All flashcards
Flashcard 1: What is the key particle-level idea that explains a new substance forming in a reaction?
Answer: Atoms rearrange to make different molecules. Chemical reactions involve breaking and forming new bonds.
Flashcard 2: What is a precipitate?
Answer: A solid that forms when two liquids react and a new substance forms. The solid is a new compound formed by the reaction.
Flashcard 3: Which option is most likely a physical change: rusting iron, burning wood, or melting ice?
Answer: Melting ice. Ice changes state but remains water molecules (H2O).
Flashcard 4: Which option is a sign that a new substance may have formed: heat/light produced, cutting, or freezing?
Answer: Heat or light produced. Energy release signals chemical bonds breaking and forming.
Flashcard 5: Which option is a sign that a new substance may have formed: gas bubbles, dissolving, or melting?
Answer: Gas bubbles. Gas formation indicates a chemical reaction producing new substances.
Flashcard 6: Which option is a sign that a new substance may have formed: color change, stirring, or pouring?
Answer: Color change. New substances often have different colors than the originals.
Flashcard 7: What is the main reason many mixtures do not create new substances?
Answer: The substances do not chemically react; they only mix physically. No bond breaking occurs; substances simply intermingle.
Flashcard 8: What is the main reason some mixtures create new substances?
Answer: The substances undergo a chemical reaction. Chemical bonds break and reform, creating new molecular structures.
Flashcard 9: Which statement best distinguishes mixing from reacting?
Answer: Mixing is physical; reacting is chemical and forms new substances. Physical mixing preserves original substances; reactions create new ones.
Flashcard 10: What is a physical change?
Answer: A change in form or state that does not make a new substance. Only appearance changes; the substance's identity remains the same.
Flashcard 11: What is a chemical change?
Answer: A change that forms one or more new substances. Atoms rearrange to create different molecules with new properties.
Flashcard 12: What is a mixture in science?
Answer: A physical combination of substances with no new substance formed. Components retain their original properties and can be separated.
Flashcard 13: Which option best describes dissolving sugar in water: chemical change or physical change?
Answer: Physical change. Sugar molecules disperse but remain chemically unchanged.
Flashcard 14: Which option best describes mixing sand and iron filings: chemical change or physical change?
Answer: Physical change. Both substances retain their properties and can be separated.
Flashcard 15: Which option best describes vinegar reacting with baking soda: chemical change or physical change?
Answer: Chemical change. Acid-base reaction produces carbon dioxide and new compounds.
Flashcard 16: Identify the best conclusion: A mixture fizzes and releases gas. Did a new substance likely form?
Answer: Yes, a new substance likely formed. Gas production is a key indicator of chemical reaction.
Flashcard 17: Identify the best conclusion: Two liquids are mixed and a solid appears. Did a new substance form?
Answer: Yes, a precipitate indicates a new substance formed. Solid formation from liquids indicates chemical reaction occurred.
Flashcard 18: Which option is most likely a chemical change: tearing paper, boiling water, or souring milk?
Answer: Souring milk. Bacteria convert lactose into lactic acid, a new substance.
Flashcard 19: Which statement is always true for a mixture that did not react chemically?
Answer: Each substance keeps its own properties. No chemical reaction means no property changes occur.
Flashcard 20: Which option best describes why filtering can separate sand from water but not salt from water?
Answer: Sand is insoluble; dissolved salt passes through the filter. Particle size determines what passes through filter pores.
Flashcard 21: What is the main difference between a solution and a chemical reaction?
Answer: A solution forms no new substance; a reaction forms new substances. Solutions involve physical mixing; reactions involve chemical bonding changes.
Flashcard 22: What is the best statement about properties after a chemical change?
Answer: The products have different properties than the reactants. Chemical reactions rearrange atoms to create substances with new properties.
Flashcard 23: What is the best statement about properties in a physical mixture?
Answer: Each substance keeps its own properties. No chemical bonds form between components in physical mixtures.
Flashcard 24: Which separation method best shows a mixture did not form a new substance: filtering or “cannot be separated”?
Answer: Filtering. Physical separation methods work only when no chemical bonds formed.
Flashcard 25: Which option is a chemical change: melting wax or burning wax?
Answer: Burning wax. Combustion breaks chemical bonds, forming CO₂ and water vapor.
Flashcard 26: Which option is a physical change: dissolving salt in water or rusting iron?
Answer: Dissolving salt in water. Salt molecules disperse in water but remain chemically unchanged.
Flashcard 27: Which option shows new substances forming: salt + water or vinegar + baking soda?
Answer: Vinegar + baking soda. Produces carbon dioxide gas and sodium acetate through chemical reaction.
Flashcard 28: Which option shows a physical mixture: sand + iron filings or vinegar + baking soda?
Answer: Sand + iron filings. Both solids retain their properties and can be separated by magnets.
Flashcard 29: What is a precipitate in the context of mixing two liquids?
Answer: A new solid that forms when two solutions are mixed. Forms when a chemical reaction produces an insoluble product.
Flashcard 30: Identify the sign of chemical change: new odor appears, evaporation, or dissolving sugar.
Answer: New odor appears. New substances often have different smells than the starting materials.