Revision for Essa

Year 7

Working as a scientist

• Identify common lab equipment• Hypothesising, observing, inferring and

concluding• Using thermometers• Format for report writing• Measuring mass and volume• Fair testing (controls and variables)

Common lab equipment

Common lab

equipment

Hypothesising, observing, inferring & concluding

• Observing – things or events that you notice. Eg. footprint, smell of perfume, sound

• You infer something when you use your observation AND previous knowledge to explain something

• Hypothesis – educated guess• Conclusion – final outcome of an investigation

Using thermometers

• A thermometer is used to measure temperature in degrees Celsius (˚C)

• When reading a thermometer you must have your eyes level with the top of the of the column (of mercury or alcohol).

Using

thermometers

Format for report writing• Aim: A short statement about what you are

trying to find out. Must start with the word TO.Eg. To determine the battery brand which will last the longest in a clock radio.

• Hypothesis: Your best educated guess of what you think you will discover. DO NOT USE THE WORDS ‘I THINK’ OR ‘I RECKON’.Eg. Duracell batteries will last the longest in a clock radio.

• Materials: A list of all the equipment/chemicals to be used. (This is sometimes called apparatus).

• Method: A set of steps outlining how to do the experiment. Eg. 1. Pour 100ml of water into a 250ml beaker2. …..

• Results and observations: a presentation of your data – this usually includes a table and a graph.

• Discussion: An explanation of your results.• Conclusion: A brief account of what you found out.

Your conclusion should answer your aim.Eg. Everlast batteries lasted the longest in a clock radio.

Measuring mass and volume• Mass = how much matter there is an object or

substance. The standard unit of mass is the kilogram (kg).

• We use a triple balance beam to measure mass.

Measuring mass and volume

• Volume is a measure of the amount of space that an object or substance occupies. The standard unit of volume for liquids is the litre (L).

• To measure volume we use calibrated glassware (measuring cylinder, pipette).

Measuring mass and volume

Measuring mass and volume

Fair testing (controls and variables)

• In a fair test all conditions (variables) except the one being tested should be the same.

• Independent variable: The ONE thing you change

• Dependent variable: The thing you measure (eg height, weight, time)

• Controlled variables: everything else that must remain constant.

Separating mixtures

• Terms: solution, solute, solvent, dissolve, soluble, insoluble, concentrated, dilute, saturated, sediment/precipitate.

• Separation techniques: crystallisation, evaporation, filtration, decanting, distillation, centrifuging, chromatography

Key terms• Solution: a mixture of one substance dissolved

in another.• Solvent: The substances in which a chemical

can dissolve (usually the liquid).• Solute: The substance that dissolves (usually

the solid).FOR YOU TO DO:• What is the solute and solvent in the following:

milo, cup of coffee, swimming pool water, sea water?

Key terms

• Soluble: substances which dissolve in a liquid.• Insoluble: substances which do not dissolve in

a solvent.• Concentrated: more solute is dissolved in the

solvent.• Dilute: less solute is dissolved in the solvent.THINK OF CORDIAL: The more cordial you add, the more concentrated your drink is!

Key terms

• Saturated: When no more solute can be dissolved in a liquid. Think of your clothes being saturated – you cant get any more wet!

• Sediment: particles that do not mix and settle to the bottom (like sand in water)

• Suspension: when the insoluble substance is dispersed (spread) throughout the liquid, making it cloudy

Separation techniques• Evaporation: when one substance is heated

and evaporates. Salt and water.• Crystallisation: separating sugar from water.• Filtration: uses filter paper to separate

insoluble substances from soluble substances.

Separation techniques

• Distillation: Separates based on differing boiling points.

Separation techniques

• Decanting: Separates a liquid and a sediment – by allowing the sediment to settle to the bottom of the container and the liquid is poured off the top.

Separation techniques

• Centrifuging: Spinning a mixture quickly – forcing the heavier substances to the sides. (eg washing machine)

• Separating funnel: an apparatus used to separate 2 liquids that do not mix (eg oil and water)

Separation techniques

• Chromatography: paints, inks and dyes are often mixtures of substances that have different colours – separating these colours out is chromatography.

Cells

• Microscopes (light and electron, monocular and stereo)• Parts of a microscope• How to use a microscope• Calculating total magnification• Rules for sketching specimens• Staining specimens• Cells: look at plant and animal cells• Basic organelles: cell wall, cell membrane, nucleus,

vacuole, chloroplast, mitochondria, cytoplasm• Unicellular vs multicellular organisms

Microscopes

• Light microscope: uses light rays to see an image.

