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8th grade chemistry
8th grade chemistry unit 8
| Question | Answer |
|---|---|
| Physical Properties | a property that can be observed without changing the identity of the substance |
| Physical Changes | occurs when matter changes its property by not in a chemical nature: texture, shape,, size, color, odor, volume, mass, weight, density |
| Chemical properties | the way a substance may change or react to form another substance-heat combustion, re-activity to water, pH, oxidation, flammability, re-activity to other chemicals |
| Chemical changes | changes matter undergoes when it becomes new or different matter |
| Boiling point | physical property- the point in which the property is from liquid to gas |
| Ability to rust | chemical property- reacts with oxygen to produce rust |
| Melting point | physical property- the point in which the property is liquid form from a solid or gas state |
| Brittleness | physical property- the property where it can break without deforming or shredding the object |
| Reactivity with vinegar | Chemical property- the ability to change the form of the property |
| elasticity | physical property- the ability to be stretched or not |
| flammability | Chemical property- the ability to burn |
| denisity | physical property- the compactness of the substance |
| transparency | physical property- the property of letting light pass through something |
| ductility | physical property- the property to be able to be flatten |
| sublimation | when anything solid turns into a gas with out being liquid first |
| combustible | ability to catch fire and burn |
| what are the five indicators of chemical reaction | emission of light or heat, formation of gas, formation of precipitate, color change, emission of odor |
| color change | when the property change from gray to brown rust- ex rust |
| precicipitate | a solid substance that forms as a result of reaction between chemicals in two liquid- ex. baking soda and vinegar |
| gas production | when two substances are mixed and forms gas. ex antacid and stomach fluid |
| temperature change | most reactions involve this. from a flame, or concrete before hardening ex. fireworks |
| change in characteristic | properties are changed by light or odor. ex. light stick |
| what are the five types of chemical reactions | synthesis, decomposition, single replacement, double replacement, combustion |
| synthesis | two or more elements or compounds combine to make a more complex substance |
| synthesis example | a + b -> AB |
| decomposition definition | compound breaks down into simpler substance |
| decomposition example | AB -> A + B |
| single replacement definition | occurs when one element replaces another one in a compound |
| single replacement example | AB + C -> AC + B |
| double replacement definition | occurs when different atoms in two different compounds trade places |
| double replacement example | AB + CD -> AC + BD |
| combustion definition | one reactant is always oxygen and another reactant often contains carbon and hydrogen. the carbon and hydrogen atoms combine with oxygen, producing |
| combustion example | C + O2-> CO2 + heat |
| what is the speed of reaction called | Rate of reaction |
| What is Activation energy | The minimum amount of energy needed for particles to react and is different for each reaction |
| What are 4 factors affect the rate of reaction | Increase temperature increased concentration of dissolved reacts or pressure of gas in teased surface area use a catalyst |
| Why does a reaction proceed faster when the react ants have greater surface area | more particles are available to collide and react when the surface area is greater Each time a large piece is broken, more surface area is exposed |
| Concentration | A number of particles present in a certain volume. Higher means more can collide |
| Catalyst | Is a substance that increases the rate of a chemical reaction without being consumed in the reaction |
| Inhibitor | Is a substance that slows or prevents a reaction |
| Why must chemical reactions be balanced | |
| To shine or not to shine what are the catalyst | Salt acted as a catalyst to help speed up the chemical reaction |
| What does lower activation energy mean | More coliseum between particles have sufficient energy to react |
| Why must chemical reactions be balanced | The law of conservation says that matter is neither created nor destroyed during a chemical reaction so the number of atoms of each element must be the same on both sides of the equation |
| What are reactants | Are the substance at the beginning of a he iCal reaction |
| Product | The substance afterit is combined by a chemalreaction |
| What is a coefficient | Indicates how many molecules take place in the reaction |
| If a chemical equation does not obey the law of conservation of mass the equation is said to be | Not to balanced |
| Who was Afntoine Lavosier | Scientist who came up with the law of conservation of mass helped construction of periodic table , named On and H |
| What is the law of conservation | Mass is neither created nor destroyed during chemical reaction or physical reaction the bond between atoms in the reaction so all chemical equations must be balanced |
| What is bond energy | The energy associated with bonds breaking |
| What is photosynthesis | It is an endothermic reaction that absorbs energy from the sun to turn carvon dioxide and water into oxygen and glucose |
| Endothermic process | A change (chemical reaction) that requires (or absorbs) heat, energy is taken in but not necessary given out |
| How can you determine if the reaction is endothermic | The temperature of the reaction mixture decrease |
| Exeothermic process | A change (a chemical reaction) that releases heat-energy is released as heat and light. More energy is given out than taken in |
| Example of Exothermic | Burning fossil fuels, combustion, salt ando water |
| Examples of endothermic | Photosynthesis, a edict acid and sodium, |
| Why were catalyst converters developed | To help cars and trucks or machines move |
| What part of Silicon makes properties important in electronics | 98%per |
| How is chemical reaction important in indusrty | To make things move, light up, heat up, pick things up,machine things |
Created by:
Flynnfamily
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