meow Flashcards
how does a bimetallic strip work
the bimetallic strip is made of 2 metals that expand at different rates upon the same temperature
the metal that expands faster becomes longer faster, thus curving
what are the different ways thermal energy can be transferred
conduction
convection
radiation
definition of conduction
the transfer of thermal energy without the physical movement of the medium
definition of convection
the transfer of thermal energy from one place to another by the physical movement of a medium
(liquids and gasses transfer heat mainly by convection
what are the steps of convection
the heat source transfers therma energy to the side of which the heat source is
as the heated fluid expands, its density decreases
the hotter and less dense water rises to top of the beaker
the cooler and denesr water in turn isnks to the bottom
htis repeats to create a convection current
how does a gas convection current with a candle work
the air above the candle heats up and expands, thus becoming less dense and rising up chimney a
defination of radiation
the transfer of thermal engery from a hotter body to a cooler body without the need for a medium
how does a vacuum flask work
conduction cannot occur in a vacuum, thus reducing heat lost through conduction
the silver inner walls reflect heat and reduce the rate of heat loss through radiation
the cap tightly screwed on reduces loss of thermal energy through convection
diff between physical and chemical changes
p- no new substances are formed
cc- one or more new substances are formed
p- the changes can usually be reversed using seperation techniques
cc- the changes are usually not easily reversed
types of chemical changes
combustion
thermal decomposition
oxidation
neutralisation
definition of combustion
a chemical reaction where a substance is heated in the presence of oxygen to form one or more new substances
heat and light are usually given out during decomposition
definition of thermal decomposition
process where a substance breaks down into two or more simpler substance
definition of oxidation
when a substance gains oxygen, it undergoes a chemical change called oxidation
what is an example of oxidation
rusting
it occurs when iron reacts with iron and oxygen to form rust
another example is an apple turning brown
defintion of neutrialisation
when an acid is mixed with an alkali
what are always made from acid + metal
salt and hydrogen gas
how do you test for hydrogen gas
use a lighted split, it goes out with a ‘pop’ sound in the presence of hydrogen gas
what is made from acid + carbonate
salt, carbon dioxide and water
what color is acidic, neutral, alkali
red, green, purple
what color does blue litmus paper turn to in acidic substance
from blue to red
what color does red litmus paper turn to in alkali
from red to blue
how can neutrailisation be used in everyday life
toothpaste neutralises any present in the mouth
different ways chemical change can occur
mixing
heating
exposure to light
interaction with oxygen
effects of carbon monoxide
highly toxic, reduces the amount of oxygen taken up by red blood cells, leading to headaches and eventually death due to suffocation
effects of sulfur dioxide and oxides of nitrogen
irritates eyes, lungs, nose, worsen symptoms of asthma, heart disease, and respiratory problems
sorce of carbon monoxide
incomplete combustion of fuels in factories and motor vehicles in the presence of insufficient oxygen
source of sulfur dioxide
burning of coal and petroleum in power stations
volcanic eruptions
source of oxides of nitrogen
burning of fuels at high temperatures in motor vehicles, factories and power stations
reaction of nitrogen and oxygen in the air during lightning strikes
