In the recently released revisions to the Australian Curriculum: Science (v9), the year level descriptions include example inquiry questions, to “help excite students’ curiosity and challenge their thinking.” Inquiry questions “could be used to prompt discussion and exploration.”
They are by no means required, and they vary in quality. Some might be useful for inspiring learning over a whole term, tying together opportunities to learn across multiple content descriptions, while others might only stimulate a brief but meaningful classroom dialogue (which nevertheless might be sufficient to address a single content description).
Here at DES, we are big fans of these inquiry questions, and some in particular stand out as worth embedding in our teaching. One Year 3 inquiry question in particular — “Is jelly a liquid or a solid?” — stands out. It’s there to support learning of the Science understanding sub-strand Chemical sciences content description “investigate the observable properties of solids and liquids and how adding or removing heat energy leads to a change of state,” as well as several of the Science inquiry strand content descriptions.
So, is jelly a liquid or a solid?
Well, the best answer is that it’s both. Edible jelly is actually a type of mixture known as a colloid.
Jelly is a product containing molecules of gelatin; a protein that by itself usually appears as a solid powder. Gelatin is soluble in water, so when we add hot water all the gelatin molecules are dispersed and move around in solution (a liquid).
As the water cools to room temperature, the gelatin molecules begin to bond with one another. However, as they bond, a matrix structure forms that traps liquid water in the spaces between the protein molecules. At room temperature, the gelatin is a sort of semi-rigid structure suspended in a liquid: this type of mixture is known as a colloid.
If we continue to cool the jelly to below 0 degrees Celsius the water will freeze, trapping the gelatin (a solid).
But at room temperature? Jelly can’t really be described as a liquid (it holds its shape and it doesn’t flow) or a solid (at the molecular level, the gelatin particles are arranged in fixed relative positions but the water molecules still flow).
Wait, is a Year 3 student expected to learn and understand this?
No! Not at all! Students do not need to learn what a mixture is, what a colloid is, and what that means at the molecular level for this question to be motivating, meaningful, and productive as an inquiry question (or even a formal assessment).
The great thing about this question is not that students learn a “correct” answer, it’s that this question prompts further questions that can drive learning, and ultimately stimulates important cognitive activities including comparing and contrasting, categorising, analysis, evaluation, logic, and reasoning, all drawing on evidence observable to Year 3 students.
We love this question because it’s the reasoning that matters, not the answer
Teachers should be seeking an extended response to this question from students. Asking them “why?” will prompt students to reason, drawing on their knowledge of states of matter and their observations of jelly as evidence for their conclusions. It doesn’t matter if students decide that jelly is a solid or a liquid — and it’s not necessary for teachers to correct them (that can come later, when students learn about mixtures and atomic theory) — because it’s not the conclusion that matters, it’s the students’ reasoning that should be evaluated. This would be an excellent activity to conclude a sequence of learning experiences, and can be a part of the formal or summative assessment of students’ learning.
This question can also be used as a diagnostic assessment at the beginning of a learning sequence. In asking students to communicate their best answer at the time to this question, teachers can find out what students know and understand about states of matter and jelly — some students may never have eaten it! Students may reveal they understand the relationship between temperature and states of matter. Through analysing students’ responses, teachers can decide what learning experiences are needed to move students forward in their understanding of states of matter.
Learning experiences should include opportunities to compare and contrast solids with solids, solids with liquids, and liquids with liquids, and both with “other” substances (including gases, but also difficult to classify materials and mixtures like smoke, shaving foam, and glue).
We suggest students could also:
classify substances as "solids," "liquids," or "other" (with a deep discussion on the "other" category and what that might mean)
investigate ice melting and water solidifying in a sealed plastic bag and describing their observations (What can be observed? How?)
explore how heating or cooling (the removal of heat energy) affects the state of a substance such as ice cream, chocolate, or jelly 🍦
consider why different substances such as ice cream, chocolate, and water appear solid or liquid at the same temperature (room temperature, the fridge, the freezer, a hot day, in the oven)
discuss how changes of state between liquid and solid help us to recycle materials such as glass
What do you think? What other activities and learning experiences might be useful for Year 3 students to learn the Science understanding sub-strand Chemical sciences content description?