Year 7 Science – Working Scientifically & Laboratory Safety Revision

Drawing & Diagram Expectations

• Be able to neatly sketch (using pencil and ruler) and correctly label:
  • Beaker
  • Test-tube
  • Measuring (graduated) cylinder
  • Conical (Erlenmeyer) flask
  • Tripod stand
  • Gauze mat
  • Bunsen burner – label base, gas hose, collar/air-hole, barrel, chimney, air vents, needle valve, flame (outer & inner cones)
  • Retort (ring) stand with boss-head & clamp – label base, rod, boss-head screw, clamp jaws
  • Full experimental set-ups such as: clamp & stand, thermometer, 250 mL beaker, 150 mL water, gauze + tripod, Bunsen burner, heatproof mat

• Scientific-drawing rules to remember:
  • Use sharp HB pencil only; no colours/shading
  • 2-D side-view unless specifically told to draw 3-D
  • Lines of uniform thickness; ruled horizontal/vertical lines for glassware
  • No sketchy or broken lines – continuous strokes
  • Labels written in print, horizontal, outside the diagram; connect with ruler-drawn lines that do not cross
  • Include a title beneath the diagram (e.g. “Apparatus for heating water”)
  • Draw to scale where possible
  • Do not close the bottom of measuring cylinders or test tubes unless fluid level is required
  • Indicate liquid levels with a straight line and shade lightly (no waves)
  • Add arrows to show direction of heat/gas if relevant

Core Laboratory Equipment & Uses

• Beaker – holding liquids/solids, rough volume estimates

• Conical (Erlenmeyer) flask – mixing by swirling, prevents splashes, can be stoppered

• Measuring cylinder – precise liquid volumes

• Test-tube – heating or reacting small samples

• Test-tube rack – supports multiple tubes upright

• Test-tube holder – wooden/metal clip for heating a single tube over flame

• Bunsen burner – heat source; produces safety (yellow) or heating (blue) flame

• Tripod stand + gauze mat – supports beaker/flask above flame; gauze disperses heat

• Heatproof mat – protects bench from heat

• Retort stand + boss-head + clamp – supports glassware (e.g. burette, thermometer)

• Thermometer – measures temperature (°C)

• Spatula – transfers small masses of solid chemicals

Branches of Science (Knowledge Questions)

• Physics – study of energy, forces, motion, matter (NOT life, NOT planets)

• Biology – study of living things

• Astronomy – study of planets, stars, universe

• Ecology – study of organisms’ relationships with each other & environment

Working Scientifically Vocabulary

• Variable – any factor that can change
  • Independent variable (IV): deliberately changed ($\to$ ‘cause’)
  • Dependent variable (DV): measured/observed result (‘effect’)
  • Controlled variables: kept the same to ensure a fair test

• Fair test – experiment where only the IV is changed, all other factors controlled

• Quantitative observation – uses numbers/measurements

• Qualitative observation – descriptive, non-numerical

• Hypothesis – testable prediction linking IV & DV

• Aim – purpose of experiment (brief statement beginning with “To…”)
  Example: “To investigate whether cane toads prefer Brand X or Brand Y dog food.”

• Method – ordered steps written in past or imperative tense, may be numbered

• Results – raw and processed data (tables, graphs)

• Discussion – interpretation of results, errors, improvements, real-world meaning

• Conclusion – sentence that answers the aim and refers to the hypothesis

• Error – unavoidable random inconsistency in measurement; reduces precision

• Accuracy – closeness of measurement to the true value

• Continuous data – any numerical value within a range (e.g. temperature, height)

• Discrete data – whole-number counts (e.g. number of cane toads)

• Line of best fit – straight or smooth curve passing near as many points as possible in a scatter graph

• Log book – bound notebook containing dated, signed experimental records

Safety Rules (General & Bunsen Burner Specific)

• Always wear correctly fitted safety glasses; protect eyes from splashes/projectiles

• Lab coats buttoned; long hair tied back; secure loose clothing

• No eating, drinking, or chewing gum in the laboratory

• Know locations of fire blanket (hook at the front), eye-wash, fire extinguisher

• Report spills, breakages, or injuries immediately

• Never taste chemicals; waft vapours toward nose if instructed

• Use smallest suitable unit & instrument for measurement to increase precision

• Follow teacher instructions exactly; deviating can cause unsafe conditions

• Repeat experiments to improve reliability & identify anomalies

Bunsen-specific:

1. Place burner on heatproof mat, attach hose to gas tap.

2. Ensure collar closed (air-hole shut).

3. Light match; hold above burner barrel.

4. Open gas tap fully; flame ignites.

5. Adjust collar to obtain required flame.
   • Yellow flame = safety / luminous flame (cooler, visible, more soot; safe to locate)
   • Blue flame = heating / non-luminous; hotter, almost invisible – HAZARD: difficult to see, can burn unnoticed

Units & Measuring Instruments

• Volume – $\text{mL},\ \text{L};$ measured with measuring cylinder, burette, pipette

