Sec 1 Science Summary notes

CHAPTER 1: SCIENTIFIC ENDEAVOUR PRACTICES OF SCIENCE 1. Posing questions and defining problems 2. Planning investigations 3. Conducting investigations 4. Evaluating results 5. Communicating findings 2. Planning investigations Variables • Changed variable – ONE factor that is changed in the experiment o It is the variable being investigated. • Measured variable – the factor that is measured / observed in the experiment. o It is the data being collected. • Controlled variables – factors that are kept constant in the experiment to ensure a fair experiment. *note: variables should be described precisely e.g. using terms like “volume” or “mass” or “number” instead of “amount” Hypotheses • A hypothesis is a proposed explanation or prediction o It should show a relationship between the changed and measured variable. o e.g. the greater the volume of water given to the plant, the taller the height of the plant. 3. Conducting investigations Measurements – measuring with scientific instruments quantity instrument SI unit mass electronic balance kilogram (kg) time digital stopwatch second (s) length ruler digital calipers (can be used for diameter and depth) metre (m) temperature thermometer Kelvin (K) * other common laboratory apparatus are shown in the table in the next page. Precision and Accuracy • Accuracy: how close the measured value is to the true value of the measured quantity. • Precision: how close measured values from repeated measurements are from each other.

CHAPTER 1: SCIENTIFIC ENDEAVOUR Apparatus Use Apparatus Use Apparatus Use Apparatus Use Test tube* • For containing or heating small amount of substances Boiling tube* • For containing or heating small amount of substances Tripod stand* • For supporting apparatus during heating Displacement can • For displaced liquid to flow out through its spout Beaker* • For containing chemicals or collecting liquids Conical flask* • For containing chemicals or collecting liquids • It has a narrow neck to decrease the rate of evaporation of liquids. Retort stand* • For supporting apparatus during experiments Bunsen burner • For heating and boiling Flat bottomed flask (FYI) • For containing chemicals when preparing gases if the process requires no heating (FYI) Round-bottomed flask • For preparation of gases if the process requires heating Wire gauze* xxxxxxxx • To support apparatus during heating Measuring cylinder • For measuring a volume of liquid to an accuracy of 0.5 cm3 Evaporating dish* • For evaporating a liquid from a solution Filter funnel* • For separating an insoluble solid from a liquid Pipette • For measuring accurately a fixed volume of liquid to 1 decimal place (e.g. 25.0 cm3) Burette For measuring accurately a variable volume of liquid to 0.05 cm3 precision. (e.g. 24.7 cm3) *required to draw Measurements – measuring with scientific instruments (laboratory apparatus)

CHAPTER 1: SCIENTIFIC ENDEAVOUR Attitudes of Science • Perseverance: determination and unwillingness to give up even when facing difficulties or failures • Curiosity: a strong desire to learn and seek out information to gain an understanding • Open-mindedness: the willingness to explore different possibilities and ideas, even if it is not the norm • Objectivity: to practice Science in an impartial manner, without influence from personal experiences and beliefs • Creativity: to explore original and unconventional methods or solutions Integrity: being honest and upright; practising Science to further knowledge rather than for personal benefit 3. Conducting investigations Measurements – Errors 1. Zero error: instrument gives a non-zero reading when the measured quantity is zero. • G3Error can be prevented / solved by: o Pressing the “tare” button on an electronic instruments (e.g. electronic balance, digital calipers) 2. Parallax error: when markings on an instrument is viewed from the wrong angle. • G3Error can be reduced by: ruler: position the eye such that the line of sight is perpendicular to the marking on the ruler. measuring cylinder: position the eye so that the line of sight is aligned with the bottom of the meniscus. spring balance: position the eye such that the line of sight is perpendicular to the marking on the scale. thermometer: position the eye such that the line of sight is level with the top of the meniscus. 3. Conducting investigations Measurements – Errors G3Errors can be classified into two types: 1. Consistent errors • Errors that result in readings that are consistently inaccurate. • E.g. using an electronic balance that has a zero error of +0.2 g → results will consistently be 0.2 g heavier than the actual mass. 2. Unpredictable errors • Errors that cause imprecise measurements • Contributed by unpredictable environmental conditions. Data Quantitative data • Results are in a numerical or measurable form. • e.g. height of a plant (1.0 cm, 2.0 cm, 3.0 cm) Qualitative data • Results are based on the five senses / observations • e.g. colour of the coconut, smell of the flower

CHAPTER 1: SCIENTIFIC ENDEAVOUR p ❑ Hazard symbols Acute Toxicity Environmental Hazard Corrosive Can cause toxic or harmful effects to body when in contact Has potential to cause harm to the environment May cause severe damage on contact with body parts Gases under pressure Explosives Flammable Stored in pressurized cylinders May explode when heated May cause fire, explosion Highly flammable May cause fire or produce poisonous gas when reacted with air, water or chemicals Harmful/Irritant Carcinogenic Oxidising Substance Can lead to irritation allergic reactions Has harmful health effects Can cause harm to ozone layer Can cause breathing difficulties Can cause infertility, birth defects, damage to organs or cancer Releases oxygen easily which can cause fire ❑ Bunsen burner Parts Function Collar • To control the amount of air entering the Bunsen burner by opening or closing the air hole Air hole • To allow air to enter the Bunsen burner Luminous flame Non-luminous flame Orange colour Blue colour Unsteady Steady Hot Very hot barrel air hole gas jet base collar gas tap ❑ To light up the Bunsen burner 1. Close the air hole. 2. Turn on the gas tap fully. 3. Light the burner. 4. Open the air hole till you see a 2-tone blue flame. * a non-luminous flame should be used for heating Safe laboratory practices 1. Do not eat or drink in the laboratory. 2. Long hair should be tied back. 3. Ties should be removed. 4. Safety goggles should be worn when there is risk of injury to eyes. 5. Wash hands before leaving laboratory. 6. Do not play in the laboratory. 7. Report breakages to the teacher immediately. (Do not clean it up by yourself.) 8. Do not ingest chemicals 9. Do not eat or drink in the laboratory. 10. Long hair should be tied back. 11. Ties should be removed. 12. Safety goggles should be worn when there is risk of injury to eyes. 13. Wash hands before leaving laboratory. 14. Do not play in the laboratory. 15. Report breakages to the teacher immediately. (Do not clean it up by yourself.) 16. Do note ingest chemicals

CHAPTER 2: EXPLORING DIVERSITY OF MATTER BY ITS PHYSICAL PROPERTIES  The physical properties of a material are qualities that can be observed and measured without changing its composition. Physical Property Explanation Examples *Strength The ability to support a heavy load without changing its shape permanently Steel is used to make bridges.