Mixtures
7 Minutes
Mixtures and their types explained for kids, covering homogeneous and heterogeneous solutions with everyday examples. A science lesson in English.
- How homogeneous and heterogeneous mixtures differ in everyday items
- True solutions like salt water and alloys like stainless steel
- Colloids with the Tyndall effect and sand settling in suspensions
What this lesson teaches
A mixture (kalavai) is a material formed when two or more different ingredients or substances are combined together. Depending on whether the individual substances can be seen after mixing, mixtures are classified into homogeneous and heterogeneous types.
Homogeneous mixtures and true solutions
In a homogeneous mixture, the different substances blend so completely that they cannot be seen separately with our eyes. For example, the sugar and milk in tea, or the red and white blood cells in blood, cannot be spotted as separate items. One major type of homogeneous mixture is a true solution. Salt water is a true solution because the salt disappears into the water, and air is another example because gases such as nitrogen, oxygen, carbon dioxide, and argon are mixed invisibly.
Alloys as homogeneous mixtures
The second type of homogeneous mixture is an alloy, which is formed by combining different metals together to create a new metal. Even though multiple metals are present, they cannot be seen or identified individually just by looking at the finished object. A stainless steel vessel is an alloy made by combining iron, carbon, nickel, and chromium. Bronze is another alloy formed by combining different metals together.
Heterogeneous mixtures
A heterogeneous mixture is one where the different substances mixed inside can easily be seen and identified with our eyes. Everyday foods like Hide-and-Seek biscuits are heterogeneous because the chocolate chips and cookies are clearly distinct, just like the peanuts, fried gram, sev, and kara boondi seen in the snack called mixture. Concrete used to build houses is another mixture found in daily life. Heterogeneous mixtures are further classified into two distinct forms based on how their particles behave in a liquid.
Colloidal solutions and suspensions
- A colloidal solution is a mixture where tiny particles stay floating throughout a liquid without dissolving and without settling to the bottom, as seen with milk, buttermilk, skin lotion, or Horlicks in water.
- When a laser beam is shone through a colloidal solution in a dark room, the Tyndall effect causes the particles to become visible as they move in a zigzag manner known as Brownian motion.
- A suspension is a heterogeneous mixture where particles do not dissolve in the liquid and eventually sink to the bottom.
- An example of a suspension is sand stirred into a tumbler of water, where the sand spreads temporarily before settling down at the bottom.