• Mass – $\text{g},\ \text{kg};$ measured with electronic balance

• Temperature – $^{\circ}C;$ measured with thermometer

• Time – $\text{s},\ \text{min};$ measured with stopwatch/clock

• Distance/Length – $\text{mm},\ \text{cm},\ \text{m};$ measured with ruler, metre rule, tape

Reading Scales Correctly

• Measuring cylinder: read at eye level, bottom of meniscus; record to nearest marked subdivision (use blue sight-line in diagrams)
  Example MCQ: cylinder shows meniscus at $44\,\text{mL}$ (choose 44 mL)

• Thermometers: read bulb level; avoid parallax. Example shown $41.3^{\circ}C$

• Displacement method for irregular volume: $V<em>{object}=V</em>{final}-V_{initial}$
  Sample: $45\,\text{mL}-40\,\text{mL}=5\,\text{mL}$

Step-wise Procedure — Lighting a Bunsen Burner (Sequencing Question)

Correct order: C (connect) $\to$ E (close air hole) $\to$ A (light match) $\to$ D (open gas) $\to$ B (adjust collar)

Designing the Cane Toad Preference Experiment

• Aim: To determine which brand of dog food is most preferred by cane toads.

• Variables:
  • IV – brand of dog food offered
  • DV – mass (or % mass) of food eaten after fixed time
  • Controls – mass of food provided, size/age of toads, time of feeding, cage size, temperature, light conditions, time since last meal, water availability

• Method (outline):

  1. Label three identical cages A, B, C; house one cane toad per cage.

  2. Fast toads for 24 h to standardise hunger.

  3. Weigh $30\,\text{g}$ of Brand X into clean dish; place in cage A.

  4. Repeat step 3 for Brand Y (cage B) and Brand Z (cage C).

  5. Leave undisturbed for 2 h at $25^{\circ}C$.

  6. Re-weigh remaining food; calculate mass consumed: $m<em>{eaten}=m</em>{initial}-m_{final}$.

  7. Repeat experiment on three consecutive nights, rotating brands between cages to remove cage bias.

  8. Analyse mean mass eaten per brand; perform statistical test if required.

• Ethical note: minimise stress; provide water; return toads to habitat or containment per local regulations.

Multiple-Choice Reminders (Know the Key Answers)

1. Study of planets $\to$ Astronomy

2. Change only ONE variable at a time

3. Fire blanket location $\to$ hook at front of lab

4. Eating NOT permitted in lab

5. Inference = logical explanation of observation

6. Study of life $\to$ Biology

7. Yellow flame = safety flame

8. Potato boiling aim option C: “To investigate the time taken to perfectly cook a potato.”

9. Measuring cylinder reading $\to$ 44 mL (example)

10. Displacement volume example $\to$ 5 mL

Matching Section (Key Pairs)

• Result – D

• Error – J

• Conclusion – E

• Aim – F

• Hypothesis – H

• Method – B

• Line of best fit – I

• Continuous data – G

• Discrete data – C

• Log book – A

Fill-in-the-Blanks Answers

1. Unit

2. Metric system

3. Laboratory

4. Apparatus

5. Fair test

6. Observation

7. Experiment

8. Scientist

9. Inference

10. Prediction

Scientific Report Headings (Correct Order)

1. Title

2. Aim

3. Hypothesis

4. Materials

5. Method

6. Results

7. Discussion

8. Conclusion

Observations vs Inferences (Neighbour’s Broken Window Scenario)

• Observations: broken front window; clothes on floor

• Inference 1: ball was thrown through window

• Inference 2: house was burgled

Why Repeat Experiments?

• Improves reliability; identifies outliers; allows mean/median calculation; increases confidence in conclusion; supports reproducibility – cornerstone of scientific method.

Why Use Correct Equipment & Smallest Unit?

• Correct apparatus ensures valid, precise, accurate data; mismatched equipment introduces systematic error.

• Smallest suitable unit increases resolution and reduces rounding error, improving accuracy and enabling detection of subtle changes.

Ethical & Real-World Context: Controlling Cane Toads

• Invasive cane toads threaten native fauna; understanding food preferences may assist in baiting or control strategies.

• Experiments must balance ecological benefit with animal welfare codes.

Practice Identifications (Visual Questions)

• Recognise graduated cylinder scales up to $200\,\text{mL}$, different thermometer ranges, micro-measuring cylinders, 800 mL beaker, filter funnel, evap. basin, etc.

• Identify largest volume among options (look at meniscus + scale spacing).

Quick Quiz – Equipment ⇄ Description

• Test tube – holds small heated samples

• Tripod – supports gauze/beaker over burner

• Gauze mat – spreads flame heat

• Heatproof mat – protects bench

• Thermometer – measures $T$

• Spatula – transfers solids

End of revision: review each section, memorise key definitions, practise drawings, rehearse safety sequences, and attempt past paper questions for mastery.