to the water.
3. the water cools down to a temperature lower than the freezing temperature of the water
4. the frozen water sticks the hand and the metal handle together.

Question 7

why temperature is unchanged while changing state

Answer 7

Energy is used to overcome the intermolecualr forces between molecule
PE increases

Question 8

in what situation will a setup suitable for calibrating the temperature in linear scale

Answer 8

when x is linear related to y

Question 9

precaution when studying Boyles law

Answer 9

syringe should be pushed slowly so that the temperature remains unchanged.

Question 10

why we cannot replace the mercury in the mercury thermometer by water

Answer 10

the expansion of water is not linear from 0C to 4C

Question 11

Use kinetic theory to explain the change in gas pressure in the bubble as its volume increases

Answer 11

Volume increases as bubble rises but the ke of the gas molecules remain unchanged
Therefore frequency of collision of molecules on bubble’s inner surface decreases, gas pressure decreases

Question 12

evaporation only takes place above room temperature?

Answer 12

wrong.

it takes place at any temperature above 0K

Question 13

explain why gas pressure increase when temperature increase using kinetic theory

Answer 13

the speed of the gas molecules increases and they collide more frequently and violently with the wall of the container. Thus the pressure increases.

Question 14

what is temperature

Answer 14

measure of the degree of hotness of an object

Question 15

what property do thermometer make use of

Answer 15

temperature-dependent property

Question 16

what is pressure

Answer 16

F/A

unit : Pa

Question 17

when will real gas behave like ideal gas

Answer 17

high temperature and low pressures

Question 18

assumption in kinetic theory

Answer 18

all molecules are in random motion
the size of a molecule is negligible with the separation between them
the duration of collision is negligible
the collision of molecules and the wall are perfectly elastic
intermolecular force are negligible
all molecules are identical and have the same mass

Question 19

why we feel cool when there is a wind

Answer 19

the rate of evaporation of sweat is higher when it is windy

the warm air around us is replaced with cooler air

Question 20

describe the procedure of determining the specific latent heat of fusion

Answer 20

note that: need wait until the drip rate of two funnels are the same before taking any record

Question 21

describe the arrangement and motion of the molecules of the substance in the solid state and liquid state

Answer 21

in solid state
molecules arrange in regular structure
can only vibrate about their mean position

in liquid state
molecules not arranged in regular structure
can freely move

Question 22

how will a layer of oil affect the rate of evaporation

Answer 22

it reduce the rate of evaporation and thus reduce the energy loss to the surrounding

Question 23

why the heating element of a water heater is usually installed on the lower position of the water tank

Answer 23

whole tank of water can be heated evenly by convection

to prevent overheating in case the water level is too low