Significant figures
2305 in scientific notation.
What is 2.305 x 103?
Heat being transferred from a saucepan handle to your hand when you pick it up.
What is conduction?
The factor that the power increases by due to a change in temperature from 350 K to 1540 K of a piece of metal.
What is 375?
Pf/Pi = Tf4/Ti4 = 15404/3504 = 375
Experiment: One chicken is injected with a growth hormone while another chicken is not injected. Both chooks are weighed after a year.
Variable: The mass of the chooks.
What is the dependent variable?
The heat per unit of mass needed to increase the temperature of a substance by one kelvin (or degree Celsius)
What is specific heat capacity?
4.62 + 9.3711
What is 13.99?
Hot water being added and heating up a cold bath.
What is convection?
The peak wavelength of a piece of steel at 3950 K. (Take b=2.898x10-3)
What is 733.7 nm?
λ = b/T = 2.898x10-3/3950 = 7.337x10-7
Experiment: A bug repellent is sprayed on one arm; the other arm is not sprayed. The number of bites is recorded after 2 hrs.
Variable: How the arm is treated (sprayed vs. not sprayed).
What is the independent variable?
A variable that the experimenter measures, which is predicted to be affected by the independent variable. Plotted on the vertical axis of graphs.
What is a dependent variable?
0.00002310 in scientific notation.
What is 2.310 x 10-5?
A microwave warming leftover lasagne.
What is radiation?
The mass of lead melted at a fixed temperature of 316°C if the amount of energy was 52 kJ. (Take Lf = 25.0 kJ kg-1 for lead)
What is 2.1 kg?
Q=mL, m = Q/L = 52/25 = 2.08
Experiment: Javier sleeps 9 hours the night before his science exam. His twin sister has the same exam and sleeps 6 hours the night before the test. Afterwards, they compare their scores.
Variable: How much study was done before the exam.
The number of cycles completed per unit time.
What is frequency?
2.2 x 3.83 in scientific notation.
What is 8.4?
A kettle heating water.
What is conduction and convection?
The specific heat capacity of a substance with mass 1420 g, initial temperature 296 K, final temperature 342 K, that was given 15.380 kJ of energy.
What is 2.35 x 10-1?
Q=mcΔT, c = Q/(mΔT) = 15.380/(1.42 x (342-296)) = 0.235
Experiment: One plant is given sunlight every day. Another plant is not given any sunlight. After 3 weeks, the height of the plants was measured.
Variable: The amount of sunlight.
What is the independent variable?
A change is amplified due to the effects of that change.
What is positive feedback?
0034 x 2.40 in scientific notation.
What is 8.2 x 101?
A stove heating water in a saucepan.
What is conduction, convection and radiation?
The total energy required to convert 2.4 kg of ice at 0.0°C to steam at 100°C. (Take Lf=3.34×105 J kg-1, Lv=2.26×106 J kg-1, c=4186 J kg-1 K-1)
What is 7.2x106?
Qtot = Qf + Qwater + Qv
Qwater = mc∆T = 2.4×4186×(100-0) = 1.0×106 J
Qf = mLf, Qv=mLv
Qtot = 2.4x3.34×105 + 1.0×106 + 2.4x2.26×106 = 7.2x106
Experiment: Group A exercises for a month. Group B does not exercise. They measure the amount of weight they gained.
Variable: The amount of junk food eaten by each group.
What is a controlled variable?
A measure of how much solar radiation is reflected by the Earth or by a particular surface.
What is albedo?