Density of water increases 0 to 4C

[leathersofa]

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TBR says, "The density of a liquid decreases (because the volume increases) with increasing temperature, with the exception of water from 0°C to 4°C."

Why does water's density increase from 0 to 4˚C?

Also, I have another question. TBR says, " When the solid is less dense than the liquid, the mass of the floating solid is equal to the mass of the liquid occupying the same volume as the submerged portion of the floating solid."
When TBR says "mass of the floating solid," does it simply mean the mass of the part of the solid that is floating or the entire mass of the solid (including floating and submerged)?

 

[enervate]

TBR says, "The density of a liquid decreases (because the volume increases) with increasing temperature, with the exception of water from 0°C to 4°C."

Why does water's density increase from 0 to 4˚C?

Also, I have another question. TBR says, " When the solid is less dense than the liquid, the mass of the floating solid is equal to the mass of the liquid occupying the same volume as the submerged portion of the floating solid."
When TBR says "mass of the floating solid," does it simply mean the mass of the part of the solid that is floating or the entire mass of the solid (including floating and submerged)?

Your second question simply states that the buoyant force is equal to the weight of the object so it indeed refers to the entire mass of the object

The answer to your first question is because water more extensively forms hydrogen bonds in the liquid state than in the solid state. Those hydrogen bonds have strong attractive forces so the molecules pack together more tightly and density increases.

 

[leathersofa]

Your second question simply states that the buoyant force is equal to the weight of the object so it indeed refers to the entire mass of the object

when you say that buoyant force = weight of the object,
is it

m(solid) * g = p(liquid) * V(liquid) * g

OR


m(solid) * g = p(solid) * V(solid) * g

 

[Heday]

when you say that buoyant force = weight of the object,
is it

m(solid) * g = p(liquid) * V(liquid) * g

OR


m(solid) * g = p(solid) * V(solid) * g

maybe it's more appropriate to use the volume of liquid displaced by the solid.

so...

p(solid) * v(solid) * g = p(liquid) * V(displaced) * g

the left hand is obviously equivalent to m*g, as p*v=m, but it just shows why you use volume displaced when objects float.

 

[leathersofa]

If the density of an object was equal to the density of the water, it would neither float nor sink. Would it still displace volume? and if yes, then woudl it displace all of its volume?

 

[enervate]

If the density of an object was equal to the density of the water, it would neither float nor sink. Would it still displace volume? and if yes, then woudl it displace all of its volume?

Even if only 1 nm of a 1 m^3 object is in contact with the fluid, it will still displace that amount of volume. There is only one situation in which the object would not displace any fluid: when it is not touching the fluid.

 

[leathersofa]

thank you so much! that really helps me out!