1. what is density?

2. why is ice less dense than liquid water?

3. why is it important to ecosystems that ice floats in liquid water?

4. why is water considered to be a universal solvent?

5. what is being measured in ph?

1) density is the degree of compactness of a substance.

Explanation:

2)When water freezes, water molecules form a crystalline structure maintained by hydrogen bonding. Solid water, or ice, is less dense than liquid water. Ice is less dense than water because the orientation of hydrogen bonds causes molecules to push farther apart, which lowers the density.

3)This ice layer insulates the water below it, allowing it to stay liquid, which allows the life within it to survive. If ice sank, the liquid water on top would also freeze and sink, until all the liquid water became frozen. Water is less dense as a solid, than as a liquid, which is why ice floats.

4)Water is capable of dissolving a variety of different substances, which is why it is such a good solvent. And, water is called the "universal solvent" because it dissolves more substances than any other liquid. This is important to every living thing on earth. It means that wherever water goes, either through the ground or through our bodies, it takes along valuable chemicals, minerals, and nutrients.

5)The pH of a solution is a measure of the molar concentration of hydrogen ions in the solution and as such is a measure of the acidity or basicity of the solution.

Density is the degree of compactness of a substance

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the correct answer is d