the atmosphere and air around us Flashcards
what is an atmosphere?
the earth is surrounded by a thin layer of air called atmosphere
what is air?
Air is the mixture of several gases which have been physically combined together
name 2 main gases in air
nitrogen, oxygen
other gases that are present in smaller amounts of air are?
carbon dioxide, noble gases
3 main noble gases are?
argon, helium, neon
name all the 5 noble gases
argon helium neon krypton xenon
argon, neon, krypton and xenon are elements/molecules/compounds?
argon, neon, krypton and xenon are elements
nitrogen and oxygen are an elements/molecules/compounds?
nitrogen and oxygen are molecules. N2, O2
water vapor and carbon dioxide are elements/molecules/compounds?
water vapor and carbon dioxide are compounds
nitrogen percentage
78 %
oxygen percentage
21 %
carbon dioxide percentage
0.04 %
noble gases percentage
0.96 %
water vapor percentage
variable
define photosynthesis
photosynthesis is the process whereby a plant manufactures their own food
what happens during photosynthesis?
during photosynthesis, the chlorophyll present in the leaves trap in energy from sunlight to use it to convert water and carbon dioxide into oxygen and glucose .
what does the plant use to carry out photosynthesis?
sunlight, water, carbon dioxide and minerals from the soil
what energy does the glucose contain and what kind of change is photosynthesis?
the glucose contains chemical energy. the process of photosynthesis is an example of a chemical change, new products are formed and the change is irreversible
what is the product of photosynthesis?
the product of this process is food for the plant in form of glucose and oxygen gas
word equation of photosynthesis
carbon dioxide +
water
–chlorophyll
sunlight ———>
glucose + oxygen.
define respiration
respiration is a biochemical process during which organisms obtain energy
what happens during respiration?
during respiration, glucose is broken down in the presence of oxygen.
define combustion?
combustion is a chemical reaction between fuel and oxygen
what is complete combustion?
complete combustion is when fuel burns in sufficient amount of oxygen and forms water and carbon dioxide
what is in incomplete combustion?
incomplete combustion is when fuel is burned in insufficient amount of oxygen and forms carbon monoxide and water
what is carbon?
carbon is an element present in all living organisms
where is carbon present in other than living organisms?
it is present in air, rocks and soil
how is carbon returned in the atmosphere?
when fossil fuels are burnt carbon is returned in the atmosphere as carbon dioxide
define carbon cycle
the carbon cycle comprises of 3 processes namely, photosynthesis, combustion and respiration. (decomposition) these 3 processes maintain the level of carbon dioxide in the atmosphere almost constant.
define greenhouse gases
greenhouse gases are gases that retain heat energy in the atmosphere
define greenhouse effect
when greenhouse gasses retain an excess of heat energy in the atmosphere it is known as greenhouse effect
importance of greenhouse gases
they keep the earth’s surface warm for survival of human beings