Characteristics of Chemical Reactions
This is the scientific term for substances that start a chemical reaction.
Reactants
This physical property can be determined using a ruler.
Length
This law states that in a closed system, the mass before and after a chemical reaction must be this.
The same or equal
This type of reaction absorbs energy and usually feels cold to the touch.
Endothermic reaction
What is the formula for finding density?
Mass/Volume
This type of change results in new substances being formed.
Chemical change
Name three examples of physical properties
color, density, hardness, melting point, boiling point, electrical conductivity, mass, volume, length, texture, and temperature
If 10 grams of hydrogen reacts with 80 grams of oxygen, this will be the total mass of water produced.
90 grams
During a reaction in a closed system, if thermal energy is released, this will happen to the temperature of the surroundings.
Increase
This is how much matter is in a given volume.
Density
This is the scientific term for substances that start a chemical reaction.
Reactants
You are given a shiny, silver-colored metal and leave it outside. After a few days, it starts to turn reddish-brown. This change indicates that a specific type of property is being observed.
Chemical Property
Imagine you burn a piece of wood in a closed container that traps all the gases and ash. Even though the wood looks different after burning, the mass in the container stays the same. This is an example of which scientific law?
The law of conservation of mass
A student observes two reactions in the lab. In Reaction A, mixing two substances causes the beaker to feel warm. In Reaction B, mixing different substances causes the beaker to feel cold. Based on these observations, determine which reaction is exothermic and which is endothermic, and explain your reasoning.
In what state of matter are particles the most spaced out and have the most kinetic energy?
Gas
You mix two clear liquids together, and the solution turns bright yellow and forms bubbles. This is evidence that what type of change has occurred?
Chemical Change
Define chemical property
Chemical properties are properties that can be observed or measured when a substance undergoes a chemical change.
What is a shorthand notation that uses chemical symbols and numbers as subscripts to represent the type and number of atoms that are present in the smallest unit of the substance?
Chemical Formula
A scientist is studying how temperature affects the rate of a reaction. In one experiment, she heats the reactants to a higher temperature and notices the reaction happens faster. Why does increasing thermal energy (temperature) generally increase the rate of a chemical reaction?
Increasing thermal energy gives the reacting particles more kinetic energy, causing them to move faster. When particles move faster, they collide more frequently and with greater energy. This increases the chances of successful collisions that can lead to a reaction, thus speeding up the reaction rate.
An unknown metal sample has a mass of 270 grams and a volume of 30 cubic centimeters. Calculate its density, and determine if it could be aluminum, which has a density of 2.7 grams per cubic centimeter.
Since the calculated density (9 g/cm³) is much higher than that of aluminum (2.7 g/cm³), the metal sample cannot be aluminum.
In a science experiment, you combine a blue liquid and a yellow liquid, and a green solid forms at the bottom of the container. This solid is an example of what, indicating a chemical reaction has taken place?
Precipitate
You are given a sample of an unknown metal. You test its ability to conduct electricity, its color, and whether it can be flattened into sheets. These characteristics help you determine what type of property?
Physical Property
When magnesium (Mg) burns in the presence of oxygen gas (O2), it produces magnesium oxide (MgO). Write and balance the chemical equation for this reaction.
2Mg+O2→2MgO
During a lab experiment, a student mixes two chemicals in a closed container, and the temperature inside the container increases by 10°C. If the container is well-insulated so no heat can enter or escape, explain what happened to the energy within the system. Was energy created, or did it transfer? Why?
Energy was not created; it transferred within the system. Since the temperature increased in the closed container, the reaction inside must have released energy, transferring it to the surrounding materials in the container, causing the temperature to rise. This is an example of an exothermic reaction
You have two blocks of the same size, one made of metal and the other made of wood. The metal block feels much heavier than the wooden block. This difference is because the metal has a higher what?
Density