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Chemical Reactions
grade 7 terms
Term | Definition |
---|---|
activation energy | amount of energy needed to start a chemical reaction |
arrow | the arrow means "is changed into" we say YIELDS |
characteristics of a chemical reaction | changes in energy or changes in properties |
chemical changes | alter the chemical properties of matter; new substances with new properties are formed |
chemical equations | a shorter, easier way to show chemical reactions by using symbols instead of words |
coefficient | a number placed in front of a chemical formula in an equation. Tells how many atoms or molecules of each reactant and product take part in the reaction |
conservation of mass | the amount of matter involved in a chemical reaction does not change. the total mass of the reactants must equal the total mass of the products |
decomposition reaction | a compound breaks down into simpler substances |
exothermic | a reaction that releases heat; gives off energy, makes it feel warmer; most chemical reactions are this type; energy is on the product side of the chemical equation |
endothermic | a reaction that takes in heat, absorbs energy, energy is a reactant side of the chemical equation |
physical changes | Alter only the physical properties of matter; no new substances are forms |
precipitate | a solid that forms from solution during a chemical reaction; observable change that shows a chemical reaction took place. |
products | the materials you have after a chemical reaction; written on the right side |
reactants | the materials you have at the beginning of a chemical reaction; written on the left side |
replacement reaction | one part of a compound is displaced by an element or compound from another substance. |
states of matter | solid, liquid,gas. Changes in state of matter are physical changes |
subscripts | show the number of atoms of an element in a molecule or the ratio of elements in a compound |
synthesis reaction | two or more substances combine to form a new compound. |
concentration | amount of material in a given amount of another material |
catalyst | materials that increase the rate of reaction, never part of the reaction |
enzymes | catalysts found in your body |
temperature/reaction rate | increase temperature increases rate of reaction |
surface area/reaction rate | increase surface area increases rate of reaction |
concentration/reaction rate | increase concentration increases rate of reaction |
temperature | a measure of the amount of kinetic energy in an object. the faster the movement, the hotter the temperature |
surface area | Surface area is the measure of how much exposed area a solid object has |
concentration | amount of a substance in a space |