Unit 6, lesson 7,8

A scientist is examining an unknown solid. Which procedure would most likely help determine a chemical property of the substance?  How many chemical changes occurred in this scenario?

• placing it in water to find out whether or not it dissolves
• hitting it with a hammer to determine if it breaks or bends
• exposing it to a flame to see if it catches on fire
• heating it to find the temperature at which it melts

Which characteristic of a substance is considered a chemical property?

• its boiling point
• its conductivity
  
• its reactivity
  
• its density
  

Which statement best describes what happens during a chemical change?

• The physical properties of a substance change, but its chemical properties remain the same.
• The chemical properties of a substance change, but its physical properties remain the same
• Some properties of a substance change, but its identity remains the same.
• Both the identity and the properties of a substance change.

In a science demonstration, a teacher mixed zinc (Zn) with hydrogen chloride (HCl) in a flask and quickly attached a balloon over the mouth of the flask. Bubbles formed in the solution and the balloon inflated.

• The Zn and HCl both retained their identity.
  
• Either Zn or HCl, but not both, retained its identity.
• Evaporation of one of the substances occurred.
  
• One or more new substances formed.
  

Which laboratory activities involve chemical changes? 

• leaving a copper penny in vinegar until it turns green
• boiling saltwater for several minutes until only solid salt remains
• extracting iron filings from a sand mixture using a magnet
• crushing a rock with a hammer to extract mineral deposits

Which event always involves a chemical change?

• boiling
  
• melting
• Burning
• conducting
  

Justin is making a snack. He toasts a piece of bread and spreads peanut butter and jelly on it. Then he cuts an apple into several slices and adds these to his plate. Next, Justin mixes a scoop of lemonade powder into a glass of water, mixes it, and adds ice.  How many chemical changes occurred in this scenario?

• one
  
• two
• three
• four

Which statement best describes a physical change?

• Changes can occur to chemical properties of a substance, but the chemical composition of the substance remains the same.
• Changes can occur to physical properties of a substance, but the chemical composition of the substance remains the same.
  
• Changes can occur to certain physical properties of the substance, but the overall shape of the substance will remain the same.
• Changes can occur to certain chemical properties of the substance, but the overall shape of the substance will remain the same.
  

Which statement describes all chemical changes, but not all physical changes?

• Phase changes occur.
  
• A new substance forms.
• Bubbles are produced.
• A color change occurs.

Jenna took an open bowl of leftover mashed potatoes from the refrigerator. She determined that chemical changes occurred since the potatoes were first placed there.

• a decrease in temperature
• a production of odor
• a decrease in mass
• a change in moisture content