Unit 3: Matter (Density) Answers to Exercises

Let’s see how you did! If you didn’t get a few of these, don’t let it stress you out – it just means you need to play with more experiments in this area. We’re all works in progress, and we have our entire lifetime to puzzle together the mysteries of the universe!

Answers:
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About Atoms:
1. The atom.

2. Billions and billions of atoms.

3. Neutron, proton (in the nucleus) and electron.

4. The number of particles inside the atom. Atoms are made of identical stuff. It’s the number of particles (neutrons, protons, and electrons) that make atoms have different characteristics.

5. Elements are specific kinds of atoms. Each element (each specific atom) has a different behavior from every other element.

6. Exploded stars.

7. Carbon, Hydrogen, Oxygen, Nitrogen, Calcium: CHONC

8. False. Matter is made of atoms that have incredible distances between their incredibly tiny bits of matter.

9. A molecule.

About Electrons:
1. They pop in and out of existence.

2. No. They tend to stay a certain distance away from the nucleus.

3. A shell is the distance that electrons tend to stay in as they pop around the nucleus.

4. Up to seven.

5. The number of electrons an atom has.

6. 18. Remember 2n2. So 2 x 32 = 18.

7. 2 atoms fill the first shell, 8 fill the second, and 1 is left in the third. So Sodium has 3 shells.

8. Because they are “unsatisfied’. They have too many or not enough electrons in their outer shell.

About Density:
1. Density is a measurement of how heavy something is and how much space it takes up. In other words, a measurement of its mass and its volume.

2. The beans are more dense since they have less volume (the can of beans is smaller then the loaf of bread).

3. Believe it or not, gasoline is less dense than water.

4. A full school bus. Both have the same volume but the full one will have more mass.

For Advanced Students:

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1. Egg 51g/50ml = 1.02 g/ml

2. Apple 165g/170ml = .97 g/ml

3. I got about 40 ml for the battery’s volume and 140 g for its mass. With those figures the density is : 140g/40ml= 3.5 g/ml

4. Ketchup is more dense.

Ketchup 680 g/ 650 ml= 1.05 g/ml

Water 500g/ 500 ml= 1 g/ml

5. The battery had the greatest density at 3.5 g/ml. The object with the least density was the apple at .97 g/ml. By the way, the objects with a lower density than water sank. The objects with a higher density than water floated. Coincidence? Nope, we’ll look into that more when we get to the buoyancy lesson.

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