Why does density vary with temperature

Also point out that when the water is cooled, the water level falls slightly in the graduated cylinder. Point out that the molecules in the hot water are moving faster and are a little farther apart than the molecules in room-temperature water. Make sure students notice that when the water is heated, the water level rises slightly in the graduated cylinder.

Tell students that in winter, ice can form on the tops of ponds and lakes. In the spring when the ice melts, the cold water sinks. This causes mixing from the bottom which brings nutrients up to the surface. Tell students that you will model this process. The coloring in the cup with the ice will move up from the bottom and begin to mix throughout the water.

The coloring in this cup will mix faster than the coloring in the cup without ice. The American Chemical Society is dedicated to improving lives through Chemistry. Skip Navigation. Lesson 3. Engage Do a demonstration to show that hot water floats on cold water. Ask students to make a prediction: Do you think the hot and cold water will mix or stay separate? Completely fill another baby food jar with very cold water and add 2 drops of blue food coloring.

Stir the water in both jars so that the coloring is well-mixed in both. Place the cold water jar on a paper towel. Hold a water-resistant card over the top of the hot water jar.

While holding the card against the jar opening, carefully turn the jar upside down. With the card still in place, position the jar of hot water directly over the jar of cold water so that the tops line up exactly. Slowly and carefully remove the card so that the hot water jar sits directly on top of the cold water jar.

Expected results Although removing the card may result in a little mixing or spilling, the hot yellow water will remain in the top jar and the cold blue water will remain in the bottom jar.

Ask students: Why do you think the hot water stayed on top of the cold water? Students should realize that there is a density difference between hot and cold water. Hot water is less dense so it floats on the denser cold water. Ask students to make a prediction: What might happen if you placed the cold blue water on top of the hot yellow water and then removed the card?

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. Ask students: Why do you think the hot and cold water mixed when the cold water was placed on top?

When the cold water is placed on top, the colors mix because the cold water is more dense and sinks in the hot water. These arrows are different lengths for each cube, indicating that the amount of the gravitational force is different for each cube. The downward pointing arrow in Fig. The downward pointing arrow is the longest in Fig 2. The density of the cube relative to the density of water determines if the cube will float, sink, or be neutrally buoyant:. This document may be freely reproduced and distributed for non-profit educational purposes.

Skip to main content. Search form Search. Join The Community Request new password. Main menu About this Site Table of Contents. Density, Temperature, and Salinity. The content and activity in this topic will work towards building an understanding of how salinity and temperature differences affect the density and buoyancy of water layers in the ocean.

Density Density is a measure of how much mass there is in a given volume or amount of space. Box A has five spheres. Box B is the same size, and has the same volume as box A, but box B has 10 spheres. Box C has the same mass as box A, with five spheres, but box C has a larger volume than boxes A and B.

Box D has the same volume and number of green spheres as part A, but also includes other types of matter than the rest of the boxes—red circles and blue cubes. Salinity Affects Density When salt is dissolved in fresh water, the density of the water increases because the mass of the water increases. Temperature Affects Density The density of water can also be affected by temperature. Relative Density In Fig. The yellow liquid and the bag are less dense than the liquid in the beaker.

The orange liquid and the bag are equal in density to the liquid in the beaker. The green liquid and the bag are more dense than the liquid in the beaker.

Light Energy 6. Heat Transfer 7. Sound 8. Objective Questions 2. Q5 How does the density of a liquid or gas vary with temperature? Looking to do well in your science exam? Learn from an expert tutor. Book a free class! Solution Transcript. Solution: As the temperature increases, volumes of most of the liquids also increases and when the volume increases density decreases.

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Biology Class 6 Class 7 Class 8. Mark Kennan is a writer based in the Kansas City area, specializing in personal finance and business topics. Related Articles Volume Vs. Mass Density. Atomic Number Vs. Atomic Density. Density Vs.