Physical and Chemical Change in the Kitchen

This term students have started to think about CHANGE, and what better place to develop our understanding of cause and effect than in the kitchen! Many physical and chemical changes happen when food is prepared – making food is all about change. 

Over the last few weeks, students have had the opportunity to think about the different physical and chemical changes that take place in the food that they prepare and cook. It has been a chance for students to develop their science inquiry skills – clearly articulating their predictions, explaining the steps of their investigation and safety precautions that were taken, and documenting and reflecting on their observations.  

In Week 2, we explored physical change and looked at mixtures such as smoothies to show how ingredients can undergo physical changes when chopped up, blended, and mixed together but the properties of the ingredient remain the same. 

  • The butter will get soft and melt when left out of the fridge. When soft and mixed with sugar and flour it will disappear into a batter. The batter can be rolled into balls and baked into biscuits. It becomes a solid again when baked. (Tristan, Melting Moments)
  • All the ingredients will mix together because they are soft. (Emma, Banana Smoothie)
  • The cocoa powder was dry at the start and wet at the end. At the beginning I could see lots of different colors but at the end all of the colors from the mixture turned into a dark brown color. At the end all of the chia seeds were all swollen because they had absorbed all of the milk. (Noni, Chia Seed Pudding)
  • I think that when I use the blender to mix things up the oats and the strawberries will change shape and size. I also think that the milk will change colour because it is blended with the strawberries and honey. I also think that the milk will thicken up because there mixed with strawberries and oats and they are not liquids. (Alessia, Strawberry and Honey Smoothie)
  • For the peanut butter and banana smoothie  I think it is going  to be cold  because of the ice cubes and that it is  not going in the oven. The banana goes from hard to naked to soup. (Hugo H, Peanut Butter and Banana Smoothie)

In Week 3, we explored chemical change. Many students used the example of cooking eggs as a way to investigate how the yolk and white of an egg undergo an irreversible chemical change when they are heated. 

  • I think the egg white will harden and become a solid because the amino acids are forming chains that connect. (Ben, Soft Boiled Egg)
  • The white will form around the yolk and the yolk gets harder. (Ozzy, Boiled Egg with Toast Soldiers)
  • First we put the raw eggs onto the hot pan. Second, it goes from clear to white and it starts getting white on the edges. It is bubbling up. It’s going from gooey to solid. Third, it’s nice and crisp on the edges. Finally, It’s all white and it’s not hard but a soft firm texture. (Charlotte, Fried Egg with Toast)

Students also showcased other recipes that they have been cooking at home as a way to deepen their understanding and share their thinking. 

  • I will observe the change in popcorn kernels. I think the popcorn kernels will overheat and the inside will burst out of the shell. (Bessie, Popcorn)

In Week 4, we combined our knowledge to create a collaborative ‘Encyclopedia of Physical and Chemical Changes in the Kitchen’ on Google Classroom. Students selected an ingredient that they cooked with at home and documented it’s transformation when they used it in a recipe.


This week we are building on our understanding of chemical change by learning more about the Maillard Reaction, which is a chemical change that happens when food is cooked and it is what is responsible for the browning and goldening, and the delicious aromas, of food as it cooks. Think seared steaks, barbequed sausages, baked bread and muffins, and roasted vegetables. As a starting point, students thought about what they were eating and helping to cook at home this week that involved the oven, bbq, deep fryer, or stove top. Many also used this investigation as a way to further develop their skills in writing ‘explanation texts’ and practice including more descriptive language in their writing, which was great to read! 

  • I think after it cooks it will be more soft and warm. I think it will look golden and crispy. I think it will have a nice cheesy smell. (Charlotte, Spinich and Ricotta Roll) 
  • My prediction was that there will be little charred bits but there was only pepper and rosemary that were black.  It tasted salty with a little hint of spice from the pepper. It smells like a salty barbeque with a little rosemary. (Hugo B, Barbequed Chicken Thigh)

Thank you to all the families who have helped students cook and bake over the last few weeks and we hope that you have enjoyed spending time experimenting in the kitchen during this period of lockdown and remote learning.