Ch. 18 Air & Water I.
O2 and CO2 Cycle Cyc le 1. The air is is made up up of nitrogen, nitrogen, oxygen oxygen,, carbon carbon dioxide, water vapour and other gases. . ! and C! cyc"e cyc"e is the constant constant exchang exchange e of ! and C! among among "iving things. things. #. ! and C! cyc"e cyc"e is important important to "iving things things because because they need need a constant constant supp"y of oxygen and carbon dioxide in the air to survive. $. %iving things need oxygen oxygen and water to stay a"ive. They a"so give out carbon carbon dioxide. . 'ue to the oxygen oxygen and and carbon carbon dioxide cyc"e, the the oxygen oxygen in the air never runs out. (. 'uring photosynthesis, photosynthesis, "iving things produced produced and re"ease re"ease ! into the air air.. ). 'uring respiration, respiration, "iving things give out out C!. *t is a"so re"eased into into the air when "iving things die and decay or when man burns oi" or or fossi" fue"s. 8. *n a daytime, p"ants ta+e in C! and give out ! during photosynthesis. photosynthesis. ut ut at night, they ta+e ta+e in oxygen oxygen and give out out carbon dioxide.
II. Water Cycl Cy cle e -. The continuous movement of water water from earth, to the the s+y and bac+ to the earth earth is ca""ed water cyc"e . 1/. 1/. *n the the wat water er cyc" cyc"e, e, the the move moveme ment nt of wate waterr re0 re0ui uirres the the hea heatt fr from the the sun sun to ta+e p"ace. 11. 11. Ther There e ar are two two proc proces esse ses s tha thatt occ occur ur in wate waterr cyc cyc"e "e,, eva evapo pora rati tion on and and condensation. 1. vap vapo oratio ation n is is th the cha chan nge of wat water er fro from "i0u "i0uid id to a gas. gas. 1#. 1#. The The cha chang nge e of of st state ate of of wat water er from from a gas gas to a "i0 "i0ui uid d is is ca" ca""e "ed d con conde dens nsat atio ion. n. 1$. 1$. The The pr proces ocess s of of wat water er cyc" cyc"e e sta start rts s whe when n the the wat water eva evapo pora ratte into into the the air air and and rise into the s+y, then it condenses to form a drop"et of water, when the drop"ets of water get too big and heavy it fa""s into the earth as rain. 1. 1. *n the the eva evapo pora rati tion on pr proces ocess s on" on"y y the the pur pure wat water er rise rises s int into o the the s+y s+y. When When it it fa""s bac+ to the earth as rain, it puri2es and he"ps to coo" the air. 1(. 1(. 3uma 3uman n act activ ivit itie ies s have have caus caused ed grea greatt har harm m to to our our envi envirronme onment nt that that a4ec a4ectt the water cyc"e. 1). 1). Thos Those e two two acti activi viti ties es that that a4ec a4ectt wate waterr cyc" cyc"e e are are def defor ores esta tati tion on and burning of fossi" fue"s. 18. 'efo 'eforresta estati tio on is the the c"ea c"earring ing of for forest est by cut cutti ting ng or burning burning trees trees for woods or "and. "and. 1-. 1-. 'efo 'eforresta estati tion on wi"" wi"" incr increa ease se the the rai rainf nfa" a""" and and it wi"" wi"" caus cause e mor more e 5o 5ood ods s and "ands"i"des in some p"aces, whi"e "ess "ess rainfa"" causes drought drought . . /. /. ur urning ning of of foss fossi" i" fue fue"s "s pr produc oduce e har harmfu" mfu" gas gases es tha thatt for form ac acid id when when it it mix with water water.. 1. ecau ecaus se of of bur burni ning ng fos fossi" si" fue fue"s "s,, th the ear earth th gets ets r rep"e ep"eni nis shed hed with acidic water instead of freshwater when it rains. . . The The per perio iod d of of tim time e wit witho hout ut rain rain is ca"" ca""ed ed dr drou ough ght t .. #. #. 6"ob 6"oba" a" war warming ming is the the in incr crea ease se in the the ea eart rth7 h7s s temp temper erat atur ure. e. $. The "ar "arge amount ount of ear earth th s"id s"idin ing g dow down n is is ca" ca""e "ed d "an "ands ds"i "ide des s .
