Professor Tidlybit explains that atoms are the fundamental building blocks of everything, from rocks to living organisms. Atoms are incredibly small, with more atoms in a grain of sand than grains of sand on a beach. There are 118 types of atoms, known as elements, listed on the Periodic Table. Surprisingly, 99% of the human body is made up of just six elements. Over a year, almost all atoms in the body are replaced through processes like eating and breathing, raising questions about identity and change.

How does the number of atoms in a grain of sand compare to the grains of sand on a beach?

• The number of atoms in a grain of sand is equal to the grains of sand on the beach

• There are fewer atoms in a grain of sand than grains of sand on the beach

• There are no atoms in a grain of sand

• There are more atoms in a grain of sand than grains of sand on the beach

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What are the fundamental building blocks of everything?

• Particles

• Cells

• Atoms

• Molecules

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How many kinds of atoms are found in nature?

• 99

• 94

• 24

• 118

What do scientists call each kind of atom?

• Particle

• Molecule

• Compound

• Element

Which element makes up 65% of the human body?

• Nitrogen

• Carbon

• Hydrogen

• Oxygen

What percentage of the human body is made up of carbon?

• 10%

• 18%

• 1.5%

• 3%

Which element is essential for strong bones?

• Nitrogen

• Calcium

• Oxygen

• Phosphorus

How often are almost all of the atoms in your body replaced?

• Every week

• Every month

• Every year

• Every decade

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Where do the atoms in your body come from?

• Only from the food you eat

• From everywhere on the planet

• Only from the place you were born

• Only from the air you breathe

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