Science 4

Garbage does not disappear: a truck takes it to a real place, such as a landfill, a recycling centre or a composting facility.

When the garbage truck drives away, your waste goes somewhere you could visit.

Dangerous materials are materials, natural or processed, that can harm people's health: drain cleaner and bleach are processed, and some wild mushrooms are natural.

A dangerous material can hurt you if you touch it, swallow it, breathe it in or get it near a flame.

A landfill is a large site where garbage is buried in layers, and burying or burning waste can harm the environment: rotting food scraps in a landfill make methane gas.

At a landfill, garbage is spread out, packed down and covered with soil, layer after layer.

Hazard symbols identify dangerous materials: an exploding container means explosive, a flame means flammable, a bony hand means corrosive, and a skull and crossbones means poisonous.

Canada uses four pictures on household products.

Waste can be a solid, a liquid or a gas: an empty box is solid waste, dirty water from washing paint brushes is liquid waste, and smoke from burning leaves is gas waste.

When people think of waste, they usually picture a garbage bag full of solids.

A non-contact force acts between objects that are not touching: a magnet pulls a paper clip toward it across a gap of air.

Most forces you met before were contact forces: a push, a kick, friction.

Gravity on Earth is a non-contact force that pulls objects toward the ground: a dropped apple falls even though nothing touches it.

Let go of an apple and it falls.

Magnetic force attracts or repels magnetic materials, which contain iron, cobalt or nickel: a magnet picks up a steel nail but not an aluminum can.

Only some materials are magnetic.

Gravity affects every object on Earth: a ball tossed straight up slows, stops for an instant at the top and falls back down.

Toss a ball straight up and watch closely.

The strength of a non-contact force decreases as objects get farther apart: a paper clip jumps to a magnet only when it is close.

Move a magnet slowly toward a paper clip on a table.

Earth scientists call Earth's four systems the spheres: the lithosphere is the rock and soil, the atmosphere is the air, the hydrosphere is the water, and the biosphere is all living things.

Each name ends in sphere, a word for a ball, because each system wraps around the whole planet.

Earth's surface is warmed by the Sun, and most organisms need that warmth and energy to live, move, grow and change: plants catch sunlight to make food, and animals eat the plants or other animals that did.

Without sunlight, Earth's surface would freeze and plants could not make food, so animals would have nothing to eat.

Natural resources are materials from nature that are used to meet human needs: air, water, soil, minerals, metals, forests and organisms.

Look around a classroom: the desk's wood came from a forest, the window's glass from sand, the pencil's grey core from a mineral called graphite, the wiring from copper, a metal, and your lunch from plants and animals.

The lithosphere is the outer layers of Earth's surface, and it is made of rocks: the Rocky Mountains, the prairie under its soil, and the pebbles in a schoolyard are all part of it.

Dig down through a garden and you pass through the lithosphere: dark soil on top, then sand or clay, then solid rock far below.

Sunlight is more direct at the equator than at the poles: near the equator the noon Sun is high overhead, while near the poles its light comes in low and slanted.

Near the equator, the Sun at noon stands almost straight overhead, and its light falls straight onto the ground.

Organisms are living things that respond to stimuli, and they include plants, humans and other animals.

An organism is any living thing: a spruce tree, a magpie, a ladybug or you.

Plants detect stimuli such as light, gravity, temperature and touch, and their responses help them grow and survive.

Plants have no eyes or ears, but their cells detect changes around them.

Organisms can be classified in different ways, by appearance, by habitat or by structures, and each way makes different groups: a frog and a duck share a wetland habitat, but by structures the duck groups with the birds.

Sorting by appearance groups living things by colour, size or covering: fur, feathers, scales or bare skin.

Plants sense light and grow toward it, which helps them catch more sunlight to make food: seedlings on a windowsill lean toward the glass.

A plant that gets more light can make more food and grow strong.

Local plants and animals can be found and classified on a walk: a schoolyard may hold dandelions, spruce trees, magpies, ants and earthworms, sorted by appearance, habitat and structures.

Take a notebook outside and list every living thing you find, with a quick sketch.

The universe includes all of space and everything in it: Earth, the Moon, the Sun, the other planets, all the stars and the space between them.

The universe is everything there is: every planet, star and galaxy, and the space in between.

A constellation is a group of stars that appears to form a shape, like Orion, whose bright stars look like a hunter with a belt of three stars in a row.

People join the dots of the night sky into pictures, the way you might see shapes in clouds.

The Sun is a star, and many other stars have planets travelling around them, just as Earth and the other planets travel around the Sun.

The Sun looks huge and blinding only because it is so close, about 150 million kilometres away.

Constellation names come from many sources, so the same stars carry different names: the Big Dipper is part of the Great Bear in stories from ancient Greece, six brothers and their little sister in a Blackfoot story, and Tukturjuit, the caribou, for Inuit.

Different peoples looked at the same stars and saw shapes from their own lives and stories.

The Moon travels around Earth, and other planets have moons of their own: Jupiter has four large moons that can be seen with binoculars.

A moon is an object that travels around a planet.

Design processes include understanding the problem, forming ideas, planning, creating, analyzing, testing and troubleshooting, and designers often loop back through the steps.

Designers rarely go straight from an idea to a finished product.

Feedback helps make sure all needs are considered during design: a younger student trying a new coat hook may show that it is too high to reach.

A designer knows what the design was meant to do, but users find out what it actually does.

Understanding the problem means finding out exactly what the design must do and for whom: 'carry six library books up the stairs without dropping any' can be designed for, but 'carry books' cannot.

Ask who will use it, where, and what would count as success.

Helpful feedback names something that works, asks a question and suggests one specific improvement.

Start with what works: the handle is comfortable.

Forming ideas, called ideating, means coming up with many possible solutions before choosing one, because the first idea is rarely the best.

Sketch at least three quite different ideas quickly, without judging them yet.

Data can be descriptive and expressed in words, which is called qualitative data: 'the leaves are yellow with brown spots' and 'the water smells like rotten eggs'.

Qualitative comes from quality, what something is like.

The Système international d'unités, or International System of Units, abbreviated SI, is the common system of measurement used to share data: metres for length, kilograms for mass, seconds for time and degrees Celsius for temperature.

SI comes from its French name.

Data can be measured and expressed in numbers and counts, which is called quantitative data: 'the plant is 14 centimetres tall' and 'we counted 23 ants on the sidewalk'.

Quantitative comes from quantity, how much or how many.

Data in SI units can be compared and interpreted directly: a seedling that grew from 3 cm to 11 cm grew 8 cm, twice as much as one that grew from 5 cm to 9 cm.

Because both measurements use the same unit, the numbers can be subtracted and compared at once.

Descriptive and expressive oral narratives include numbers or counts: a story told by an Elder about a hard winter may tell how many days a blizzard lasted and how many caribou passed.

Spoken stories carry data too.