Chemical Changes
Yes
Can the number of reactants and products vary?
Endothermc reactions need energy to keep going. The energy of the products is higher than that of the reactants. This difference thells you that the reaction must absorb energy to continue.
Explain how much energy an endothermic reaction need
color change, the formation of a gas from solid or liquid reactants, texture, hardness
What are signs of chemical reactions?
two or more elements or compounds combines to make more of a complex substance
What is a synthesis?
when water boils, the gas bubbles you see are made of molecules of water, just as the liquid was.
What is an example of a property change in matter but the change does not always indicate that a chemical reaction has taken place?
Concentration is the amount of a substance in a given volume
What is concentration?
occurs when compounds break down into simpler products
What is decomposition?
is anything that has mass and takes up space
What is matter?
temperature
What is one common indication of a change in energy?
a solid that forms from solution during a chemical reaction
What is precipitation?
plus signs are used to separate two or more products
When are plus signs used?
a number placed in front of a chemical formula in an equation
what is a coefficient?
Chemical changes occur when bonds break and new bonds form.
when do chemical changes occur?
products with different properties
when reactant atoms and molecules form what happens?
although catalysts affect a reaction's rate, they are not permanently changed by a reaction. For this reason catalysts are not considered reactants
why are catalysts now considered a reactant?
The new substances formed by the reaction
What are products?
during a chemical reaction, matter is neither created or destroyed, the total mass of the reactants must equal the total mass of the products
What does the conservation of matter state?
the total number of atoms of each element in the reactants must equal the total number of atoms of each element in the product
What does the principle of conservation of matter means?
absorb or release energy
What happens as matter changes?
slows the reaction reate
What happens if you reduce the temperature?
Many endothermic reactions occur only when heat is constantly added.
When do many endothermic reactions occur?
left, followed by an arrow
Where are the reactants written on in the formulas?
right
Where is product written on in the formula?
Yes
Do all chemical equations have a common structure?
Color, hardness, texture, shine, and flexibility
What are examples of physical properties?
Yes
Are all atoms present at the start of the reaction are all present at the end of reaction?
The dotted line marks the energy of the reactants before the reaction begins. The peak in the graph shows the activation energy. The end of the reaction, the products have less energy than the reactants. This difference results in a release of heat.
Explain how much energy an exothermic reactions need.
1.write the correct formulas for both reactants and product. Place the reactants, H2 and O2 on the left side of the arrow, separated by a plus sign. Then write the product, H2O on the right side of the arrow. 2. Count the number of atoms of each element on each side of the equation. you find two atoms of oxygen in the reactants but only one atom of oxygen in the product. 3. To balance the equation, you can change the coefficients. Change the balance number of O atoms by changing the coefficient of H2O to 2. To balance the equation, you can change the coefficients. Now the right side of the equation has two water molecules, each containing an O atom. By balancing the oxygen, you unbalanced the number of hydrogen atoms. There are now two hydgron atoms in the reactants and four in the in the product. To balance the hydrogen; change the coefficient of H2 to 2. All atoms in the reactants are now accounted for in the products. 4. Look Back and Check
Explain how you can write a balanced chemical equation with hydrogen and oxygen
This reaction gives off a large amount of energy. But if you just mix the two gases together, they can remain unchanged for years. For the reaction to start, a tiny amount of activation energy is needed-even just an electric spark. Once a few molecules of hydrogen and oxygen react, the rest will quickly follow because the first few reactions provide activation energy for more molecules to react. Overall, the reaction releases more energy than it uses.
Explain the reaction between hydrogen and oxygen
1. the partilces come on contact more often, which means there are more chances for a reaction to happen. 2. faster moving particles hav more energy. this increased energy causes more particles of the reactants to get over the activation energy
Faster moving particles increase the reaction rate in what two ways?
1. Write the Equation 2. Count the Atoms 3. Use Coefficients to Balance Atoms 4. Look Back and Check
How can you write a balanced chemical equation?
Changes in matter can be described in terms of physical changes and chemical changes.
How changes in matter can be described as?
most inhibitors work by preventing reactants from coming together. Usually they combine with one of the reactants either permanently or temporarily.
How do most inhibitors work?
To describe a reaction accurately, a chemical equation must show the same number of each type of atom on both sides of the equation.
How do you describe a reaction accurately?
"yields"
How do you read the arrow?
Reactant + Reactant (arrow) Product + Product
How do you write a chemical equation? (example)
A reaction wont begin until the reactants have enough energy to push them. The energy is used to break the chemical bonds of the reactants. Then, the atoms begin to form the new chemical bonds of the products
How does a reaction begin, what is the energy used for, and what happens to the atoms?
to contain it
If you want to measure the matter before and after a reaction, how will you be able to do that?
