Most of what you pour, pump or breathe is a mixture

Word	What it means
Fluid	Anything that flows: a liquid or a gas.
Particle model of matter	The idea that all matter is made of tiny particles, always moving, with spaces between them, that attract each other.
Pure substance / mixture	Made of only one kind of particle, like distilled water or sugar / two or more substances together, each keeping its own properties.
Mechanical mixture / suspension	A mixture whose parts you can see, like trail mix / a cloudy liquid whose bits settle out if it stands, like muddy water.
Solution	A mixture that looks like one substance: salt water, vinegar, air.
Solute / solvent	What dissolves / what it dissolves in. In salt water, salt is the solute and water the solvent.
Concentration	How much solute is in a given amount of solution; here, grams per 100 mL.
Solubility / saturated	The most solute that dissolves in a given amount of solvent at a given temperature / holding all it can. An unsaturated solution could hold more.
Viscosity / flow rate	Resistance to flowing: honey's is high, water's low / how fast a fluid flows.
Mass / volume / density	The amount of matter, in grams / the space something fills, in mL or cm³, which are the same size / mass per unit of volume, in g/mL or g/cm³.
Buoyancy	The upward push of a fluid. An object floats if it is less dense than the fluid.
Pressure / pascal (Pa)	Force per unit of area / its unit: 1 Pa is a force of 1 newton (N) on each square metre (1 N/m²); 1 kPa = 1000 Pa.
Compressibility	How much something can be squeezed into less space.
WHMIS	The Workplace Hazardous Materials Information System: Canada's hazard labels and safety data sheets for workplaces and school labs.

Kind	What you see	Examples
Pure substance	One substance, the same all through	Distilled water, sugar, baking soda, copper wire
Mechanical mixture	Different parts you can see and pick apart	Trail mix, gravel, a salad
Suspension	Cloudy; the bits settle out if it stands	Muddy water, orange juice with pulp
Solution	Looks like one substance, even under a microscope	Salt water, vinegar, tap water, air

Why a solution looks like one substance. The solute breaks into particles far too small to see, which spread evenly between the solvent's particles. The two kinds attract each other, so the solute never settles out. Dissolved sugar has not vanished: boil the water away and it is still there.

Worked: sorting a kitchen. Tap water carries dissolved minerals, so it is a solution, not a pure substance. A bottle labelled “shake well” is usually a suspension. Water is not the only solvent: nail polish remover dissolves nail polish, which water cannot.

WHMIS 2015. Hazardous products at work and in labs carry pictograms: black symbols in a red-bordered diamond. Four you will meet in school:

Pictogram	Means	So you
Flame	Catches fire easily	Keep it away from heat, sparks and flames
Corrosion	Burns skin and eyes; eats into metal	Wear goggles and gloves
Skull and crossbones	Poisonous, even in small amounts	Never taste it; wash your hands after
Exclamation mark	Can irritate skin, eyes or lungs	Avoid contact; use it where air moves

The signal word Danger marks the more severe hazards, Warning the less severe, and the safety data sheet (SDS) gives the details. At home too: read the label first, never mix cleaners — bleach and ammonia together give off poisonous gases — and do not pour chemicals down the drain.

concentration = grams of solute per 100 mL of solution

Worked: which is stronger? Drink A has 15 g of sugar in 250 mL. Drink B has 12 g in 150 mL. Scale each to 100 mL:

A: 15 ÷ 250 × 100 = 6 g/100 mL  ·  B: 12 ÷ 150 × 100 = 8 g/100 mL

B is more concentrated, though it holds less sugar: there is less water sharing it.

Worked: reaching saturation. About 36 g of salt dissolves in 100 mL of water at 20 °C. Stir in 50 g and about 50 − 36 = 14 g stays on the bottom, however long you stir. The solution is saturated.

Temperature changes solubility. Most solids dissolve better in hot water: water near boiling holds more than twice as much sugar as water at 20 °C. Salt barely changes, to about 39 g at 100 °C. Gases go the other way: they dissolve less in warm water, which is why warm pop fizzes over and a warm lake holds less oxygen for fish.

