units, variables & practicals

Units for Temperature, temperature change, energy, mass, density, distance,area, volume, speed, acceleration, force, pressure- and specific heat capacity

°C, Kelvin (K), Joules (J), kg, (kg/m3), (m), m2, m3, m/s, m/s2, N, Pa,(J/kg°C,

How can you set up a practical to investigate Hooke’s law?

Puta weighted stand with a clamp attached and hang a spring from it. Measure the length of the spring and ensure other control variables. Add a mass and measure the extension and add another one after another (no fewer than 6). Repeat the experiment and figure out the mean. Plot the results andit should indicate that force is proportional to extension until its elastic limit is reached.

How can you investigate thermal energy transfer by conduction?

Attach beads to one half of a metal bar using wax, then heat the other end with a Bunsen burner. As heat travels along the bar through conduction, the wax melts, causing the beads to fall off, starting from the heated end. This demonstrates conduction.

can you investigate thermal energy transfer by convection?

Place potassium permanganate crystals in cold water on one side of a beaker. Heat that side with a Bunsen burner. As the water warms, the crystals dissolve, creating a purple solution that moves through the water, tracing the convection currents.

How can you investigate thermal energ transfer by radiation?

Place an empty Leslie cube on a heatproof mat, fill it with boiling water, and let it warm up. Use a thermometer to check the temperature of each face (they should all be the same). Then, use an infrared detector at a set distance from each face and record the detected radiation. You'll find more infrared radiation from black, matte surfaces than from white or shiny ones.

When you’re asked how you would do a practical, what do you need to keep in mind?

State the equipment, describe the practical and state risks and how they could be minimised, plus all the independant, dependant and contol variables.

Describe a practical to invesigate hoe insulating materials can be charged by friction.

Get two rods, one polythene and one acetate. Rub both with a cloth duster:

• Polythene rod → Negative charge, cloth positive.

• Acetate rod → Positive charge, cloth negative.

Suspend a known charged rod and bring the test rod close:

• Repulsion → Same charge.

• Attraction → Opposite charge.

What is independant variable, dependant variable and control variable?

Ind: Variable you change

Dep: Variable you measure

Con: To ensure a fair test