Scientific Principles of Water PDF

PowerPoint 2 Scientific properties and principles of water LESSON INTENT. All learners will be able to describe the different types of water that we have in our homes. Learners will be able to describe the different property's of water when its in a certain state. Learners will be able...

PowerPoint 2 Scientific properties and principles of water LESSON INTENT. All learners will be able to describe the different types of water that we have in our homes. Learners will be able to describe the different property's of water when its in a certain state. Learners will be able to describe the difference between temporary hard water and permanent hard water  Water Steam expands 1,600 times Boiling point 1000C at sea level From 40C to 990C water expands by 4% Maximum 40C density Freezing point Ice expands by 00C or 2730K 10%  QUICK FIRE QUESTIONS!! In groups can you answer the following in 1 minute? 1. What is the boiling point of water? 100 degrees 2. What temperature is water most density? 4 Degrees 3. How much dose water expand by from 4 to 99? 4% 4. How much does water expand by when it turns to steam? 1,600 TIMES 5. How much does water expand by when it freezes? 10% When water is heated it expands. For temperatures up to 100ºC, this expansion is usually up to 4% of the system contents at cold start up. When water exceeds 100ºC it can turn to steam and expand to almost 1,600 times its original volume. Water is a chemical compound of hydrogen and oxygen (H2O). It is very rare to get pure water (H2O) and nothing else, as water is a very powerful solvent. Given enough time it will: erode, corrode, absorb almost anything. Depending upon where water collects, it will absorb and contain a number of substances. This gives the water the characteristics of: hardness or softness acid or alkaline Temporary hard water, if heated to 650C and above, will form limescale (calcium carbonate). This causes problems for appliances and the efficiency of appliances. Hardness in water is known as the soap destroying factor. The harder the water, the more soap is needed for a lather, and more sediment is produced. There are two types: 1.Temporary hardness Contains calcium carbonates and can be removed by heating the water above 650C. The temporary hardness is released as scale. 2. Permanent hardness Contains calcium sulphates; can only be removed by a base exchange method (water softener) – zeolite material. All water contains temporary and permanent hardness, which gives the total hardness of water. Hard water is measured in PARTS PER MILLION (PPM) Anything over 200PPM requires some kind of treatment e.g. WATER SOFTNER or a SCALE INHIBITOR  Depending upon what has been absorbed, water will either be acidic, neutral or alkaline. The amount of absorption is registered on the pH scale (potential hydrogen), depending on what strata water falls through. The pH scale 1 2 3 4 5 6 7 8 9 10 11 12 Acidic Neutral Alkaline Acidic Pure water is Limescale, corrosion neutral blocking less and pitting efficient Water has the ability to dissolve lead; this is called: Plumbosolvent Water that is aggressive towards copper is called: Cuprosolvent Water is aggressive towards ferrous (iron) metals and, in any unprotected areas, will quickly form ferrous oxide (rust). Iron pipework, as we have covered, needs to be protected by painting the pipe with red oxide paint, zinc galvanising or denso. Ferrous oxide can build up inside radiators on central heating systems, which in turn means the radiators need bleeding of hydrogen. A chemical inhibitor can be used to protect central heating pipework and components.  Can you Define these key words? Evaporate When liquid turns into a gas (e.g. boiling at 1000C). Freezing When a liquid turns solid (e.g. water freezes at 00C). Condensation When a gas turns into liquid – when it rains or when water droplets form on cold surfaces. Capillary action of water This is when water can be drawn sideways or upwards between two close-fitting surfaces against gravity. The wider the gap, the less capillary action there is. Capillary action of water Plumbers face this as a problem: 1.Water can be drawn up underneath the lead weathering on tiles, resulting in water leaking inside the property. 2.Water can be drawn up between lead weathering surfaces. 3.Loss of trap seal (S trap) under an appliance. Discuss these points and see if you can find out how they can be overcome. Capillary action of water Conversely plumbers can use this to their advantage: To make soldered joints on fittings: the solder can be drawn between the two close-fitting surfaces of the copper tube and fitting. Properties of water The water molecules have a cohesive nature in the way they stick together. This creates the surface tension on top of water. The water molecules also have an adhesive nature and tend to stick to other materials they comes into contact with. This gives the water a curved appearance. In a manometer, we have to read the water level from the bottom of the meniscus or curve.  Solid (Ice) – Liquid (Water) – Gas (Steam) H2O = Chemical symbol for water 100= Boiling point of water 0 C (at sea level) Increase the pressureIncrease = the boiling point of water When boiling it expands1,600 by =times 40 C = Maximum density of water Water freezes at 0= 0 C or 2730K Add glycol (antifreeze) to water = freezing point Reduces When frozen, water expands10% by = 1 = Relative density of water 10-900C Water heating from Expands by 4% = Sensible heat When heat is applied to water the temperature will rise, but it remains water. It can then be cooled (a change in temperature without a change in state). Latent heat If you keep heating water, it will change from water to steam; this is a change in state. (Change in Temperature = Change in state) The heat required to raise the water temperature to 100 0C is sensible heat. The heat required to keep it boiling is latent heat. Water softener The only way to fully remove hard water and prevent scale, scum and tide marks is to fit a water softener. Water is taken through a zeolite or resin bed then flows out of the top of the vessel to the tap. The resin holds the calcium and magnesium in the filter. The unit is then back-washed by a brine solution (salt or sodium chloride). Chemicals These do not soften the water; they stabilise the salts to prevent scale. Salt crystals tend to bind together to form hard scale. Polyphosphate chemicals form on the salt crystals, preventing them sticking together and getting caught in the cartridge filter. Used on combination boilers. Magnetic scale inhibitor The water is passed through a strong magnetic field running across the water flow. This alters the physical nature of the water and breaks the salt crystals down into small pieces so they cannot stick together. Electrical scale inhibitor This works in a very similar way to the magnetic inhibitor except it uses a magnetic field to produce low level radio waves that pass through the water. Galvanic cell scale inhibitor This uses a combination of zinc and copper to form an electron flow (zinc being the anode which will break down). Corrosion can reduce the life of pipework or components. Limescale will block pipes and components so it reduces the flow. It will also coat components, thus reducing the efficiency of an appliance. Soft water is acidic so will also affect the life of pipework. CHECK YOUR KNOWLEDGE WITH THESE QUESTIONS. 1. What is the boiling point of water at sea level? 2. When water reaches 100 degrees and turns to steam how much does it expand by? 3. what is temporary hardness? 4. What is permanent hardness? 5. With reference of the PH scale water that is between 1-6 in classed as what? 6. What is capillary attraction and give a example? 7. If water is heated up to 100 degrees and it changes state to steam what type of heat would this be classed as? Sensible heat or latent heat? 8. What is the purpose of a water softener? TRAFFIC LIGHT IT: WHERE IS YOUR LEARNING AT? Red = I have not really understood the content we have studied today (write down 2 questions that you need help with) Amber = I have understood the content on Effective Questionning (write down 1 one question you need to clarify) Green = I have understood all the content (write down one example from what we have studied)