Density
Pressure
Endothermic and Exothermic Reactions
100
What is the mass of a 450 centimeter³ block of silicon if the density of silicon is 2.336 grams/centimeter³?
1051.2 grams
100
A brick delivery truck parks on a roadside scale that measures 4m by 6m. If the brick truck weighs 60,000N, what pressure does the scale put on the spring below?
2500 Pa
100
What type of energy conversion occurs during an endothermic reaction?
Chemical energy to kinetic energy
Temperature to chemical energy
Kinetic energy to potential energy
Nuclear energy to chemical energy
Kinetic energy to chemical energy
Kinetic energy to chemical energy
Explanation:
In an endothermic reaction, heat is absorbed and converted into chemical energy. Heat is the sum of molecular kinetic energy in a sample, so kinetic energy is converted into chemical energy. Note that temperature is a measure of heat, and is not a type of energy in itself.
200
The density of pure solid copper is 8.94 grams per milliliter. What volume does 5 kilograms of copper occupy?
559 milliliter
200
A swordfish jumps out of the water and the tip of its pointy upper jaw strikes a wooden wall of a fishing boat with 7500N of force. If the tip of the pointy jaw has an area of 0.0004 m2, what pressure is placed on the part of the wooden wall that is struck by the jaw?
18 750 000 Pa
200
What will happen to the rate of an exothermic reaction if the temperature is increased?
It will be unaffected
It will increase
It depends on the initial concentrations of the reactants
It will decrease
It will increase
Explanation:
The rate of a reaction will always increase with temperature.
Do not confuse the rate at which a reaction proceeds with the final equilibrium of the reaction. Yes, increasing the temperature of an exothermic reaction will push the equilibrium towards the reactant's side, but this equilibrium will be achieved much more quickly at higher temperatures. Kinetics and thermodynamics are two completely different ways to observe a reaction.
300
An object has a mass of 570 g and a volume of 2280 cubic centimetres. Calculate its density.
We’re looking for density, so constructing the triangle and covering d, we see we must divide the mass by the volume. So
density =570/2280 =0.25 g/cubic centimetres
300
A skateboarder lands on all four wheels after riding a railing. If the skateboarder has a weight of 900N and the area on the bottom of a single wheel is 0.0001m2, what pressure does the skateboard put on the ground?
2 250 000 Pa
300
What can be said about the rates of exothermic and endothermic reactions?
The rates of endothermic reactions are faster than the rates of exothermic reactions
None of these are valid answers
Exothermic reactions are more common than endothermic reactions
The rates of exothermic reactions are faster than the rates of endothermic reactions
Endothermic reactions are more common than exothermic reactions
None of these are valid answers
Explanation:
The definition of an endothermic reaction is that the products have higher energy than the reactants, resulting in a positive enthalpy of reaction. For the reaction to run, there must be an input of energy. The opposite is true for exothermic reactions: the products have lower energy than the reactants, enthalpy of reaction is negative, and heat is released.
Nothing is can be definitively stated about the rates of either type of reaction without additional information, as that will depend on the specific reactions and their respective activation energies.
400
A cat has volume 0.004 cubic metres and density 980 kg/cubic metres. Calculate the mass of the cat.
We’re looking for mass, so constructing the triangle and covering mm, we see that to calculate the mass we must multiply the density by the volume. So
Mass =980×0.004=3.92 kg
400
A forestry worker accidently strikes a pipe with the end of a pickaxe while trying to dig a hole. If the pickaxe strikes with a force of 2000N and the end of the pickaxe measures 0.02m by 0.01m, how much pressure is exerted on the pipe by the pickaxe?
10 000 000 Pa
400
The combustion of propane gas in a camping stove is an example of what type of reaction?
Exothermic reaction, with heat being released
Endothermic reaction, with heat being absorbed
It depends on the temperature at which the reaction occurs
Exothermic reaction, with heat being absorbed
Endothermic reaction, with heat being released
Exothermic reaction, with heat being released
Explanation:
Combustion reactions occur when a compound is oxidized in a highly exothermic reaction. Most commonly, the reactant is a hydrocarbon (such as propane) and the oxidizing agent is oxygen gas. The result is a large release of heat energy, frequently visualized as a flame.
Note that exothermic reactions by definition release heat, while endothermic reactions absorb heat.
500
A bottle of water has a density of 1000 kg/cubic metres and mass of 0.5 kg. Calculate the volume of the water bottle giving your answer in litres.
We’re looking for volume, so covering V, we must divide the mass by the density. So
Volume= 0.5/1000 = 0.0005 cubic metres
Multiplying this by 1000 to convert into litres, gives us the final answer,
Volume = 0.5 Volume =0.5 L
500
A football player is tackled by another player and lands with the combined weight of both players on his knee. If the combined weight of the players is 2400N and the player's knee measures 0.1m by 0.1m, how much pressure is exerted on the turf when the player lands on his knee?
240 000 Pa
500
The reaction shown is __________, and heat is __________ by the reaction.
endothermic . . . absorbed
exothermic . . . released
endothermic . . . released
exothermic . . . absorbed
exothermic . . . released
Explanation:
Negative enthalpy change(ΔH) indicates that heat is on the product side of the reaction, or, is released by the reaction. This is also the definition of an exothermic reaction.