Matter and Mass
|Air Pressure and the Mass of Air|
Matter is anything that has volume and mass. Mass is how much stuff is inside a particular material.
Does Air Have Mass?
They remembered the demonstration we did a few years back in which we first tied two identical balloons on the ends of the pole and they balanced, of course. Then I blew one of the balloons up. The pole was was very out of balance, leaning to the side of the blown-up balloon, thus proving that air does have mass.
Weight vs. Mass
We discussed the difference between weight and mass, which can sometimes be confusing, especially to younger students as everything in their experience correlates mass and weight...the more stuff there is in a substance, the more it weighs. Remind them, however, that if you were to take an object into space, where there is no weight, the object still has the same mass. Even though weight may be relative, mass never changes.
The amount of space something takes up is its volume. We recalled the demonstration we did a few years ago in which we showed that a submerged object would displace an amount of water equal to its own volume, and we talked about Archimedes and how he discovered this concept.
|Density in Nature|
The discussion of volume naturally leads into another one about density. Density is how much mass is in a certain volume of matter. Density columns, in which various substances are layered on top of each other due to their density, is such a fun thing to do, that we have done this on various occasions. The boys are therefore quite familiar with the concept of density. We made a density column in which we used the various densities that things naturally have in them to make up the layers.
We also used temperature and salinity in colored water to make a density column in a straw.
|Seeing Rainbows: Rainbow Density|
We have also used varying amounts of sugar in colored water to make a density column in a test tube. We have also talked about density in relation to learning about fish.
We have also used the fact that Alka-Seltzer tablets don't react in vegetable oil, but they do in water, to make a wonderfully fun demonstration. When the Alka-Seltzer tablet touches the water, the chemicals react, causing a gas to form, and these gases are less dense than the oil, so they float up into the oil, causing a bubbling effect.
|Erupting Lava Bottle|
BuoyancyBuoyancy is how capable an object is of floating. We have experimented with varying amounts of water in a plastic bottle floating in a large bowl of water and how its buoyancy is affected.
Qualities of Matter
In the past, I have given the boys various mystery substances and had them try to figure out what they are by just examining the qualities of the substances.
This time, we looked at some of the many properties that things have using our rocks and minerals collection. We discussed and classified them according to their luster, or amount of shine, their color, their shape, their hardness, their smell, their density and their magnetism.
sources, inspiration and additional activities:
- Air Pressure and the Mass of Air
- Archimedes Fun
- Measuring Volume
- Density in Nature
- Layering Liquids
- Density, Buoyancy and Fish
- Layering Liquids Density Experiment at Inspiration Laboratories
- Kirigami Water Blossoms at Babble Dabble Do
- Fall Science for Children: Pomegranates at Almost Unschoolers
- Exploring Creation with Chemistry and Physics, Jeannie Fulbright