# Surface tension: Quiz

Question 1: What does the following picture show?

 Illustration of capillary rise and fall. Red=contact angle less than 90°; blue=contact angle greater than 90° Surface tension forces acting on a tiny (differential) patch of surface. δθx and δθy indicate the amount of bend over the dimensions of the patch. Balancing the tension forces with pressure leads to the Young–Laplace equation Surface tension can be measured using the pendant drop method on a goniometer. Intermediate stage of a jet breaking into drops. Radii of curvature in the axial direction are shown. Equation for the radius of the stream is $\scriptstyle R\left( z \right) = R_0 + A_k \cos \left( kz \right)$, where $\scriptstyle R_0$ is the radius of the unperturbed stream, $\scriptstyle A_k$ is the amplitude of the perturbation, $\scriptstyle z$ is distance along the axis of the stream, and $\scriptstyle k$ is the wave number

Question 2: This equation is also used in ________ chemistry to assess mesoporosity for solids.
CatalysisAlkeneOxygenHydrogen

Question 3: An old style mercury ________ consists of a vertical glass tube about 1 cm in diameter partially filled with mercury, and with a vacuum (called Toricelli's vacuum) in the unfilled volume (see diagram to the right).

Question 4: Surface tension is visible in other common phenomena, especially when certain substances, ________, are used to decrease it:
AmphiphileSurfactantSodium lauryl sulfatePerfluorooctanoic acid

Question 5: The two are equivalent — but when referring to energy per unit of area, people use the term surface energy — which is a more general term in the sense that it applies also to ________ and not just liquids.
SiliconMaterials scienceSolidCarbon

Question 6: which is equivalent to the ________ when Rx = Ry.
CurvatureCapillary surfaceYoung–Laplace equationSurface tension

Question 7: Photo showing the "tears of wine" phenomenon, which is induced by a combination of surface tension modification of water by ________ together with ethanol evaporating faster than water.
Alcoholic beverage1,4-ButanediolFlumazenilEthanol

Question 8: What does the following picture show?

 Forces at contact point shown for contact angle greater than 90° (left) and less than 90° (right) Profile curve of the edge of a puddle where the contact angle is 180°. The curve is given by the formula[6] :$\scriptstyle x - x_0 \ = \ \frac {1} {2} H \cosh^{-1}\left(\frac {H}{h}\right) - H \sqrt{1 - \frac{h^2} {H^2}}$ where $\scriptstyle H \ = \ 2 \sqrt{\frac {\gamma} {g \rho}}$ Surface tension prevents the paper clip from submerging. Small puddles of water on a smooth clean surface have perceptible thickness.

Question 9: ________ have very large surface areas with very little bulk.
Surface tensionFoamSoap bubbleHelium

Question 10: What does the following picture show?

 Diagram shows, in cross-section, a needle floating on the surface of water. Its weight, Fw, depresses the surface, and is balanced by the surface tension forces on either side, Fs, which are each parallel to the water's surface at the points where it contacts the needle. Notice that the horizontal components of the two Fs arrows point in opposite directions, so they cancel each other, but the vertical components point in the same direction and therefore add up[1] to balance Fw. Intermediate stage of a jet breaking into drops. Radii of curvature in the axial direction are shown. Equation for the radius of the stream is $\scriptstyle R\left( z \right) = R_0 + A_k \cos \left( kz \right)$, where $\scriptstyle R_0$ is the radius of the unperturbed stream, $\scriptstyle A_k$ is the amplitude of the perturbation, $\scriptstyle z$ is distance along the axis of the stream, and $\scriptstyle k$ is the wave number Surface tension can be measured using the pendant drop method on a goniometer. Diagram of a Mercury Barometer