Speeding it up. Heating, stirring, and breaking the solute into smaller pieces, which exposes more surface, all make it dissolve faster. Granulated sugar beats a sugar cube. Of the three, only temperature changes how much can dissolve in the end.

Mining by dissolving. Deep layers of salt and potash, a potassium salt used in fertilizer, can be mined by pumping water down a well to dissolve them, then pumping the solution up and evaporating the water. Some Saskatchewan potash mines work this way.

Viscosity. In a thick fluid the particles attract each other strongly, or are large and tangled, so they slide past each other slowly. Warming gives them more energy: warm syrup pours faster than cold. In a motor oil grade such as 5W-30, the W stands for winter, and the lower that first number, the better the oil flows in the cold.

Oil sands. Bitumen, the oil in Alberta's oil sands, is too viscous to flow into a well, and most of it lies too deep to dig up. One method pumps steam down one well; the heated bitumen thins, flows into a second well below, and is pumped up. For a pipeline, it is thinned with lighter oils.

density = mass ÷ volume  ·  d = m/V

Worked: a liquid. 50.0 mL of a liquid has a mass of 46.0 g. d = 46.0 g ÷ 50.0 mL = 0.92 g/mL. Water is 1.00 g/mL, so this liquid floats on water, as cooking oil does.

Worked: a solid. A metal block has a mass of 54 g. Lowered into a graduated cylinder, it raises the water from 50 mL to 70 mL, so its volume is 70 − 50 = 20 mL, or 20 cm³. d = 54 ÷ 20 = 2.7 g/cm³, the density of aluminum.

Substance	Approximate density (g/mL or g/cm³)
Air	0.0012
Cooking oil	0.92
Fresh water	1.00
Ocean water	1.03
Aluminum	2.7
Iron	7.9
Gold	19.3

A gas's particles are far apart, so air has very little mass per millilitre. Water is unusual: ice is less dense than liquid water, so it floats.

Changing a fluid's density. Dissolving salt packs more mass into each millilitre, so salt water pushes up harder: a fresh egg sinks in tap water but floats in strong salt water. Cold, salty ocean water sinks beneath warmer, fresher water, driving slow currents deep in the ocean.

pressure = force ÷ area  ·  p = F/A

Worked: snowshoes. A student weighs 600 N. In boots, her weight rests on about 0.06 m² of sole: p = 600 ÷ 0.06 = 10 000 Pa, or 10 kPa. On snowshoes with a total area of 0.30 m²: p = 600 ÷ 0.30 = 2000 Pa. Five times the area gives one-fifth of the pressure, so she stays on top of the snow. A stiletto heel does the opposite: the same weight on a tiny area can dent a wooden floor.

Compressibility. Push the plunger of a sealed syringe full of air and it moves: gas particles have room to crowd closer. Full of water, it barely moves. Air in a bike tire compresses to soak up bumps; a fire extinguisher holds carbon dioxide squeezed under pressure. Where a push must be passed along, not soaked up, a liquid is used, as in car brakes (Unit D).

Technology	How it moves the fluid
Pipeline	Pump stations along the line push oil or natural gas forward; valves open, close or limit the flow
IV drip in a hospital	The bag hangs above the arm, so gravity moves the fluid into a vein; a clamp controls the flow rate
The heart	A living pump; its valves let blood through in one direction only

• Calling a solution a pure substance because it looks like one. Tap water, vinegar and air are solutions.
• Saying stirring makes more dissolve. It only makes it dissolve faster; temperature changes how much can dissolve.
• Comparing grams without scaling to 100 mL. 12 g in 150 mL is 8 g/100 mL.
• Mixing up viscosity and density. Cooking oil is thicker than water, yet less dense, so it floats.
• Dividing the wrong way. The unit tells you: g/mL is grams ÷ millilitres, and N/m² is newtons ÷ square metres.
• Saying heavy things sink. A huge log floats and a small pebble sinks: floating depends on density, not weight.