Cake batter solidifies when cooked because of chemical reactions due to the heat of baking.
1) it loses water
2) the starches expand (a bit like popcorn).
3) the proteins in the cake mix tun stiff (denature) with heat (like cooking an egg white)
yes
The sponge cake has its own form.
It is a cylinder.
a cake is a solid
This sponge ha a form.
a sphere
It's a solid
Cake batter turns solid when baked for several reasons. Moisture turns into steam and evaporates, and eggs become solid as their protein molecules bind together in reaction to heat. Sugar also melts and binds with flour which also undergoes molecular changes. The result is liquid batter turns into light but solid cake.
Moisture leaves the cake, and the ingredients turn form liquid to solid. As moisture and steam / hot air leave the cake, it can shrink a little.
It's not a liquid or a gas so Yes
cylinder
Yes, in some cake recipes, canola oil can be substituted for shortening.
Both. While the cake changes form a thick liquid to a spongy solid the foundations of it are changing as well.