Properties of Matter
What are the 2 properties of matter?
Physical and Chemical Properties
Ice melts into liquid water. Is this a physical or chemical change?
Physical Change
What are the three types of reactions you must know on your test?
Synthesis, Decomposition, and Replacement reactions
What is the Law of Conservation of Matter?
The amount of matter in the universe remains constant. Matter CANNOT be created or destroyed.
In a chemical equation, what is a coefficient, and what does it tell you?
A coefficient is a number placed in front of a chemical formula. It tells you how many molecules of that substance are present.
What are 3 physical properties?
Flammability, toxicity, reactivity
A student mixes two substances and observes bubbles, a color change, and a temperature change. What do these observations suggest happened?
A chemical change / reaction happened.
What is found at the left of the arrow in a chemical equation? What is found at the right of the arrow?
Reactions are found at the left of the arrow.
Products are found at the right of the arrow.
Answer both parts to earn points.
Where does matter come from? What verse tells us that God created the world at the beginning?
God is the original source of all things including energy and matter.
Genesis 1:1
In the equation below, how many molecules of water are produced?
2H₂ + O₂ → 2H₂O
2 molecules of water.
What are the 4 physical properties?
Color, density, transparency, conductivity, boiling and melting point, magnetism, reflectivity, and flexibility
A student says that every time a substance changes color, a chemical reaction has occurred. Is the student always correct? Explain your answer.
No. A color change can be evidence of a chemical reaction, but it does not always mean a chemical reaction occurred. Other evidence should be considered to determine whether a new substance formed.
This reaction combines two or more simpler substances to form one more complex substance.
Synthesis Reaction
A chemical reaction begins with 35 grams of reactants. If one product has a mass of 30 grams, what is the total mass of the remaining products?
5 grams, because the total mass of the products must equal the total mass of the reactants.
A student writes the equation H₂ + O₂ → H₂O. Explain if the equation is not balanced or not balanced?
No the equation is NOT balanced. There are 2 hydrogen and 2 oxygen atoms in the reactants. There are 2 hydrogens, but only one oxygen in the product.
A student needs to identify an unknown substance. The substance is transparent, has a density of 2 g/mL, and is toxic. Which observations describe physical properties, and which describes a chemical property?
Transparency and density are physical properties. Toxicity is a chemical property.
A student burns a piece of wood and then breaks the remaining charcoal into smaller pieces. Identify which change is physical and which is chemical, and explain why.
Burning the wood is a chemical change because new substances form. Breaking the charcoal is a physical change because its size and shape change, but its identity does not.
You must answer both parts to get points.
1. This type of reaction releases more energy than it absorbs.
2. 1. This type of reaction takes in more energy than it releases.
2 Endothermic Reaction
A sealed container has 776 g of reactants. After a chemical reaction, a gas forms. What must the total mass of the products be, and why?
776g. Matter can not be created or destroyed. It just changes forms.
A reaction absorbs 50 units of energy to break bonds and releases 30 units of energy when new bonds form. Is the reaction endothermic or exothermic?
Endothermic, because it absorbs more energy than it releases.
A student observes that a metal spoon conducts heat and has a shiny surface. The student then discovers that the metal reacts with acid and produces bubbles. Identify the two physical properties and the one chemical property.
Physical properties: conductivity and reflectivity.
Chemical property: reactivity.
A candle is burning. The wax melts near the flame, and the wax vapor burns, producing light and heat. Identify one physical change and one chemical change.
Melting wax is a physical change because it changes state. Burning the wax vapor is a chemical change because new substances form.
A student combines two substances. The reaction causes the container to feel colder. What type of reaction likely occurred, and what happened to the energy?
An endothermic reaction happened and more energy was absorbed.
A student burns a piece of wood that has a mass of 100 grams. After burning, only 15 grams of ash remain. The student claims that 85 grams of matter disappeared. Explain why the student is incorrect.
Matter was not destroyed. The wood reacted with oxygen and formed gases, smoke, and other substances that escaped into the air. If all the products were captured and measured, the total mass would equal the total mass of the wood and the oxygen that reacted with it.
In the equation below, how many total atoms are on the reactant side, and how many total atoms are on the product side? Explain how this demonstrates the Law of Conservation of Matter.
2H₂ + O₂ → 2H₂O
There are 6 total atoms on each side: 4 hydrogen atoms and 2 oxygen atoms. The atoms are rearranged, but none are created or destroyed.