You can only measure the smallest unit on the measuring instrument. Mass and volume are the same thing. Mass and weight are the same thing. You should start at the end of the measuring device. The 5 senses are always right.
Heat is a substance.
Heat and temperature are the same. Heat and cold are the opposite. Two objects with different shapes cannot have the same density. In fact, usually what will happen is the thermometer will strike a table edge and break. Most classroom thermometers are now alcohol thermometers so you will not need worry about mercury spills.