Thermal Properties Of Matter — study notes

Turn a stove up under a small saucepan of water and it's steaming within a minute. Do the same under a full bathtub and barely anything happens. Same flame, same time, wildly different outcome — and the reason comes down to one quantity every O-Level physics student needs to pin down.

Why Mass and Material Both Decide How Fast Something Heats Up

Every substance is a swarm of particles jostling and bonded together, and that jostling stores what physicists call internal energy. Pump energy in and those particles either speed up or push further apart. But two objects made of different stuff, or holding different amounts of the same stuff, soak up that pumped-in energy at completely different rates.

To pin a single material down, we use specific heat capacity, symbol c: it tells you how many joules push exactly one kilogram of that substance up by one degree Celsius. Water sits near the top of the scale at 4200 J/kg°C, which is exactly why oceans warm and cool so sluggishly compared with dry sand nearby — each kilogram of seawater has to soak up huge amounts of energy before its temperature budges at all. Combine mass, the size of the temperature jump you want, and c, and out pops the governing equation: Q = mcΔT, where Δ simply means "change in".

Worked Example — Heating Cooking Oil

1. A cook heats 1.5 kg of oil from 18 °C to 98 °C. The oil's specific heat capacity is 2000 J/kg°C.
2. Find the temperature change first: ΔT = 98 − 18 = 80 °C.
3. Substitute into Q = mcΔT: Q = 1.5 × 2000 × 80.
4. Multiply through: Q = 240 000 J (240 kJ) of energy transferred into the oil.

Skip step 2 and plug in 98 directly, and you'd get 294 000 J — over 50 kJ too high — because ΔT must always be a difference, never a raw thermometer reading.

That's the heating half of the story. What happens once a substance actually starts melting or boiling — where all that energy goes once the thermometer stops climbing — plus the full set of worked examples, an audio walkthrough and the practice worksheet, are waiting in the full lesson below.