[Cheistrynoob768]

I'm pretty confident in my selections, I just wanted some confirmation and an explanation if I was incorrect somewhere.

Which ones are chemical changes and physical changes?

1. The fuel in a nuclear reactor changes and produces heat. CHEM
2. Propane is burned in a barbeque. CHEM
3. A car battery is charged by the alternator. CHEM
4. The refrigerant in a freezer changes from a liquid to a gas. PHYS
5. Water freezes to ice on a lake. PHYS
6. A puddle dies up in the sunlight. PHYS
7. The rocket engine in the space shuttle burns hydrogen and oxygen gases. CHEM
8. Cells in a plant leaf produce glucose from carbon dioxide and water. CHEM

Which ones are endothermic changes and exothermic changes?

1. Water on a pond freezes to form ice. ENDO
2. Propane is burned in a barbeque. ENDO
3. A drop of water evaporates. EXO
4. Cells in a plant leaf produce glucose from carbon dioxide and water. EXO
5. The refrigerant in a freezer changes from a liquid to a gas. EXO

Which ones involve intramolecular changes and intermolecular changes?

Water on a pond freezes to form ice. INTER
Propane is burned in a barbeque. INTRA
A drop of water evaporates. INTER
Cells in a plant leaf produce glucose from carbon dioxide and water. INTRA
The refrigerant in a freezer changes from a liquid to a gas. INTER

Thanks for any feed back!

[Stovn0611]

You seem to be misunderstanding the exothermic and endothermic.

For 1. in the endo/exo section, write out the reaction

H₂O(l) -> H₂O(s)

I'm not sure if you've learned about enthalpy yet, but if you have then you should know that enthalpy increases in the order solid -> liquid -> gas

When liquid water freezes to form ice, the change in enthalpy of the reaction is negative - meaning an exothermic reaction.

Consider another example - when you're done taking a shower, why does it feel cold when you step out? The liquid water on your skin is evaporating and to do this it needs to absorb heat from your skin, so even though your skin is losing heat, the water is actually gaining heat, making it an endothermic reaction.