Introduction to Endothermic & Exothermic Reactions

Which statement best defines reactants in a chemical reaction?

• Substances present before a reaction occurs

• Substances formed after a reaction happens

• Energy absorbed during bond breaking

• Energy released when bonds are made

In an endothermic reaction, how does energy transfer occur between the system and surroundings?

• Energy moves from surroundings into the system

• Energy moves from the system into surroundings

• No energy moves between either group

• Energy alternates randomly between both

Tags

NGSS.HS-PS1-4

A campfire feels warm because burning wood releases heat as new bonds form. Which type of reaction is this and what happens to product energy compared to reactants?

• Exothermic; products have lower energy

• Exothermic; products have higher energy

• Endothermic; products have lower energy

• Endothermic; products have higher energy

Tags

NGSS.MS-PS3-5

Two reactions are shown on energy diagrams. Diagram A shows products higher than reactants; Diagram B shows products lower than reactants. Which matching is correct?

• A: endothermic, B: exothermic

• A: exothermic, B: endothermic

• A: both endothermic reactions

• B: both exothermic reactions

Tags

NGSS.HS-PS1-4

Which process is an example of an endothermic change because it absorbs heat from the surroundings?

• Melting an ice cube on your hand

• Burning wood in a campfire

• A hand warmer releasing heat

• Condensation on a cold glass

Tags

NGSS.MS-PS1-4

NGSS.MS-PS3-4

A disposable cold pack becomes cold when activated. How should this be classified?

• Endothermic because it absorbs heat

• Exothermic because it gives off light

• Exothermic because it releases heat

• Endothermic because it releases heat

Tags

NGSS.MS-PS1-4

NGSS.MS-PS3-4

NGSS.MS-PS3-5

Which reaction is exothermic because energy is released to the surroundings?

• Rocket fuel burning during launch

• Egg warming in a saucepan

• Mint cooling sensation on tongue

• Leaf absorbing sunlight for sugar

Tags

NGSS.MS-PS1-2

Identify the correct labels for the photosynthesis equation: 6CO2 + 6H2O + sunlight → C6H12O6 + 6O2. Which side lists the reactants?

• 6CO2, 6H2O, and sunlight

• C6H12O6 and 6O2 only

• C6H12O6, 6O2, and sunlight

• Sunlight and glucose only

Tags

NGSS.MS-LS1-6

NGSS.MS-LS2-3

Liquid water forming droplets on the outside of a cold glass is best described as which process, and why?

• Exothermic because gas turns to liquid

• Endothermic because liquid gains heat

• Endothermic because gas releases heat

• Exothermic because liquid absorbs heat

Tags

NGSS.MS-PS1-4

NGSS.MS-PS3-4

NGSS.MS-PS3-5

Two chemicals only react when the mixture is heated continually. What does this suggest about the reaction type?

• Endothermic because energy is required

• Exothermic because bonds form faster

• Exothermic because temperature falls

• Endothermic because heat is released

Tags

NGSS.MS-PS3-4

NGSS.MS-PS3-3