Scientific Skills: Estimating & Measuring

Scientific Processes: Scientific Skills

• Scientific skills include estimating, measuring, observing, classifying, and handling data.

Estimating

• Estimating involves making a sensible or educated guess of a quantity using the correct unit, for example, estimating time in hours, seconds or minutes.

Measuring

• Measuring involves choosing the correct instrument to find the actual measurement of an object as specified by units.
• Temperature is measured by a thermometer.

Quantities and Units of Measurement

• Time is measured in hours, seconds, and minutes using a watch, clock, or stopwatch.
• Length is measured in centimeters (cm), millimeters (mm), kilometers (km), or meters (m) using a ruler or measuring tape.
• Temperature uses Kelvin, degrees Celsius (°C) and a thermometer.
• Volume is measured in cubic centimeters (cm³), cubic millimeters (mm³), or milliliters (ml³) using a measuring cylinder.
• Force is measured in Newtons (N) using a force meter, spring balance, or Newton meter.
• Current is measured in Amperes (A) using an ammeter.
• Voltage is measured in Volts (V) using a voltmeter.
• Resistance is measured in Ohms (Ω) using an ohmmeter.
• Mass is measured in tones (t), kilograms (kg), or grams (g) using a triple beam balance, top-pan balance, kitchen scale, bathroom scale, level arm scale, electronic pan scale, or balance scale.

Accurate Measurement Tips

• Using the correct instrument, the correct unit and understanding the scale on the instrument, such as a ruler, are techniques for accurate measurement.
• Ensure your eye is level with the object to avoid parallax error.
• When using a measuring cylinder, ensure your eye is at the meniscus level.
• Adjust the instrument to zero before use, for example, a bathroom scale.
• Repeat the experiment more than twice and calculate the average to improve accuracy.

Conversion of Units

• Conversions involve changing units from one to another.
• 1 cm is equal to 10 mm.
• 1/2 cm is equal to 5 mm.
• 1 m is equal to 100 cm.
• 1/2 m is equal to 50 cm.
• 1 km is equal to 1000 m.
• 1/2 km is equal to 500 m.
• 1 m is equal to 1000 mm.
• 1/2 m is equal to 500 mm.

Area

• Area of a rectangle is length × breadth, and area of a square is side × side.
• Units of area include square centimeters (cm²) and square meters (m²).
• Area consists of Square Units.

Volume

• Volume of a cuboid is length x breadth x height.
• Volume of a cube: side x side x side.
• Cubic centimeter (cm³) and cubic meter (m³) are units to measure volume.
• Volume is how much 3D space is occupied, and is measured in cubes.
• Volume consists of Cube Units.

Practical Investigation Procedures

• Identify the question or state the aim of the investigation.
• Form a hypothesis or predict the outcome.
• Design the experiment and plan how to conduct it, including listing materials needed.
• Making a test fair means controlling variables so that only the variable under investigation causes the difference.

Variables in Investigations

• A dependent variable is what you observe in an investigation and changes depending on the independent variable.
• An independent variable is something you change in an investigation.
• A control variable refers to quantities a scientist wants to remain the same or unchanged throughout the experiment.
• Conducting the experiment to observe and record results is the next step.
• The appropriate conclusion should link to the investigation's aim or the hypothesis.

Practical Investigation Steps

• State the aim of the investigation.
• Make a hypothesis (prediction).
• List the procedures (methods).
• List Materials needed.
• Make sure to make a fair test.
• The experiment is then carried out.
• Next record findings.
• Finally make a conclusion.

Proportionality

• Direct proportionality means when one quantity increases, the other increases at the same rate.
• Indirect proportionality means when one value increases, the other value decreases at the same rate.

Observing

• Observing is using the five senses to gather information, and to make descriptions and draw conclusions.

Examples of Observations Using Senses

• Taste with a tongue will determine if something is salty, sweet, bitter, sour, or tasteless.
• Touch with hands will determine if something is smooth, rough, dry, wet, hot, or cold.
• Smell with a nose will determine if something smells like smoke, rotten, or decaying.
• Hearing with ears will determine if something sounds loud, breaking, drumming, or singing.
• Sight with eyes will determine the color, states, shape, size, or movement.

Classifying

• Classifying groups things based on similar properties (e.g., water, hydrogen, brick, book, milk, carbon dioxide, table, smoke, oil, petrol, and oxygen).

Recording

• Recording involves noting findings from practical investigations or experiments.
• Findings will be recorded in a table with heading in each column with the name of physical quantity and appropriate unit.

Handling and Presenting Data

• Handling data means to locate, organize, and present results clearly for scientists and non-scientists.
• Ways to present results are with graphs, line graph, bar graph, histogram and pictograph.
• Including pie charts, posters, pictures, charts, as well as drawings.

Graph Plotting

• Identify two variables: dependent and independent.
• Dependent variable is tested or measured, always plotted on the Y-axis.
• Independent variable is changed or controlled, always plotted on the X-axis.
• The graph's heading describes the dependent vs. independent variable relationship.
• Axes will have labels with the name of physical quantity and appropriate unit.
• Axes scales must start at zero.
• There MUST be axes scales.
• Anomalous or inconsistent results indicate experimental error.

