# Density and temperature relationship

### Temperature Effects on Density | Sciencing

Mar 14, Density is a physical property of substances that compares the relationship between volume and mass. Density is affected by temperature. Feb 13, Density changes with temperature because volume changes with temperature. Density is mass divided by volume. Density = massvolume. Dec 17, Density is inversely proportional to the temperature. exactly why this is the case , we will examine the relationship between water's density and temperature.

Cold water on top Use the same procedure as above, but place the jar of cold water, upside down over the jar of hot water. Expected results The cold blue water will immediately fall into the hot yellow water causing mixing.

The water will quickly become green throughout. Why do you think the hot and cold water mixed when the cold water was placed on top?

## Why does density change with temperature?

When the cold water is placed on top, the colors mix because the cold water is more dense and sinks in the hot water. Give each student an activity sheet.

Students will record their observations and answer questions about the activity on the activity sheet. The Explain It with Atoms and Molecules and Take It Further sections of the activity sheet will either be completed as a class, in groups, or individually depending on your instructions. Look at the teacher version of the activity sheet to find the questions and answers.

### Water, density and temperature

Explore Have students try adding cold and hot water to room-temperature water. Question to investigate Is there a density difference between hot and cold water? Materials for each group Cold water colored blue in foam cup Hot water colored yellow in foam cup Room-temperature water in clear plastic cup colorless 2 droppers Teacher preparation Add ice to water to make very cold water.

Half-fill one foam cup with cold water no ice cubes and another with hot water for each group. Add 2 drops of yellow food coloring to the hot water and 2 drops of blue food coloring to the cold water. Distribute the set of 3 cups to each group. Procedure Fill one dropper with blue cold water. Poke the end of the dropper about halfway into the colorless room-temperature water. While observing from the side, very gently squeeze the dropper so that the cold water slowly flows into the room-temperature water.

• Have students try adding cold and hot water to room-temperature water.
• Temperature Effects on Density

Remember that temperature is related to the average kinetic energy of the atoms or molecules within the substance. Pure Water The density of liquid water is approximately 1. Let's look at the density of water at 25 deg C and compare that to a higher temperature, 80 deg C. The density decreases from 0. This makes sense because, as heat is added to the liquid water, there is greater kinetic energy of the molecules and there are also more vibrations of the water molecules.

Together these mean that each H2O unit in liquid water takes up more space as the temperature increases. We see the same trend in going from liquid water at 25 deg C 0.

## Temperature Affects Density

Density increase as the temperature decreases. Below 4 deg C, however, the density decreases again.

How can we explain this? Remember that liquid water and solid water have the same network of bonds.

### Density - Wikipedia

Liquid water at 25 deg is so rapidly breaking bonds between H2O units and reforming them that extra water molecules get trapped inside the water lattice. This is the reason why liquid water is more dense than solid water. The bonds in water break more slowly as temperature decreases and the structure tend to trap fewer extra water molecules.

At low temperature, more of the water has the same lattice as ice.