Creative, Collaborative, Lifelong learners: back to basics

Many students find Science difficult, it really doesn't have to be.

Science and particularly Chemistry, requires students to visualise particles, atoms, molecules etc on a microscopic scale. So, most teachers frequently use models on a macroscopic scale to help students with this crucial part of the learning process. Here's my back to basics on the particles that make up water.

Place 3 beakers containing ice, water and steam on a desk at the front of the room. Get your students to draw a quick sketch of what they see.

If you work in a laptop school, students may like to use diagram maker or lab equipment for their sketches, but hey, there's nothing wrong with a simple pen and pencil.

Next step, ask your students to draw particles in the beaker that make up the 3 different states of water. Students usually represent particles as circles (although they could be shown as triangles, squares, hexagonals, any shape really!). Here's 3 simple animations showing the particles in water in 3 different states.

animations are from the Royal Society of Chemistry

There are many experiments that can be carried out that involve a change of state, students can make models, do a class roleplays etc... The bottom line is that science students need to have a clear idea of the movement and energy of the particles and their resultant effect on the volume, shape and relative density of solids, liquids and gases.
Following on from the movement of particles, students may carry out a heating curve experiment, plot a graph and analyse each step in detail, see below a graph showing the changes of a state.

animation from Footprints

Finally, onto step 3...recap on the chemistry term for water being H2O, which can be shown visually as

and moving away from the phrase "particles" but making use of the words atoms and molecule to describe water, get your students to sketch the beakers of ice, water and steam in terms of atoms and molecules. Vision Learning has 3 superb and clear animations detailing the molecules of water in the 3 different states, see the screen shots below.

images from Vision Learning

For senior students, hydrogen bonds between the water molecules are shown.

As a teacher, you may be surprised the learn that the majority of students assume that in the gas state, the water molecules separate to form oxygen and hydrogen atoms, this isn't the case. A simple demo of the hydrogen balloon (or hydrogen and oxygen balloon) and prior knowledge that a match near water vapour from a kettle does not result in an explosion, will help students to realise this.

Also, worth a mention is this interactive animation "Particle viewer of objects in a room", whereby students can click on different objects and get a peak at how the atoms are arranged. This again, helps students to visualise the atoms in the objects on a microscopic level.

And molecule 3d, mentioned on my previous blog "water hydrant" in which students can make up their own simple molecules, then view them in 3d. It's quick and straightforward, although for senior students I'd recommend Chemsketch and Chime.

This document titled "On the Ball" from The University of Southhampton, 2001 emphasises the importance of using models in the teaching of Science and has many suggestions and ideas on the uses of models in junior science.

This report "Beyond appearances, students misconceptions about basic chemical ideas", Vanessa Barker highlights in detail many misconceptions that students have and suggestions on what we can do as teachers to help students develop the "molecular spectacles" required to progress further with their chemistry knowledge.

Finally, here is a wonderful animation on dissolving salt in water which shows clearly that even though the salt cannot be seen it has not "disappeared" and that the mass of the beaker containing dissolved salt and water is not the same as the beaker of water. Yep, another couple of common misconceptions there.

Senior students will find this animation useful to help them to visualise and explain in detail the solubility of an ionic substance such as NaCl in a polar solvent such as water and here is a worksheet from the RSC on mass and dissolving.

I hope those of you in the Northern Hemisphere are enjoying a steaming and stinking hot summer, I'm off to splash about in puddles as its raining cats and dogs down here.