Water

1. Water

2. What is water made up of? • Water is made up of two elements, hydrogen and oxygen. • Its chemical formula is H2O. • Each molecule of water is made up of two hydrogen atoms bonded to a single oxygen atom.

3. The 3 different states of water • What are they? • Water has three different states, liquid, solid and gas. • The word water usually refers to water in its liquid state. The solid state of water is known as ice while the gas state of water is known as steam or water vapour.

4. A few sea water facts • Water covers around 70% of the Earth’s surface. • The three largest oceans on Earth are the Pacific Ocean (largest), the Atlantic Ocean (second largest) and the Indian Ocean (third largest). • Water from a sea or ocean is known as seawater. On average, every kilogram of seawater contains around 35 grams of dissolved salt. • The freezing point of water lowers as the amount of salt dissolved in at increases. With average levels of salt, seawater freezes at -2 °C

5. Water as a solvent • What is a solvent? • Asolvent is a liquid in which various substances can be dissolved • Water makes a good solvent with sugars, salts and acids easily dissolving in it. • On the other hand oils and fats don’t mix well with water.

6. What happens when water freezes? • Water expands as it cools from 4 °C to 0 °C (above 4 °C it does the opposite). • In freezing conditions, water has been known to burst water pipes as it freezes to ice. • Water has the unique property of expanding as it freezes. Because water expands becoming less dense, frozen water, more commonly known as ice, floats. • This is very important because it protects the water underneath, insulating it from freezing. • Imagine what would happen if water became more dense? It would sink, allowing another layer of water to freeze. Eventually all the water across the entire surface of our planet would freeze, making life impossible.

7. Uses of water • Drinking water is needed for humansto avoid dehydration, the amount you need each day depends on the temperature, how much activity you are involved in and other factors. • An important use for water is in agricultural irrigation, this is when water is artificially added to soil in order to assist the growth of crops. • Water is used frequently by firefighters to extinguish fires. Helicopters sometimes drop large amount of water on wildfires and bushfires to stop fires spreading and limit the damage they can cause.

8. Water also plays a role in cooking. Steaming and boiling food are well known cooking methods. You may have noticed this last time you made pasta or noodles. • Water is also used for fun. Water sports are a very popular recreational activity and include things like swimming, surfing and waterskiing. Ice and snow is also used in ice skating, ice hockey, skiing and snowboarding.

9. Water molecules • Water is a basic molecule made up of two hydrogen atoms and one oxygen atom. When these three atoms come together, they form a strong bond that is difficult to break. The strength of this bond keeps a water molecule together for millions and even billons of years.

10. Do water molecules move faster in hot water or cold water? • Predict…… • Carry out experiment: • Fill the glasses with the same amount of water, one cold and one hot. • Put one drop of food coloring into both glasses as quickly as possible. • Watch what happens to the food colouring.

11. What is happening? • The food colouring in the warm water is spreading out faster than the food colouring in the cold water. • Water is made of molecules (two hydrogen atoms and one oxygen atom stuck together). Molecules in a liquid have enough energy to move around and pass each other. This is why water can flow and take the shape of the glass you pour it into. • The molecules in solids, like ice, don’t have enough energy to move around very much so the solid keeps its shape. • Warm water has more energy than cold water, which means that molecules in warm water move faster than molecules in cold water. The food colouring you add to the water is pushed around by the water molecules. Since the molecules in warm water move around faster, the food coloring spreads out quicker in the warm water than in the cold water.