This is a problem is some situations. An automobile engine is cool or cold when the car is turned off, but gets very hot inside when it has been running for a while. The oil used to lubricate the engine has to maintain viscosity at high temperature but not get so thick at low temperature that it interferes with the operation of the engine. Multigrade oils include additives that help them retain a relatively uniform viscosity over a range of temperatures. Viscosity and Density Density is mass per unit of volume.
Corn syrup is denser than water.
A liter of water has a mass if 1000 grams, or 1 kilogram. A liter of corn syrup has a mass of about 1380 grams. It may seem that heavy, dense liquids are also more viscous, but this is not necessarily the case. The Buoyancy experiment explores the density of liquids. It might be good to work on that one in conjunction with this exploration of viscosity.