What is in a Mixture?
Lesson 6 of 7
Objective: Students will be able to compare the observable properties of objects before and after various processes are applied.
I will begin the lesson, by asking students to share their thoughts about what a mixture is. As students share, I will have them give examples of different mixtures that they are aware of. Having the students share their ideas, activates their background knowledge and allows me to gain an understanding of how much the students know.
I will ask the students, "when we mix two substances, does that mean that they both have become one substance or does each individual substance maintain it's properties?" Students will be given time to think, pair, share with an elbow partner. Allowing the students to think, pair, and share gives the students the opportunity to have discourse and share ideas. Students will share their ideas with the class.
I will provide students with sand, rocks, table salt, and a zip lock bag. I will instruct the students to mix the materials together. Next, I will ask them what materials have changed? I will inform the students that a combination or mixture of materials that does not change the basic properties or characteristics of the material is called a mixture. Most mixtures are combinations of various materials that can be physically separated or separated again.
Now that we have created a mixture, I am going to allow the students time to brainstorm ways to separate the mixture back into their original forms. Students will share their ideas. I will ask the students, "how can we easily separate the stones from the mixture? Which properties of stone make it easy to separate it from the salt and sand?" Asking students questions throughout the experiment encourages critical thinking. It allows students to identify alternative solutions and problem solving skills.
I will ask the students to remove the stones. Next, I will ask the students to brainstorm ways to remove the salt from the sand. What properties of the salt and the sand make it difficult to separate them? I will ask the students to think of any processes that they may already know of to separate the sand. If students do not mention dissolving, then I will inform them that the process of dissolving may be helpful. I will use the example of losing a tooth. I will have students think about a time when they lost their tooth and having to gargle with salt water. What happens to the salt in the water... it dissolves. I will inform the students, anytime you mix water with another substance, it is called a solution. I will ask the students, can the process of dissolving help us separate the salt from the sand? I will provide each student with a plastic spoon, a cup, a Styrofoam bowl, a coffee filter and water. I will instruct them to dissolve the salt.
Students are to keep observational notes in their science journal as a reference throughout the experiment.
To conclude the lesson, we will put away our materials and transition back to the carpet for a whole group discussion. I will ask the students, "how did the properties of sand help us to separate it from the salt? How did the properties of the salt change? How did changing the properties of salt help us to separate the salt from the total mixture? How can we separate the salt from the water? What technology did we use to separate all of the materials from the mixture? Students will complete the Exit Card and share their ideas and thoughts to conclude the lesson.