unit 5 - thermal effect

Question 1

structure of solid

Answer 1

fixed structure
molecules held very closely by strong forces
can vibrate backwards and forward but cannot change position

Question 2

structure of liquid

Answer 2

irregular structure ( shape of the container )
molecules are close together and attract each other
they can slide past each other

Question 3

structure of gas

Answer 3

no fixed structure
molecules well-spaced, weak forces between them
move freely and fast and can collide with each other and wall of the container

Question 4

what are two fixed points in the thermometer?

Answer 4

0 and 100 degree celcius

Question 5

what is calibrating

Answer 5

putting a scale on an instrument

Question 6

how to put a scale on a thermometer

Answer 6

put the thermometer in the melting ice, wait until the thermometer value to decrease and mark the point

put the thermometer in the boiling water, wait until the thermometer value to increase and mark the point

divide the distance between two points into 100 equal divisions

Question 7

how to improve sensitivity in the thermometer

Answer 7

the narrower the tube, the higher the sensitivity

Question 8

what is the range in the thermometer

Answer 8

the lowest and the highest temperature that the thermometer can measure

Question 9

how to increase responsiveness in thermometer

Answer 9

thinner glass in the bulb

Question 10

what is the linearity of the liquid in the thermometer

Answer 10

the expansion to increase in temperature is linear

Question 11

describe thermal expansion

Answer 11

when the object gets heated, the particle gets speed up. their vibration takes up more space so the object will expand slightly.

Question 12

what happens to the volume of the gas if the temperature increases

Answer 12

volume increases

Question 13

what happens to the pressure in the sealed tube if the temperature increases

Answer 13

pressure increases

Question 14

what is conduction

Answer 14

thermal energy is transferred from the hot end to the cold end as the faster particles pass on their extra motion to particles all along the bar

Question 15

what is another word for poor conductor

Answer 15

insulator

Question 16

why metal is a good conductor

Answer 16

they have free electrons that get speed up when they are heated and they collide with atoms and make them vibrate faster.

Question 17

what happen to the density when the water get heat up

Answer 17

the density decreases because volume expands

Question 18

which factors increase the energy radiated per second

Answer 18

surface temperature and area

Question 19

what colour is the best emitter and absorbers

Answer 19

black

Question 20

what colour is the best reflector

Answer 20

silver

Question 21

feature of vacuum flask

Answer 21

stopper ( like a lid) to reduce conduction and convection

vacuum gap to reduce convection or conduction

silvery surface to reduce radiation

Question 22

difference between evaporation and boiling

Answer 22

evaporation

• can happen at any temperature
• only happen on the surface

boiling

• only happens at boiling point
• happen throughout the whole liquid

Question 23

what affects the rate of evaporation

Answer 23

temperature, surface area, humidity, presence of wind across the surface

Question 24

how evaporation gives a cooling effect

Answer 24

as the particle evaporates, it takes energy away

Question 25

how to calculate energy transferred ( using specific heat capacity)

Answer 25

E= mc ( difference in T)

Question 26

how to calculate thermal capacity

Answer 26

mc

Question 27

what is the latent heat of fusion

Answer 27

the energy needed to separate the particles so that they can form the liquid from solid

Question 28

what is the latent heat of vaporization

Answer 28

the energy needed to separate particles so that they can form gas from liquid

Question 29

how to calculate the energy transferred in terms of specific latent heat

Answer 29

E=mL