Possible Sources of Error in Experiments

• Error of parallax.
• Adjust the instrument to zero.
• Taking wrong readings.
• Reading volume of liquid above the meniscus.

Evaluation of Results

• The evaluation involves using scientific knowledge to interpret results and draw appropriate conclusions from the practical investigation.

Observations and Conclusions Examples

• If a white solid object changes to a colorless liquid, the conclusion is that the ice is melting.
• If you feel water getting warmer, the temperature is rising.
• If bubbles form in water, the water is boiling.
• If steam is seen above the beaker, water vapor is condensing.

Matter: Chemical and Physical Changes

• Chemical change creates a new substance.
• Physical change does not create a new substance.

Chemical Change

• New substances are formed with different properties.
• It is a permanent change and not easily reversed.
• An energy change is always involved such as temperature increases or decreases.
• Examples include digestion and cooking food, burning, photosynthesis, rusting, and decomposition.

Physical Change

• No new substances are formed.
• It is a temporary change and easily reversed.
• Energy is sometimes involved.
• Examples include a change in size or shape (expansion and compressibility) as well as a state change (melting, freezing, condensation, evaporation) and making a solution.

Chemical Change Equation

• Reactants yield products.
• Wood + oxygen produces ashes, magnesium + oxygen yields magnesium oxide.

Other Chemical Changes

• Food and oxygen give carbon dioxide, water, and energy through natural respiration in plants and animals.
• Photosynthesis, carbon dioxide and water yield carbohydrates and oxygen.
• Fermentation involves yeast and sugar producing alcohol and carbon dioxide.

Properties of Water

• Colorless, odorless, and tasteless.
• Boils at 100°C.
• Melts at 0°C.

Matter

• Matter is anything with mass and occupies space.
• Matter exists in three states: solid, liquid, and gas.

Kinetic Particle Theory of Matter

• All matter is made up of tiny, invisible particles in constant motion.
• Particles have a force of attraction between them.
• Particles have kinetic (movement) energy.
• There is spacing between the particles.
• Particles collide against each other.

Arrangement of Particles

• Solid particles are tightly packed and vibrate at a fixed position, strong force of attraction, as well as less energy.
• Liquid particles are loosely arranged and slide over each other, particles have more energy than solid.
• Gas particles are far from each other and move freely, large space between particles, have weak attractive force between particles.

Changes in States of Matter

• Melting (fusion) is a change from solid to liquid with heating.
• Evaporation (vaporization) is a change from liquid to gas.
• Condensation is a change from gas to liquid with cooling.
• Freezing (solidification) is a change from liquid to solid with cooling.
• Boiling is a change from liquid to gas and Sublimation.
• Sublimation- Is change from solid to gas or from gas to solid without undergoes the liquid state.

Examples of Sublimation

• Examples of substances are Carbon dioxide, Iodine, Sulfur, Ammonium chloride and Naphthalene sublimation.
• Expansion is an increase in size with heating, opposite of Contraction with cooling.
• Heated particles get energy from heat, they move faster and further apart.

Expansion in Solids

• Solids have limited expansion because particles are tightly packed (e.g., ball and ring).
• Bimetallic strips of 2 metals are used in thermostats for devices because of their different expansion rates when heated.

Expansion in Liquids

• Liquids expand at different rates, with ethanol expanding more than other liquids; it is used in thermometers with mercury.

Expansion in Gases

• Gases expand more than solids and liquids.
• Expansion and contraction of air is a result of heating and cooling (e.g., hot air balloon).
• Gases expand because particles are spaced apart, have more energy, as well as weak attraction.

Compressibility

• Compressibility is to push particles together and fill spaces between them.
• Solids are difficult to compress, as their particles are tightly packed.
• Liquids cannot be compressed due to minimal free particle space.
• Gases are compressible because particles are far apart.

Diffusion

• Diffusion is the movement of particles from high to low concentration areas.
• Diffusion cannot occur and is slow due to tightly packed particles in solids and liquids.
• Diffusion in gas is fast because particles are far apart.

Examples of Diffusion

• It includes smells of food, perfume, and air fresheners.

Building Blocks of Matter

• Atoms are elements broken down into simpler substances by chemical means.
• Elements contain identical atoms (e.g., H, Ne, K, Na, Cl).
• Molecules consist of ≥2 covalently bonded atoms (e.g., H2O, CO2).
• Compounds are substances with ≥2 chemically combined elements.

The Periodic Table

• The periodic table arranges elements and classifies them by properties into periods and groups.
• Semi-metals have properties of both metals and non-metals along the zigzag line.

Atom Structure

• The atom's three subatomic particles are protons, electrons, and neutrons.
• Electrons orbit the nucleus in energy levels or shells.
• Chemical reactivity is determined by the outer shells only.
• When atoms take part in a chemical reaction only the outer shell takes part.

Types of Bonding

• The three types of bonding include covalent, ionic and metallic.
• Atom share, gain or lose electrons to obtain a stable outer shell, gas structure, as well as gain a full outer shell.
• The atomic number is the number of protons or electrons.
• Mass number = proton number + neutron number.
• Electron configuration describes their arrangement in an element.

