Yes, it certainly can. If you have a gas fireplace, I would certainly suggest adding a simple fireplace blower kit. They take the heated air created by your fireplace and force it back into your room. Adding a blower can save you hundreds of dollars a year in energy costs.
From the air in the room where the fireplace is.
Fireplaces are generally pretty bad at heating. A set of doors for the fireplace can help. A heat exchange grate with a blower can get more warm air out into the room. The best solution is also the most expensive- a properly installed fireplace insert. This is basically a wood stove that fits into the fireplace.
If you do not close it then you basically have a hole in your roof that is sucking out all the warm air. This will lead to even higher heating and cooling costs.
Yes, cold air does have a higher density than warm air. For example, if you turn on the fireplace, all of the warm air rises to the ceiling. On the floor, the air is cooler.
Burning wood in air/oxygen is a combustion reaction, a type of oxidation-reduction reaction.
Why not, it can pull warm air into the room.
It can pull cold air down from Canada to the U.S and pull warm air up to Canada.
Fireplace inserts are an extra effective heat resource than traditional fire places. The increased efficiency is because of the layout of a fireplace inserts developing a shut combustion system. In a shut combustion system, the gadget takes the air required for combustion from an outside source, recirculates the hot air, as well as permits it to leave through a duct (generally referred to as a flue). This system enables clean burning of your picked fuel source as well as optimum warmth effectiveness. The distinction between a closed burning system produced by a fire place insert and also an open burning system produced by a standard fireplace is where the air/oxygen is being taken in from. In a open combustion system, the air is being taken in from the room in which the fireplace lives and then the air, ash, as well as smoke getaway through a different air duct (normally a chimney). This system results in a much less heat efficient system, as many runs away with the chimney.
The purpose of the fireplace damper is to keep the outside elements, outside. The damper is opened only when there is a fire in the fireplace.
It is as safe as having an indoor gas fireplace. Some people would consider it much more environmentally friendly since your are not sending smoke into the air like you would if you were burning wood.
You ARE going to lose heat up the chimney. Couple of things you can do to keep SOME of it in the room. Got a set of doors for the fireplace? They need to be open while burning, but can be closed as fire goes out, keep from sucking warm air out of the room. There are heat exchangers that are metal tubes with a fan. Tubes heated by the fire, fan pushes air thru the tubes, out into the room. The "Heatilator" style fireplaces have a heat exchanger built in to the fireplace. The heat exchangers are not cheap, and are still not as efficient as a wood stove.
Heat that comes from burning fuels warm the air. The heat also warms anything that lies near it in the environment.