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What is the primary method used to measure the wettability of a solid surface?
What is the primary method used to measure the wettability of a solid surface?
What is the term used to describe the tendency of similar molecules to attract each other?
What is the term used to describe the tendency of similar molecules to attract each other?
What is the formula used to represent Young's equation?
What is the formula used to represent Young's equation?
What is the characteristic of a solid surface that is ideal for measuring wettability?
What is the characteristic of a solid surface that is ideal for measuring wettability?
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What is the significance of a contact angle greater than 90°?
What is the significance of a contact angle greater than 90°?
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What is the term used to describe the attraction between dissimilar molecules?
What is the term used to describe the attraction between dissimilar molecules?
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What is the purpose of measuring the surface energy of a solid?
What is the purpose of measuring the surface energy of a solid?
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What is the advantage of using contact angle measurement to determine the wettability of a solid surface?
What is the advantage of using contact angle measurement to determine the wettability of a solid surface?
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What is the significance of a contact angle of 0°?
What is the significance of a contact angle of 0°?
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What is the term used to describe the balance between cohesion and adhesion?
What is the term used to describe the balance between cohesion and adhesion?
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Study Notes
Atomic Models
- Thomson's model of the atom: electrons in homogeneous spheres of positive charge (plum-pudding model)
- Thomson's model limitations: only determined relative charge-to-mass ratio of electron and proton
- Robert Millikan's contribution: determined actual charge on the electron, allowing Thomson to calculate actual mass of electron and proton
Rutherford's Alpha Particle Experiment
- Rutherford's experiment: firing alpha particles at thin gold foils
- Unexpected observation: alpha particles deflected at large angles, contradicting the plum-pudding model
- Rutherford's conclusion: alpha particles are helium atoms that have lost all their electrons
Metallic Bonding
- Electron sea model: positively charged metal atoms embedded in a sea of shared electrons
- Characteristics of metals: low to moderate hardness, very malleable and ductile, soluble in acids, good thermal and electrical conductors
Chemical Equilibrium
- Chemical equilibrium: a dynamic, reversible process where reactants and products are constantly being formed
- Equilibrium constant expression: [B] / [A]^2
- Equilibrium constant (K): a measure of the ratio of concentrations of products to reactants at equilibrium
Equilibrium Expressions Involving Pressures
- For gases: PV = nRT or P = CRT / V
- Equilibrium constant expression for gases: KP = KC.RT^Δn
- Δn: the difference between the number of moles of products and reactants
Heterogeneous Equilibria
- Heterogeneous equilibrium: a reaction where one of the substances is in a different physical state
- Equilibrium constant expression: concentrations of liquids and solids are omitted
- Example: CaCO3(s) ⇌ CaO(s) + CO2(g)
Shifts in Gaseous Equilibria
- Le Chatelier's principle: the equilibrium shifts to relieve the stress when a reversible reaction is disturbed
- Effect of concentration: increasing the amount of reactants or products shifts the equilibrium to the right or left
- Effect of temperature: increasing the temperature favors the endothermic reaction, while decreasing the temperature favors the exothermic reaction
- Effect of pressure: increasing the pressure favors the reaction with fewer gas molecules
Wettability
- Wettability: a measure of the ease at which liquids spread on solid surfaces
- Contact angle measurement: a method to determine wettability
- Ideal solid surface: flat, rigid, perfectly smooth, chemically homogeneous, and has zero contact angle hysteresis
- Real surfaces: unlike ideal surfaces, they do not have perfect smoothness, rigidity, or chemical homogeneity
Cohesion and Adhesion
- Wettability as a balance between cohesion and adhesion
- Cohesion: the tendency for similar molecules to attract each other
- Adhesion: the degree to which dissimilar molecules attract each other
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Description
This quiz is about J.J. Thomson's model of the atom, which proposes that electrons are embedded in a sphere of positive charge. It's also known as the plum-pudding model of the atom.
