Properties & Changes, Factors affecting chemical reactions

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What is a physical change?

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A physical change is a change that affects one or more physical properties of a substance without altering its chemical composition. Examples include tearing paper, melting ice, or dissolving sugar in water.

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What is a chemical change?

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A chemical change is a change that results in the formation of new chemical substances. Examples include rusting iron, burning wood, or cooking an egg.

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What is density?

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Density is the mass of a substance divided by its volume, typically expressed in grams per cubic centimeter (g/cm³). It helps identify substances.

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How do you calculate density?

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Density = Mass / Volume. For example, if a substance has a mass of 10g and a volume of 2cm³, its density is 5g/cm³.

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What is the state of matter where particles are tightly packed?

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Solid. In solids, particles are closely packed together and vibrate in place, giving them a definite shape and volume.

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What happens to heat in an exothermic reaction?

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In an exothermic reaction, heat is released into the surroundings, making the surroundings warmer.

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What is surface area and how does it affect reaction rates?

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Surface area is the total area of the surface of a three-dimensional object. Increasing the surface area of reactants increases the rate of reaction because more particles are exposed to react.

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What factors affect the rate of chemical reactions?

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Factors include temperature, concentration of reactants, surface area, and the presence of catalysts.

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What is a catalyst?

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A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process.

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What is the difference between an endothermic and exothermic reaction?

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An endothermic reaction absorbs heat from the surroundings, while an exothermic reaction releases heat.