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Chem Exam 1
| Question | Answer |
|---|---|
| atom | basic building block of chemistry |
| compound | a thing that is composed of two or more separate elements |
| element | a fundamental item that can't be easily broken into smaller pieces |
| molecule | a group of atoms bonded together |
| Electrons are negatively charged. Which experiment provided evidence to support this claim? | The cathode ray tube experiment. |
| What is the specific evidence used to support the claim that electrons are negatively charged? | The beam of particles emitted from the cathode bent toward the positively charged plate. |
| How would the strength of the electrostatic force change if the distance between two charged objects is decreased? | The electrostatic force would become stronger or weaker depending on whether the force is attractive or repulsive. |
| Which of the following contain(s) atoms? | dust |
| Consider two balls, 1) is perched atop a high cliff, and 2) is on the ground 100 feet below. The one that has higher potential energy is... | 1 |
| Consider two balls, 1) is perched atop a high cliff, and 2) is on the ground 100 feet below. The one that has higher potential energy is... because.. | The potential energy of the system is directly proportional to the height above the earth. |
| The diagram below is for two subatomic particles. What does the curve show? | The potential energy decreases as the objects get closer together. |
| Which two subatomic particles could this curve represent? | One proton and one electron |
| Why would two helium atoms stick together in the solid state? | The partial positive end of one atom’s instantaneous dipole attracts the partial negative end of the neighboring atom’s induced dipole. |
| The London dispersion force between two helium atoms compared to the London dispersion force between two xenon atoms where both systems are the most stable is: | weaker |
| The London dispersion force between two helium atoms compared to the London dispersion force between two xenon atoms where both systems are the most stable is: weaker because.... | Helium has a smaller electron cloud, therefore there will be a smaller separation of charge resulting in a weaker force |
| Consider a system of two atoms with a stable interaction between them (the atoms are stuck in the bottom of the potential energy well). What would happen to the system for the potential energy to change from Y to Z? | a third atom from the surroundings would collide with the system. energy would transfer from the surroundings to the system. the interaction between the atoms in the system would be overcome |
| between argon (Ar) and chlorine (Cl) atoms. In nature, argon exists as individual atoms, while chlorine exists as a diatomic molecule, Cl2. Which statement below is the best answer regarding the melting point for argon compared to chlorine? | Chlorine features the higher (hotter) melting point because LDF between Cl2 molecules are stronger than those between Ar atoms |
| When milk is added to hot coffee, the coffee: | Gets colder |
| When milk is added to hot coffee, the coffee: gets colder because... | Collisions of excited coffee molecules with less excited milk molecules results in a lowering of energy to coffee |
| Which has atoms in it? | Cells, Air, and Gold |
| Which is biggest? | a cell |
| How big do you think an atom (H) is? | About 0.1 nanometer (0.1 x 10–9 m) |
| Which subatomic particle was discovered first? (and why do you think this is so?) | Electron |
| What do you think is the evidence from Thompson’s experiment that all atoms contain electrons? | The particles were identical regardless of the metal used for the cathode (where they were emitted from). |
| They’re discovering parts of an atom – so how did they know about alpha particles? | They knew something positive had to be there. They studied radioactive elements so they knew that they kicked off something positive. They had a model understanding of their atom so they could get the protons out. |
| Elements are composed of small indivisible, indestructible particles called atoms. | false |
| All atoms of an element are identical and have the same mass and properties. | false |
| Atoms of a given element are different from atoms of other elements. | true |
| Compounds are formed by combinations of atoms of two or more elements. | true |
| Chemical reactions are due to the rearrangements of atoms, atoms (matter) are neither created nor destroyed during a reaction. | true |
| Here is Katie, she has thrown a ball in the air. What forces are acting on the ball when it is in the air? | gravitational |
| What happens to the gravitational force of attraction as: 1. The mass of the interacting objects increases? | increases |
| What happens to the gravitational force of attraction as: The distance between the objects increases? | decreases |
| If the puck and the charge are the same charge what happens? | they repel eachother |
| If the puck and the charge are opposite charges what happens? | they attract eachother |
| Here is Katie. She has a ball in her hand. What forces are acting on the ball? | gravitational and electrostatic |
| Here is Katie again. The ball is falling down. As the ball moves towards the ground what happens to the kinetic energy? | increase |
| Here is Katie again, the ball is falling down. As the ball moves towards the ground what happens to the potential energy of the system (ball + Earth)? | decrease |
| Here is Katie again. The ball is falling down. What causes the potential energy to decrease? | The gravitational interaction between the Earth and the ball |
| Here is Katie again. The ball is falling down. What causes the ball to fall down? | The gravitational interaction between the Earth and the ball |
| Here is Katie again. The ball is falling down. As the ball moves towards the ground what happens to the total energy of the system (ball + Earth)? | Stays the same |
| The temperature at which a solid changes to a liquid (of the same chemical identity) is | The melting point |
| As the helium atoms approach what happens to:The total energy | stays the same |
| As the helium atoms approach what happens to:The kinetic energy | increases |
| As the helium atoms approach what happens to: The potential energy | decreases |
| As the helium atoms get very close (overlapping electron clouds) what happens to: the total energy | stays the same |
| As the helium atoms get very close (overlapping electron clouds) what happens to: the potential energy | decreases |
| As the helium atoms get very close (overlapping electron clouds) what happens to: the kinetic energy | increases |
| Compared to He, the London Dispersion Forces between Xe atoms are expected to be | stronger |
| Which do you think would have higher melting and/or boiling points? | Xe |
| Consider a Potential Energy curve comparing Xe and He. Are attractive forces referring to the x axis or the y axis? | X-axis |
| Would Xe minimum be lower or higher than He? | higher |
| Would Xe minimum be shifted left or right compared to He? | right |
| Which type of interaction is stronger? | covalent |
| Which statement about the breaking of a single chemical bond is true? | Energy is absorbed |
| Which statement about the forming of a chemical bond or LDF interaction is true? | Energy is released |
| At 5 K, what holds the nuclei together within an H2 molecule? | covalent bond |
| At 5 K, why do molecules of H2 stick to other molecules of H2? | LDF |
| What types of bonds and/or interactions are represented for H2 in the solid phase? | Both covalent bonds and London dispersion forces |
Created by:
beatya23