In Chemical Reactions, the number of atoms stays the same no matter how they are arranged. So their total mass stays the same.
In chemical reactions, the number of atoms_________. So their total mass________.
bending, crushing, breaking, and cutting, changes of state, such as melting, freezing, boiling, and condensing
What are examples of physical change?
surface area, temperature, concentration and the presence of catalysts or inhibitors
What are factors that affect the rates of reaction?
material's ability to rust or tarnish
What are other chemical properties?
the substances that undergo change in a chemical reaction
What are reactants?
observe changes in properties of the materials involved. Changes in properties result when new substances form.
What are ways to detect chemical reactions?
all
What chemical reactions require a certain amount of activation energy to get started?
Chemical reactions usually absorb heat or liberate heat.
What do chemical reactions usually abosrb or liberate?
enzymes provide a surface on which reactions can take place. By bringing reactant molecules close together, the enzyme lowers the activation energy needed. In this way enzymes make chemical reactions that are necessary for life happen at a lower temperature
What do enzymes provide?
Inhibitors include preservatives added to food products to prevent them from becoming stale or spoiling.
What do inhibitors include?
Chemical Equations use chemical formulas and other symbols instead of words to summarize a reaction
What do you use in chemical equation?
A chemical equation tells you the substances you start with in a reaction and the substances you get at the end.
What does a chemical equation tell you?
the relative amount of a reactant or a product that takes part in the reaction
What does a coefficient tell you?
the ratio between elements
What does the chemical formula tell you between elements?
you need to get more reactant particles together more often and with more energy. To slow down a reaction, you need to do the opposite.
What happens if you want to make a chemical reaction happen faster or slower?
the total making and breaking of bonds results in a net of absorption of energy.The energy is absorbed as heat from nearby matter, which cools.
What happens in an endothermic reaction?
breaking bonds between atoms requires energy, making a bond releases energy
What happens the bond is broken between atoms?
only the particles on the surface of the solid come into contact with the other reactant.
What happens when a chunk of solid substance reacts with a liquid or a gas?
they are separated by a plus sign
What happens when there are two or more reactants?
more particles are exposed and the reaction happens much faster
What happens when you break the solid into smaller pieces? (concerning with surface area)
its particles move faster
What happens when you heat a substance?
a material that increases the rate of a reaction by lowering the activation energy
What is a catalyst?
A change in matter that produces one or more new substances
What is a chemical change?
A chemical equation is a short, easy way to show a chemical reaction, using symbols instead of words.
What is a chemical equation?
Flammability
What is a chemical property that is able to burn in oxygen?
is a characteristic of a substance that describes its ability to change into other substances.
What is a chemical property?
In a double replacement reaction, elements in one compound "trade places" with elements in another compound.
What is a double replacement?
is any change that alters the form or appearance of a substance but does not make the substance into another substance
What is a physical change?
a characteristic of a substance that can be observed without changing the substance into substance
What is a physical property?
when one element replaces another in a compound, or when two elements in different compounds trade places, the reaction is classified as a replacement.
What is a replacement?
when only one element in one compound trade places with the other one element in the other compound
What is a single replacement?
Activation energy is the minumim amount of energy needed to start a chemical reaction.
What is an activation energy?
the reaction between fuel and oxygen in an airplane engine releases energy, mostly in the form of heat. The heat causes gases in the engine to expand. The expansion and movement of the gases out of the plane exert a force that moves the plane forward.
What is an example of an exothermic reaction?
The reaction of baking soda and vinegar is endothermic. During the reaction, energy is absorbed causing surroundings to become cooler. However, endothermic reactions do not always result in a decrease in temperature.
What is an example of endothermic reaction?
the total making and breaking of bonds results in a net release of energy. It is released as heat into nearby matter
What is an exothermic reaction?
matter can enter from or escape to the surroundings
What is an open system?
the study of matter and how matter changes
What is chemistry?
to represent the substances involved in a reaction
Why do all chemical equations use formulas?
no
Do chemical reactions occur at the same rate?
no
Does the amount of matter change during a chemical equation?
matter is not allowed to enter or leave
What is a closed system?
Three general types of chemical reactions are synthesis, decomposition, and replacement.
what are three general types of chemical reactions?
The cells in your body contain biological catalysts
What are enzymes?
The burning of fuel, such as wood, natural gas, or oil
What are examples of exothermic reactions?
a material is used to decrease the rate of a reaction is an inhibitor
What is an inhibitor?
Chemical Reactions involve changes in properties and changes in energy that you can observe.
what do chemical reactions involve in changes of what?
In a chemical change, the atoms are rearranged to form new substances with different chemical and physical properties.
what happens to the atoms in a chemical change?
increasing the concentration of reactants supplies more particles to react
what happens when you increase concentration?
