Practice Test 11 - High School Chemistry

20 questions. Answer them in any order, then submit to see your score and every explanation.

Start practice test

1. A student wants to investigate whether heating sugar causes a chemical change (caramelization) rather than just melting, because the result affects a cooking science project. Which investigation design best tests for chemical change while identifying variables, controls, and evidence to collect?
2. A small piece of magnesium ribbon is lit and burns with a bright white light. The air near the flame becomes noticeably warmer. Which choice best describes the energy transfer for this reaction?
3. A student heats 15 g of a white solid labeled "wax" in a small metal dish. Observations and data: - The wax melts into a clear liquid at about $60^\circ\text{C}$ - No bubbling or smoke is observed - The mass is 15.0 g before heating and 15.0 g after cooling back to room temperature - After cooling, the liquid becomes a solid again with the same appearance as before Which CER justification best supports whether a chemical reaction occurred?
4. Given the balanced equation: $2\text{Na} + \text{Cl}_2 \rightarrow 2\text{NaCl}$ If $3.0$ mol of $\text{Cl}_2$ react completely, how many moles of NaCl form?
5. Three nuclear changes are described: 1) One heavy nucleus splits into two smaller nuclei and releases neutrons. 2) Two small nuclei join to form one larger nucleus. 3) One unstable nucleus emits a particle and becomes a different nucleus. Which matching correctly identifies 1, 2, and 3?
6. Photosynthesis can be represented by the balanced equation: $6\text{CO}_2 + 6\text{H}_2\text{O} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2$ If a plant uses $12 \text{mol}$ of $\text{CO}_2$ completely, how many moles of $\text{O}_2$ are produced?
7. A student mixes baking soda and vinegar in an open beaker. The reaction is: NaHCO$_3$(s) + CH$_3$COOH(aq) → CH$_3$COONa(aq) + CO$_2$(g) + H$_2$O(l). Masses measured: - Before: beaker + contents = 200 g - After bubbling stops: beaker + contents = 196 g Which statement best explains the 4 g decrease?
8. A city replaced old lead service lines with copper pipe for drinking water connections. After the change, routine water tests showed lead levels dropped from 18 ppb to <1 ppb at household taps, while copper levels remained below regulatory limits. Which reasoning best justifies choosing copper over keeping the lead pipes, using chemical properties and the evidence?
9. Two substances are combined at room temperature. The student measures mass and observes changes. Which option best uses the data to support that a chemical reaction occurred?
10. In a lab, 25 mL of hydrochloric acid is mixed with 25 mL of sodium hydroxide in a beaker. The temperature rises from 20°C to 29°C without any external heating. What does the temperature change indicate?
11. Three students each run the same reaction: CaCO$_3$ + vinegar, using the same mass of CaCO$_3$, the same vinegar concentration, and the same temperature. Only the surface area of CaCO$_3$ differs.

    Setup	CaCO$_3$ form	Reaction appearance
    A	one large chunk	few bubbles at a time
    B	several small chips	steady bubbling
    C	fine powder	very vigorous bubbling

    Which setup has the greatest reaction rate, and why?
12. A student claims: "Increasing temperature increases the rate of the reaction between sodium thiosulfate and hydrochloric acid." In each trial, students mixed the same amounts of reactants and measured the time until a black X under the beaker could no longer be seen (solution became cloudy). Do the data support the claim?
13. A community science club is building a small outdoor sensor housing. It will be exposed to rain (slightly acidic), sunlight, and temperature changes. Requirements: weather/corrosion resistance (critical), low maintenance (important), and low cost (constraint). Which material choice best balances trade-offs? Options: - Unpainted steel: strong and cheap; rusts in rain; needs frequent maintenance. - Aluminum: good corrosion resistance in outdoor conditions; lightweight; moderate cost; can dent more easily than steel. - Wood: inexpensive; easy to work with; can swell/rot unless sealed and maintained.
14. A reaction is described as "releases 85 kJ of heat to the surroundings for each mole of reaction as written." Which $\Delta H$ value matches this description?
15. A student adds a small scoop of a white solid to water and stirs. The solid seems to disappear and the water remains clear. Which observation would be the best evidence that a chemical reaction (not just dissolving) occurred?
16. Students test: How does the identity of a metal affect its reaction with hydrochloric acid? They place 50.0 mL of 1.0 M HCl into three identical beakers at room temperature. They add a 3.0 cm × 1.0 cm strip of zinc to Beaker 1, iron to Beaker 2, and copper to Beaker 3. For 5 minutes, they observe the reaction and record the total volume of gas collected using a gas syringe attached to each beaker. What is the dependent variable?
17. A student reacts identical masses of iron in two forms with the same volume of dilute acid at the same temperature. Setup A: one iron nail → slow bubbling Setup B: iron filings (same total mass) → rapid bubbling Which factor best explains why Setup B reacts faster?
18. A lab safety sheet warns that alkali metals (Group 1) become more reactive down the group. A student must choose the safest (least reactive) metal to use in a controlled water-reaction demo from: sodium (Na, period 3), potassium (K, period 4), and rubidium (Rb, period 5). Which is least reactive with water?
19. A student reacted 1.00 g of calcium carbonate (marble chips) with 25.0 mL of 1.0 M HCl at 24.0°C and measured the total volume of $\mathrm{CO_2}$ produced after 3 minutes. The procedure was repeated three times. Table: Repeated trials (same conditions)

    Trial	$\mathrm{CO_2}$ volume after 3 min (mL)	Observation
    1	92	Steady bubbling
    2	95	Steady bubbling
    3	93	Steady bubbling

    Which statement best describes the data quality and what it suggests?
20. A student claims: "Adding a catalyst increases the reaction rate." In a decomposition reaction, the student measures the time for a fixed amount of product to form. Data: - Without catalyst: 120 s, 118 s, 123 s - With catalyst: 42 s, 39 s, 41 s How well do the data support the claim?

Practice tests