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Science - 2nd Grade
Standard 3 Objective 2
1 class periods of 60 minutes each
The Law of Conservation of Mass states that mass is conserved during physical and chemical changes. Students explore this concept by taking initial masses, making predictions, and finding final masses of physical changes. Students observe that the mass of aluminum foil in a sheet is the same as the mass of that piece of Aluminum foil formed into a small ball. Students will use a balance and begin to learn terms such as mass and grams.
Matter is anything that takes up space and has mass. Matter is composed of atoms and molecules and is always changing its form by either physical or chemical changes. The Law of Conservation of Mass states that mass is neither created nor destroyed during any physical or chemical changes.
A physical change occurs when the appearance of a substance changes but its chemistry remains the same. No new substance is formed in a physical change; water moving between states of matter, a Popsicle melting, and a paper crumbled are examples of physical changes.
A chemical change occurs when bonds are broken between atoms and rearranged into new, entirely different substances such as burning a log and frying an egg.
Pre-lab Discussion: Write the words physical change and chemical change on the board in two columns. Ask several students what they ate for breakfast that morning. As they tell you, place the different items in the appropriate column being sure you use a verb each time. For example, for physical changes they might have poured milk, mixed milk and dry cereal, squeezed a gogurt, or buttered plain bread. For chemical changes they might have toasted bread, cooked an egg, fried bacon, or cooked a pancake. Explain to them the difference between physical and chemical changes. Tell the students they are focusing on physical changes today and want to determine if the mass of an object changes when it undergoes a physical change.
I. Using the balance - The students are going to find the mass of an object on the balance. They will physically change the form or shape of the object and see if the mass changes.
** Be careful to not lose any of the object along the way or else the two masses wont be equal!!
II. Physical changes - Be sure and make predictions about the change in mass before each final mass reading is taken.
Rio Tinto Hands-on Science Curriculum Team