Ch.1- 6ravitationa" and rictiona" orces I.
Gravitational force 1. The force between things and the earth that pu""s the thing c"ose to the ground is gravitationa" force . 6ravitationa" forces pu"" a"" things down, towards the centre of the earth. #. The earth exerts a gravitationa" force on the moon that ma+es the moon orbit around the earth. $. 6ravitationa" force a""ows us to stand on the ground and not 5oat away. . 9ore e4ect of gravitationa" force are, it speeds the s+iers as they s+ies downhi"", it pu""s the swimmer down towards the water, it cause water to fa"" downwards and it pu""s the c"imbers bac+ down as they c"imb. (. 6ravitationa" force between ob:ects and earth is ca""ed weight. ). The gravitationa" force becomes wea+er as we move away from earth, that7s why the astronaut is 5oating in the space because there is very "itt"e gravitationa" force pu""ing them to the ground 8. Weight is a force and it can be measured by spring ba"ance. -. ;n"i+e weight, mass is not a force. *t is constant wherever the ob:ect is. 1/. ven mass is not a force, it sti"" can be measured.
II. Frictional force 1. The force that opposes motion is ca""ed frictiona" force< this frictiona" force can be a pu"" or a push. . =ome e4ect s of frictiona" motion is> to s"ow down and stop the moving ob:ect, to prevent ob:ect from starting to move, to a4ect the movement of an ob:ect on di4erent surfaces. #. A toy car moving on the tab"e can be stop because there is the frictiona" force that acts in the direction opposite to the direction of the motion of toy car. $. =mooth surface a""ows the ob:ect to move faster than a rough surface because it gives "ess frictiona" force. . riction a"so produce heat by rubbing the surface of each ob:ects (. ?ot on"y frictiona" force occurs between two ob:ects, it a"so produced when ob:ects move through air and water. ). The frictiona" force that s"ows ob:ects down as they move through air is ca""ed air resistance, whi"e the one that s"ows ob:ects down as they move through water is ca""ed water resistance. 8. The amount of air resistance acting on an ob:ect depends on many factors such as shape. -. @acing car is designed with a shape that a""ows air to move over smooth"y to reduce air resistance. 1/. Water resistance pushes against a moving ob:ect and s"ows it down as it move through the water. 11. *t is hard to wa"+ through water in a swimming poo" because water resistance s"owing down our movement. 1. *n our dai"y "ife, frictiona" force between the so"es of our shoes and the ground stop us from s"ipping when we wa"+. 1#. The tread patterns on the tyres increase the frictiona" force between tyres and the ground, it a""ows vehic"e to stay on the road. 1$. *n an ancient time peop"e ma+e 2re by rubbing hard wooden stic+ on a piece of soft wood that generate heat. 1. We can grip things better because there is 2ne ridge pattern on our 2nger. 1(. rictiona" force can be both usefu" and cause prob"ems in our dai"y "ife.
