All flashcards
Flashcard 1: Which option is the best evidence of a chemical change: temperature change from reaction or bending a wire?
Answer: Temperature change from reaction. Heat from mixing chemicals indicates a chemical reaction.
Flashcard 2: Which option is the best evidence of a physical change: forming a precipitate or crushing a can?
Answer: Crushing a can. Crushing only changes shape, not chemical composition.
Flashcard 3: Which observation is strong evidence of a new substance: a new odor appears or the material is flattened?
Answer: A new odor appears. New odors mean new molecules with different properties formed.
Flashcard 4: Which observation is strong evidence of a new substance: a solid precipitate forms or the object is cut?
Answer: A solid precipitate forms. Precipitates are new solid substances formed from mixing liquids.
Flashcard 5: Which observation is strong evidence of a new substance: gas bubbles forming or melting?
Answer: Gas bubbles forming. Gas production indicates a chemical reaction creating new substances.
Flashcard 6: Which observation is strong evidence that a new substance has formed: color change or shape change?
Answer: Color change. New substances often have different colors than the originals.
Flashcard 7: What is the best definition of a physical change in matter?
Answer: A change in form or state with no new substance formed. The same substance exists before and after, just in a different form.
Flashcard 8: What is the best definition of a chemical change in matter?
Answer: A change that forms one or more new substances. New substances have different properties than the original materials.
Flashcard 9: Which option is NOT strong evidence of a new substance forming: change in size or new odor?
Answer: Change in size. Size changes are physical; the substance composition stays the same.
Flashcard 10: Which option is NOT strong evidence of a new substance forming: change of state or gas produced?
Answer: Change of state. State changes are physical; the substance remains the same.
Flashcard 11: Which option is NOT strong evidence of a new substance forming: dissolving or precipitate forming?
Answer: Dissolving. Dissolving is physical; the substance can be recovered unchanged.
Flashcard 12: Which observation is strong evidence of a new substance: heat/light produced or dissolving in water?
Answer: Heat or light produced. Energy release indicates chemical bonds breaking and forming.
Flashcard 13: What is the name for a solid that forms when two liquids react and a new solid appears?
Answer: Precipitate. Forms when dissolved substances react to create an insoluble solid.
Flashcard 14: Which statement best describes why bubbles can indicate a new substance has formed?
Answer: A new gas may have been produced. Chemical reactions often produce gases not present before.
Flashcard 15: Which statement best describes why a temperature change can indicate a chemical change?
Answer: Energy is absorbed or released in a reaction. Breaking and forming chemical bonds releases or absorbs energy.
Flashcard 16: Which term means matter changes in size, shape, or state but stays the same substance?
Answer: Physical change. The substance remains chemically the same despite appearance changes.
Flashcard 17: Which term means matter changes into one or more new substances with new properties?
Answer: Chemical change. New substances have different properties than the original matter.