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Atoms in Motion Worksheet

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Atoms in Motion Worksheet

Read the science story, then solve each question. Atoms are far too small to see, but scientists use evidence to work out how they move.

A tiny-motion mystery

Ruby-Mae sprinkled pepper onto a shallow dish of still water. The pepper specks seemed to wiggle and drift, even though nobody stirred the dish. Ruby-Mae learned that matter is made of atoms and molecules—tiny building blocks too small to see with the naked eye. In a liquid, these tiny particles are always moving in different directions. They bump into other particles. Their bumps can make much smaller particles move in a random, wiggly way. This kind of movement, caused by unseen particles bumping visible particles, is called Brownian motion. Pepper specks are much too large to demonstrate Brownian motion. Their movement on water may be caused by flows at the water’s surface. The pepper activity is only a model for thinking about how unseen particles might affect visible particles. Heating a liquid usually makes its particles move faster, so their bumps can become more energetic.

1.What are atoms and molecules described as in the story?

Tiny building blocks that make up matter
Small animals living in water
Specks of pepper you can see

2.Why can’t Ruby-Mae see the atoms and molecules in the water?

3.Complete the sentence: In a liquid, tiny particles are always . They move in different .

4.In the story’s model of Brownian motion, what makes a visible particle wiggle?

Unseen moving particles bump into it
The visible particle makes its own water
The dish pulls it towards the bottom

5.True or false: Brownian motion is the random movement of visible tiny particles caused by bumps from unseen particles.

TrueFalse

6.Put these events in order by writing 1, 2, and 3 in the model: ___ The model’s visible particle moves. ___ Water particles move. ___ Moving particles bump the model’s visible particle.

7.Ruby-Mae compares water that is cool with water that is warmed. What does the story suggest may happen to the particles in the warmer water?

They usually move faster
They stop moving
They turn into pepper

8.Which is the fairest test of whether warmer water changes how quickly pepper specks move at the surface?

Use the same amount of water and pepper, change only the water temperature, and observe for the same time
Use different dishes, different amounts of pepper and different temperatures
Stir one dish but leave the other still

9.Draw a simple model of moving particles in a liquid. Show at least six particles and arrows pointing in different directions. Add one visible particle being bumped, and label the drawing as a model—not a picture of what happens to pepper specks in water.

10.Why is the pepper activity a model rather than evidence that pepper specks show Brownian motion?