Chapter 9: Heat Flashcards
What is heat?
energy that makes an object hot
What is another name for the energy from Sun that is reflected back by clouds?
thermal energy
What is heat in humans?
digestion
metabolism
What is the difference between heat and temperature?
Heat:
- form of energy
- object absorb heat=hotter
- object loses heat = colder
- measured in joule(J)
- flows from hotter to cooler
Temperature:
- the measure of degree of hotness or coldness of an object
- thermometer is used
- Unit: celcius(℃) and kelvin (K) [Extra: Farenheit(℉)]
What are the factors that affect heat?
TQT=抬起头，太阳在那儿(tai yang=heat)
Type
Quantity
Temperature of material
What are the factors that affect temperature?
degree of movement of particles
Why when a spark fall on your hand, you don’t feel any pain, but a few drops of boiling water will?
Amount of heat in the spark is less than the amount of heat in the drops of boiling water
Does two objects at the same temperature have the same amount of heat
No, objects at the same temperature may not have the same amount of heat
From which temperature to which temperature does heat energy travels to?
Higher temperature to lower temperature
What is the relationship between the difference in temperature and heat flow?
The greater the difference in temperature, the faster the heat flows
State 3 ways that heat travels.
- convection
- conduction
- radiation
What is conduction?
The process at which heat flows from the hot to the cold end of solid
Do particles in the medium flow?
no
try to explain the concept of conduction.
the particle of the solid are arranged very
closely together (1),
particle that recieve heat energy directly vibrate FASTER, collide with neighbouring particle FREQUENTLY(2),
in this way heat is transferred to the cold end of spoon (3)
What is convection?
The process in which heat is transferred from one place to another by particles which move (move to transfer)
What does convection occur in?
liquids and gases
Try to explain convection.
When fluid is heated, it expands and becomes less dense, causing it to move upwards (1)
The cold and dense fluids moves downwards to take it’s place (2)
This in turn gets heated and rises and repeats the cycle (3)
What is radiation?
The transfer of heat through vacuum
Does radiation require any medium?
no
Give an example of radiation.
The heat of the Sun is transferred to the Earth by radiation
Can the thermometer be placed on top of the lighted bulb?
wants to have the temperature through radiation
No, to prevent heat from beig transferred to the thermometer through convection, since hotter air goes up
Can the thermometer be places in contact with the lighted bulb?
(wants to have the temperature through radiation)
No, to prevent heat from being transferred to the thermometer through conduction.
Why is only radiation used in the warming of earth?
Because there is no medium in space to transfer the heat
Try to explain how sea breeze is formed.
During the day, both land and sea absorb heat from the Sun. Since the land becomes hot faster than the sea, the air above land is heated, becomes less dense and rises, meanwhile cool air above the sea moves towards the land to take the place of the hot air.And this is why wind blows from the sea to the land
Try to explain how land breeze is formed.
At night, the land cools faster than the sea, therefore, the sea is warmer than the land. The air above the sea rises as it is hotter, while cool air above te land moves towards the sea to occupy the place left by the warm air. And this is why wind blows the land to the sea.
What are heat conductors?
Substances which conduct heat rapidly and becomes hot or cold quickly
What are heat insulators?
Substances which do not conduct heat and prevent heat from flowing.
State some examples of heat conductors
- mercury
- silver
- copper
- aluminium
- zinc
- iron
- lead
State some examples of insulators.
- water,ice
- glass
- rubber
- wood
- cotton
- asbestos
- plastic
- polystrene
- air
What is thermal equilibrium?
When 2 objects reach the same temperature when in thermal contact
What happens when solid is heated?
Particles in solid vibrate faster, causing them to move apart from on another, making the solid expand, so their volume increases
What happens when solid is cooled?
Particles in solid vibrates slower, causing them to move closer to one another, making it contract, so their volume decreases
What is the observation of this picture (after heating)?
https://drive.google.com/file/d/1XQWdJue1ClZG3dZiZ9hBk1KWsqyZL78F/view?usp=sharing
The ball cannot go through the ring
Why could the ball go through the ring again after cooling?
because the ball contracted
What happens when liquid or gas is heated?
Particles move faster and randomly, causing the distance between particles increase, making te liquid or gas expand, so their volume increases
What happens when liquid or gas is cooled?
Movement of the particles slow down and move closer to one another,making it contract, so their volume decreases
Why did the balloon become inflated when put in hot water?
Air in the bottle expands, and then moves into the balloon.
Why did the balloon become deflated when put into cold water?
air in balloon contracted, moving back into the bottle
Why did the coloured liquid droplet in flask moves downwards when put in ice?
air inside the flask contracts because it lost heat
Why did the coloured liquid droplet in flask moves upwards in hot water?
air inside the flask expands because it absorbs more heat
Try to explain the use of expansion and contraction in thermometer.
When the surrounding temperature rises, the mercury expands and columns up to the capillary tube.
But when the surrounding temperature falls, the mercury contracts and returns to the bulb
How is a bimetallic strip formed?
combining 2 types of different metals that have different rates of expansion and contraction
What will happen when the bimetallic strip is heated?
It will curve with the metal with higher expansion rate on the outside
What will happen when the bimetallic strip is put into cold surrounding?
It will curve with the metal with lower expansion rate on the outside
Why are there small gaps between sections of rail?
to allow the tracks expand
Why are electric cable and telephone wires fitted loosely?
to allow room for expansion and contraction
How did people solve the expansion of a curved bridge?
One end of bridge is fixed while the other rest on rollers, so when it expands or contracts, it wont be damaged
How to make a dented ball return to its original shape?
put it in hot water, as the air in ball expands, the ball will no longer be dented
How to open a tighten jar lid?(if plastic cannot save u dy ahhaa)
put it in hot water, as (jar lids mostly are metal) metal absorbs heat faster and expands faster
What does the amount of heat that is absorbed depends on?
type and colour of surface
What type of surface absorbs heat better?
dark and dull
Is a good heat radiator also a good heat absorber?
yes
State the heat concepts used in daily life by using green building technology.
- Using recycled materials
- Using water efficiently
- Using renewable energy
- Using environment-friendly equipment
- Reducing damage to the original landscape
- Using good ventilation, drainage and lighting system
What are the 10 ways to make our home eco-friendly?
- eco-friendly building materials
- LED lightning
- solar panels
- household water conversion
- wind turbines
- harness geothermal energy
- sustainable insulation
- energy efficient appliances
- water re-use
- rainwater harvesting
