Student preconceptions (misconceptions, naïve understandings) are important for teachers to uncover, address, challenge and extend. These are commonly held (but not always scientifically accurate) ideas that children bring to the classroom. Students come to school with ideas about the world and science principles because of experiences and observations that have helped to shape those beliefs. Learners hang onto those ideas until multiple experiences cause them to question previously-held beliefs and to form new explanations.
Educators need to discover student preconceptions and be aware of the related scientifically accurate ideas. It is the teacher’s role to facilitate learning experiences that challenge inaccurate ideas, solidify developing ideas, and reinforce and extend scientifically accepted ideas. Knowing student preconceptions helps educators to ask probing questions and craft experiences to move students along to greater science understanding.
Below is a summary of the preconceptions and scientifically accurate ideas related to the Floating and Sinking unit:
Preconceptions about floating:
Floating is when a portion of an object is above water and a portion is below; part of the object that is above water is floating and that part below water is sinking.
Scientifically Accepted Ideas:
Floating refers to an object that rests on the surface of the water and is partly immersed.
Preconceptions about floating:
Objects float in water because they are “lighter” than water.
Objects float in water because they are “heavier” than water.
Scientifically Accepted Ideas:
When an object is placed in a fluid, the difference in the weights of equal volumes of the object and fluid determine the buoyant force that acts on the object.
Preconceptions about buoyancy:
Heavy objects always sink; light objects always float.
Scientifically Accepted Ideas:
Weight alone will not determine whether an object will float or sink.
Preconceptions about buoyancy:
The depth of the water may affect the floatation of an object.
Scientifically Accepted Ideas:
The depth of the water has no affect on the buoyancy of an object.
Preconceptions about buoyancy:
Holes in an object cause it to sink; the holes let the water in to make the weight of the object heavier, therefore it sinks.
Holes in an object cause it to float; the holes let in air to make the weight of the object lighter, therefore it floats.
Scientifically Accepted Ideas:
Holes in an object may affect the object’s buoyancy by altering the buoyant force on an object.
Preconceptions about buoyancy:
Objects float due only to buoyancy, “the water pushed it up”.
Scientifically Accepted Ideas:
Floating and sinking depends on more than just the size, weight, design of an object, or type of liquid – it depends on a combination of these variables.
Preconceptions about properties of objects and materials:
Wood floats and metal sinks.
Scientifically Accepted Ideas:
Several variables, including the properties of an object, affect buoyancy.
Preconceptions about properties of objects and materials:
All objects containing air float.
Scientifically Accepted Ideas:
When an object is placed in a fluid, the difference in the weights of equal volumes of the object and fluid determine the buoyant force that acts on the object.
Preconceptions about properties of objects and materials:
Mass, volume, weight, heaviness, size, and density may be perceived as being synonymous.
Scientifically Accepted Ideas:
Each of these concepts is distinct, and terms should not be used interchangeably. Refer to individual lessons for accurate definitions of terms.
Preconceptions about displacement:
The weight of an object affects the amount of water displaced.
Scientifically Accepted Ideas:
The amount of water an object displaces is directly related to the object’s volume and weight.
Preconceptions about mass:
When changing the shape of something, the mass is changed.
Scientifically Accepted Ideas:
The total mass of an object does not change if the shape is altered.
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