Water

Why is water so important

List 5 reasons you think it is important

  1. ____________________
  2. ____________________
  3. ____________________
  4. ____________________
  5. ____________________

Homework

Please bring in a sample of water!

Welcome to the Global Water Experiment!

http://water.chemistry2011.org/web/iyc

Test for water is to use Cobalt Chloride test papers

*Cobalt Chloride is on the banned substance list*

is blue when it is dry

and pink when it is in the presence of water!

Cobalt chloride comes as test papers, these test papers are very hard to keep dry. The Colours will degrade unless stored in a dry container with some dessicate

You could also use white anhydrous copper sulphate which will turn blue in the presence of water

OC34 investigate the de-composition of water by electrolysis; recall the composition of water

electrolysis

What happens when water freezes,

When water freezes the molecules (H2O) line up and make a solid.

It turns out that these molecules push each other back more, they take up more space.

This means they have a greater volume (have you ever frozen a full bottle?? What happened it?)

The mass of the ice is the same as that of the water, but its volume is less thus its density is less,

thus ice floats on cold water

find out here http://sites.google.com/site/giantscience/science/physics/heat-1

Surface Tension

Solubility of water

OC30 conduct a qualitative experiment to detect the presence of dissolved solids in water samples, and test water for hardness (soap test)

Water is known as the Universal solvent, as it dissolves many substances. Not all substances can be dissolved in water .... can you name any that do not dissolve in water?

So water gets 'dirty' very quickly. This changes things about water, it can change its boiling temperature, its electrical conductivity, its safety to drink.

How could we see what is dissolved in a water sample.

We could filter it and then we could see the in-soluble substances come out of the water.

Is the water Pure now ??

Lets see in Solubility of Water

Water test 1

suspended solids in water Vs dissolved solids in water

Stir some sugar in some tea. What happens? The masses?

Stir some salt into some water. What happens? The masses?

Stir some sand in some water. What happens?

Carefully measure the mass of this solution overtime.

It still has solute dissolved in it? How can we get this out and see it?

Evaporation of the water?

http://sites.google.com/site/giantscience/science/chemistry/separations/evapouration

Experiment

To measure the %volume of

dissolved and suspended substances

in a sample of water.

Apparatus

Water sample, 200ml beaker, filter paper, funnel, evaporating dishs (2), scales.

Method

  1. Find the Mass of an empty evaporating dish
  2. Find the Mass of a clean filter paper
  3. Shake the water sample,
  4. Into a beaker place 60-70 cm3 of water.
  5. Pour 25g of water directly into an evaporating dish.
  6. Pour the remainder through the filter paper
  7. Place the evaporating dish somewhere dry and warm for a day or two.
  8. Find the mass of the dishes now, find the mass of the residues at the bottom of both dishes.
  9. When the filter paper is dry find its mass.

1, 3, 5, 7, 8

Results

Mass of Evaporating dish = g

Mass of Evaporating dish + water = g

Mass of water = g

Mass of Filter Paper = g

After

Mass of Evaporating dish = g

Mass of Filter Paper = g

Calculate

Mass of suspended solids (6-4) = g

Mass of dissolved materials (5 - 1) = g

Mass of Unfiltered Residue / 25g

84.8 g 187.9g

Gases also can be dissolved in water,

Fish depend on oxygen dissolved in water, as do seaplants (seaweed)

to observe the dissolved gases try this little experiment

Title

What did you see or notice

Apparatus

2 Ice cube trays, kettle, freezer

Method

  1. Boil the kettle, and allow stand for 10 minutes
  2. Rinse both the ice cube trays in the recently boiled water
  3. Label or mark each tray.
  4. Fill both trays
    1. with the boiled water
    2. with regular tap water
  5. Freeze ice trays
  6. Leave for a day
  7. Remove and Examine both type of ice cubes.

Diagram

setup and results

Safety Concerns

allow the kettle to cool before pouring it

Results / Observations

What did you see or notice

Maths

??

Conclusions

What did you see or notice

Comments

What did you see or notice

test water for hardness (soap test)

What is HARD WATER and includes OC31

OC32 carry out a simple distillation, and obtain a sample of water from sea-water

Conduction in water, it doesnt seem like these topics are related but just you look.

http://www.andybrain.com/sciencelab/2007/12/20/multimeter-experiments-with-electricity-and-water/#more-77

OC33 describe the processes involved in the treatment of water supplied to domestic consumers

We in Hartstown CS live in the Fingal County, and here is a look at the most important water treatment facility in the county

http://www.fingalcoco.ie/Water/WaterResources/WaterandWastewatercollectiontreatment/WaterSupply/FileDownload,16882,en.pdf

thanks to Longford County Council for this very good description of the processes involved in water treatment.

http://www.longfordcoco.ie/coco_content.aspx?id=10428

write notes on the following .....

Screening

Screening is very simple process, a mesh or a grid goes over the inlet pipe that takes in the water from the river or lake that feeds the water supply agency. This process keeps branches, leaves, fish, and other large debris from passing inside to the water treatment facility. A possible problem can be that fresh water mussels grow on the grid. This will at the very least hinder the intake of water.

Flocculation (like the word it sounds like, flock) brings the smaller suspended particles together and they make up a larger particle. In order for this to happen the water is again mixed/stirred in a tank. The water is then allowed to settle again, and these flocculated particles fall out.

to add a coagulant like Alum (aluminium sulphate (Al2(SO4)3)) to the water, encourages the other particles in the water that will not flocculate, to come together. This Alum is a salt that will react with other ions in the water and form particles that are large enough to be removed by sedimentation.

Settling

Settling is another very simple process.

The water that has just been taken in flows into a large resevoir, through some pipes, where Aluminium Sulphate is added to the water. This chemical brings together other 'dirt' particles.

It then flows in to some large settling tanks, here it is left to sit for a number of days. As the water is not moving it allows the heavy and cogulated particles in the water to fall to the bottom (as they did in decanting).

The water can be drawn off above this sediment, this water is now free of any of most of the large suspended particles.

Another method of further reducing the amount of suspended particles in the water is flocculation and cogaulation

Filtration

When we do filtration we use paper filters, but when you are filtering such large volumes of water you need something a little bigger. The water to be treated is poured into the top of another reservoir, this one is filled with sand, at the bottom of the tank is an outlet that takes very clean water to the last stage of process

Chemical additions

Chlorination

Chlorine is added to water to kill and the bacteria the water will meet on it journey to the tap

Fluoridation

Fluorine is added to water in many countries in order to reduce tooth decay water fluoridation may increase the risk of kidney stone formation

further invesigations might include

Water pollution Culture bacteria and/or fungi.

Agar plates. Inoculating loop. Bunsen burner. Oven. Labels. Microscope. Slides & coverslips

Pre-prepared plates.

Use two water samples from different sources.

Lake or stream water could be used.

Compare both samples.

Observe and draw.

Tabulate.

How effective are water filters?

Plastic litre bottle. Glass wool/ cotton wool. Stones. Gravel. Sand.

Litres of water. Beakers. Microscope, slides and coverslips. pH meter. Buffer tablets. Filtration apparatus. Filter paper. Electronic

balance .

Carry out physical and pH analyses before and after filtration.

Cut end off bottle.

Wear gloves if glass wool is used.

Use water samples from different sources.

Compare waters before and after.