how does increasing the temp. of a gas in a rigid, sealed container affect density?

it increases.

Take a balloon for example. If it is correctly sealed, is it not a 'sealed container'? The answer is that it is.

So when you heat up molecules, they travel around much faster bouncing off walls more quickly and such. This in turn increases the volume.

what happens when you dip a balloon into nitrogen? it shrivels up because the nitrogen essentially cuases the molecules to come to a halt because the temp is so low.

Remember, volume and temperature are directly proportional, so when temperature goes up, so must the volume go up.

Haven't you ever heard of batteries exploding in the heat? Aren't they metal, or solid, or "rigid" as you say? with enough heat and constant pressure over time, if the container cannot expand--it will explode.

Pressure, volume, and temperature are all directly proportional. Thanks for the thumbs down, i was trying to help YOU and this is how you accept it?

increasing temp gas rigid sealed container affect density

well you have the equation V1P1/T1 = V2P2/T2 The volume stays constant. So for the two sides of the equation to be equal (that is V is constant, and P2 > P1) T2 would also have to increase. When you heat up a gas the particles get excited and start to move around more causing the pressure to increase as the volume must remain constant.

Your first instinct is correct. Density is mass/volume, and if neither variable can change (no gas gained/lost because it is sealed and no volume change because the container is rigid) then density does not change.

sophisticated point. try searching over google or bing. just that could actually help!