Science 7 Semester 2

Choose the image where a chemical reaction has NOT taken place.

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Which method of testing substances is a sure way to identify a chemical reaction?

• change in color

• formation of bubbles

• change in density

• increase in temperature

• solubility in water

Which changes will increase the rate of reaction during combustion?

• decreasing the area of contact between the reactants

• adding more oxygen to the reaction

• removing heat from the reaction

• changing the reactants from solid form to powdered form

• lowering the exposure of the reactants to air

Which chemical reaction absorbs energy?

• photosynthesis

• explosion

• current produced by a battery

• combustion of fuels

• activated hand warmers

Steel is an alloy of ____.

• copper

• silver

• aluminum

• iron

A company develops a new synthetic product and prepares to sell it to the public. Customers ask questions about how to properly dispose of the product. Which word is related to disposal?

• cost

• performance

• productivity

• profitability

• recyclability

Plastic is a synthetic material. What are three advantages of using plastic?

• It’s strong and durable.

• It’s easy to recycle.

• It’s relatively inexpensive.

• It’s a good conductor of heat.

• It repels water.

According to Newton’s law of universal gravitation, which statement is true?

• Lighter objects experience a higher acceleration than heavier objects.

• Falling objects accelerate as they approach the ground.

• The weight of an object increases as it moves away from the ground.

• Lighter objects experience a lower acceleration than heavier objects.

• The mass of an object increases as it moves closer to the ground.

A silver coin rubs vigorously against a wool cloth. The cloth becomes positively charged. Which statements are true?

• The silver coin lost electrons.

• The wool cloth lost electrons.

• The silver coin gained electrons.

• The wool cloth gained protons.

• The wool cloth lost protons.

Jeff puts on a leather jacket over his sweater. The sweater becomes negatively charged. Which statements about Jeff’s situation are true?

• The sweater has a tendency to repel electrons.

• The sweater has a tendency to attract protons.

• The leather jacket has a tendency to attract electrons.

• The leather jacket has a tendency to attract protons.

• The leather jacket has a lower tendency to repel electrons than the sweater.