We did some extension work to follow on from our states of matter activity last week - a great little experiment involving dried peas.
We 'pretended' the chick peas represented the molecules in each state of matter - first came solid where the peas were packed close together
then water - they stirred the peas with their finger to make it appear separated and to move freely
then gas - the peas were poured into a zip lock bag and shaken vigorously, the result was the 'molecules' spread out and free to move.
once the 3 main states were reviewed we used our 3 part cards and looked at the different properties of each (liquid moves freely to fill its container, is visible etc)
Next we discussed how solids, liquids and gasses exert pressure
We started with the solid - lifting it and describing it - discussing how gravity pulls the block down and how it shows that a solid exerts a pressure downwards not sideways or upwards.
next we half filled a zip lock bag with water - again lifting and describing it - poked a finger into the side of the bag and watched the indentation fill in again when the finger was removed followed by a discussion on how the downward force of gravity causes the water to spread out evenly (causing sideways pressure in this instance) the bag of water shows that liquids exert pressure downwards and sidewards but not upwards.
For gas we used a filled balloon - again lifted and described it - push a finger gently into the top of the balloon and watched what happened when we removed it - this happened because the air molecules inside the balloon push in all directions at once - as gravity does not noticeably pull air downwards this allows gases to exert pressure in all direction -downwards, sideways and upwards.
Finally we used a candle to again demonstrate how you can change states using energy (in this case heat) and the best part of this activity is that when the wax liquid drips off the candle (away from the heat source) it set back into a solid reinforcing the concept that when the energy is removed it reverts back into its original state.