water & changes of state boiling, evaporation & condensation p6 science extra class 4 may...
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Water & Changes of State
Boiling, Evaporation & Condensation
P6 Science Extra Class 4 May 2011
How much do I know? True False
1 Water exists in three states.
2 Ice and snow is water in its solid state; water vapour and steam is water in the gaseous state.
3 Melting, evaporation, boiling, condensation, freezing causes water to change from one state to another.
4 Melting point of ice (or freezing point of water) and boiling point of water is 0oC and 100oC.
True False
4 When ice is heated, it melts and changes to water at 0oC.
5 When water is cooled, it freezes and changes to ice at 0oC.
6 When water is heated, it boils and changes to steam at 100oC.
7 When steam is cooled, it condenses to water
8 When ice melts, it is still gaining heat (but the temperature remains at 0oC) to help the particles in ice to break away from each other until all the ice becomes water.
True False
9 Wind, temperature and exposed surface area affect the rate of evaporation.
10 Steam is water in the gaseous state, therefore it is invisible.
11 Mist (the white cloud from kettle spouts) made of tiny water droplets, is condensed steam.
11 Evaporation does not only take place when there is sunlight.
12 The bubbles in boiling water contain water (not air). These bubbles are formed when water gains heat and changes into a gas which will then rise and escape into the surrounding air.
True False
13 The volume of an ice cube is bigger than liquid water having the same mass. (water expands during freezing)
14 There is no loss in mass when ice changes to water. (assuming no evaporation has taken place)
15 Water cycle is a continuous movement of water from the Earth’s surface into the air and back again.
16 Water cycle involves changes in the state of water through evaporation and condensation.
True False
17 Rain falls when clouds get cold or become hot or when cloud condenses.
18 Clouds are made of tiny water droplets, (they are in the liquid state) and they fall as rain, snow or hail when the water droplets are big and heavy.
19 Life processes such as transport and photosynthesis need water.
20 Blood which helps to transport materials in the human body is largely made up of water.
True False
21 Water is needed to carry oxygen, digested food and other nutrients to different parts of body while carbon dioxide and other waste substances are carried away from the various parts of body.
22 Causes of water pollution include •oil spills from ships, •poisonous wastes from factories,•untreated waste water from houses and buildings, •litter thrown on land and in water,
• deforestation.(soil erosion pollutes water bodies, water
clouded with soil reduces the amount of sunlight for aquatic
plants)
ICE
WATER
STEAM
WATERVAPOUR
Freezes at 0oC
melts at 0oC
Boils at 1000C
Condenses(no specific temp)
Evaporates below 1000C
gains heat &
into
loses heat &
gains heat &
into
into
loses heat &
loses heat &
gains heat &
to become
into
Concept Map
1 (a). Safia and Josh are doing experiments with ice cubes.
First Safia puts ice cubes on a plate over a bowl of hot water
ice
bowl
hot water
water droplets
plate
Explain how the water droplets formed in the bowl underneath the plate.__________________________________________________________
After some time, Safia sees droplets of water drip from underneath the plate. Water from the melting ice cannot pass through the plate and the bowl has not moved.
Hot water evaporates into water vapour and loses heat as it touches the cooler surface to condense into the water droplets underneath the plate.
(b) In winter, people put salt on the road to make the ice melt.
Josh investigates the effect of salt on melting ice. He puts the same amount of ice in two funnels.He adds salt to the ice in one funnel.
The ice starts to melt. Every ten minutes, Josh measures how much water is in each cylinder.
The graph below gives Josh’s results.
cm 3
20
18
16
14
12
10
8
6
4
2
Ice only
cm 3
20
18
16
14
12
10
8
6
4
2
Ice and salt
One axis on the graph has been labelled.Write the label and the units for the other
axis.
volume of wat er (cm )3...........................................
14
12
10
8
6
4
2
00 10 20 30 40 50 60 70 80 90 100
with salt
without salt
........................................................................( )Time (minutes)
(c)What has Josh found out about the effect of salt on melting ice?
(d)Josh concludes ‘The more salt I add, the steeper the line
on the graph will be’. Josh’s results on the graph do not support his conclusion.
Explain why his results do not support his conclusion.
_____________________________________________
_____________________________________________
Ice melts more quickly when salt is added.
He did not try different amounts of salt.
2. (a) Rose knows that water and vinegar evaporate.
Rose sets up a test to find out if more water or more vinegar evaporates over 3 days.She puts water in one container and vinegar in another container, like this:
Water Vinegar
Rose places both containers on the same windowsill.
(i)Use the information above to describe ONE thing that is not fair in her test.
The containers are of different sizes / there is more vinegar than water
(ii) Why does it matter if her test is not fair?
The results will not be reliable and she will not be able to interpret or compare her results/ know that the results are the true results of her test.
(The results will not be accurate – 0m)
(c) Rose changes her test to make it fair. She measures the volumes of water and vinegar twice each day to see how much has evaporated.
The table below shows her results.
Day Time Volume of
water (cm3)
Volume of
Vinegar(cm3)
Mon 10am3pm
10099
10098
Tues 10am3pm
9788
9170
Wed 10am3pm
9486
8280
Rose wanted to compare water and vinegar to find out which evaporated the most over 3 days.
Use Rose’s results to write an observation for her test.
More vinegar than water evaporated over the three days.
(d) Rose notices that more water and vinegar evaporated between 10am and 3pm on Tuesday than between the same times on Monday or Wednesday.Suggest ONE possible reason why more water and vinegar evaporated on Tuesday.
Air temperature increased/ it was hotter/ It was more windy/ Less humid/ Cooler on Monday.
5. The diagram below shows particles in a gas, a solid and a liquid.Each arrow, A, B, C and D, represents a change of state.
B
C
A
D
Choose from the following words to complete the sentences below.
boiling condensing evaporating filtering freezing melting
• Change of state A is called Evaporation/ boiling• Change of state B is called melting• Change of state C is called freezing.• Change of state D is called condensing
8. The graph shows the temperature change of pure water in a beaker that was left on a table in a room over a period of time.
(a) Based on the graph, explain why the temperature of water stopped decreasing after the second minute.
Tem
pera
ture
(oC
)
Time ( min)
20
60
40
80
100
2 4 6 8 10 12 14
The temperature of water has reached the temperature of the room/ surroudings.
(b) A heat source was introduced at the 6th minute. The water boiled after heating for four minutes. The heat source was removed at the 12th minute. Complete the graph until the 12th minute.
Tem
pera
ture
(oC
)
Time ( min)
20
60
40
80
100
2 4 6 8 10 12 14