Lab tools, hazard symbols and Safety Data Sheets

Answer Key - Grade 10 Science Worksheet - Building Confidence

Circle the best answer, or write your answer on the line.

1. 1.

   Ari reads 5 mL on a cylinder whose readings are good to ±0.5 mL. What percent of the reading is that uncertainty?

   10 %
2. 2.

   Esme reads 25 mL on a cylinder whose readings are good to ±1 mL. What percent of the reading is that uncertainty?

   4 %

3. Read this first

   Measuring tools (example set)

   tool	holds	smallest mark
   10 mL cylinder	10 mL	0.2 mL
   100 mL cylinder	100 mL	1 mL
   250 mL cylinder	250 mL	2 mL
   250 mL beaker	250 mL	25 mL

4. 3.

   Jun needs 8.4 mL of water. Which tool gives the most precise reading?

   • The 10 mL cylinder, whose 0.2 mL marks are the finest that can hold 8.4 mL
   • The 100 mL cylinder, since it holds far more than 8.4 mL
   • The 250 mL beaker, since its wide opening makes pouring easy
5. 4.

   Kira needs 180 mL of water to within 2 mL. Which tool fits?

   • The 100 mL cylinder, since its marks are finer and it holds 180 mL
   • The 250 mL beaker, which holds 180 mL and fills quickly
   • The 250 mL cylinder, which holds 180 mL and has marks fine enough
6. 5.

   A 4.0 mL sample is read on a 100 mL cylinder (±0.5 mL) and on a 10 mL cylinder (±0.1 mL). Which reading is better, Luz?

   • Both are equal, since both are cylinders and both read 4.0 mL
   • The 10 mL cylinder: ±0.1 mL is 2.5% of 4.0 mL, against 12.5% for the larger one
   • The 100 mL cylinder: ±0.5 mL is a bigger number, so it covers more of the 4.0 mL sample

7. Hazard pictograms (OSHA Hazard Communication Standard)

   pictogram	warns of
   flame	flammable liquids and gases
   corrosion	skin burns and eye damage
   gas cylinder	gases under pressure
   exclamation mark	irritant, harmful if swallowed
   skull and crossbones	fatal or toxic if swallowed, breathed or touched
   flame over circle	oxidizers, which help other materials burn

8. 6.

   Where should a bottle with the flame over circle pictogram be stored, Noah?

   • Away from the flammable-liquids cabinet, since oxidizers feed other fires
   • On any shelf, as long as the cap is tight
   • Next to the flammable-liquids cabinet, since both of these involve fire and heat
9. 7.

   Bottle P: Danger with skull and crossbones. Bottle Q: Warning with exclamation mark. What do the labels show, Pia?

   • P warns of a more severe hazard, since Danger marks the more severe level
   • Q is the more hazardous, because Warning means you must be warned
   • They are equally hazardous, since both labels name a hazard
10. 8.

    Ren pours leftover salt solution back into the stock bottle. Why is that a problem?

    • The stock bottle will overflow, because every leftover adds more liquid to a full bottle
    • The stock becomes more concentrated, because leftover solution is always stronger
    • The stock may now be contaminated, so every later user could get different results
11. 9.

    A bottle is labeled only Soln A. Which missing information matters most for safety, Tala?

    • What the substance is and its hazards, so nobody has to guess how to handle it
    • Who poured it, so that person can be asked to come and clean up any spill that happens
    • The date it was bought, since older bottles are weaker

12. Parts of a Safety Data Sheet (OSHA, 16 sections in all)

    section	title
    4	First-aid measures
    6	Accidental release measures
    7	Handling and storage
    8	Exposure controls and personal protection
    9	Physical and chemical properties
    10	Stability and reactivity

13. 10.

    A bottle of solution tips over on the bench. Which section tells how to clean it up safely, Zee?

    • Section 6, accidental release measures, which covers clean-up
    • Section 9, physical and chemical properties, since it says what the liquid is like
    • Section 4, first-aid measures, since a spill could reach skin