Physical change involves something that changes physically like cutting, freezing, and melting/boiling something. Like my first example cutting apples can be a physical change because it is still the same thing/substance but changed the shape. Freezing Ice is also a physical change it is still water but is in a different shape. Boiling water my last example the same as freezing but it's boiling. Those are a few examples of the wonderful Physical Change.
A Chemical change is when a new substance is formed like color change, baking/cooking, and when light is formed (glowing, exploding, etc). like my three examples below baking is taking flour, water, milk, eggs ,and sugar and making it into a cake making a new substance. Fireworks is a chemical change because light is formed it takes a giant pack of fireworks exploding in the air. and water with food coloring before it was water then you add color and it is a different color than before. Chemical change involves everything around us in our daily life.
Diffusion involves high concentration to low concentration. Like in the picture below you put a drop of food coloring it absorbs into the water slowly without mixing in the food coloring.
Density is to see which liquid or item has more Mass and Volume the way to figure is out exactly is to divide mass/volume. The honey is the most dense cause it's at the bottom, and the second dense is the Golden syrup Washing up liquid is the third dense, also the milk is the second least dense, and finally but not least the vegetable oil is the least dense.