• Electron microscope: uses electrons to see an image.We use light microscopes at school!

• Monocular microscope: you use only one eye.• Stereo microscope: you use both eyes.

Microscopes

Calculating total magnification

• To calculate the total magnification, you must multiply the magnification of your eyepiece lens and the objective lens.

Eyepiece lens Objective lens Magnification

5 x 5 x 25 x

5 x 10 x

10 x 100 x

40 x 400 x

Rules for sketching

• Use a sharp pencil• Draw only the lines you see• Your diagram should take up about a third of

the page• Record the total magnification• State the name of the specimen and the date

observed• Label what you can

Staining specimens

• Many specimens are colourless when viewed down a microscope, so specimens are often stained (or coloured) to make them easier to see.

Cells – plant and animal

• All living things are made of cells.• The tiny ‘organs’ of a cell are called the

organelles.• Plant cells have different organelles to animals

cells.

Cell organelles• Nucleus: control centre of cell• Cell membrane: controls what goes into and

comes out of cell.• Cytoplasm: where chemical reactions take place.• Cell wall: protection, support and shape.• Mitochondria: supplies energy.• Chloroplasts: photosynthesis.• Vacuole: large cavity (hole) storing water and

other substances.

Plants cells vs animal cells

Plants cells vs animal cells

Unicellular vs multicellular

• Some organisms are made up of a single cell – they are described as unicellular.

• Multicellular organisms are made up of many cells with different types of cells doing different jobs.

• What are some of the cells making up humans?

Solids, liquids and gases

• What is matter/states of matter• What is volume, how can we measure volume• Particle model• Changing states: melting, freezing, evaporation/

boiling, condensation, sublimation, • Water cycle: cloud and fog• Convection, conduction, radiation

What is matter/states of matter

• Matter is anything with mass and volume.• Matter can exist in 3 states: solid, liquid and

gas.• Water is a liquid. What is the name of the solid

and gas forms of water?

States of matter

• The different states of matter have different properties.

Substance State Can the shape changed easily?

Does it take up space?

Can it be compressed?

Ice Solid

Water Liquid

Air Gas

Volume

• The amount of space taken up by a solid, liquid or gas is called its volume.

• The volume of liquids is measured in litres or millilitres.

• The volume of solids are measured in cubic metres or cubic centimetres.

• How can you measure the volume of an irregular shaped rock?

Particle model

There are 4 parts to the particle model:• All substances are made of tiny particles• The particles are attracted towards each other

and surrounding particles• The particles are always moving or vibrating.• The hotter the substance is, the more energy

the particles contain and the faster they move!

Balloon experiment

Changing states

The water cycle

• Cloud: When water vapour becomes cold enough it condenses to form clouds.• Fog: Clouds close to the ground.

Convection, conduction & radiation

Classification

• Living, nonliving, dead• Dichotomous keys• 5 vertebrate groups

Classification

• Classify means to sort into groups.• Taxonomy is the science of classifying

organisms.• One feature that can be used in forming

groups is whether something is living, non living (was never alive) or dead.

• Sort the following: sun, leaf, bird, rose, water, wooden table.

Dichotomous keys

• There are only 2 choices at each branch.

Vertebrate groups

• Vertebrates: animals which have internal skeletons or backbones.

• Invertebrates: animals which have an external skeleton or no skeleton.

• 5 vertebrate groups: mammals, aves, reptiles, amphibia, fish.

Forces

• Speed• Types of forces: gravity, magnetic, electrostatic• Contact and non-contact forces, buoyancy,

friction

Speed

• Speed is a measure of how quickly distance is covered.

• Speed: distance ÷ time• Units: km/hr, m/sec, cm/min…..

Types of forces

• Contact forces: require contact (eg friction)• Non-contact forces: no contact is required

between objects (eg magnetism)• Gravity: pull towards Earth• Buoyancy: upwards push of object while it is

floating• Friction: force applied to the surface of an object

when it moves against the surface of another object

The Earth and Our Solar System

• Earths structure• Importance of gases in atmosphere

(greenhouse and ozone gases)• Night and day, seasons• Major features of universe (galaxies, stars,

nebulae, solar systems)