Changing states Solids, liquids and gases

Three states of matter… Solids Liquids Gases Solids: The strong bonds between molecules make solids rigid and very difficult to deform. Liquids: The relatively weak bonds between molecules allow liquids to be deformed without effort. Liquids have a fixed volume, but their shape is determined by the shape of the container holding them. Gases: Virtually no bonds exist between gas molecule so that gases can spread into any available space. The volume of a gas is determined by the size of the container holding it. In their groups ask each to think for a couple of minutes about examples in each – feedback and note down responses under each.

Let’s test our knowledge! QUIZ 10 questions prepare answers in your groups Handout: ‘Solid, liquid or gas’ quiz sheet and ask students to complete their own sheets and then agree a group response once they’ve discussed with each other.

Let’s test our knowledge! 1. Which of the following is NOT a gas? Air Car exhaust fumes The sea Answer: the sea is a liquid, the others are mixtures of gases.

Let’s test our knowledge! 2. You blow up a balloon. Is it heavier or lighter than the un-inflated balloon? Heavier Lighter They weigh the same Answer: It's heavier than the un-inflated balloon because it contains more air.

Let’s test our knowledge! 3. Which material is a solid? Syrup Cooking oil Cotton wool Answer: Cotton wool is a solid! It stays in one place and is easy to hold.

Let’s test our knowledge! 4. When you squeeze a sponge under water, what are the bubbles that escape? Pieces of sponge Air coming from the spaces in the sponge Water Answer: The bubbles are air coming from the spaces in the sponge.

Let’s test our knowledge! 5. Which material is a liquid? Sponge Shampoo Salt Answer: Shampoo is a liquid! It can be poured and takes the shape of the container it is in.

Let’s test our knowledge! 6. To change a solid metal to a liquid, you would: heat it cool it bend it Answer: Heating a metal would turn it into a liquid. Most metals need a lot of heat before they turn into liquids.

Let’s test our knowledge! 7. Which one of these best describes a liquid? My particles are packed tightly together. I keep my shape. My particles are loosely packed. I take the shape of my container. My particles have lots of room. I try to spread out in every direction. Answer: My particles are loosely packed. I take the shape of my container.

Let’s test our knowledge! 8. Which one of these best describes a gas? My particles are packed tightly together. I keep my shape. My particles are loosely packed. I take the shape of my container. My particles have lots of room. I try to spread out in every direction. Answer: My particles have lots of room. I try to spread out in every direction.

Let’s test our knowledge! 9. Which of these is NOT an example of a solid? Dust Runny honey Gravel Answer: Runny honey is not a solid, it's a liquid.

Let’s test our knowledge! 10. Which one of these best describes a solid? My particles are packed tightly together. I keep my shape. My particles are loosely packed. I take the shape of my container. My particles have lots of room. I try to spread out in every direction. Answer: My particles are packed tightly together. I keep my shape.

When is a fluid not really a fluid? Newton’s theory: Normal liquid – Newtonian Strange liquids – non-Newtonian Many people have heard of Sir Isaac Newton. He is famous for developing many scientific theories in mathematics and physics. Newton described how ‘normal’ liquids or fluids behave, and he observed that they have a constant viscosity (flow). This means that their flow behaviour or viscosity only changes with changes in temperature or pressure. For example, water freezes and turns into a solid at 0˚C and turns into a gas at 100˚C. Within this temperature range, water behaves like a ‘normal’ liquid with constant viscosity. Typically, liquids take on the shape of the container they are poured into. We call these ‘normal liquids’ Newtonian fluids. But some fluids don’t follow this rule. We call these ‘strange liquids’ non-Newtonian fluids. As pressure or speed is applied to non-Newtonian fluids their structure (viscosity) changes – which can make them appear to be solid!

Slime: a non-Newtonian fluid? Let’s make some slime! Preparation 1. To prepare the Borax solution, mix 1 tsp of Borax powder for every 125 mL of water. 2. Have food colouring, glitter, popsicle sticks and plastic cups laid out for the students use. 3. Ensure that wet wipes and paper towels are easily accessible. Procedure 4. Give each student a lollipop stick and a plastic cup. 5. Place approximately 50 mL of PVA glue into each student’s plastic cup. 6. Distribute 2-3 drops of food colouring in each plastic cup and have students mix in the colouring. Students can mix colours, add glitter or create a marble affect in their glue by half-stirring in the food colouring. 7. Place approximately 25 mL of borax solution into the plastic cups and have students mix their solution well. The slime should turn into a more solid solution. Continue to add borax solution incrementally until it reaches a good consistency. 8. Students and empty the contents of the plastic cups into their hands to further stir the slime together. Store the slime in a plastic bag to keep it from drying out.

What are the uses for non-Newtonian fluids? Houses? Body armour? Filling in holes in the road? If a house is built on certain types of clays and an earthquake puts stress on this material through the sudden movement, the apparently solid clay can turn into a runny liquid. Body armour that behaves like a liquid so that you can move easily but turns into a solid on impact from stress could be useful for police or the military. Could we use Non-Newtonion fluid to fill holes in the road? – some researchers in the USA thought this would be a good idea – do you?

RAF examples: non-Newtonian fluids The RAF utilise some of the principles of liquid to solid (non-newtonian fluids) to create body armour. Here we can see a member of the Royal Air Force wearing Body Armour protection. The material is relatively flexible and supple until it receives a dramatic impact – it then becomes a solid!