# Would 10.0 mL of water at 10 °C have the same mass as 10.0 mL of water at 25 °C? [closed]

No, the density of water changes with temperature. 10.0 mL of water at 10 °C would have a higher mass than 10.0 mL of water at 25 °C because the density is higher at 10 °C.

For me it doesn't make sense. In other part of the book it states "Mass is defined as the amount of matter in an object". How can a change in temperature change the amount of matter of an object? So mass of an object is dependent on temperature?

• Heating up 10 g of water does not change its mass, as you say. But that's not what this question is about. This is about two different amounts of water: 10 mL of water at 10 °C (let's say in a measuring cylinder), and 10 mL of water at 25 *C (in, let's say, a different measuring cylinder). The amount of water in the two measuring cylinders is not the same. Commented Jan 27, 2021 at 15:34
• In fact, heating up 10 mL of water does not change its mass, either. However, it will change its volume, such that at 25 °C it is no longer 10 mL. Hence, 10 mL of water at 10 °C is not the same thing as 10 mL of water at 25 °C. Hence my suggestion to think of them as completely different samples. They are not the same object. Commented Jan 27, 2021 at 15:36
• $m_1 = \rho_1V;$ $m_2 = \rho_2V.$ When $\rho_1 > \rho_2,$ $m_1 > m_2.$ What is the problem? And, yes, comparing two identical bodies at different temperatures will result in minuscular difference in mass (hotter one will be a slight bit heavier), but this is not what your textbook (which, by the way, should be properly referenced) is trying to say. Commented Jan 27, 2021 at 15:36
• Thanks for your comments, I understand now! Commented Jan 27, 2021 at 16:24
• @M.Farooq why? Is the sentence too obvious? Commented Jan 28, 2021 at 11:05