Lab tools, hazard symbols and Safety Data Sheets
Grade 10 Science Worksheet
Circle the best answer, or write your answer on the line.
A stone has mass 26.70 g (±0.01 g) and displaces 10.0 mL (±0.1 mL). What is the percent uncertainty of its density, to 0.01%, Ari?
A stone has mass 21.60 g (±0.01 g) and displaces 8.0 mL (±0.1 mL). What is the percent uncertainty of its density, to 0.01%, Bo?
A stone has mass 45.80 g (±0.01 g) and displaces 15.0 mL (±0.2 mL). What is the percent uncertainty of its density, to 0.01%, Esme?
Read this first
Measuring tools (typical uncertainties)
tool reading good to 100 mL cylinder ±0.5 mL 25 mL pipet ±0.03 mL 50 mL buret ±0.02 mL per reading 250 mL beaker ±5 mL balance A ±0.01 g balance B ±0.001 g Jun must deliver 20.0 mL with the smallest percent uncertainty from one fill. Which tool should be used?
- The 25 mL pipet: ±0.03 mL is 0.15% of 20.0 mL
- The 100 mL cylinder: ±0.5 mL is 2.5% of 20.0 mL, but it is the quickest to read
- The 250 mL beaker: it holds the 20.0 mL and its wide mouth makes pouring easy
A buret reads 3.20 mL at the start and 28.45 mL at the end. Which report of the volume delivered is justified, Luz?
- 25.25 mL ± 0.02 mL, since the buret is good to ±0.02 mL per reading
- 25.25 mL ± 0.04 mL, since two readings each ±0.02 mL add
- 25.3 mL ± 0.04 mL, since a volume is reported to one decimal place
A cylinder is wet inside with about 1 mL of water when Milo pours in acid to the 20.0 mL mark. How does the acid in it compare with the plan?
- Weaker: the wet cylinder holds about 1 mL of water, so only about 19 mL is acid
- Stronger: the extra water pushes the acid up to a higher mark
- The same: the 20.0 mL mark fixes the amount of acid poured in
A stone trial (example data)
measurement reading empty dish (g) 18.40 dish and stone (g) 45.10 water before (mL) 20.0 water after (mL) 30.0 student's density (g/mL) 4.51 accepted density (g/mL) 2.67 The student's density is far above the accepted value. Which error explains it, Noah?
- The first level was read at the top edge: a 0.5 mL slip gives about 2.81, not 4.51
- Water splashed out as the stone went in: even 1 mL lost gives about 2.97, not 4.51
- The empty dish was not subtracted: 45.10 ÷ 10.0 gives exactly 4.51
Four trials give 2.66, 2.68, 2.67 and 2.74 g/mL. The 2.74 stone was weighed straight from the water. Which explanation fits, Pia?
- Water clinging to the stone added mass, so the density came out too high
- A wet cylinder shifted the starting level, which fits a high value
- Air bubbles on the stone added to the volume rise, which fits a high value
Table
Two SDS excerpts (made-up products), 2 rows. Columns: chemical | Section 2 hazard | Section 7 storage | Section 10 incompatible with. Row 1: Cleaner T | Danger. Oxidizer. Causes serious eye damage. | Store cool, away from fuels and combustible materials. | Flammable liquids and strong acids.. Row 2: Solvent S | Danger. Highly flammable liquid and vapor. | Store in a flammables cabinet, away from heat and sparks. | Oxidizers..
Can Cleaner T and Solvent S share a shelf, Ren?
- Yes: both are Danger products, so they belong together
- Yes: neither Section 10 names the other chemical, so nothing forbids it
- No: T is an oxidizer and S a flammable liquid, and each lists the other's class in Section 10
Cleaner T sits on a shelf with a bottle of strong acid and no flammables. Is the shelf safe by the excerpt, Zee?
- Yes: no flammable liquid is on the shelf, which is what Section 10 is about
- Yes: Section 7 asks just for a cool place, and a shelf is cool
- No: Section 10 lists strong acids as well as flammable liquids, so the acid must go elsewhere