liquids and solids
How many dairy products are you familiar with? There are many dairy products. Some are liquids. Others are solids.
How many dairy products can you identify that are solids? How many can you identify that are liquids?
Foods go through different types of changes. Sometimes, these changes occur when you prepare or cook food. Other times, these changes occur naturally. This is an example of a physical change and it changes the state of matter of the food. There are three states of matter – liquid, solid and gas.
Think about ice cream. If the ice cream melts, it changes from a solid to a liquid. Its state of matter has changed. However, it is still ice cream. When you mix fruit into yogurt, you might change its colour. However, the yogurt is still yogurt and the fruit is still fruit.
Next, think about a banana. As it ripens, it also changes colour. However, more than the colour changes. The banana gets softer and its sugar content changes. Ripening fruit is an example of a chemical change.
Now, consider milk. Milk and cream are liquids. If you leave milk or cream out of the fridge overnight or for a few days, its state of matter changes. Solid chunks can form in the milk and cream. However, this is a chemical change because a new substance is being formed. The sour smell that results is also a sign that a chemical change is taking place!
What dairy products do you think are made that involve chemical changes? Why do you think this?
