Chemical Changes

Chemical Changes

Practice important ideas

Physical Change

• a change that alters the form or appearance of a substance without changing its into a different substance.

Physical Change

• the characteristic physical properties of the matter remain the same

• Physical properties include: density, conductivity, malleability, melting point, freezing point, and boiling point.

Chemical Change

• change in matter that produces one or more new substances.

• atoms and molecules rearrange to form new ones.

chemical change

• substances that undergo change in areaction are called reactants

• substances produced/formed in a reaction are called products

Examples of chemical changes

• burning

• rusting

Evidence of chemical reactions

• Color change

• Gas Production

• formation of a precipitate

Exothermic reaction

• the energy released as the products form is greater than the energy required to break the bonds of the reactants.

• reaction between oxygen and flammable fuels (wood, coal, wax, or oil)

• 
  

Endothermic Reaction

• More energy is required to break the bonds of the reactants that is released by the formation of products.

• Some leave surrounding areas feeling cold.

• (frying an egg on stove, baking soda and vinegar.

• The reaction absorbs the heat from the surrounding air

Multiple Choice

Slicing an onion is an example of what kind of change?

• physical

• Chemical

Multiple Choice

A change in properties indicates which type of change?

• physical

• chemical

Multiple Choice

physical changes don't have reactants or products

• true

• false

Multiple Choice

color change, gas production, and formation of a precipitate are examples of chemical changes evidence

• true

• false

Affecting Rates of Reactions

• Surface Area

• Temperature

• concentration of reactant

• catalysts

• inhibitor

Multiple Choice

In an exothermic reaction, the energy released as the products form is greater than the energy required to break the bonds of the reactants.

• true

• false

Multiple Choice

In an endothermic reaction, more energy is required to break the bonds of the reactants than is released by the formation of the products.

• true

• false

Multiple Choice

At the end of an exothermic reaction, the products have less energy than the reactants did.

• true

• false

Multiple Choice

In an endothermic reaction, the energy in the products is greater than the energy of the reactants. Therefore, the reaction must continually absorb energy to keep going.

• true

• false