Tutor profile: Kristen L.
Is the melting of an ice cube an example of an exothermic or endothermic change?
Exothermic changes release energy, while endothermic changes absorb energy. When an ice cube melts, the water molecules much gain energy in order to move out of their fixed positions within the crystalline ice cube. In order to gain energy, it must be absorbed from the surrounding environment, which means that the melting of an ice cube is an example of an endothermic change.
Subject: Basic Chemistry
Imagine you have an unknown solid substance, and you wanted to determine if it amorphous or crystalline. Explain how you could use heat to determine it is an amorphous or crystalline solid.
If I were heating an amorphous solid, I would expect that the solid would get softer and softer as it warmed up. It would get quite soft before finally melting to a liquid. If I were heating a crystalline solid, I would expect that it would remain solid until it reaching its melting point, at which time it would melt.
Compare and contrast active transport and facilitated diffusion.
Both active transport and facilitated diffusion make use of proteins that lie within the cell membrane. During facilitated diffusion, carrier proteins facilitate the movement of larger molecules, such as glucose, into the cell membrane with the molecules moving with the concentration gradient, from higher to lower concentrations of those molecules. This process does not require the cell to use any cell energy. Active transport is a process that requires cell energy. Molecules move against the concentration gradient, moving from a low to a high concentration of that molecule. Transport proteins within the cell membrane help to move these molecules into the cell.
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