Bonding

• Covalent bonding is sharing electrons to obtain an outer shell that is full.

Composition of Air

• Air consists of about 78% nitrogen, 21% oxygen, 0.9% argon, 0.03% carbon dioxide, and 0.07% other gases.
• Nitrogen does not take part in chemcial reactions.

Nitrogen

• Nitrogen Advantages include slowing down burning, preventing overly vigorous oxygen reactions.

Uses of Nitrogen

• Nitrogen is used as a petrol unreactive blanket in storage tanks and freezing food, manufacture ammonia, nitric acid and nitrates fertilizers.
• Gases are dissolved in water and aquatic plants and animals use oxygen in water for respiration.

Air Support

• Air and oxygen support combustion.
• Argon fill house hold bulbs.

Oxygen

• Oxygen is generally colorless, tasteless, odorless gas that is slightly denser than air, the boiling point is -183°C.
• Oxygen supports combustion.
• In the laboratory, heat potassium permanganate or a mixture of potassium chlorate and manganese dioxide to make oxygen.
• Test for Oxygen by putting A glowing splint in to container and Oxygen relights Oxygen.

Oxygen Chemical Properties

• Oxygen reacts with metals to form oxides and non-metals to form dioxides.

Safety Precautions for Reactions

• Appropriate safety precautions should be used that there are safety goggles to be worn to protect eyes.
• Not breathing in gases produced that they may be poisonous.

Respiration & Combustion

• Respiration is a slow reaction that produces energy.
• Carbon dioxide, water and energy are produced by respiration and water through chemical reaction.
• The two industrial and medical uses are medical purposes for patients with breathing problems.

Ozone

• Ozone molecule that consists of 3 oxygen atoms.
• Protect the earth from harmful ultraviolet rays that cause skin cancer.

Carbon Dioxide

• Carbon dioxide is a products of burning fuel (carbon dioxide, water and energy are the products of the process).

CO2 Properties

• It is colourless and odorless gas and soluble in water, also denser than air.
• Carbon dioxide dissolves in lime water (calcium hydroxide) to form calcium carbonate and water.

CO2 uses

• CO2 is used in fire extinguishers against combustion.
• The greenhouse effect means raising the levels of CO2 causing global warming.

Carbon Dioxide

• Combustion releases carbon dioxide into the atmosphere.
• Rising carbon dioxide levels increases temperature and sea level.

Suggestions to Reduce Carbon Emissions

• Plant trees to use carbon dioxide by growing by photosynthesis and avoid both cutting down trees plus burning fossil fuels
• Also use alternative sources of energy.

Force

• Force is a push or pull, measured with a spring or newton balance in newtons (N).

Line and Arrow

• Line and arrow: length indicated size and arrow indicates direction.

What Force Can Affect

• Forces can cause objects to move or stop, change an objects size, direction, speed, and shape.
• Forces can cause have electric effects when charging rulers by rubbing.

Types of Forces

• Attractive forces pull together (e.g. gravitational), and repulsive forces push apart.
• Weight is the force of gravity on an object and there are many types of forces like gravity, friction, electronic and magnetic.
• Contact is a force that acts when objects are touching each other.
• Noncontact the force that acts over a distance.

Friction

• Friction opposes movement.
• Friction slows down and stops the momentum of object.
• Smooth and rough surfaces affects friction.
• The weight or mass affects the friction.
• Friction prevents cars from skidding, helps us stop and walk and to hold pens.

Advantages of Friction

• Without Friction cars would not be able to move forward.
• Disadvantage of Friction, is causing damage and overheating the object.

Reducing Friction

• We may reduce friction by making the face smoother, using materials, as well as making an object more streamlined.

Concluding Friction

• Solids have the most friction due to tightly packed particles, and gases have the least.
• To overcome air resistance in air travel must be stream lined.

Mass and Weight

• Mass: amount of matter in an object, weight: gravity that pulls an object to centre of the earth or grams or Kilograms and Instruments and units of weight is newtons.

Mass vs Weight

• Weight is the force of gravity that pulls an object toward the centre of the earth and measured in Newtons (N). Whereas, Mass, is the amount of matter.
• Gravitational field strength is a constant force of 10N on 1kg of mass on or near Earth and weight changes on the moon but mass stays constant.

Work

• Work is force applied over distance, same direction and is measured in joules.

What Work Is

• Work is done when moving an object.

Energy Types

• The two types of energy are force x distance x energy, there are many forms of energy.

Calculating Energy

• When work is done with body of energy, energy is transferred.
• Energy is measured in Joules (J).

Types of Source of Energy

• Sources of energy include chemical potential storage, nuclear energy, kinetic and also electrical charges.
• Energy can be converted not created.

Two Types of Energy Source

• Renewable resources energy types (solar, wind, water) energy.
• Non-renewable energy sources (nuclear energy and fossil fuels).

Electricity

• Positive (+) and negative (-) charges are electrical charges and are in every atom as well as electrical charges.

Protons and Electrons

• Protons = positive and Electrons = negative charges.