What is a tough, rigid, outer covering that protects some cells and gives them shape?

Idon't know hope someone you

Answerδh > 0explanationc₆h₆  (s)  → c₆h₆ (l)if you are changing it from a solid to a liquid, you are pretty much melting the solid. this requires heat energy. therefore, the reaction is endothermic (takes in energy); the system enthalpy increases as the reaction proceeds: δh > 0.

Higher temperature = molecules move around faster. and vice versa.

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