1). riction cause ob:ect to s"owdown, overheat and wear out. 18. *n order to overcome the prob"em cause by friction we can reduce the friction between surfaces with "ubricant and ro""erswhee"s. 1-. or the overheat prob"em, we can app"y "ubricant on the moving part of machine, and to move heavy ob:ects easi"y we can use ro""ers and whee"s. /. %ubricant is materia"s used to ma+e surface s"ippery to reduce friction. Ch. 18 Air & Water III. O2 and CO2 Cycle .The air is made up of , , , and . (.! and C! CBC% is the constant exchange of ! and C! among the . ).! and C! cyc"e is important to "iving things because they need a supp"y of and in the air to . 8.%iving things need and to stay a"ive. They a"so carbon dioxide. -.'ue to the and cyc"e, the in the air never . #/.'uring photosynthesis, "iving things produced and ! into the air. #1.'uring respiration, "iving things C!. *t is a"so re"eased into the air when "iving things and or when man burns or . #.*n a daytime, p"ants C! and ! during photosynthesis. ut at night, they ta+e in and give out . IV. Water Cycle ##.The continuous movement of water from earth, to the s+y and to the earth is ca""ed . #$.*n the water cyc"e, the movement of water the from the sun to ta+e p"ace. #.There are two processes that occur in water cyc"e, evaporation and . #(.vaporation is the change of from to a gas. #).The change of state of water from a to a "i0uid is ca""ed condensation. #8.The process of water cyc"e starts when the water into the air and rise into the s+y, then it condenses to form a of water, when the drop"ets of water get too big and heavy it into the earth as . #-.*n the evaporation process on"y the pure water rises into the s+y. When it fa""s bac+ to the earth as rain, it and he"ps to the air. $/.3uman activities have caused to our environment that a4ect the water cyc"e. $1.Those two activities that a4ect water cyc"e are and of . $.'eforestation is the c"earing of forest by or trees for woods or "and. $#.'eforestation wi"" increase the rainfa"" and it wi"" cause more and in some p"aces, whi"e "ess rainfa"" causes . $$.urning of fossi" fue"s produce harmfu" gases that form when it with water. $.ecause of burning fossi" fue"s, the earth gets with acidic water instead of when it rains. $(.The period of time without rain is ca""ed . $).6"oba" warming is the in the earth7s temperature. $8.When the "arge amount of earth s"iding down it means .
Ch.1- 6ravitationa" and rictiona" orces III. Gravitational force 11.The force between and that pu""s the thing c"ose to the ground is gravitationa" force 1.6ravitationa" forces pu"" a"" things down, the center of the earth. 1#.The earth exerts a gravitationa" force on the moon that ma+es the moon the earth. 1$.6ravitationa" force a""ows us to stand on the ground and not away. 1.9ore e4ect of gravitationa" force are, it speeds the s+iers as they , it pu""s the swimmer down towards the water, it cause water to fa"" and it pu""s the c"imbers bac+ down as they c"imb. 1(.6ravitationa" force between and is ca""ed weight. 1).The gravitationa" force as we move away from earth, that7s why the astronaut is 5oating in the space because there is gravitationa" force pu""ing them to the ground 18.Weight is a force and it can be measured by . 1-.;n"i+e weight, mass is . *t is constant wherever the ob:ect is. /.ven mass is not a force, it sti"" can be . IV. Frictional force 1.The force that motion is ca""ed frictiona" force< this frictiona" force can be a or a . .=ome e4ect s of frictiona" motion is> to and stop the moving ob:ects, to ob:ect from starting to move, to a4ect the movement of an ob:ect on di4erent . #.A toy car moving on the tab"e can be stop because there is the that acts in the direction opposite to the direction of the motion of toy car. $. surface a""ows the ob:ect to move faster than a rough surface because it gives "ess frictiona" force. .riction a"so produce heat by the surface of each ob:ects (.?ot on"y frictiona" force occurs between two ob:ects, it a"so produced when ob:ects move through air and water. ).The frictiona" force that s"ows ob:ects down as they move through air is ca""ed air , whi"e the one that ob:ects down as they move through water is ca""ed water resistance. 8.The amount of air resistance acting on an ob:ect depends on many factors such as . -.@acing car is designed with a shape that a""ows air to move over smooth"y to air resistance. #/.Water resistance a moving ob:ect and s"ows it down as it move through the water. #1.*t is to wa"+ through water in a swimming poo" because water resistance s"owing down our movement. #.*n our dai"y "ife, frictiona" force between the of our shoes and the ground stop us from when we wa"+. ##.The tread patterns on the tyres the frictiona" force between tyres and the ground, it a""ows vehic"e to stay on the road. #$.*n an ancient time peop"e ma+e 2re by rubbing hard wooden stic+ on a piece of soft wood that .
#.We can things better because there is 2ne ridge pattern on our 2nger. #(.rictiona" force can be both usefu" and in our dai"y "ife. #).riction cause ob:ect to , and wear out. #8.*n order to overcome the prob"em cause by friction we can reduce the friction between surfaces with and ro""erswhee"s. #-.or the overheat prob"em, we can app"y "ubricant on the moving part of machine, and to move easi"y we can use ro""ers and whee"s. $/.%ubricant is materia"s used to ma+e surface to reduce friction.
