water Flashcards
state the purpose of sedimentation
removes large particles
state the process off filtration
removes smaller particles
state the process of chlorination
kills bacteria
what can desalination be carried out by and what’s its purpose
distillation and removes salt from sea water
how can temporary hard water be softened
By boiling it
How do you investigate hardness in water
Put a known volume of water into a boiling tube.
Add soap solution, one drop at a time, and shake the mixture for 10 seconds.
Record the number of drops of soap needed to make a lather. The greater the number of drops needed to make a stable lather, the harder the water.
To separate temporary and permanent hard water samples, boil the water.
Repeat steps two and three with the boiled samples.
what does distillation do
Distillation can be used to separate and collect a liquid from a solution
what is the process used to soften hard water
Distillation can be used to soften water as the water evaporates as it is heated and the ions are left behind
what ion softens hard water
Sodium carbonate
What does the layer of temporary boiling water form a layer of
Limescale
why is rainwater naturally acidic
because it contains dissolved carbon dioxide from the air
what is permanent hardness caused by
Permanent hardness is caused by dissolved calcium sulfate which does not decompose when heated
give some advantages of hard water
some people prefer the flavour
calcium helps strengthens child’s teeth and bones
give some disadvantages of hard water
difficult to form a lather with soap
limescale can form on appliances such as kettles and washing machines
suggest a reason why energy may be wasted in homes in hard water areas
Hard water contains dissolved rock that accumulates on heating elements and the internal surfaces of boilers, causing scale build-up and impairing efficiency
Which method can be used to remove temporary hardness but not permanent hardness from a sample of water?
Boiling water will remove temporary hardness but not permanent
What ions cause hardness in water
Calcium and magnesium
What dissolved compound is responsible for causing temporary hardness in water?
Calcium hydrogencarbonate causes temporary hardness in water
Which statement correctly describes the method for determining the hardness of water?
Add soap solution to the water, shake until a lather is formed - the more soap added, the harder the water
if a water sample has a volume of 7.0 before boiling and a volume of 2.5 after boiling what happened? And what type of water is it
Temporary hard water, as the volume of soap decreases a lot after boiling.
What can be used to identify whether a sample of water is hard or soft?
Soap solution is added drop by drop and the water sample is shaken. The more drops it takes to get a stable lather (bubbles), the harder the water is.
State why the temperature scale on a solubility graph ranges from 0°c to 100°c
as water is a liquid over this range. Each point along the curve represents a saturated solution at that temperature. Each point below the curve represents an unsaturated solution.
Why is it important to quote solubility at a given temperature?
All major substances have solubilities affected by temperature, so it is important to quote the temperature at which the solubility measurements were taken
What will happen to a hot saturated solution of copper(II) sulfate as the temperature decreases?
Crystals will form, As the temperature falls, so does the solubility.
Why does the temperature scale on a solubility graph range from 0°C to 100°C?
Water solidifies at 0°C and boils at 100°C.
What does desalination do
Removes salt from seawater
Discuss why some people are against fluoridation of water supplies
Mass medication - takes away individuals choice
Discolouring teeth - fluorosis
