All flashcards
Flashcard 1: Identify the evidence: A candle burns and gives off heat and light. Did a new substance form?
Answer: Yes, a new substance formed. Combustion produces new substances like CO₂ and water vapor.
Flashcard 2: 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 3: 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 4: Which statement best supports that a new substance formed: only size changed or gas and odor appeared?
Answer: Gas and odor appeared. Multiple signs (gas + odor) strongly indicate chemical change.
Flashcard 5: Identify the evidence: Ice melts into liquid water. Did a new substance form?
Answer: No, no new substance formed. Melting is a physical change; water remains H₂O.
Flashcard 6: Identify the evidence: Water boils and becomes steam. Did a new substance form?
Answer: No, no new substance formed. Boiling is a physical change; steam is still water molecules.
Flashcard 7: Identify the evidence: Paper is cut into smaller pieces. Did a new substance form?
Answer: No, no new substance formed. Cutting only changes size and shape, not chemical composition.
Flashcard 8: Identify the evidence: An iron nail turns reddish-brown after days outside. Did a new substance form?
Answer: Yes, a new substance formed. Rust (iron oxide) is a new substance formed by oxidation.
Flashcard 9: 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 10: 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 11: 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 12: 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 13: 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 14: 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 15: Identify the evidence: Vinegar and baking soda fizz and release gas. Did a new substance form?
Answer: Yes, a new substance formed. Gas production indicates a chemical reaction occurred.
Flashcard 16: Identify the evidence: Two clear liquids mix and a cloudy solid appears. Did a new substance form?
Answer: Yes, a new substance formed. A precipitate forming is strong evidence of a chemical change.
Flashcard 17: 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 18: 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 19: 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 20: 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 21: Which observation is strong evidence of a chemical change: heat is released without heating, or a balloon inflates by air?
Answer: Heat is released without heating. Chemical reactions release energy; inflating is just adding existing air.
Flashcard 22: Which observation is strong evidence of a chemical change: new odor appears, or salt dissolves in water?
Answer: New odor appears. New odors indicate different molecules formed; dissolving is physical.
Flashcard 23: Which observation is strong evidence of a new substance: a precipitate forms, or paper is cut?
Answer: A precipitate forms. Precipitates are new solid substances formed from chemical reactions.
Flashcard 24: 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 25: 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 26: 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 27: Which test result supports new substance formation: mixture cannot be easily separated, or mixture is filtered apart?
Answer: Mixture cannot be easily separated. Chemical changes create substances that can't be physically separated.
Flashcard 28: Which option is the strongest evidence of a new substance: multiple signs like gas and heat, or only a shape change?
Answer: Multiple signs like gas and heat. Multiple evidence types confirm chemical change; shape alone is physical.
Flashcard 29: What is the best conclusion if a reaction produces gas, a new odor, and a precipitate?
Answer: A new substance has formed. Multiple evidence types strongly indicate chemical change occurred.
Flashcard 30: Which observation is NOT strong evidence of a new substance: change in size, or precipitate formation?
Answer: Change in size. Size changes are physical; precipitates are new chemical substances.