Motion & Forces
A horse runs 3200 m in 200 s. Calculate its average speed in m/s.
3200/200 = 16m/s
What is the type of energy that is stored in stretched or compressed objects
Elastic potential energy
What is the difference between artificial and natural selection?
Natural selection - natural process in the wild environment
Artificial selection - human made process
What is an endothermic and exothermic reaction?
Endothermic - absorbs heat
Exothermic - releases heat
What is the main source of genetic variation in a population?
mutations
The equation for calculating force is Force = mass x acceleration.
What are the units for each of these?
Force = N
Mass = kg
Acceleration = m/s2
The two calculations for energy are: E = mgh AND E = 1/2mv2
Which is for kinetic energy and which is for potential energy?
PE: E = mgh
KE: E = 1/2mv2
Name 2 conditions needed for fossilisation
Low oxygen, quick burial, presence of hard parts (bones/shells), away from scavengers, low temperatures
What are the 2 general equations for Neutralisation reactions?
acid + base --> water + ionic compound
acid + base --> water + carbon dioxide + ionic compound
Define 'vestigial structure' and give 2 examples
Features that were inherited from an ancestor but not longer needed in current species (e.g., tailbone, appendix, tonsils in humans, pelvis in snakes and whales)
Convert the following...
20 m/s --> km/h
20 km/h --> m/s
30 m/s --> km/h
20 m/s --> 72 km/h
20 km/h --> 5.56 m/s
30 m/s --> 108 km/h
A 1500 kg car is moving at 20 m/s. What is its energy?
(show working and unit)
E = 1/2 x m x v2
E = 1/2 x 1500 x 202
E = 300 000 J
Name and explain 3 types of evidence for evolution.
Biogeography - analysing the geographical distribution of living and past species
Comparative anatomy - analysing structures on living and past species
Embryology - analysing structures of the embryo for different species
Molecular biology - analysing DNA or protein sequences for different species
Fossilisation - preserved remains of past organisms
The mass of the products in a decomposition reaction are: 21g CaCl2, 15g CO2 and 20g H2O. What is the mass of the reactant?
Explain this in reference to the law of conservation of mass.
56g (21 + 15 + 20)
Mass cannot be created or destroyed so must have the same total mass of the products that you have of the reactants
A hiker starts at a campsite and walks 3 km east to a lookout, then 4 km north to a waterfall, and finally 3 km west to a picnic area.
Determine their total distance and displacement.
Distance: 3 + 4 + 3 = 10 km
Displacement: 3 km east - 3 km west = 0 km (cancel out). So final displacement is 4 km north
Draw a distance time graph for this scenario...
A cyclist rides along a straight road: Starts from rest and accelerates steadily for 5 minutes, reaching a distance of 2 km. Then, stops for a 5-minutes without moving.
Teacher will show but must include...
correctly labeled x-axis, correctly labeled y-axis, first stage plotted correctly, 2nd stage plotted correctly
Describe what each of the following represents on a d-t graph and on a v-t graph...
- flat, horizontal line
- straight diagonal line (increasing)
d-t graph: flat, horizonal line means object is stationary where straight diagonal line means moving forward at constant speed
v-t graph: flat, horizonal line means constant speed where straight diagonal line means accelerating
Define homologous and analogous structures and give an example for each
Homologous - same internal structure but different function (e.g., arm of human and wing of chicken)
Analogous - different internal structure but same function due to same environment (e.g., flipper of a shark and a dolphin)
What are the reaction types of the following?
1. 2H2 + O2 --> 2H2O
2. Na2SO4 + BaCl2 --> BaSO4 + 2NaCl
3. CH4 + O2 --> H2O + CO2
4. CaCO3 --> CaO + CO2
1. combination
2. displacement
3. combustion
4. decomposition
Identify the following as being aqueous (aq) or solid (s)...
AgCl, Na2SO4, Pb(NO3)2, CaCO3, CuSO4
aqueous (aq): Na2SO4, Pb(NO3)2, CuSO4
solid (s): AgCl, CaCO3
What are Newton's three laws?
First = an object will remain at rest or not change speed/direction unless acted upon by an outside force
Second = an object will accelerate in the direction of an unbalanced force acting on it (F = m x a)
Third = every action has an equal and opposite reaction
A hydroelectric power station generates electricity using water stored in a dam. Water flows down through turbines, which then power generators to produce electricity. The electricity is transmitted to homes where it powers an electric kettle to boil water.
List the 5 energy transformations from this scenario (in order)
1. potential energy (water stored in dam)
2. kinetic energy (water moving as it flows down turbines)
3. mechanical energy (turbines spinning)
4. electrical energy (generator produces electricity in kettle)
5. heat energy (kettle heats water)
A population of frogs lives in a large rainforest. Some frogs have dark green skin, which helps them blend into shaded areas better, while others are yellow. After a major flood, a group of these frogs becomes isolated on a higher field where the vegetation is light brown and dry. Thousands of years later, scientists observe that the most frogs on the field have yellow skin.
Explain 6 steps of this natural selection/speciation process.
1. Variation - frogs have both green and yellow skin
2. Isolation - groups are geographically isolated by the flood
3. Selection pressure - both are exposed to different selection pressures (different predators)
4. Advantage - green camouflaging/survive from predator better in forest, yellow in field
5. Hereditary/allele frequency - forest has now has more green while field more yellow
6. Speciation - difference continue to build that now the different groups are different species
Name and explain the 4 ways in which the speed of a chemical reaction can be increased in relation to collision theory OR activation energy required.
Temperature - higher temps increases collisions of reactant particles
Concentration - higher concentration increases collisions of reactant particles
Surface area - more surface exposed increases collisions of reactant particles
Catalyst - presence of a catalyst will lower the activation energy and speed up the reaction
When solutions of calcium chloride (CaCl₂) and sodium hydroxide (NaOH) are mixed, a reaction occurs. Write the word equation, formula equation and identify the precipitate.
word: calcium chloride + sodium hydroxide --> sodium chloride + calcium hydroxide
formula: CaCl2 + 2NaOH --> Ca(OH)2 + 2NaCl
precipitate: Calcium hydroxide (Ca(OH)2)