Homework Help: science

Posted by Bri on Monday, January 10, 2011 at 4:01pm.

here are some science questions I've been trying to do for over an hour and i just cant figure them out!
1.how does a fan convert energy?
2.what happens to matter during both a physical and chemical change?
3.give an example of a simple closed system
4. in a fire, why does the wood have less mass after the fire is done?

thanks! :)

science - helper, Monday, January 10, 2011 at 4:21pm
1.fan converts the electrical energy into kinetic energy. this kinetic energy causes the wind to blow..

2.physical change-no change in composition. Ice melts, water boils, water condenses to liquid, liquid freezes.

chemical change- chemical composition changes.

Wood burns to give carbon dioxide, carbon dioxide, smoke, wood ash. No reverse reactions possible.
3. ?
4.The mass loss is due to the burning, which both drives out water and other fluids by converting them to vapor, and gasses like carbon dioxide when oxygen in the air combines with carbon in the log. A very small amount of mass is also converted into energy, and radiated from the log.

I am not a tutor and I googled the answers
science - Bri, Monday, January 10, 2011 at 4:37pm
i don't understand how you got the answer to number 2. is matter the composition?

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