Describe a situation where you add heat to a substance or material but there is no change in temperature. what does this look like on a heating curve?

ONE CAN perform this by doing an ideal experiment
by creating an isothermal system
its like you supply heat to a body and that body is present at very low temperature the amount of heat you supply is equal to the amount of heat lost by that body due to difference in the temperature of the body and the surrounding. heating curve will be constant as there is no change in the internal energy of the system ..

Kinetic energy = 1/2mv^2. since the mass is constant we can form a ratio of it's kinetic energy at 60 divided by that at 30 to see ke(60)/ke(30) = +(60^2)/30^2). this may be said to 300% increase.