This compilation covers the Secondary 1 Science year in one set of notes. It covers how to choose and describe separation techniques, hazard symbols and Bunsen burner flames, and animal, plant and specialised cells. It also covers elements, compounds and mixtures, solutions, suspensions and solubility, measuring length, volume and density, and light and reflection.
The notes are organised for exam revision. Key points are tagged to remember or revise, and likely exam questions come with model answers. Chapters include summaries and flash cards for quick recall.
What these notes cover
- •Separation techniques
- •Hazard symbols and Bunsen burner flames
- •Animal and plant cells
- •Unicellular and multicellular organisms
- •Division of labour, tissues, organs and systems
- •Specialised cells
- •Elements and the periodic table
- •Compounds, mixtures, atoms and molecules
- •Solutions, suspensions and solubility
- •Length, volume and density
- •Properties of light, rays and beams
- •Reflection and plane mirrors
Key definitions
- Filtration
- The separation of substances with different particle sizes by using a membrane, filter or sieve. The larger particles left behind are the residue and the smaller particles that pass through are the filtrate.
- Cell
- The basic structural and functional unit of life, and the smallest unit of life.
- Tissue
- A group of similar cells working together to perform a specific function.
- Element
- A substance that cannot be broken down into simpler substances by chemical reactions.
- Solubility
- The maximum amount of solute that can dissolve in 100 g of solvent at a fixed temperature.
Key formulas
Rf value
Rf = distance travelled by solute ÷ distance travelled by solvent front
Used in chromatography. The solvent front is the farthest point reached by the solvent. A substance that stays on the start line is insoluble in the solvent.
Density
density = mass ÷ volume
Mass and volume are those of the same object or substance.
Mass from density
mass = volume × density
Rearranged form of density = mass ÷ volume.
Volume from density
volume = mass ÷ density
Rearranged form of density = mass ÷ volume.
First law of reflection
angle of incidence = angle of reflection
Second law: the incident ray, the normal and the reflected ray all lie in the same plane. The normal is an imaginary line perpendicular to the mirror.
Worked example
Calculate the relative molecular mass of carbon dioxide, CO₂, given the relative atomic masses C = 12 and O = 16.
- 1CO₂ is a compound made of one carbon atom and two oxygen atoms chemically combined.
- 2Mass of the two oxygen atoms = 16 × 2 = 32.
- 3Add the carbon atom: 32 + 12 = 44.
- 4The relative molecular mass of CO₂ is 44.
Watch out: Multiply each relative atomic mass by the number of atoms shown in the formula (the 2 in CO₂) before adding. Adding only one oxygen gives the wrong answer.
Common mistakes
Writing 'surface area' instead of 'surface area to volume ratio'
Wrong: The root hair cell's long, narrow extension increases its surface area.
Right: The root hair cell's long, narrow extension increases its surface area to volume ratio, so it absorbs water and mineral salts at a faster rate.
Writing 'water' when describing crystallisation
Wrong: Heat the solution to remove the water.
Right: Heat the solution to remove the excess water (or excess solvent) until it is saturated, then leave it to cool to crystallise.
Using evaporation to dryness for a solute that is not heat stable
Wrong: Obtain the crystals by heating the solution to dryness.
Right: Use crystallisation, because strong heating would burn the substance and make it decompose. Heat only until the solution is saturated, then cool it, filter, rinse the crystals with distilled water and dry them with filter paper.
Questions students ask
What is the difference between animal and plant cells?
Plant cells have a cell wall made of cellulose, so they have a regular shape. Animal cells have no cell wall and have an irregular shape. Plant cells have one to a few large central vacuoles containing cell sap, while animal cells have many tiny vacuoles, and leaf cells also contain chloroplasts with chlorophyll for photosynthesis.
How is a red blood cell adapted to its function?
A red blood cell transports oxygen from the lungs to different parts of the body. It has no nucleus, so it can carry more haemoglobin. Its biconcave shape increases its surface area to volume ratio, so it exchanges gases more efficiently, and it lets the cell travel through narrow capillaries.
Why is a pencil used instead of a pen in chromatography?
Pencil marks are made of an element, so they are not separated by the solvent and do not interfere with the chromatogram. Ink is made of different dyes that may dissolve when they come into contact with the solvent.
How do you make a solute dissolve faster?
You can increase the temperature, stir the mixture, or break the solute into smaller pieces. At a higher temperature the particles move more quickly and come into contact faster. Stirring moves dissolved particles away so that more solute can contact the solvent, and smaller pieces have a larger surface area in contact with the solvent.
In the full PDF
- •Full descriptions of sublimation, simple distillation, fractional distillation and the separating funnel
- •Flash cards for separation techniques, cells and chemical compositions
- •Easy and difficult question sets on cells with model answers, including the 'new cell' analysis questions
- •Step-by-step method for drawing ray diagrams for a plane mirror
- •Tables comparing metals, non-metals and metalloids, and the five types of mixtures
- •How to read vernier callipers, plus parallax error, zero error and the remaining points to remember