Give any two examples where substance become harder on heating and two examples where substance become softer on heating

Hi,

The two substance on heating become hard are given below:

• When vulcanised rubber is heated it gets solidifies and its chemical composition remain same.
• Egg is made up of proteins ,so when an egg is boiled at high temperature,entropy of it's molecule increases . This increase in entropy causes denaturation of protein present in egg and results in coagulation of proteins. Thus it gets solidified.

 The two substance on heating become soft are given below:

• Ice on heating turns into water
• Vegetable ghee on heating turns into liquid.

Regards