Science 5

The particle model of matter says that all matter is made up of particles far too small to see: a desk, the air and the water in a glass are all made of them.

A glass of water holds more water particles than there are glasses of water in all the oceans on Earth.

Physical properties of matter include its state, mass, volume, density and compressibility, which can be observed or measured without changing what the matter is.

State tells whether matter is a solid, a liquid or a gas.

Particles of matter have spaces between them, even in a solid rock.

In a solid the particles are packed close together, yet there is still space between them.

Mass is the amount of matter in a solid, liquid or gas, measured in grams (g) and kilograms (kg): a paper clip has a mass of about 1 g, and a litre of water about 1 kg.

A kilogram is 1 000 grams.

Particles of matter are always moving, in solids as well as in liquids and gases: in a solid they vibrate in place, in a liquid they slide past each other, and in a gas they fly about.

Nothing anywhere is completely still.

Buoyant force is an upward force that a fluid exerts on anything placed in it, opposing the object's weight: a beach ball pushed under water is pushed back up.

Water is not something an object just sits in.

Forces change a flyer's speed: more thrust than drag makes it speed up, and more drag than thrust slows it down.

A plane taking off has its engines at full power, so thrust is much bigger than drag and it gains speed down the runway.

Humans rely on energy resources to fulfill energy needs, and the electricity at an outlet came from a resource somewhere else: lights, computers and fridges run on electricity, furnaces burn natural gas, and buses burn diesel.

Think about one school day.

Whether an object floats or sinks is a contest between two forces: it floats on the surface when the buoyant force equals its weight, and it sinks when the buoyant force is less than its weight, even with the object all under water.

Weight, the pull of gravity, acts downward; the buoyant force acts upward.

Forces change a flyer's altitude: more lift than weight makes it climb, and less lift than weight makes it sink, so a gull folds its wings to dive and spreads them to level out.

Lift and weight decide the vertical movement.

Weather is the short-term conditions experienced in a region: temperature, wind speed and direction, amount of sunlight, precipitation, humidity and cloud cover.

Weather is what you check before going outside: today is 8°C, with a cold north wind, rain showers, damp air and grey clouds.

Climates depend on factors including geographical location, landforms, altitude and proximity to bodies of water.

Geographical location means how far a place is from the equator, which decides how direct its sunlight is.

Thermometers measure temperature, rain or snow gauges measure precipitation, and hygrometers measure humidity, how much water vapour is in the air.

A thermometer should hang in the shade, out of direct sunlight, or it reads too warm.

Conservation agriculture is a sustainable way of farming that responds to local climate and weather events and is adapted to the plants and animals farmed, so the soil and water stay healthy for future harvests.

Sustainable means the farm can keep producing year after year without wearing out its soil or water.

Climate is the long-term weather patterns of a region over a period of at least 30 years, worked out from many years of weather records.

Weather is measured day by day; climate comes out of averaging those measurements over decades.

Vital biological processes keep complex organisms alive: movement, nutrition, respiration, growth and reproduction.

Nutrition is getting food and the materials in it; respiration means taking in oxygen and getting rid of carbon dioxide; movement is moving the body or its parts; growth is getting bigger and repairing; reproduction is making offspring.

Plant transport systems include xylem and phloem, bundles of tiny tubes that run through the roots, stems and leaves.

Like the blood vessels of an animal, these tubes reach every part of the plant.

Vital biological processes in complex organisms are carried out by biological systems, groups of organs that each do one job together, and the systems rely on each other.

The digestive system is not just the stomach: the mouth, stomach, intestines, liver and pancreas each do part of one job.

Xylem transports water and nutrients from the roots up to the rest of the plant: a celery stalk standing in coloured water shows coloured dots, the cut ends of its xylem tubes.

Water taken in by the roots climbs through the xylem to the stem and leaves, carrying dissolved minerals from the soil.

Humans and many other animals have internal biological systems that include the digestive, respiratory, circulatory and musculoskeletal systems.

These systems are inside the body, which is why they are called internal.

Astronomical phenomena are observable events that happen among objects in space, such as the seasons, Moon phases, eclipses, equinoxes and solstices, the length of day and night, and auroras.

Each one involves the Sun, Earth or the Moon, or particles from the Sun reaching Earth.

Observations and interpretations of astronomical phenomena can inform daily living: the Sun's daily path sets the day, the Moon's cycle the month, and the seasons the year's work.

Before clocks and printed calendars, people everywhere planned by the sky.

Many astronomical phenomena have predictable patterns and cycles: Moon phases repeat about every 29 and a half days, the seasons every year, and day and night every 24 hours.

Because the motions of Earth and the Moon are regular, these events can be predicted years ahead.

Observations of the sky are applied to planting and harvesting crops: the Harvest Moon, the full Moon nearest the fall equinox, rises at nearly the same time for several evenings, giving farmers extra light to bring in their crops.

Usually the Moon rises about 50 minutes later each night, but around the Harvest Moon it rises only 10 to 20 minutes later each night in Canada, so several evenings in a row have moonlight right after sunset.

Some phenomena are cyclic and some are harder to predict: Moon phases, seasons, equinoxes and solstices repeat on a fixed schedule, while auroras depend on bursts of particles from the Sun and can be forecast only a short time ahead.

Sorting phenomena by how predictable they are shows what causes them.

Designing an artifact to meet a need starts with the need itself: who will use the artifact, what must it do, and how will you know it works.

Building first usually solves a problem nobody had.

Design can be used to create algorithms and translate them into code, and code is any language that can be understood by and run on a computer.

An algorithm is the plan: a sequence of steps written in everyday words.

Design can better meet needs through the development of multiple iterations: each version of an artifact is tested, and what the test shows shapes the next version.

An iteration is one round of designing, building and testing.

There are many ways to code, including visual block-based languages such as Scratch, where prepared chunks of instructions sit in drag-and-drop blocks that fit together like puzzle pieces.

Instead of typing commands, you snap blocks like move 10 steps or turn right together in order.

Design processes that support multiple iterations include enhancing, adding a new feature, and refining, improving a feature that is already there.

Adding a light to a bike helmet is an enhancement; making its strap easier to buckle is a refinement.

Phenomena are facts or events that can be observed, and some can be observed directly with the human senses: a thunderclap is heard, ice melting is seen, and wind is felt.

A phenomenon can be as ordinary as a puddle drying or as rare as an eclipse.

A variable is a condition or factor that can influence the outcome of an experiment: in a test of how fast ice melts, the amount of salt, the room temperature and the size of the ice cubes are all variables.

Anything that could change the result is a variable.

Representations of data can include all or some of the data: a graph of every trial shows how much the results varied, while a graph of averages shows only the typical result.

Both are honest if they are labelled, but they communicate differently.

Phenomena that cannot be directly observed with the human senses can be observed and measured with technologies: telescopes show faraway galaxies, microscopes show cells, and X-rays show bones inside the body.

Each technology extends a sense.

The manipulated, or independent, variable is the one changed on purpose to find its effect on the responding, or dependent, variable, which is measured: adding salt to one dish of ice is the manipulated variable, and the time to melt is the responding variable.

The manipulated variable is the cause being tested; the responding variable is the effect being measured.