Chemical Reactions

When a scientist mixed two chemicals, an exothermic reaction takes place. Which of the following would be proof that the reaction was exothermic?

• a change of color
• a change of state
• a temperature decrease
• a temperature increase

A scientist combines chemicals and produces an exothermic reaction. What byproduct of this reaction would show that it is exothermic?

• heat
• coolness
• a precipitate
• gas bubbles

Which of the following is a chemical change?

• water freezes to form ice
• sugar dissolves in water
• gasoline burns in a car engine
• a piece of metal expands when it is heated

In the reaction methane + oxygen turns into carbon dioxide + water, the methane and oxygen are called _______________.

• reactants
• products
• neutrals
• energizers

A change in the shape of an object is an example of _________________.

• a chemical change
• energy
• an endothermic change
• a physical change

What type of change occurs when a new substance is formed that has different properties from the original substances?

• chemical change
• nuclear change
• physical change
• mutation

Which of the following represents a chemical change?

• cutting a piece of paper with scissors
• cooling a mixture of air and kerosene vapor to obtain liquid kerosene
• burning a piece of notebook paper in the presence of oxygen
• heating water over a flame to its boiling point

Which of the following is an example of a physical change?

• souring milk
• mixing baking soda and vinegar
• rusting metal
• mixing oil and vinegar

Which of the following is a chemical change?

• the rusting of iron
• dissolving salt in water
• melting an ice cube
• bending a copper wire

Which of the following is an example of a chemical change?

• rusting of a bicycle
• painting a house
• washing a dog
• tearing up a newspaper